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  • 1.
    Abdallah, Ali
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Det smarta hemmet – Energianvändarens framtid: En studie om smarta hem och vilka möjligheter Jämtkraft har att satsa på dessa2014Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Energianvändningen i Sverige är relativt stort med avseende på befolkningsmängden. Det beror givetvis mycket på behovet av uppvärmning under större delen av året som det kalla klimatet leder till men även på det kontinuerliga behovet av energi i det vardagliga livet. Den stora energianvändningen medför dock stora belastningar på både klimat och miljö. I dagsläget finns det flera uppsatta mål som är riktade till att minska energiintensiteten i landet samt energianvändningen i bostäder och lokaler. Således är energieffektivisering ett viktigt medel för att minska klimat- och miljöbelastningen. Många energianvändare utför olika vardagliga rutiner som bidrar till energieffektivisering som att bland annat släcka lampor, stänga av elektriska apparater när de inte används och inte använda disk- eller tvättmaskinen om den är halvfull. De ovannämnda åtgärderna är dock inte tillräckliga. Det krävs mer och därför är smarta hem en viktig lösning. Smarta hem är ett komplext system som täcker olika aspekter i hemmet men anses vara ett effektivt medel för energieffektivisering. Hur energianvändningen i bostäder utvecklas i framtiden kommer med stor sannolikhet bero på smarta hem och smarta produkter.

    Syftet med detta examensarbete är att undersöka hur man skulle kunna utveckla eller kombinera energismarta produkter på bästa möjliga sätt. Utifrån en enkätundersökning riktad mot energianvändare och intervjuer med energianvändare och aktörer på den smarta hemmarknaden har energikonsumenternas behov och beteende analyserats och en marknadsanalys av de produkter som finns på marknaden idag utförts.

    Denna studie har visat att energianvändarna allmänt inte är så insatta i energianvändningen hemma trots att många påstår sig vara engagerade i energieffektivisering. Energianvändarna visade samtidigt på bristande kunskap om smarta hem och energismarta produkter, vilket kan bero på att smarta hemmarknaden fortfarande är ny i Sverige och de flesta aktörer har ännu inte lyckats marknadsföra sig och sina produkter. Det kan även bero på andra faktorer som brist på intresse hos energianvändarna att energieffektivisera som i sin tur kan bero på det låga elpriset i Sverige. De ovannämnda faktorerna kan göra att utvecklingen av smarta hem i Sverige tar längre tid än förväntat. Energianvändarna visade sig prioritera främst kostnader, och utför ofta energieffektiviserings åtgärder för att spara pengar snarare än att bidra till klimatet.

    Studien visade att ett smart hem bör innehålla produkter som bidrar till komfort, säkerhet och ekonomiska besparingar. Produkter som prioriteras hos energianvändarna och efterfrågas mest på marknaden är smarta brandvarningssystem, smarta dörrlås, smarta energidisplayer, smarta inbrottslarm samt smarta system för styrning av värme och belysning. Samtliga ovannämnda produkter erbjuds på marknaden idag, även om många av dessa är i utvecklingsfasen. Elföretaget Jämtkraft bör ta hänsyn till resultaten i detta examensarbete inför framtida satsningar på smarta hem.

  • 2. Abegunawardana, Sidath
    et al.
    Bodhika, J A P
    Abewardhana, Ruwan
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sound Source Localization of Lightning Discharges2018Konferensbidrag (Refereegranskat)
  • 3. Abegunawardana, Sidath
    et al.
    Bodhika, J A P
    Nanayakkara, Sankha
    Sonnadara, Upul
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Audible Frequency Analysis of Ground Flashes2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thunder signatures categorized into three types based on peak pressure and variation in fundamental frequency, have been studied by using acoustic spectrum of thunder. S-transformation has been used to estimate the dominant frequency variation around the peak pressure. The mean fundamental frequencies of type 3 ground and cloud flashes are 160 Hz and 98 Hz respectively. The mean frequencies of type 2 ground and cloud flashes are 108 Hz and 82 Hz respectively.

