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  • 51.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    On the efficacy of using ground return in the broadband power-line communications: A transmission-line analysis2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 1, s. 132-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The power-line infrastructure has been identified as an efficient system suitable for broadband power-line communication (BPLC) to connect and control various end users. However, the network is affected by stochastic attenuations due to the number of interconnected branches, their line lengths, associated terminal loads, etc. There is yet another parameter that could influence the above stated attenuations or distortions depending on the way the signals are allowed to return to the transmitting end. In this paper, we investigate whether a finitely conducting ground return could be used for BPLC and to investigate its performance over the conventional methods Where one of the adjacent power-line conductors is-used as signal return. This study could be helpful to those who are proposing the use of ground as a return conductor in BPLC systems. It will be shown that the use of ground return for the BPLC system is effective or better only when the ground conductivity is high (>50 mS/m). When ground conditions are poorer, attenuations increase with., making them unsuitable for BPLC. There are situafrequency tions where poor ground conditions can still be used but only the transmission-line lengths are shorter. The analysis presented here is based on transmission-line solutions both under lossless (without ground return) and lossy (with ground return) conditions and are applied to typical low-voltage and medium-voltage channels. Comparisons are also made based on the power spectral densities and channel capacities.

  • 52.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Kissaka, Mussa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Mvungi, Nerey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Broadband Powerline Communications: Performance Analysis2006Inngår i: Enformatika Trans. on Engineering, Computing and Technology, Vol. 18, s. 250-254Artikkel i tidsskrift (Fagfellevurdert)
  • 53.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Channel characterization for indoor power-line networks2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 4, s. 1883-1888Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power-line networks are promising mediums by which broadband services can be offered, such as Internet services, voice over Internet protocol, digital entertainment, etc. In this paper, an analysis of delay spread, coherence bandwidth, channel capacity, and averaged delay in the frequency bands up to 100 MHz for typical indoor power-line networks are studied. Earlier studies for indoor power-line networks considered frequencies up to 30 MHz only and earlier works have shown that at these frequency bands, the data rates are generally low and are inefficient for digital entertainment in comparison with wireless local-area networks standards, such as IEEE 802.11 n. In this paper, it is shown that at 100 MHz, the average channel capacity for typical indoor power-line networks can be up to 2 Gb/s and it is found that by increasing the number of branches in the link between transmitting and receiving ends, the average channel capacity decreases from 2 Gb/s to 1 Gb/s (when the number of branches was increased by four times for a power spectral density of -60 dBm/Hz). At the same time, the coherence bandwidth decreased from 209.45 kHz to 137.41 kHz, which is much better than the coherence bandwidths corresponding to 30-MHz systems. It is therefore recommended to operate the indoor power-line networks at 100-MHz bandwidths for a wide variety of broadband services.

  • 54.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Effects of multipath on OFDM systems for indoor broadband power-line communication networks2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 3, s. 1190-1197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power-line networks are an excellent infrastructure for broadband data transmission. However, various multipaths within a broadband power-line communication (BPLC) system exist due to stochastic changes in the network load impedances, branches, etc. This further affects network performance. This paper attempts to investigate the performance of indoor channels of a BPLC system that uses orthogonal frequency-division multiplexing (OFDM) techniques. It is observed that when a branch is added in the link between the sending and receiving end of an indoor channel, an average of 4-dB power loss is found. Additionally, when the terminal impedances of the branch change from the line characteristic impedance to impedance of lower values, the power loss (signal-to-noise ratio) is about 0.67 dB/. On the contrary, for every increase in the terminal impedances by 100 , above the line characteristic impedance, the power loss is 0.1 dB/. When the line terminal impedances are close to short or open circuits, OFDM techniques show degraded performance. This situation is also observed when the number of branches increases. In this paper, it is shown that to overcome such performance degradation, the concatenated Reed-Solomon codes/interleaved Viterbi methods can be used. The observations presented in the paper could be useful for an efficient design of a BPLC system that uses OFDM techniques.

  • 55.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Performance of underground cables that use OFDM systems for broadband power-line communications2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 4, s. 1889-1897Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power-line networks are proposed for broadband data transmission. The presence of multipaths within the broadband power-line communication (BPLC) system, due to stochastic changes in the network load impedances, branches, etc. pose a real challenge as it affects network performance. This paper attempts to investigate the performance of an orthogonal frequency-division multiplexing (OFDM)-based BPLC system that uses underground cables. It is found that when a branch is added in the link between the sending and receiving end, there is an average of 4-dB power loss. In addition, when the terminal impedances of the branches that are connected to the link between the transmitting and receiving end vary from line characteristic impedance to low-impedance values, the power loss (signal-to-noise ratio) is about 0.35 dB/ . On the contrary, for an increase in the terminal impedances by 100 above line characteristic impedance, the power loss is 0.23 dB//. When the branch terminal impedances are close to short or open circuits, OFDM techniques show degraded performance. This situation is also observed when the number of branches increases. It is shown that to overcome degraded network performance, the concatenated Reed-Solomon codes/interleaved Viterbi methods can be used, which could be used for an efficient design of the BPLC system that uses OFDM techniques.

  • 56.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power-line communication channel model for interconnected networks. Part I: two-conductor system2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 1, s. 118-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a generalized transmission-line approach to determine the transfer function of a power-line network of a two-conductor system (two parallel conductors) with distributed branches. The channel frequency responses are derived considering different terminal loads and branches. The model's time-domain behavior is validated using commercial power system simulation software called Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP). The simulation results from the model for three different topologies considered have excellent agreement with corresponding ATP-EMTP results. Hence, the model can be considered as a tool to characterize any given power-line channel topology that involves the two-conductor system. In the companion paper (Part II), the proposed method is extended for a multiconductor power-line system.

  • 57.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power-line communication channel model for interconnected networks: Part II: multiconductor system2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 1, s. 124-128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we present an approach to determine the transfer function for multiconductor power-line networks with distributed branches and load terminations for broadband power-line communication (BPLC) applications. The applicability of the proposed channel model is verified numerically in time domain using the finite-difference-time domain (FDTD) method for the solution of transmission lines. The channel model simulation results are in excellent agreement with the corresponding FDTD results. The model therefore could be useful in the analysis and design of BPLC systems involving multiconductor power-line topology.

  • 58.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kissaka, M. M.
    Mvungi, N. H.
    The influence of load impedance, line length, and branches on underground cable power-line communications (PLC) systems2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 1, s. 180-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An underground cable power transmission system is widely used in urban low-voltage power distribution systems. In order to assess the performance of such distribution systems as a low-voltage broadband power-line communication (BPLC) channel, this paper investigates the effects of load impedance, tine length, and branches on such systems, with special emphasis on power-line networks found in Tanzania. From the frequency response of the transfer function (ratio of the received and transmitted signals), it is seen that the position of notches and peaks in the magnitude are largely affected (observed in time-domain responses too) by the aforementioned network configuration and parameters. Additionally, channel capacity for such PLC channels for various conditions is investigated. The observations presented in this paper could be helpful as a suitable design of the PLC systems for better data transfer and system performance.

  • 59.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kissaka, M.
    Mvungi, Nerey
    The effects of load impedance, line length, and branches in typical low-voltage channels of the BPLC systems of developing countries: transmission-line analyses2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 2, s. 621-629Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the influence of line length, number of branches (distributed and concentrated), and terminal impedances on the performance of a low-voltage broadband power-line communication channel. For analyses, the systems chosen are typical low-voltage power-line networks found in Tanzania. The parameters varied were the network's load impedances, direct line length (from transmitter to receiver), branched line lengths, and number of branches. From the frequency responses of the transfer functions (ratio of the received and transmitted signal), it is seen that the position of notches and peaks in the amplitude responses are affected by the aforementioned network parameters and topology. As a result, the time-domain responses are attenuated and distorted. Time-domain responses of power-line channels under various conditions are also investigated for a given pulse input at the transmitter. The observations presented in this paper could be useful for suitable power-line communication system design.

  • 60.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kissaka, Mussa M.
    Mvungi, Nerey H.
    An experimental validation for broadband power-line communication (BPLC) model2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 3, s. 1380-1383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, different models have been proposed for analyzing the broadband power-line communication (BPLC) systems based on transmission-line (TL) theory. In this paper, we make an attempt to validate one such BPLC model with laboratory experiments by comparing the channel transfer functions. A good agreement between the BPLC model based on TL theory and experiments are found for channel frequencies up to about 100 MHz. This work with controlled experiments for appropriate validation could motivate the application and extension of TL theory-based BPLC models for the analysis of either indoor or low-voltage or medium-voltage channels.

  • 61.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kissaka, Mussa M.
    Mvungi, Nerey H.
    Broadband power-line communications: The channel capacity analysis2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 1, s. 164-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The power line has been proposed as a solution to deliver broadband services to end users. Various studies in the recent past have reported a decrease in channel capacity with an increase-in the number of branches for a given channel type whether it is an indoor or low-voltage (LV) or medium-voltage (MV) channel. Those studies, however, did not provide a clear insight as to how the channel capacity is related to the number of distributed branches along the line. This paper attempts to quantify and characterize the effects of channel capacity in relation to the number of branches and with different terminal loads for a given type of channel. It is shown that for a power spectral density (PSD) between -90 dBm/Hz to - 30 dBm/Hz, the channel capacity decreases by a 20-30 Mb/s/branch, 14-24 Mb/s/branch, and a 20-25 Mb/s/branch for an MV channel, LV channel, and indoor channel, respectively. It is also shown that the channel capacity is minimum when the load impedance is terminated in characteristic impedances for any type of channel treated here. It is shown that there could be a significant loss in channel capacity if a ground return was used instead of a conventional adjacent conductor return. The analysis presented in this paper would help in designing appropriate power-line communication equipment for better and efficient data transfer.