  • 4. Abewardhana, Ruwan
    et al.
    Abegunawardana, Sidath
    Fernando, Mahendra
    Sonnadara, Upul
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lightning Localization Based on VHF Broadband Interferometer Developed in Sri Lanka2018Konferensbidrag (Refereegranskat)
  • 5.
    Abrahamsson, Curt Johan David
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Pérez-Loya, Jesús José
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fregelius, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Evestedt, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bladh, Johan
    Lundin, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Magnetic thrust bearing for a 10 MW hydropower generator with a Kaplan turbine2018Konferensbidrag (Refereegranskat)
  • 6.
    Abrahamsson, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kinetic Energy Storage and Magnetic Bearings: for Vehicular Applications2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    One of the main challenges in order to make electric cars competitive with gas-powered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficientlyhigh specific energy, their applicability is limited due to low specific power. It would therefore be advantageous to create a driveline with the main energy storage separated from a smaller energy buffer, designed to have high power capabilities and to withstand frequent and deep discharge cycles. It has been found that rotating kinetic energy storage in flywheels is very well suited for this type of application.

    A composite shell, comprising an inner part made of glassfiber and an outer part made of carbonfiber, was analyzed analytically and numerically, designed, and constructed. The shell was fitted onto a metallic rotor using shrinkfitting. The cost of the shell, and the complexity of assembly, was reduced by winding the glass- and carbonfiber consecutively on a mandrel, and curing the complete assembly simultaneously. Thereby, the shell obtained an internal segmentation, without the need for fitting several concentric parts onto each other. The radial stress inside the composite shell was kept compressive thanks to a novel approach of using the permanent magnets of the integrated electric machine to provide radial mechanical load during rotation.

    Two thrust bearing units (one upper and one lower) comprising one segmented unit with the permanent magnets in a cylindrical Halbach configuration and one non-segmented unit in a up/down configuration were optimized, constructed and tested. Each thrust bearing unit generated 1040 N of repelling force, and a positive axial stiffness of 169 N/mm at the nominal airgap of 5 mm. 

    Two radial active magnetic bearings (one upper and one lower) were optimized, constructed and tested. By parameterizing the shape of the actuators, a numerical optimization of force over resistive loss from the bias currentcould be performed. The optimized shape of the electromagnets was produced by watercutting sheets of laminated steel. A maximum current stiffness of120 N/A at a bias current of 1.5 A was achieved.

    Delarbeten
    1. Prototype of electric driveline with magnetically levitated double wound motor
    Öppna denna publikation i ny flik eller fönster >>Prototype of electric driveline with magnetically levitated double wound motor
    Visa övriga...
    2010 (Engelska)Ingår i: Electrical Machines (ICEM), 2010 XIX International Conference on, 2010Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper presents the ongoing work of constructing a complete driveline for an electric road vehicle, using a flywheel as auxiliary energy storage. The flywheel energy storage system (FESS) is connected in series between the main energy storage (batteries) and the wheel motor of the vehicle, allowing the batteries to deliver power to the system in an optimized way, while at the same time making efficient use of regenerative braking. A double wound permanent magnet electric machine is used to electrically separate the two sides. In order to minimize losses, the machine has a double rotor configuration and is suspended with magnetic bearings. A bench test set-up is being constructed to investigate the properties of this system in detail. This set-up will achieve a level of power and energy close to that of a full scale system. This will allow measurements of complete drive cycles to be performed, improving the understanding of the constituting components and optimization of the complete system.