  • 62.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kissaka, Mussa M.
    Mvungi, Nerey H.
    Expressions for Current/Voltage distribution in broadband power-line communication networks involving branches2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 1, s. 188-195Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Estimation of electromagnetic (EM)-field emissions from broadband power-line communication systems (BPLC) is necessary, because at its operating frequencies, the radiated emis sions from BPLC systems act as sources of interference/crosstalk to other radio-communication systems. Currently, the transmission-line (TL) system used for BPLC is complex, involving arbitrarily/irregularly distributed branched networks, arbitrary termination loads, varying line lengths, and line characteristic impedance. In order to study the electromagnetic-compatibility (EMC) issues associated with the radiated emissions of such complex BPLC networks, knowledge of current and voltage distributions along the length of the power-line channels is needed. This paper attempts to derive and present generalized expressions for either the current or voltage distribution along the line (whose TL parameters are known) between the transmitting and receiving ends for any line boundary condition and configuration based on the TL theory. The expressions presented in this paper could be beneficial for direct calculation of EM emissions from BPLC systems.

  • 63.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mvungi, N. H.
    A broadband power-line communication system design scheme for typical Tanzanian low-voltage network2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 3, s. 1218-1224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Information and communications technologies (ICTs) are gaining importance in developing countries. Power-line network is a potential infrastructure for ICT services provision. Power-lines are highly interconnected network with stochastic variation in number of branches. Under such distributed network conditions the design of a broadband power-line communication (BPLC) system is a challenge. In this paper a case study of an actual power-line network, representative of a low-voltage BPLC channel in Dar es Salaam, Tanzania is considered. We shall investigate the performance of such a low-voltage channel that uses orthogonal frequency division multiplexing (OFDM) technique with binary phase shift keying (BPSK) modulation scheme for communication. For sensitivity analysis, three different transmitter locations were chosen and receiver points were varied to identify the possible degraded performance scenarios. Analysis show that in the frequency bands of 100 MHz, the channel delay spread for such networks is about 4 s, giving a maximum number of subchannels 4096 with 512 cyclic prefix. To improve the degraded performance scenarios, the concatenated Reed Solomon outer code with punctured convolution inner code was applied to the network. It was found that when the branches were terminated by its corresponding characteristic impedances the performance is improved by 10-20 dB compared to a corresponding uncoded system. On the contrary for a coded system when the branches were terminated either in low or higher impedances compared to branch characteristic impedances the improvement was greater than 2-15 dB. This study demonstrates that the specification proposed by IEEE-802.16 broadband wireless access working groups can be used for performance improvement of distributed low-voltage systems.

  • 64.
    Anatory, Justinian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Theethayi, Nelson
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thottappillil, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mwase, C.
    Mvungi, N.H.
    The Effects of Multipath on OFDM Systems for Broadband Power-Line Communications a Case of Medium Voltage Channel2009Inngår i: World Academy of Science, Engineering and Technology, ISSN 2070-3724, Vol. 54, s. 205-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power-line networks are widely used today for broadband data transmission. However, due to multipaths within the broadband power line communication (BPLC) systems owing to stochastic changes in the network load impedances, branches, etc., network or channel capacity performances are affected. This paper attempts to investigate the performance of typical medium voltage channels that uses Orthogonal Frequency Division Multiplexing (OFDM) techniques with Quadrature Amplitude Modulation (QAM) sub carriers. It has been observed that when the load impedances are different from line characteristic impedance channel performance decreases. Also as the number of branches in the link between the transmitter and receiver increases a loss of 4dB/branch is found in the signal to noise ratio (SNR). The information presented in the paper

  • 65. Andersen, Kristin
    et al.
    Chapman, A.
    Hareide, N. R.
    Folkestad, A. O.
    Sparrevik, E.
    Langhamer, Olivia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Environmental Monitoring at the Maren Wave Power Test Site off the Island of Runde, Western Norway: Planning and Design2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper provides a general description of theenvironmental monitoring programme currentlyongoing at Vattenfall’s/Tussa’s wave power testsite "Maren", on the Norwegian west coast. Thepurpose of the environmental monitoring istwofold: (i) to monitor the potential impact of theMaren installation on the environment, therebyfulfilling the consent requirements of theNorwegian authorities, (ii) more generally, to gainexperiences about the design and management ofan environmental monitoring programme and testa variety of monitoring methodologies andequipment. The primary environmentalparameters assessed in the monitoring programmeinclude fish, benthos and seabird communities.Observations on marine mammals are includedmarginally and underwater noise measurementsare scheduled to be included at a later stage. Therationale for choosing the specific components ofthe monitoring programme is elucidated in thecontext of site specific environmental features, aswell as project-specific technical characteristics.Generally, the monitoring strategy follows amodified so-called BACI (Before-After, Control-Impact) design, i.e. takes place before and afterdeployment of the wave power devices and duringoperation over a period of approximately 3 years.A communication plan accompanies theprogramme and is considered an essentialprerequisite for transparency and publicacceptance of the programme.

  • 66.
    Andersson, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Wengberg, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Utvärdering av konsekvenserna för nätanslutning av vindkraftparker i Sverige vid införandet av nätkoden Requirements for Generators2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Grid codes are becoming more demanding on power generating units due to the factthat the complexity of the power grid is increasing. The penetration of wind powerhas grown over the last years and it is clear that wind farms need to be addressedwith the same type of grid codes as conventional generation units. There is howeveran undeniable difference between the technology in conventional synchronousgeneration units, and the asynchronous generation units in wind farms.

    This thesis has reviewed the current grid code in Sweden and compared it to the newcode proposed by ENTSO-E, “the Requirements for Generators”, in the aspect ofwind farms with an installed power of 30 MW or more. The comparison has beencomplemented by an analysis of how wind farms of two different technologies(Doubly fed induction generators and full power converters) can meet therequirements and technical proposals have been given on how to be able to meetcompliance with the new grid codes.

    The Requirements for Generators contains many non-exhaustive and optionalrequirements, because of this it has been difficult to, at this stage, exactly point outthe technical impact on the grid connection of future wind farms in Sweden. For manyof the requirements in the Requirements for Generators there is no equivalent in theSwedish Grid Code (SvK FS2005:2) but counterparts can thus be found in existingpractices and therefor does not imply any major differences for the industry.

    The requirements of frequency regulation, synthetic inertia and reactive powercapability are the main components of the RfG which will require additional softwareand hardware installations for future wind farms in Sweden.

    Fulltekst (pdf)
    fulltext
  • 67.
    Andersson, Joakim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialvetenskap. Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Materialvetenskap.
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialvetenskap. Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. M.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialvetenskap. Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Elektricitetslära och åskforskning.
    Diamanter blir var mans egendom2003Inngår i: Forskning & Framsteg, nr 1, s. 38-41Artikkel i tidsskrift (Annet vitenskapelig)
  • 68.
    Andersson, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ensure the electric power system's durability through battery monitoring2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Battery monitoring is used to acquire information about battery conditions. It’s a regular technology that most of us uses on daily bases. The charge gauge in a cellphone, consisting of bars which indicate the degree of charge left in the battery is an example. Battery monitoring gives the cellphone user information about the battery. The background to the thesis work is that this technology is requested for vehicles because empty or broken batteries are one of the most common causes for involuntary stops. One way to monitor battery conditions is with a battery sensor, which is a mechanical device that measures and calculates battery conditions.

    This thesis’ purpose is to develop evaluation criteria and evaluation methods to assess the possibility for battery sensors to deliver competent information in order to ensure functionality of electric systems. To enable generalized evaluations of battery sensors, their delivered information are delimited to three different and defined battery conditions which are State-Of-Charge (SOC), State-Of-Function (SOF) and State-Of-Health (SOH).

    To be able to compare battery sensor calculations and actual battery conditions, a method to obtain the battery conditions was needed. To determine this method a literature review was performed and because of an accurate and continuous method was needed, Coulomb counting was selected. Coulomb counting is a book-keeping method which calculates the SOC accurate based on current integration.

    To develop criteria that evaluate battery sensors possibilities to deliver competent information, tests about how vehicles starting affect batteries as well as tests about battery sensors performance in different scenarios have been investigated. The thesis work shows that the SOC has to be limited based on the degree of charge left in a battery, SOF has to be limited to batteries potential to deliver a certain voltage for a specific constant current and for SOH it is most important to maintain a continuous countdown.

    The evaluation methods to evaluate battery sensors according to the criteria have been developed to test and ensure the battery sensors performance based on several test-cycles. The evaluation methods with certain conditions and test-cycles should be comparable to actual conditions for battery sensors installed on vehicles to ensure a continuous delivering of competent information.

    To summary the thesis work has developed and partly verified evaluation criteria and evaluation methods to evaluate battery sensors possibility to deliver competent information about the battery conditions SOC, SOF and SOH. These criteria and methods make it possible to evaluate if a battery sensor, any battery sensor calculating these battery conditions based on similar parameters, could deliver enough competent information in order to ensure functionality of electric systems.

    Fulltekst (pdf)
    fulltext
  • 69.
    Andersson, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Energy storage solutions for electric bus fast charging stations: Cost optimization of grid connection and grid reinforcements2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This study investigates the economic benefits of installing a lithium-ion battery storage (lithium iron phosphate, LFP and lithium titanate, LTO) at an electric bus fast charging station.  It is conducted on a potential electric bus system in the Swedish city Västerås, and based on the existing bus schedules and routes as well as the local distribution system. The size of the energy storage as well as the maximum power outtake from the grid is optimized in order to minimize the total annual cost of the connection. The assessment of the distribution system shows that implementing an electric bus system based on opportunity charging in Västerås does not cause over-capacity in the 10 kV grid during normal feeding mode. However, grid reinforcements might become necessary to guarantee potential backup feeding modes. Batteries are not a cost effective option to decrease grid owner investments in new transformers. However, battery energy storage have the possibility to decrease the annual cost of connecting a fast charging station to the low-voltage grid. The main advantage of the storage system is to decrease the fees to the grid owner. Of the studied batteries, LTO is the most cost effective solution because of its larger possible depth-of-discharge for a given cycle life. The most important characteristics, that determine if a fast charging station could benefit economically from an energy storage, is the bus frequency. The longer the time in between buses and the higher the power demand, the more advantageous is the energy storage.

    Fulltekst (pdf)
    fulltext
  • 70.
    Andersson Sundén, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Sjöstrand, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Conroy, Sean
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Ericsson, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Gatu Johnson, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Giacomelli, L
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Hellesen, Carl
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Hjalmarsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Ronchi, E
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Weiszflog, Matthias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Källne, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Gorini, G
    Univ Milano -Bicocca, Milano, Italy.
    Tardocchi, M
    Univ Milano -Bicocca, Milano, Italy.
    Combo, A
    IST, Portugal.
    Cruz, N
    Batista, A
    Pereira, R
    Fortuna, R
    Sousa, J
    Popovichev, S
    The thin-foil magnetic proton recoil neutron spectrometer MPRu at JET2009Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 610, nr 3, s. 682-699Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neutrons are produced in fusion energy experiments with both deuterium (D) and deuterium–tritium (DT) plasmas. Neutron spectroscopy is a valuable tool in the study of the underlying fuel ion populations. The magnetic proton recoil neutron spectrometer, originally installed at JET in 1996 for 14-MeV neutron measurements, has been upgraded, with the main aim of improving its signal-to-background ratio (S/B), making measurements of the 2.5-MeV neutron emission in D plasmas possible. The upgrade includes a new focal-plane detector, based on the phoswich technique and consequently less sensitive to background, and a new custom-designed digital data acquisition system based on transient recorder cards. Results from JET show that the upgraded MPRu can measure 2.5-MeV neutrons with S/B=5, an improvement by a factor of 50 compared with the original MPR. S/B of 2.8×104 in future DT experiments is estimated. The performance of the MPRu is exemplified with results from recent D plasma operations at JET, concerning both measurements with Ohmic, ion cyclotron resonance (ICRH) and neutral beam injection (NBI) plasma heating, as well as measurements of tritium burn-up neutrons. The upgraded instrument allows for 2.5-MeV neutron emission and deuterium ion temperature measurements in plasmas with low levels of tritium, a feature necessary for the ITER experiment.

  • 71.
    Andersson, Tobias
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Toft, Jonathan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Data communication and power supply on a two conductor system2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis aimed to develop a prototype of a hardware platform which allowed digital communication as well as DC power to be transmitted over one pair of wires. The prototype was used as a pre-study for Axis Communications AB that wanted a bit rate high enough to transmit digital audio, as well as enough power to supply a set of speakers.

    The prototype included one circuit to send power and data (master), as well as two receivers (slaves). With this configuration data rates of up to 17 Mbps were achieved as well as an output power of 90 W from master. The data was transmitted on a RS-485 bus type, which was AC coupled to a 48 V DC bias. Because of the AC coupling, the bit stream needed to alternate, therefore Manchester encoded data, or similar, was recommended.

    The receiver cards included a buck converter to supply the circuits with a stable 5 V DC. The converters needed at least 10 V supply voltage to function, which gave a theoretical max range in cabling when accounting for voltage drop in the cables. For a 0.75 mm² power cord at max allowed current, this range was 500 metres per wire.

    Fulltekst (pdf)
    fulltext
  • 72.
    Anker, A.
    et al.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Barwick, S. W.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Besson, D. Z.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA;Natl Res Nucl Univ MEPhI Moscow Engn Phys Inst, Moscow 115409, Russia.
    Bingefors, Nils
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Garcia-Fernandez, D.
    DESY, D-15738 Zeuthen, Germany;Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany.
    Gaswint, G.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Glaser, C.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Hallgren, Allan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Hanson, J. C.
    Whittier Coll, Dept Phys, Whittier, CA 90602 USA.
    Klein, S. R.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA.
    Kleinfelder, S. A.
    Univ Calif Irvine, Dept Elect Engn & Comp Sci, Irvine, CA 92697 USA.
    Lahmann, R.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA;Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany.
    Latif, U.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA.
    Nam, J.
    Natl Taiwan Univ, Dept Phys, Taipei 10617, Taiwan;Natl Taiwan Univ, Leung Ctr Cosmol & Particle Astrophys, Taipei 10617, Taiwan.
    Novikov, A.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA;Natl Res Nucl Univ MEPhI Moscow Engn Phys Inst, Moscow 115409, Russia.
    Nelles, A.
    DESY, D-15738 Zeuthen, Germany;Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany.
    Paul, M. P.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Persichilli, C.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Plaisier, I.
    DESY, D-15738 Zeuthen, Germany;Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany.
    Prakash, T.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA.
    Shively, S. R.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Tatar, J.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA;Univ Calif Irvine, Res Cyberinfrastruct Ctr, Irvine, CA 92697 USA.
    Unger, Elisabeth
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Wang, S. -H
    Welling, C.
    DESY, D-15738 Zeuthen, Germany;Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany.
    Zierke, S.
    Rhein Westfal TH Aachen, Phys Inst 3, Aachen, Germany.
    Neutrino vertex reconstruction with in-ice radio detectors using surface reflections and implications for the neutrino energy resolution2019Inngår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, nr 11, artikkel-id 030Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultra high energy neutrinos (E-nu >10(16.5) eV) are efficiently measured via radio signals following a neutrino interaction in ice. An antenna placed O(15 m) below the ice surface will measure two signals for the vast majority of events (90% at E-nu = 10(18) eV): a direct pulse and a second delayed pulse from a reflection off the ice surface. This allows for a unique identification of neutrinos against backgrounds arriving from above. Furthermore, the time delay between the direct and reflected signal (D'n'R) correlates with the distance to the neutrino interaction vertex, a crucial quantity to determine the neutrino energy. In a simulation study, we derive the relation between time delay and distance and study the corresponding experimental uncertainties in estimating neutrino energies. We find that the resulting contribution to the energy resolution is well below the natural limit set by the unknown inelasticity in the initial neutrino interaction. We present an in-situ measurement that proves the experimental feasibility of this technique. Continuous monitoring of the local snow accumulation in the vicinity of the transmit and receive antennas using this technique provide a precision of O(1mm) in surface elevation, which is much better than that needed to apply the D'n'R technique to neutrinos.

  • 73.
    Anker, A.
    et al.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Barwick, S. W.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Besson, D. Z.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA;Natl Res Nucl Univ, MEPhI Moscow Engn Phys Inst, Moscow 115409, Russia.
    Bingefors, Nils
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Gaswint, G.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Glaser, C.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Hallgren, Allan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Hanson, J. C.
    Whittier Coll, Dept Phys, Whittier, CA 90602 USA.
    Lahmann, R.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA;Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany.
    Latif, U.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA.
    Nam, J.
    Natl Taiwan Univ, Dept Phys, Taipei 10617, Taiwan;Natl Taiwan Univ, Leung Ctr Cosmol & Particle Astrophys, Taipei 10617, Taiwan.
    Novikov, A.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA;Natl Res Nucl Univ, MEPhI Moscow Engn Phys Inst, Moscow 115409, Russia.
    Klein, S. R.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA.
    Kleinfelder, S. A.
    Univ Calif Irvine, Dept Elect Engn & Comp Sci, Irvine, CA 92697 USA.
    Nelles, A.
    DESY, D-15738 Zeuthen, Germany;Humbolt Univ Berlin, Inst Phys, D-12489 Berlin, Germany.
    Paul, M. P.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Persichilli, C.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Shively, S. R.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Tatar, J.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA;Univ Calif Irvine, Res Cyberinfrastruct Ctr, Irvine, CA 92697 USA.
    Unger, Elisabeth
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Wang, S-H
    Yodh, G.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
    Targeting ultra-high energy neutrinos with the ARIANNA experiment2019Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 64, nr 12, s. 2595-2609Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The measurement of ultra-high energy (UHE) neutrinos (E > 10(16) eV) opens a new field of astronomy with the potential to reveal the sources of ultra-high energy cosmic rays especially if combined with observations in the electromagnetic spectrum and gravitational waves. The ARIANNA pilot detector explores the detection of UHE neutrinos with a surface array of independent radio detector stations in Antarctica which allows for a cost-effective instrumentation of large volumes. Twelve stations are currently operating successfully at the Moore's Bay site (Ross Ice Shelf) in Antarctica and at the South Pole. We will review the current state of ARIANNA and its main results. We report on a newly developed wind generator that successfully operates in the harsh Antarctic conditions and powers the station for a substantial time during the dark winter months. The robust ARIANNA surface architecture, combined with environmentally friendly solar and wind power generators, can be installed at any deep ice location on the planet and operated autonomously. We report on the detector capabilities to determine the neutrino direction by reconstructing the signal arrival direction of a 800 m deep calibration pulser, and the reconstruction of the signal polarization using the more abundant cosmic-ray air showers. Finally, we describe a large-scale design - ARIA - that capitalizes on the successful experience of the ARIANNA operation and is designed sensitive enough to discover the first UHF neutrino.

  • 74.
    Anttila, Sara
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cardoso da Silva Júnior, Dalmo
    Temiz, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Oliveira, Janaína Goncalves de
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Jennifer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Parwal, Arvind
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Boström, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power Control Strategies for a Smoother Power Output from a Wave Power Plant2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents power output and power control strategies for a wave power plant. Three cases are presented; active power output without power smoothing control, active power output with an energy storage to smooth the power output to the grid, active- and reactive power control using the grid side inverter and an energy storage. The model is constructed in MATLAB Simulink and is based on the wave energy converter technology developed at Uppsala University. The model input is wave height data from the Wave Hub test site, UK. The study show that without power control, the output power is fluctuating significantly during a 60 second time period. The difference between the average power output and the maximum power peaks can be as high as a factor of 6. By using an energy storage a significant reduction of the power fluctuation, to approximately ± 10 %, can be achieved. Even with the high intermittency of the input power, it is possible to control the active- and reactive power output to the grid. Thus, it is shown that it is possible to provide grid support functions, which are needed in the transition to a higher penetration of renewable energy sources on the grid.