    Nyckelord
    electric drives, flywheels, magnetic bearings, permanent magnet machines, regenerative braking, road vehicles, auxiliary energy storage, double rotor configuration, double wound permanent magnet electric machine, electric driveline, electric road vehicle, flywheel energy storage system, magnetically levitated double wound motor, wheel motor
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-140370 (URN)
    Konferens
    International Conference on Electrical Machines, ICEM
    Tillgänglig från: 2011-01-05 Skapad: 2011-01-05 Senast uppdaterad: 2016-04-18Bibliografiskt granskad
    2. Magnetic bearings in kinetic energy storage systems for vehicular applications
    Öppna denna publikation i ny flik eller fönster >>Magnetic bearings in kinetic energy storage systems for vehicular applications
    2011 (Engelska)Ingår i: Journal of Electrical Systems, ISSN 1112-5209, Vol. 7, nr 2, s. 225-236Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The rotating Kinetic Energy Storage System (KESS) is suitable as temporary energy storage in electric vehicles due to its insensitivity to the number of charge-discharge cycles and its relatively high specific energy. The size and weight of the KESS for a given amount of stored energy are minimized by decreasing the moment of inertia of the rotor and increasing its speed. A small and fast rotor has the additional benefit of reducing the induced gyroscopic moments as the vehicle turns. The very high resulting rotational speed makes the magnetic bearing an essential component of the system, with the Active Magnetic Bearing (AMB) being the most common implementation. The complexity and cost of an AMB can be reduced by integration with the electric machine, resulting in a bearingless and sensorless electric machine. This review article describes the usage of magnetic bearings for FESS in vehicular applications.

    Nyckelord
    Magnetic bearing, FESS, flywheel, energy storage, electric vehicle
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-165038 (URN)
    Tillgänglig från: 2012-01-02 Skapad: 2012-01-02 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    3. Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic
    Öppna denna publikation i ny flik eller fönster >>Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic
    2012 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Ort, förlag, år, upplaga, sidor
    Arlington, Virginia, USA: , 2012
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-190197 (URN)
    Konferens
    13th International Symposium on Magnetic Bearings
    Tillgänglig från: 2013-01-07 Skapad: 2013-01-07 Senast uppdaterad: 2017-04-06
    4. On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline
    Öppna denna publikation i ny flik eller fönster >>On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline
    Visa övriga...
    2012 (Engelska)Ingår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 5, nr 8, s. 2794-2817Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 x 10(-8) +/- 3.5 x 10(-9). Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.

    Nyckelord
    kinetic energy storage, flywheel, electric machine, driveline, electric vehicle, losses
    Nationell ämneskategori
    Elektroteknik och elektronik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-182543 (URN)10.3390/en5082794 (DOI)000308241500011 ()
    Tillgänglig från: 2012-10-11 Skapad: 2012-10-11 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
    5. A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
    Öppna denna publikation i ny flik eller fönster >>A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
    2014 (Engelska)Ingår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 50, nr 9, artikel-id 8101809Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.

    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:uu:diva-212105 (URN)10.1109/TMAG.2014.2321104 (DOI)000343036900019 ()
    Tillgänglig från: 2013-12-05 Skapad: 2013-12-05 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
    6. Passive Axial Thrust Bearing for a Flywheel Energy Storage System
    Öppna denna publikation i ny flik eller fönster >>Passive Axial Thrust Bearing for a Flywheel Energy Storage System
    Visa övriga...
    2013 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Elektroteknik och elektronik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212104 (URN)
    Konferens
    The 1st Brazilian Workshop on Magnetic Bearings
    Tillgänglig från: 2013-12-05 Skapad: 2013-12-05 Senast uppdaterad: 2017-10-24
    7. High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings
    Öppna denna publikation i ny flik eller fönster >>High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings
    2014 (Engelska)Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, nr 6, s. 3012-3021Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

    Nationell ämneskategori
    Annan elektroteknik och elektronik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212101 (URN)10.1109/TIE.2013.2259782 (DOI)000329055300039 ()
    Tillgänglig från: 2013-12-05 Skapad: 2013-12-05 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
  • 7.
    Abrahamsson, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kinetic Energy Storage and Magnetic Bearings, for vehicular applications2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    One of the main challenges in order to make electric cars competitive with gaspowered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficiently high specific energy, their applicability is limited due to low specific power. It would therefore be advantageous to create a driveline with the main energy storage separated from a smaller energy buffer, designed to have high power capabilities and to withstand frequent and deep discharge cycles. It has been found that rotating kinetic energy storage in flywheels is very well suited for this type of application. The work presented in this thesis and the included papers span a number of topcis Introductory overview - This section explains the concept of the modern flywheel, and investigates some of its properties. It illustrates the concepts with a number of examples, relevant for the usage of flywheels in vehicular applications. Experimental set-up - The construction of a complete electric driveline is ongoing within the division for Electricity at Uppsala University. An optimized electric machine has been constructed and connected with a programmable load, as well as with a DC power source through power electronics controlled by PWM. As a part of this system, an experimental set-up of an active magnetic bearing for two degrees-of-freedom has been constructed. The work with this device is described in detail and some preliminary results are presented. Self-bearing machine - The electric machine developed for the existing driveline is coreless, double wound and with a double rotor. In order to achieve magnetic bearing functionality in this device for all DOF, a novel Lorentz force self-bearing machine is suggested. The design is analyzed analytically and numerically.