  • 75. Anttila, Sara
    et al.
    Silva, Dalmo
    Temiz, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Oliveira, Janaína Goncalves de
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Jennifer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Parwal, Arvind
    Boström, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power Control Strategies for a Smoother Power Output from a Wave Power Plant2019Inngår i: 13th European Wave and Tidal Energy Conference (EWTEC), Napoli, Italy, September 1-6, 2019, Napoli, Italy: European Wave and Tidal Energy Conference , 2019Konferansepaper (Fagfellevurdert)
  • 76.
    Apelfrojd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ekström, Rickard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thomas, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter2015Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, nr 2, s. 808-820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper proposes a back-to-back 2L-3L grid connection topology for a marine current energy converter. A prototype marine current energy converter has been deployed by a research group at Uppsala University. The concept behind the prototype revolves around a fixed pitch vertical axis turbine directly connected to a permanent magnet synchronous generator (PMSG). The proposed grid connection system utilizes a well known and proven two level voltage source converter generator-side combined with a three-level cascaded H-bridge (CHB) multilevel converter grid-side. The multilevel converter brings benefits in terms of efficiency, power quality and DC-link utilization. The system is here presented for a single marine current energy converter but can easily be scaled up for clusters of marine current energy converters. Control schemes for both grid-side and generator-side voltage source converters are presented. The start-up, steady state and dynamic performance of the marine current energy converter are investigated and simulation results are presented in this paper.

    Fulltekst (pdf)
    fulltext
  • 77.
    Apelfröjd, Senad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Electrical System for a Variable Speed Vertical Axis Wind Turbine2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The wind has been used as a source of energy for a long time. Wind power in power production has had a upswing in the last decade due to its renewable and clean nature. This thesis contributes to the wind power research done at the division of Electricity at Uppsala University. The research is aimed towards increasing the understanding of vertical axis wind turbines. The thesis focuses on vertical axis wind turbines of the H-rotor type with a directly driven permanent magnet synchronous generator. In this thesis a full-scale variable speed electrical grid connection system is developed and evaluated for a 12 kW prototype turbine. The proposed electrical system consists of a diode rectifier, IGBT inverter, LCL-filter and tap transformer. The full variable speed operation is achieved by adjusting transformer taps and adjusting the modulation of the inverter. The system has been assembled in a lab environment where efficiency and harmonic content have been evaluated for the operational scheme and site specifics of the 12 kW turbine. The work also looks into transformer magnetization losses, permanent magnet generator air cooling and control system design for a similar system. The results from simulations and experiments show that the tap transformer system has a high efficiency at nominal power and that the system efficiency at nominal power is increased by going up in tap. The study also shows that the total demand distortion for the system is well below 5% for full operating range of the 12 kW turbine.

    Keywords: VAWT, H-rotor, tap transformer, stall control, renewable energy, variable speed operation, transformer magnetization losses

  • 78.
    Apelfröjd, Senad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Renewable energy is harnessed from continuously replenishing natural processes. Some commonly known are sunlight, water, wind, tides, geothermal heat and various forms of biomass. The focus on renewable energy has over the past few decades intensified greatly. This thesis contributes to the research on developing renewable energy technologies, within the wind power, wave power and marine current power projects at the division of Electricity, Uppsala University. In this thesis grid connection of permanent magnet generator based renewable energy sources is evaluated.

    A tap transformer based grid connection system has been constructed and experimentally evaluated for a vertical axis wind turbine. Full range variable speed operation of the turbine is enabled by using the different step-up ratios of a tap transformer. This removes the need for a DC/DC step or an active rectifier on the generator side of the full frequency converter and thereby reduces system complexity. Experiments and simulations of the system for variable speed operation are done and efficiency and harmonic content are evaluated. 

    The work presented in the thesis has also contributed to the design, construction and evaluation of a full-scale offshore marine substation for wave power intended to grid connect a farm of wave energy converters. The function of the marine substation has been experimentally tested and the substation is ready for deployment. Results from the system verification are presented. Special focus is on the transformer losses and transformer in-rush currents.

    A control and grid connection system for a vertical axis marine current energy converter has been designed and constructed. The grid connection is done with a back-to-back 2L-3L system with a three level cascaded H-bridge converter grid side. The system has been tested in the laboratory and is ready to be installed at the experimental site. Results from the laboratory testing of the system are presented.

    Delarbeid
    1. Implementation of control system for hydro-kinetic energy converter
    Åpne denne publikasjonen i ny fane eller vindu >>Implementation of control system for hydro-kinetic energy converter
    (engelsk)Inngår i: Journal of Control Science and Engineering, ISSN 1687-5249, E-ISSN 1687-5257Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-181554 (URN)
    Tilgjengelig fra: 2012-09-26 Laget: 2012-09-26 Sist oppdatert: 2017-12-07bibliografisk kontrollert
    2. Evaluation of a Blade Force Measurement System for a Vertical Axis Wind Turbine Using Load Cells
    Åpne denne publikasjonen i ny fane eller vindu >>Evaluation of a Blade Force Measurement System for a Vertical Axis Wind Turbine Using Load Cells
    Vise andre…
    2015 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, nr 6, s. 5973-5996Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Unique blade force measurements on an open site straight-bladed vertical axis wind turbine have been performed. This paper presents a method for measuring the tangential and normal forces on a 12-kW vertical axis wind turbine prototype with a three-bladed H-rotor. Four single-axis load cells were installed in-between the hub and the support arms on one of the blades. The experimental setup, the measurement principle, together with the necessary control and measurement system are described. The maximum errors of the forces and accompanying weather data that can be obtained with the system are carefully estimated. Measured forces from the four load cells are presented, as well as the normal and tangential forces derived from them and a comparison with theoretical data. The measured torque and bending moment are also provided. The influence of the load cells on the turbine dynamics has also been evaluated. For the aerodynamic normal force, the system provides periodic data in agreement with simulations. Unexpected mechanical oscillations are present in the tangential force, introduced by the turbine dynamics. The measurement errors are of an acceptable size and often depend on the measured variable. Equations are presented for the calculation of measurement errors.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-260148 (URN)10.3390/en8065973 (DOI)000357489700067 ()
    Forskningsfinansiär
    StandUpStandUp for Wind
    Tilgjengelig fra: 2015-08-17 Laget: 2015-08-17 Sist oppdatert: 2017-12-04
    3. The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
    Åpne denne publikasjonen i ny fane eller vindu >>The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
    Vise andre…
    2013 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    The Division of Electricity at Uppsala University recently deployed an experimental hydrokinetic power station for in-stream experiments at a site in a river. This paper briefly describes the deployment process and reports some initial results from measurements made at the test site.

    Emneord
    Marine Current Power, Renewable energy, Söderfors, Strömkraft, Förnybar energi, Söderfors
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-209220 (URN)
    Konferanse
    10th European Wave and Tidal Energy Conference (EWTEC), 2-5 september, 2013, Aalborg, Denmark
    Prosjekter
    Marine Current Power
    Forskningsfinansiär
    StandUpSwedish Research Council, 621-2009-4946
    Tilgjengelig fra: 2013-10-15 Laget: 2013-10-15 Sist oppdatert: 2019-01-22bibliografisk kontrollert
    4. On a Two Pole Motor for Electric Propulsion System
    Åpne denne publikasjonen i ny fane eller vindu >>On a Two Pole Motor for Electric Propulsion System
    Vise andre…
    2013 (engelsk)Inngår i: International Journal of Engineering Science and Innovative Technology, ISSN 2319 - 5967, Vol. 2, nr 1, s. 99-111Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-207170 (URN)
    Tilgjengelig fra: 2013-09-10 Laget: 2013-09-10 Sist oppdatert: 2016-10-06bibliografisk kontrollert
    5. Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
    Åpne denne publikasjonen i ny fane eller vindu >>Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
    2013 (engelsk)Inngår i: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, s. 978140-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    An experimental setup for hydrokinetic energy conversion comprising a vertical axis turbine, a directly driven permanent magnet generator, and a control system has been designed and constructed for deployment in the river Dalälven in Sweden. This paper is devoted to discussing the mechanical and electrical design of the generator used in the experimental setup. The generator housing is designed to be water tight, and it also acts as a support structure for the turbine shaft. The generator efficiency has been measured in the range of 5–16.7 rpm, showing that operation in the low velocity range up to 1.5 m/s is possible with a directly driven generator.

    Emneord
    permanent magnet, cable wound, tidal energy, ocean energy, generator
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-195876 (URN)10.1155/2013/978140 (DOI)000325895100001 ()
    Tilgjengelig fra: 2013-02-28 Laget: 2013-02-28 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    6. Inverter topology with integrated on-load tap change for grid-connection of renewable electric energy sources
    Åpne denne publikasjonen i ny fane eller vindu >>Inverter topology with integrated on-load tap change for grid-connection of renewable electric energy sources
    2014 (engelsk)Konferansepaper, Poster (with or without abstract) (Fagfellevurdert)
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-230780 (URN)
    Konferanse
    Grand Renewable Energy Conference on Energy Network and Power Electronics, Tokyo, Japan
    Tilgjengelig fra: 2014-08-29 Laget: 2014-08-29 Sist oppdatert: 2016-10-06
    7. Experimental Verifications of Offshore Marine Substation for Grid-Connection of Wave Energy Farm
    Åpne denne publikasjonen i ny fane eller vindu >>Experimental Verifications of Offshore Marine Substation for Grid-Connection of Wave Energy Farm
    2013 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Istanbul, Turkey: , 2013
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212686 (URN)
    Konferanse
    3rd International Conference on Electric Power and Energy Conversion Systems (EPECS)
    Tilgjengelig fra: 2013-12-13 Laget: 2013-12-13 Sist oppdatert: 2016-10-06
    8. Transformer Magnetization Losses Using a Nonfiltered Voltage-Source Inverter
    Åpne denne publikasjonen i ny fane eller vindu >>Transformer Magnetization Losses Using a Nonfiltered Voltage-Source Inverter
    2013 (engelsk)Inngår i: Advances in Power Electronics, Vol. 2013, s. 7-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Results from the magnetization of an 80 kVA power transformer, using a directly coupled nonfiltered three-phase voltage-source inverter (VSI), are presented. The major benefits of this topology are reduction in switching filter size as well as filter losses. Drawbacks include higher stress on the transformer windings and higher transformer magnetization losses. In this paper, the total magnetization losses are presented for different voltage levels. The transformer has been magnetized with the rated frequency of 50 Hz at various voltage levels. The saturation characteristics as well as the magnetizing resistance are derived as functions of the voltage. These are used as inputs for the simulations. The magnetization losses have been experimentally measured and simulated for three different DC levels. Results from the simulations show good agreement with the experimental results. As expected, the pulsed voltage waveforms generate larger magnetization losses than the corresponding 50 Hz case. The losses are strongly dependent on the DC level.

    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212665 (URN)10.1155/2013/261959 (DOI)
    Tilgjengelig fra: 2013-12-13 Laget: 2013-12-13 Sist oppdatert: 2016-10-06
    9. Transformer Magnetizing Inrush Currents Using a Directly Coupled Voltage-Source Inverter
    Åpne denne publikasjonen i ny fane eller vindu >>Transformer Magnetizing Inrush Currents Using a Directly Coupled Voltage-Source Inverter
    2013 (engelsk)Inngår i: ISRN Electronics, Vol. 2013, s. 8-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The connection of a power transformer to the grid is associated with magnetizing inrush currents that may result in power quality issues as well as faulty relay tripping. In distributed generation, the transformer may instead be premagnetized from the source to avoid this. In this paper, a VSI is directly coupled to a transformer. Three different strategies of premagnetization are implemented into the control system, and the inrush currents are measured for various values of the remanent flux in the core. The results show good reduction in the peak magnetizing inrush currents without using any external circuitry.

    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212663 (URN)10.1155/2013/361643 (DOI)
    Tilgjengelig fra: 2013-12-13 Laget: 2013-12-13 Sist oppdatert: 2016-10-06
    10. Wireless System for Tidal Effect Compensation in the Lysekil Research Site
    Åpne denne publikasjonen i ny fane eller vindu >>Wireless System for Tidal Effect Compensation in the Lysekil Research Site
    Vise andre…
    2012 (engelsk)Inngår i: Proceedings of the ASME 31st International Conference on Ocean, Offshore and Arctic Engineering, vol. 7, 2012, s. 293-298Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This paper describes, firstly, the rope adjustment device for wave energy converters (WECs) to minimize the tidal effect on the electricity production and, secondly, a wireless communication network between point absorbing WECs in the Lysekil Research Site and a computer station at the Department of Engineering Sciences at Uppsala University. The device is driven by a motor that activates when the main water level deviates from the average. The adjustment is achieved through a screw that moves upwards during low tides and downwards during high tides. For the purpose of testing the device in the research site, a wireless connection between the buoy in the sea and a computer on land will be designed. A sensor located close to the research site monitors the sea water level and, every time a significant variation is registered, it sends wirelessly a signal to the data logger that controls the power to the motor The position of the screw is observed by a second sensor and the measurements are retrieved back to Uppsala via GSM connection. The full scale device is tested in the lab and it is demonstrated to work properly, requiring less than 750 W to lift and lower different loads. Moreover, the wireless communication network is designed and once it will be built, it will allow to recall and store data, send information from one node of the system to another, monitor the proper functioning of the device and modify the control as desired.

    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-190207 (URN)10.1115/OMAE2012-83361 (DOI)000324507000036 ()978-0-7918-4494-6 (ISBN)
    Konferanse
    31st International Conference on Ocean, Offshore and Arctic Engineering, July 1-6, 2012 Rio de Janeiro, Brazil
    Tilgjengelig fra: 2013-01-07 Laget: 2013-01-07 Sist oppdatert: 2016-10-06bibliografisk kontrollert
    11. Experimental Verification of a Back-to-Back 2L-3L Grid Connection System for a Marine Current Energy Converter
    Åpne denne publikasjonen i ny fane eller vindu >>Experimental Verification of a Back-to-Back 2L-3L Grid Connection System for a Marine Current Energy Converter
    2016 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Rivers, tides and other ocean currents are renewable energy sources with great potential across the globe.A research group at Uppsala University is working on converting the power in rivers and ocean tidesusing a vertical axis turbine with a directly driven permanent magnet generator. The concept in focususes an omnidirectional, fixed pitch vertical axis turbine directly connected to a permanent magnetgenerator. Few moving parts and an overall low mechanical complexity is the main idea behind theconcept. A first full prototype was deployed in 2013 in the river Dalälven in the town of Söderfors. Thework presented here is a step towards grid connection of the marine current energy converter prototype.A back-to-back 2L-3L grid connection topology has been proposed. The system is adapted to the scaledprototype but is intended for larger turbines. The proposed grid connection system utilizes a three-levelcascaded H-Bridge voltage source converter (3L-CHBVSC) on the grid side together with a well knowtwo-level voltage source converter on the generator side. The use of a multilevel converter brings severaladvantages such as higher efficiency, more sinusoidal voltages and currents and smaller grid filtersamong other advantages. The proposed grid connection system has been constructed in the laboratory.The work presented here aims to evaluate the system in the laboratory. A synchronous generator with avery similar design to the on-site generator is used for the tests. The generator, driven by an inductionmotor, is connected to the system and power is successfully transferred to the grid. The conducted testsare used to verify the functionality of the system before installation at the research site.

    Emneord
    marine current energy converter, grid connection, three-level cascaded H-bridge
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-304658 (URN)
    Konferanse
    2nd International Conference on Offshore Renewable Energy (CORE2016), Glasgow, UK, Sep. 12-14, 2016.
    Prosjekter
    Marine Current Power
    Tilgjengelig fra: 2016-10-06 Laget: 2016-10-06 Sist oppdatert: 2016-10-12
    12. A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University
    Åpne denne publikasjonen i ny fane eller vindu >>A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University
    2016 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, nr 7, artikkel-id 570Artikkel, forskningsoversikt (Fagfellevurdert) Published
    Abstract [en]

    This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of the work done on the 12 kW prototype VAWT in Marsta, Sweden. Several key aspects have been tested and successfully demonstrated at our two experimental research sites. The effort of the VAWT research has been aimed at developing a robust large scale VAWT technology based on an electrical control system with a direct driven energy converter. This approach allows for a simplification where most or all of the control of the turbines can be managed by the electrical converter system, reducing investment cost and need for maintenance. The concept features an H-rotor that is omnidirectional in regards to wind direction, meaning that it can extract energy from all wind directions without the need for a yaw system. The turbine is connected to a direct driven permanent magnet synchronous generator (PMSG), located at ground level, that is specifically developed to control and extract power from the turbine. The research is ongoing and aims for a multi-megawatt VAWT in the near future.

    Emneord
    wind power, vertical axis wind turbine (VAWT), permanent magnet synchronous generator (PMSG)
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-304654 (URN)10.3390/en9070570 (DOI)000381497300092 ()
    Forskningsfinansiär
    Swedish Energy Agency
    Tilgjengelig fra: 2016-10-06 Laget: 2016-10-06 Sist oppdatert: 2017-11-30bibliografisk kontrollert
    13. Evaluation of Harmonic Content from a Tap Transformer Based Grid Connection System for Wind Power
    Åpne denne publikasjonen i ny fane eller vindu >>Evaluation of Harmonic Content from a Tap Transformer Based Grid Connection System for Wind Power
    2013 (engelsk)Inngår i: Journal of Renewable Energy, Vol. 2013, s. 8-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Simulations done in MATLAB/Simulink together with experiments conducted at the Ångströms laboratory are used to evaluate and discuss the total harmonic distortion (THD) and total demand distortion (TDD) of a tap transformer based grid connection system. The grid connection topology can be used with different turbine and generator topologies and is here applied on a vertical axis wind turbine (VAWT) with a permanent magnet synchronous generator (PMSG) and its operational scheme. The full variable-speed wind conversion system consists of a diode rectifier, DC link, IGBT inverter, LCL-filter, and tap transformer. The full variable-speed operation is enabled by the use of the different step-up ratios of the tap transformer. In the laboratory study, a full experimental setup of the system was used, a clone of the on-site PMSG driven by a motor was used, and the grid was replaced with a resistive load. With a resistive load, grid harmonics and possible unbalances are removed. The results show a TDD and THD below 5% for the full operating range and harmonic values within the limits set up by IEEE-519. Furthermore, a change in tap, going to a lower step-up ratio, results in a reduction in both THD and TDD for the same output power.

    sted, utgiver, år, opplag, sider
    Hindawi Publishing Corporation, 2013
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212639 (URN)10.1155/2013/190573 (DOI)
    Tilgjengelig fra: 2013-12-12 Laget: 2013-12-12 Sist oppdatert: 2016-10-06
    14. System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power
    Åpne denne publikasjonen i ny fane eller vindu >>System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power
    2014 (engelsk)Inngår i: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, s. 784295-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-237603 (URN)10.1155/2014/784295 (DOI)000343577000001 ()
    Tilgjengelig fra: 2014-12-03 Laget: 2014-12-03 Sist oppdatert: 2017-12-05bibliografisk kontrollert
    15. Evaluation of Damping Strategies for Maximum Power Extraction from a Wave Energy Converter with a Linear Generator
    Åpne denne publikasjonen i ny fane eller vindu >>Evaluation of Damping Strategies for Maximum Power Extraction from a Wave Energy Converter with a Linear Generator
    2014 (engelsk)Konferansepaper, Poster (with or without abstract) (Fagfellevurdert)
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-230783 (URN)
    Konferanse
    Asian Wave and Tidal Energy Conference, Tokyo, Japan,
    Tilgjengelig fra: 2014-08-29 Laget: 2014-08-29 Sist oppdatert: 2016-10-06
    16. Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
    Åpne denne publikasjonen i ny fane eller vindu >>Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
    2012 (engelsk)Inngår i: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Konferansepaper, Poster (with or without abstract) (Fagfellevurdert)
    Abstract [en]