  • 8.
    Abrahamsson, Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Magnetic bearings in kinetic energy storage systems for vehicular applications2011Ingår i: Journal of Electrical Systems, ISSN 1112-5209, Vol. 7, nr 2, s. 225-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rotating Kinetic Energy Storage System (KESS) is suitable as temporary energy storage in electric vehicles due to its insensitivity to the number of charge-discharge cycles and its relatively high specific energy. The size and weight of the KESS for a given amount of stored energy are minimized by decreasing the moment of inertia of the rotor and increasing its speed. A small and fast rotor has the additional benefit of reducing the induced gyroscopic moments as the vehicle turns. The very high resulting rotational speed makes the magnetic bearing an essential component of the system, with the Active Magnetic Bearing (AMB) being the most common implementation. The complexity and cost of an AMB can be reduced by integration with the electric machine, resulting in a bearingless and sensorless electric machine. This review article describes the usage of magnetic bearings for FESS in vehicular applications.

  • 9.
    Abrahamsson, Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    de Santiago, Juan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Oliveira, Janaína Gonçalves de
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lundin, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Prototype of electric driveline with magnetically levitated double wound motor2010Ingår i: Electrical Machines (ICEM), 2010 XIX International Conference on, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the ongoing work of constructing a complete driveline for an electric road vehicle, using a flywheel as auxiliary energy storage. The flywheel energy storage system (FESS) is connected in series between the main energy storage (batteries) and the wheel motor of the vehicle, allowing the batteries to deliver power to the system in an optimized way, while at the same time making efficient use of regenerative braking. A double wound permanent magnet electric machine is used to electrically separate the two sides. In order to minimize losses, the machine has a double rotor configuration and is suspended with magnetic bearings. A bench test set-up is being constructed to investigate the properties of this system in detail. This set-up will achieve a level of power and energy close to that of a full scale system. This will allow measurements of complete drive cycles to be performed, improving the understanding of the constituting components and optimization of the complete system.

  • 10.
    Abrahamsson, Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Gonçalves de Oliveira, Janaína
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    de Santiago, Juan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lundin, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline2012Ingår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 5, nr 8, s. 2794-2817Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 x 10(-8) +/- 3.5 x 10(-9). Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.

  • 11.
    Abrahamsson, Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hedlund, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic2012Konferensbidrag (Refereegranskat)
  • 12.
    Abrahamsson, Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hedlund, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kamf, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings2014Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, nr 6, s. 3012-3021Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

  • 13.
    Abrahamsson, Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ögren, Jim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hedlund, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings2014Ingår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 50, nr 9, artikel-id 8101809Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.

  • 14.
    Abuzohri, Ahmed
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Effektförstärkare med strömkontroll2012Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Energin är ett begrepp som används dagligen i vårt samhälle. Energin kan inte skapas men däremot kan den omvandlas till olika former, förbrukas och lagras i vissa fall. Men att omvandla energi från en form till en annan form för att sedan lagra den är en av dagens stora utmaningar inom tekniken då vi måste följa de regler som naturen dikterar. Forskning på detta område har pågått i flera decennier för att kunna ta fram lämpliga och effektiva sätt att lagra energi på. Svänghjul-system är ett sådant sätt där man kan lagra energi under begränsad tid.

    I mitt examensarbete har jag utnyttjat kunskapen som jag har lärt mig från elektronik kurserna för att konstruera en effektförstärkare med strömkontroll som användes för att driva ett svänghjul-system. Förstärkaren har byggts med elektronikkomponenter och styrs från datorn med m.h.a. styrprogrammet LabVIEW som kommunicerar med hårdvaran och kontrollerar svänghjulets rörelse.