    In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

    Emneord
    VAWT, Tap transformer, LCL-filter, voltage source inverter
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-182434 (URN)
    Konferanse
    EWEA 2012 Annual Event, Copenhagen, Denmark, 2012
    Tilgjengelig fra: 2012-10-10 Laget: 2012-10-10 Sist oppdatert: 2018-05-30
    17. A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter
    Åpne denne publikasjonen i ny fane eller vindu >>A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter
    2015 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, nr 2, s. 808-820Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The paper proposes a back-to-back 2L-3L grid connection topology for a marine current energy converter. A prototype marine current energy converter has been deployed by a research group at Uppsala University. The concept behind the prototype revolves around a fixed pitch vertical axis turbine directly connected to a permanent magnet synchronous generator (PMSG). The proposed grid connection system utilizes a well known and proven two level voltage source converter generator-side combined with a three-level cascaded H-bridge (CHB) multilevel converter grid-side. The multilevel converter brings benefits in terms of efficiency, power quality and DC-link utilization. The system is here presented for a single marine current energy converter but can easily be scaled up for clusters of marine current energy converters. Control schemes for both grid-side and generator-side voltage source converters are presented. The start-up, steady state and dynamic performance of the marine current energy converter are investigated and simulation results are presented in this paper.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-253090 (URN)10.3390/en8020808 (DOI)000353555400001 ()
    Tilgjengelig fra: 2015-05-26 Laget: 2015-05-20 Sist oppdatert: 2017-12-04bibliografisk kontrollert
    18. Electrical Motor Drivelines in Commercial All Electric Vehicles: a Review
    Åpne denne publikasjonen i ny fane eller vindu >>Electrical Motor Drivelines in Commercial All Electric Vehicles: a Review
    Vise andre…
    2012 (engelsk)Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, nr 2, s. 475-484Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    This paper presents a critical review of the drivelines in all Electric Vehicles (EVs). The motor topologies that are the best candidates to be used in EVs are presented. The advantages and disadvantages of each electric motor type are discussed from a system perspective. A survey of the electric motors used in commercial EVs is presented. The survey shows that car manufacturers are very conservative when it comes to introducing new technologies. Most of the EV’s in the market mount a single induction or permanent magnet motor with a traditional mechanic driveline with a differential. The study illustrates that comparisons between the different motors are made difficult by the large number of parameters and the lack of a recommended test scheme. The authors propose that a standardized drive cycle is used to test and compare motors.

    Emneord
    Motor drives, Road vehicle electric propulsion, Road vehicle power systems, Traction motors
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-157858 (URN)10.1109/TVT.2011.2177873 (DOI)000300427400005 ()
    Tilgjengelig fra: 2012-04-19 Laget: 2011-08-24 Sist oppdatert: 2017-12-08bibliografisk kontrollert
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    preview image
  • 79.
    Apelfröjd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bülow, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kjellin, Jon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator2012Inngår i: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

  • 80.
    Apelfröjd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ekström, Rickard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thomas, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Evaluation of Damping Strategies for Maximum Power Extraction from a Wave Energy Converter with a Linear Generator2014Konferansepaper (Fagfellevurdert)
  • 81.
    Apelfröjd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Evaluation of Harmonic Content from a Tap Transformer Based Grid Connection System for Wind Power2013Inngår i: Journal of Renewable Energy, Vol. 2013, s. 8-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Simulations done in MATLAB/Simulink together with experiments conducted at the Ångströms laboratory are used to evaluate and discuss the total harmonic distortion (THD) and total demand distortion (TDD) of a tap transformer based grid connection system. The grid connection topology can be used with different turbine and generator topologies and is here applied on a vertical axis wind turbine (VAWT) with a permanent magnet synchronous generator (PMSG) and its operational scheme. The full variable-speed wind conversion system consists of a diode rectifier, DC link, IGBT inverter, LCL-filter, and tap transformer. The full variable-speed operation is enabled by the use of the different step-up ratios of the tap transformer. In the laboratory study, a full experimental setup of the system was used, a clone of the on-site PMSG driven by a motor was used, and the grid was replaced with a resistive load. With a resistive load, grid harmonics and possible unbalances are removed. The results show a TDD and THD below 5% for the full operating range and harmonic values within the limits set up by IEEE-519. Furthermore, a change in tap, going to a lower step-up ratio, results in a reduction in both THD and TDD for the same output power.

  • 82.
    Apelfröjd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power2014Inngår i: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, s. 784295-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.

    Fulltekst (pdf)
    fulltext
  • 83.
    Apelfröjd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University2016Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, nr 7, artikkel-id 570Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of the work done on the 12 kW prototype VAWT in Marsta, Sweden. Several key aspects have been tested and successfully demonstrated at our two experimental research sites. The effort of the VAWT research has been aimed at developing a robust large scale VAWT technology based on an electrical control system with a direct driven energy converter. This approach allows for a simplification where most or all of the control of the turbines can be managed by the electrical converter system, reducing investment cost and need for maintenance. The concept features an H-rotor that is omnidirectional in regards to wind direction, meaning that it can extract energy from all wind directions without the need for a yaw system. The turbine is connected to a direct driven permanent magnet synchronous generator (PMSG), located at ground level, that is specifically developed to control and extract power from the turbine. The research is ongoing and aims for a multi-megawatt VAWT in the near future.

    Fulltekst (pdf)
    fulltext
  • 84.
    Apelfröjd, Senad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thomas, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Experimental Verification of a Back-to-Back 2L-3L Grid Connection System for a Marine Current Energy Converter2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Rivers, tides and other ocean currents are renewable energy sources with great potential across the globe.A research group at Uppsala University is working on converting the power in rivers and ocean tidesusing a vertical axis turbine with a directly driven permanent magnet generator. The concept in focususes an omnidirectional, fixed pitch vertical axis turbine directly connected to a permanent magnetgenerator. Few moving parts and an overall low mechanical complexity is the main idea behind theconcept. A first full prototype was deployed in 2013 in the river Dalälven in the town of Söderfors. Thework presented here is a step towards grid connection of the marine current energy converter prototype.A back-to-back 2L-3L grid connection topology has been proposed. The system is adapted to the scaledprototype but is intended for larger turbines. The proposed grid connection system utilizes a three-levelcascaded H-Bridge voltage source converter (3L-CHBVSC) on the grid side together with a well knowtwo-level voltage source converter on the generator side. The use of a multilevel converter brings severaladvantages such as higher efficiency, more sinusoidal voltages and currents and smaller grid filtersamong other advantages. The proposed grid connection system has been constructed in the laboratory.The work presented here aims to evaluate the system in the laboratory. A synchronous generator with avery similar design to the on-site generator is used for the tests. The generator, driven by an inductionmotor, is connected to the system and power is successfully transferred to the grid. The conducted testsare used to verify the functionality of the system before installation at the research site.

  • 85.
    Appelgren, Filiph
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power System Software Development: with possible SCADA System Integration2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In order for power system operators (such as TRANSCO) to maintain and operatethe transmission grid in a safe, secure and effcient way, automatic tools such asSCADA systems is necessary to meet demand at all times. The main purpose of thisthesis was to develop a software/prototype at the load despatch centre at TRANSCOwith the ability to monitor and communicate with power plants. The software issupposed to work in a real-time electronic market. The power plant operators candeclare their availability and capability parameters of their generating and producingunits to TRANSCO and LDC operators can send load despatch instructions to thepower plants (such as load changes and other ancillary instructions). The prototypealso has a compliance monitoring application that validates unit outputs againstdespatched instructions. If the output is outside a specific interval, a transgressionwarning is sent to the power plant informing them that they should adjust their unitoutput against the target load. If further transgression is continued, the operator atLDC can re-declare the units availability on the power plants behalf and issue a newload despatch instruction to the unit. The re-declared availability level will be valid allthe way back to when the unit issued the last availability declaration.The software was successfully developed and could perform all tasks that it wassupposed to in a satisfactory way. In order to make the development as sufficient andeffective as possible, a "dummy" power plant was created and was used to simulateunit outputs and plant operator behaviour. As the time was too short, the SCADAintegration was never investigated and was left to whom is taken over after this thesishas ended.

    Fulltekst (pdf)
    Master Thesis, Filiph Appelgren
  • 86. Appelgren, P
    et al.
    Andreasson, S.
    Hurtig, T
    Larsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Nyholm, S. E
    Modelling of a small helical magnetic flux compression generator2007Konferansepaper (Annet vitenskapelig)
  • 87. Appelgren, P
    et al.
    Bjarnholt, G
    Elfsberg, M
    Hurtig, T
    Larsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Nyholm, S. E
    Small helical magnetic flux compression generators: experiment and analysis2007Konferansepaper (Annet vitenskapelig)
  • 88. Appelgren, Patrik
    et al.
    Bjarnholt, Gert
    Brenning, Nils
    Elfsberg, Mattias
    Hurtig, Tomas
    Larsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Novac, Bucur M.
    Nyholm, Sten E.
    Small Helical Magnetic Flux-Compression Generators: Experiments and Analysis2008Inngår i: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 36, nr 5, s. 2673-2683Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to gain experience in explosive pulsed power and to provide experimental data for modeling, a small high-explosive-driven helical magnetic flux-compression generator (FCG) was designed at the Swedish Defence Research Agency (FOI). The generator, of which three have been built, has an overall length of 300 mm and a diameter of 70 mm. It could serve as the energy source in a pulse-forming network to generate high power pulses for various loads. This paper presents the design of, and tests with, this helical FCG. The generator had an initial inductance of 23 mu H and was operated into a load of 0.2 mu H. The generator is charged with 0.27 kg of high explosives (PBXN-5). Various types of diagnostics were used to monitor the operation of the generator, including current probes, optical fibers, and piezo gauges. With seed currents of 5.7 and 11.2 kA, final currents of 269 and 436 kA were obtained, corresponding to current amplification factors of 47 and 39. The peak of the current was reached about 30 mu s after the time of crowbar. The two generators showed only small losses in terms of 2 pi-clocking. Using signals from optical fibers, the deflection angle of the armature could be determined to be 10 degrees in good agreement with hydrodynamic simulations of the detonation process and the detonation velocity to be 8.7 km/s in agreement with tabulated value.

  • 89. Appelgren, Patrik
    et al.
    Brenning, Nils
    Hurtig, Tomas
    Larsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Novac, Bucur M.
    Nyholm, Sten E.
    Modeling of a Small Helical Magnetic Flux-Compression Generator2008Inngår i: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 36, nr 5, s. 2662-2672Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to gain experience in explosive pulsed power and to provide experimental data as the basis for computer modeling, a small high-explosive-driven helical magnetic flux-compression generator (FCG) was designed at the Swedish Defence Research Agency. The generator, of which three have been built, has an overall length of 300 mm and a diameter of 70 mm. It could serve as the energy source in a pulse-forming network to generate high-power pulses for various loads. This paper presents a simulation model of this helical FCG. The model, which was implemented in Matlab-Simulink, uses analytical expressions for the generator inductance. The model of resistive losses takes into account the heating of the conductors and the diffusion of the magnetic field into the conductors. The simulation results are compared with experimental data from two experiments with identical generators but with different seed currents, influencing the resistive losses. The model is used to analyze the performance of the generator.

  • 90.
    Appelstål, Sophia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Teknisk utvärdering av befintliga och potentiella teknologier för automatisk frekvensreglering i det svenska elnätet2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The increasing amount of renewable energy in the power system have led to new challenges to balance supply and demand in the electric grid. To maintain the balance in the power system the system operator can activate power reserves to restore the balance at a frequency deviation. Today these reserves consist exclusively of hydropower in Sweden. With more volatile power generation new types of technologies to provide these reserves are desirable.

    The aim of this master thesis is to investigate the technical potential for using wind power, demand response and energy storage for automatic frequency control in the Swedish power system. The thesis examines the performance of the different technologies to see if they meet the technical requirements for delivering reserves set by the TSO. Moreover, the available capacity from the technologies throughout the year are estimated.

    The results show that all three technologies potentially could be used for frequency control. However, the technical requirements are not always fulfilled. In order to enable new technologies to provide power reserves some of the requirements needs to be modernized. Generally, demand response proved to have the largest available capacity for frequency control today. The study shows that demand response from industries and electric heated households could potentially provide all automatic frequency control. Modern wind turbines can be used for frequency control and for down regulation of the frequency the potential is considerable. Energy storages are not yet widely used in Sweden but with reduced costs they can play an important role in regulating the frequency in the future.  

    Fulltekst (pdf)
    fulltext
  • 91. Arevalo, L.
    et al.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Corona charge produced by thundercloud fields in grounded rods2012Inngår i: 31st International Conference on Lightning Protection ICLP 2012, 2012, s. 6344365-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Electrostatic fields below the thundercloud lead to the formation of glow charge from grounded objects. The charge accumulated after certain time can initiate or inhibit the called streamer formation and consequently the inception and development of upward leaders. By means of a two dimensional numerical model that takes into account the particles behavior is observed that glow charge can smooth the electric field on top of the grounded rod and consequently hinder the inception of streamers and upward leaders from the grounded rod. It is concluded that to be able to initiate unstable upward leaders from the shielded grounded rod a sudden change of electric field is necessary. A two dimensional numerical model that solves the continuity equations for positive and negative ions and electrons coupled with Poisson equation was implemented. Comparison for different magnitudes of electric field and characteristics of rod are included as well.

  • 92.
    Arevalo, L.
    et al.
    ABB Power Syst HVDC, R&D Dept, Ludvika, Sweden..
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    The mesh method in lightning protection analyzed from a lightning attachment model2016Inngår i: 2016 33RD INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Based on the well-known rolling sphere method, international standards recommend the location of the external lightning protection system of structures. The design of the external lightning protection system of structures of height of less than 60 m can be done by installing a mesh on top of a roof of the structure or by creating a mesh with wires at certain distance from the roof of the structure. The prospective downward leader current that the mesh can incept depends on the size of the mesh and the current magnitude is given as recommendation in the international standards. This paper analyses the relation prospective negative downward leader current vs. mesh size from a lightning attachment model. The model is applied to a perfectly grounded structure with maximum height of 50 m protected by two different external lightning protection systems recommended by the international standards. The results showed difference on magnitude of the prospective downward leader current the standards recommend and the ones obtained using the lightning attachment model for meshes of shorter size. Discrepancies concerning the minimum downward leader current that can be incepted by a mesh made by wires located at certain distance from the ground structure and a mesh located on top of the building are obtained.

  • 93.
    Arevalo, Liliana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Numerical Simulations of Long Spark and Lightning Attachment2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The research work presented here is concerned with numerical simulations of two different electrical phenomena: Long gap electrical discharges under switching impulses and the lightning attachment process associated with positive upward leaders. The development of positive upward leaders and the progression of discharges in long gaps are attributable to two intertwined physical phenomena, namely, the leader channel and the streamer zone. The physical description and the proposed calculations of the above-mentioned phenomena are based on experimental tests conducted in long spark gaps.

    The methodology presented here proposes a new geometrical approximation for the representation of the streamer and the calculation of the accumulated electrical charge. Furthermore, two different approaches to representing the leader channel are applied and compared. Statistical delays before the inception of the first corona, and random distributions to represent the tortuous nature of the path taken by the leader channel were included based on the behavior observed in experimental tests, with the intention of ensuring the discharge behaved in a realistic manner. A reasonable agreement was found between the physical model and the experimental test results.

    A model is proposed to simulate the negative discharges produced by switching impulses using the methodology developed to simulate positive leader discharges and the physics underlying the negative leader phenomena. The validation of the method demonstrated that phenomena such as the pilot leader and negative leader currents are successfully represented.

    In addition, based on previous work conducted on the physics of lightning and the lightning attachment process, a new methodology is developed and tested. In this new approach, the background electric field and the ionized region, considered in conjunction with the advance of the leader segment, are computed using a novel method. The proposed methodology was employed to test two engineering methods that are accepted in international standards, the mesh method and the electro-geometrical method. The results demonstrated that the engineering approximations are consistent with the physical approach.

    In addition to the electrical phenomena mentioned above, one should remember that, to simplify the calculation, there are certain real effects arising from the lightning attachment process that have not been considered. In fact, when a structure is subjected to a strong electric field, it is possible to generate multiple upward leaders from that structure. This effect has not been taken into account in the numerical models available previously, and therefore the process of generating multiple upward leaders incepted over a structure is incorporated here. The results have shown that a slight advantage from the background electric field is enough for one upward connecting leader to take over, thereby forcing the others to abort the attachment process.

    Delarbeid
    1. Modelling of Positive Discharges in Laboratory Gaps under Switching impulses
    Åpne denne publikasjonen i ny fane eller vindu >>Modelling of Positive Discharges in Laboratory Gaps under Switching impulses
    2008 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Cardiff, UK: , 2008
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-113403 (URN)
    Konferanse
    XVII International Conference on Gas Discharges and Their applications
    Tilgjengelig fra: 2010-01-28 Laget: 2010-01-28 Sist oppdatert: 2016-04-12bibliografisk kontrollert
    2. Breakdown effect on long gaps under switching impulses statistical variation
    Åpne denne publikasjonen i ny fane eller vindu >>Breakdown effect on long gaps under switching impulses statistical variation
    2008 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Uppsala, Sweden: , 2008
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-113402 (URN)
    Konferanse
    29th International Conference on Lightning Protection
    Tilgjengelig fra: 2010-01-28 Laget: 2010-01-28 Sist oppdatert: 2016-04-12bibliografisk kontrollert
    3. Breakdown times and voltages probability calculation using a simplified numerical methodology
    Åpne denne publikasjonen i ny fane eller vindu >>Breakdown times and voltages probability calculation using a simplified numerical methodology
    2008 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Florianopolis Brazil: , 2008
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-113401 (URN)
    Konferanse
    International Conference on Grounding and Earthing and 3rd International Conference on Lightning Physics and Effects
    Tilgjengelig fra: 2010-01-28 Laget: 2010-01-28 Sist oppdatert: 2016-04-12bibliografisk kontrollert
    4. Numerical simulation of long laboratory sparks generated by positive switching impulses
    Åpne denne publikasjonen i ny fane eller vindu >>Numerical simulation of long laboratory sparks generated by positive switching impulses
    2009 (engelsk)Inngår i: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 67, nr 2-3, s. 228-234Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A numerical methodology using two different leader channel criteria has been implemented. The methodology is based on Bondiou and Gallimberti's proposition [A. Bondiou, I. Gallimberti, Theoretical modelling of the development of the positive spark in long spark, J. Phys. D: Appl. Phys. 27 (1994) 1252-1266]. The leader channel criteria used are Rizk engineering criterion [Rizk, A model for switching impulse leader inception and breakdown of long air gaps, IEEE Trans. Power Deliv., 4(1) (1989)] and Local thermodynamic - L.T.E. - physical concept [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193]. The methodology was tested in three different cases; a deterministic case, a statistical variation and a typical constant level test. Deterministic calculation considered corona inception using stabilization corona electric field criterion of Gallimberti [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193] and the leader moving as segments. The statistical simulation has two different statistical delays, one at inception and the other due to the tortuous characteristics of the leader channel. The constant level test consists of 200 positive switching impulses with the same characteristics such as maximum applied voltage, time to crest and time to fall. Time to breakdown and breakdown voltage were found based on the results obtained from the constant level test characteristics. All the numerical results presented are based on experimental conditions reported in [Les Renardières Group, Research on long gap discharges at Les Renardières, Electra N 35 (1973)] from the world class research group namely Les Renardieres Group.