  • 15.
    Adrian, Ehrnebo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Single Crystalline CVD Diamond Based Devices for Power Electronics Applications2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Chemical vapor deposited single-crystalline diamond has rare material properties such as thermal conductivity five times as high as copper, a wide band gap, a high breakdown field and high carrier mobilities. This makes it a very interesting material for high power, high frequency and high temperature applications.

    In this thesis work, metal oxide semiconductor (MOS) capacitors of diamond substrate were fabricated and analyzed. The MOS capacitor is a building block of the metal oxide semiconductor field effect transistor (MOSFET). Capacitance-voltage (C-V) measurements can provide useful information of the operation of a MOS. Electrical characterization by C-V and current-voltage (I-V) measurements at temperatures ranging from 20 to 150 degrees Celsius were performed on the MOS capacitors to examine flatband and threshold voltages, oxide charge, and oxide thickness.

    At elevated temperatures, low frequency C-V curves with threshold voltages of approximately 5 V were obtained for MOS capacitors consisting of aluminum gates, a 30 nm layer of aluminum oxide, and boron doped diamond with acceptor concentration 3.1 x 1017 cm-3. The C-V measurements also showed large variations in flatband voltage for different contacts of the MOS capacitor, indicating the presence of oxide charge. Oxide thickness was also extracted from the C-V measurements, typically showing thicknesses around 15-19 nm.

    Also in this  thesis, an alternative method for reducing the electric field strength around the edges of the contact of a Schottky diode has been examined. This method consists of alternating the geometry by etching the semiconductor where the contact is to be placed. Simulations performed in Comsol Multiphysics showed that a reduction of the field strength of approximately 30 % at the contacts could be achieved by etching the substrate.

  • 16.
    Ahlström, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Åsktransienter och överspänningar: En spänningsfylld simulering av elkraftsystemet vid Forsmark 32014Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    A power system will inevitably be subjected to transient overvoltages, most often produced by switching operations and lightning strikes. These transient overvoltages may harm sensitive equipment without sufficient protection, but it is not an easy task to predict what transients may occur or how they affect the system. A fault occurred in a low voltage system at Forsmark 2012 and overvoltages from lightning were concluded as the probable cause. The three aims with this thesis are to develop and test a model of the power system at Forsmark 3, analyse the transient behaviour of the system when subjected to lightning surges and identify critical parameters, and lastly to provide a tool for investigating the protection of the system. The modelling and simulations were performed in the freely available simulation program LT Spice. Challenges and difficulties have been to obtain parameter values for components that are relevant for the high frequencies produced by the short rise time in lightning surges. The main conclusions are: the maximum current in the lightning discharge has the largest impact on the system voltages and surges in the external grid can produce standing waves in the system, causing significant overvoltages even in low voltage systems. The simulations produced larger overvoltages than would occur in a real system, which also would dampen the high frequency signals to a larger extent. Further work to obtain models better suited for high frequency simulation is suggested.

  • 17. Ahmad, H.
    et al.
    Coppens, S.
    Uzunoglu, Bahri
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Connection of an Offshore Wind Park to HVDC Converter Platform without Using Offshore AC Collector Platforms2013Ingår i: Green Technologies Conference, 2013 IEEE, 2013, s. 400-406Konferensbidrag (Refereegranskat)
  • 18. Ahmad, M R
    et al.
    Esa, M R M
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Measurement of bit error rate at 2,4 GHz due to lightning interference2012Ingår i: Proceeding of the 31st International Conference on Lightning Protection ICLP 2012, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper analyzes the interference of lightning flashes with wireless communication systems operating in the microwave band at 2.4 GHz. A bit error rate (BER) measurement method was used to evaluate BER during 3 heavy thunderstorms on January 25, March 17 and March 20, all in year 2011. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW) conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-of-sight (LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higher recorded BER. The maximum recorded BER was 9.9·101 and the average recorded BER was 9.95·10 -3 during the thunderstorms with the average fair weather BER values under the influence of adjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10 -6 respectively. We conclude that wireless communication systems operating at 2.4 GHz microwave frequency can be significantly interfered by lightning.