    Emneord
    Discharge, Leader, Modeling, Switching
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-113133 (URN)10.1016/j.elstat.2008.12.022 (DOI)000266019500029 ()0304-3886 (ISBN)
    Tilgjengelig fra: 2010-01-25 Laget: 2010-01-25 Sist oppdatert: 2017-12-12bibliografisk kontrollert
    5. LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION
    Åpne denne publikasjonen i ny fane eller vindu >>LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION
    2010 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Cagliary, Italy: , 2010
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-140390 (URN)
    Konferanse
    30TH International Conference on Lightning Protection, ICLP
    Tilgjengelig fra: 2011-01-05 Laget: 2011-01-05 Sist oppdatert: 2016-03-03
    6. A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES
    Åpne denne publikasjonen i ny fane eller vindu >>A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES
    2010 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Cagliary, Italy: , 2010
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-140391 (URN)
    Konferanse
    30TH International Conference on Lightning Protection, ICLP
    Tilgjengelig fra: 2011-01-05 Laget: 2011-01-05 Sist oppdatert: 2014-12-10
    7. A new static calculation of the streamer region for long spark gaps
    Åpne denne publikasjonen i ny fane eller vindu >>A new static calculation of the streamer region for long spark gaps
    2012 (engelsk)Inngår i: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 70, nr 1, s. 15-19Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Different electrostatic approximations have been proposed to calculate the streamer region without going in deep details of the behavior of density of particles under the effect of high electric fields; this kind of approximations have been used in numerical calculations of long spark gaps and lightning attachment. The simplifications of the streamer region are achieved by considering it to be a geometrical region with a constant geometrical shape. Different geometrical shapes have been used, such as cones or several parallel filaments. Afterward, to simplify the procedures, the streamer region was approximated by two constants, one denoted K-Q, called the geometrical constant and in other cases K named as geometrical factor. However, when a voltage that varies with time is applied to an arrangement of electrodes (high voltage and grounded electrodes), the background electric field will change with time. Thus, if the background electric field is modified, the streamer zone could cover a larger or smaller area. With the aim of reducing the number of assumptions required in the calculation of long gap discharges, a new electrostatic model to calculate the streamer region is presented. This model considers a variable streamer zone that changes with the electric field variations. The three-dimensional region that fulfills the minimum electric field to sustain a streamer is identified for each time step, and the charge accumulated in that region is then calculated. The only parameter that is being used in the calculation is the minimum electric field necessary for the propagation of streamers.

    Emneord
    charge, leader, Streamer, Electrical charge, Electric field, Corona inception, Discharge
    HSV kategori
    Forskningsprogram
    Elektricitetslära, ssk studiet av transienter och urladdning; Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-150528 (URN)10.1016/j.elstat.2011.07.013 (DOI)000300804300003 ()
    Tilgjengelig fra: 2011-03-31 Laget: 2011-03-31 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    8. The development of long spark gaps: Simulation including a variable streamer region
    Åpne denne publikasjonen i ny fane eller vindu >>The development of long spark gaps: Simulation including a variable streamer region
    (engelsk)Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Emneord
    Breakdown, streamer, discharge
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-150531 (URN)
    Tilgjengelig fra: 2011-03-31 Laget: 2011-03-31 Sist oppdatert: 2016-03-03
    9. Reliable model for the calculation of negative leader discharges under switching impulses
    Åpne denne publikasjonen i ny fane eller vindu >>Reliable model for the calculation of negative leader discharges under switching impulses
    2010 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    Emneord
    negative streamer, space leader, breakdown
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-150533 (URN)
    Konferanse
    36th grounding and 4th Lightning Physics conference GND&LPE
    Tilgjengelig fra: 2011-03-31 Laget: 2011-03-31 Sist oppdatert: 2016-04-18
    10. A preliminary model to simulate negative leader discharges
    Åpne denne publikasjonen i ny fane eller vindu >>A preliminary model to simulate negative leader discharges
    (engelsk)Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Emneord
    Negative streamer, pilot system, breakdown
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-150532 (URN)
    Tilgjengelig fra: 2011-03-31 Laget: 2011-03-31 Sist oppdatert: 2017-12-11
    11. On the interception of lightning flashes by power transmission lines
    Åpne denne publikasjonen i ny fane eller vindu >>On the interception of lightning flashes by power transmission lines
    2011 (engelsk)Inngår i: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, nr 3, s. 220-227Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The design of the lightning protection system LPS of transmission lines is based on the well knownelectro-geometrical model. The electro-geometrical model assumes that the first point on a powertransmission line that will come within striking distance of the tip of a down-coming stepped leaderchannel is the strike point of the lightning flash. The model neglects almost all of the physics associatedwith the lightning attachment.Nowadays, as it is possible to use modern hardware and software tools and several different numericalmethods, it is feasible to apply the physics of the discharge process to the study of lightning attachment.Such models take into account the movement of the downward and the resulting upward leaders fromdifferent points on the structures under consideration.In this paper, a procedure based on lightning physics was used to analyze the lightning attachmentphenomena in EHV transmission lines of 230 kV and 500 kV and the results were compared with thepredictions of the electro-geometrical method.

    Emneord
    power system, lightning attachment, breakdown, downward leader
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-150534 (URN)10.1016/j.elstat.2011.03.013 (DOI)000292230300012 ()
    Tilgjengelig fra: 2011-03-31 Laget: 2011-03-31 Sist oppdatert: 2017-12-11
    12. 'The mesh method' in lightning protection standards - Revisited
    Åpne denne publikasjonen i ny fane eller vindu >>'The mesh method' in lightning protection standards - Revisited
    2010 (engelsk)Inngår i: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 68, nr 4, s. 311-314Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    At present the design of the Lightning protection systems (LPS) for structures as stipulated in standards is based on the electro - geometrical method, which was initially used to protect power lines from lightning. A derivative of the electro-geometrical method is the rolling sphere method. This method together, with the protection angle method and mesh method are used almost in all lightning standards as the measure in installing the lightning protection systems of grounded structures. In the mesh method, the dimension of the cell size in different levels of protection is determined using the rolling sphere method. Since the rolling sphere method does not take into account the physics of the lightning attachment process there is a need to evaluate the validity of the stipulated value in standards of the minimum lightning current that can penetrate through the mesh in different levels of protection. In this paper, meshes of different sizes as stipulated in the lightning protection standards were tested for their ability to intercept lightning flashes using a lightning attachment model that takes into account the physics of connecting leaders on. The results are in reasonable agreement with the specifications given in the lightning protection standards.

    Emneord
    Dynamic leader, Electro-geometrical method, Lightning inception, Mesh method, Upward leader, Standards
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-135183 (URN)10.1016/j.elstat.2010.03.003 (DOI)000281211700004 ()
    Tilgjengelig fra: 2010-12-06 Laget: 2010-12-06 Sist oppdatert: 2017-12-12bibliografisk kontrollert
    13. Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process
    Åpne denne publikasjonen i ny fane eller vindu >>Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process
    2009 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    Emneord
    electric field, inhibit discharge, breakdown, streamer, lightning, attachment
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-150535 (URN)
    Konferanse
    X International symposium on lightning protection - SIPDA
    Tilgjengelig fra: 2011-03-31 Laget: 2011-03-31 Sist oppdatert: 2016-04-14
    14. Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM
    Åpne denne publikasjonen i ny fane eller vindu >>Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM
    2010 (engelsk)Inngår i: 30TH International Conference on Lightning Protection, ICLP, Cagliary, Italy, 2010Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Cagliary, Italy: , 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-142452 (URN)
    Konferanse
    30TH International Conference on Lightning Protection, ICLP
    Tilgjengelig fra: 2011-01-14 Laget: 2011-01-14 Sist oppdatert: 2016-04-19bibliografisk kontrollert
    Fulltekst (pdf)
    FULLTEXT01
  • 94.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Becerra, Marley
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Roman, F
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. elektricitetslära och åskforskning.
    Understanding the point discharge DC current produced by corona needles2006Inngår i: Proceedings of the 28th Internat Conference on Lightning Protection, ICLP, Kanazawa, Japan, 2006, s. 1328-1333Konferansepaper (Fagfellevurdert)
  • 95.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A preliminary model to simulate negative leader dischargesInngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463Artikkel i tidsskrift (Fagfellevurdert)
  • 96.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES2010Konferansepaper (Fagfellevurdert)
  • 97.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process2009Konferansepaper (Fagfellevurdert)
  • 98.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION2010Konferansepaper (Fagfellevurdert)
  • 99.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    On the interception of lightning flashes by power transmission lines2011Inngår i: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, nr 3, s. 220-227Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The design of the lightning protection system LPS of transmission lines is based on the well knownelectro-geometrical model. The electro-geometrical model assumes that the first point on a powertransmission line that will come within striking distance of the tip of a down-coming stepped leaderchannel is the strike point of the lightning flash. The model neglects almost all of the physics associatedwith the lightning attachment.Nowadays, as it is possible to use modern hardware and software tools and several different numericalmethods, it is feasible to apply the physics of the discharge process to the study of lightning attachment.Such models take into account the movement of the downward and the resulting upward leaders fromdifferent points on the structures under consideration.In this paper, a procedure based on lightning physics was used to analyze the lightning attachmentphenomena in EHV transmission lines of 230 kV and 500 kV and the results were compared with thepredictions of the electro-geometrical method.

  • 100.
    Arevalo, Liliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Preliminary study on the modelling of negative leader discharges2011Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 44, nr 31, s. 315204-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nowadays, there is considerable interest in understanding the physics underlying positive and negative discharges because of the importance of improving lightning protection systems and of coordinating the insulation for high voltages. Numerical simulations of positive switching impulses made in long spark gaps in a laboratory are achievable because the physics of the process is reasonably well understood and because of the availability of powerful computational methods. However, the existing work on the simulation of negative switching discharges has been held up by a lack of experimental data and the absence of a full understanding of the physics involved. In the scientific community, it is well known that most of the lightning discharges that occur in nature are of negative polarity, and because of their complexity, the only way to understand them is to generate the discharges in laboratories under controlled conditions. The voltage impulse waveshape used in laboratories is a negative switching impulse. With the aim of applying the available information to a self-consistent physical method, an electrostatic approximation of the negative leader discharge process is presented here. The simulation procedure takes into consideration the physics of positive and negative discharges, considering that the negative leader propagates towards a grounded electrode and the positive leader towards a rod electrode. The simulation considers the leader channel to be thermodynamic, and assumes that the conditions required to generate a thermal channel are the same for positive and negative leaders. However, the magnitude of the electrical charge necessary to reproduce their propagation and thermalization is different, and both values are based on experimental data. The positive and negative streamer development is based on the constant electric field characteristics of these discharges, as found during experimental measurements made by different authors. As a computational tool, a finite element method based software is employed. The simulations are compared with experimental data available in the literature.

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