  • 19.
    Ahmad, Mohd Riduan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Universiti Teknikal Malaysia Melaka.
    Interaction of Lightning Flashes with Wireless Communication Networks: Special Attention to Narrow Bipolar Pulses2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. Occurrence of NBPs in Sweden has been reported for the first time in this thesis. The electric field waveform characteristics of NBPs as part of cloud-to-ground flashes were similar to isolated NBPs found in Sweden and South Malaysia and also to those isolated NBPs reported by previous studies from various geographical areas. This is a strong indication that their breakdown mechanisms are similar at any latitudes regardless of geographical areas.

    A comparative study on the occurrence of NBPs and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics is presented. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent.

    In this thesis, the interaction between microwave radiations emitted by cloud-to-ground and cloud flashes events and bits transmission in wireless communication networks are also presented. To the best of our knowledge, this is the first time such effects are investigated in the literature. Narrow bipolar pulses were found to be the strongest source of interference that interfered with the bits transmission.

    Delarbeten
    1. Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    Öppna denna publikation i ny flik eller fönster >>Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    2014 (Engelska)Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Artikel i tidskrift (Refereegranskat) Submitted
    Nyckelord
    Narrow bipolar pulse; Return stroke; Tropical thunderstorm.
    Nationell ämneskategori
    Meteorologi och atmosfärforskning Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233624 (URN)
    Tillgänglig från: 2014-10-07 Skapad: 2014-10-07 Senast uppdaterad: 2017-12-05
    2. Narrow bipolar pulses and associated microwave radiation
    Öppna denna publikation i ny flik eller fönster >>Narrow bipolar pulses and associated microwave radiation
    2013 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Ort, förlag, år, upplaga, sidor
    Stockholm: , 2013
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212898 (URN)
    Konferens
    Progress in Electromagnetics Research Symposium
    Tillgänglig från: 2013-12-16 Skapad: 2013-12-16 Senast uppdaterad: 2015-01-23
    3. Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Öppna denna publikation i ny flik eller fönster >>Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Visa övriga...
    2014 (Engelska)Ingår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikel i tidskrift (Refereegranskat) Submitted
    Nyckelord
    Electric field; Narrow bipolar pulse; Sweden.
    Nationell ämneskategori
    Meteorologi och atmosfärforskning Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233636 (URN)
    Tillgänglig från: 2014-10-07 Skapad: 2014-10-07 Senast uppdaterad: 2017-12-05
    4. Latitude Dependence of Narrow Bipolar Pulse Emissions
    Öppna denna publikation i ny flik eller fönster >>Latitude Dependence of Narrow Bipolar Pulse Emissions
    Visa övriga...
    2015 (Engelska)Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, s. 40-45Artikel i tidskrift (Refereegranskat) Published
    Nyckelord
    Latitude; Narrow bipolar pulse; Thunderstorm.
    Nationell ämneskategori
    Meteorologi och atmosfärforskning Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233638 (URN)10.1016/j.jastp.2015.03.005 (DOI)000355717500005 ()
    Tillgänglig från: 2014-10-07 Skapad: 2014-10-07 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
    5. Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    Öppna denna publikation i ny flik eller fönster >>Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    2014 (Engelska)Ingår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, s. 810-813Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

    Ort, förlag, år, upplaga, sidor
    IEEE conference proceedings, 2014
    Nyckelord
    Narrow bipolar pulse; Preliminary breakdown pulse; Relativistic runaway electron avalanches.
    Nationell ämneskategori
    Meteorologi och atmosfärforskning Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233639 (URN)000358572100153 ()978-1-4799-3544-4 (ISBN)
    Konferens
    International Conference on Lightning Protection (ICLP), OCT 11-18, 2014, Tsinghua Univ, Shanghai, PEOPLES R CHINA
    Tillgänglig från: 2014-10-07 Skapad: 2014-10-07 Senast uppdaterad: 2015-09-03Bibliografiskt granskad
    6. Lightning interference in multiple antennas wireless communication systems
    Öppna denna publikation i ny flik eller fönster >>Lightning interference in multiple antennas wireless communication systems
    Visa övriga...
    2012 (Engelska)Ingår i: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, s. 155-165Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

    Ort, förlag, år, upplaga, sidor
    Bentham open, 2012
    Nationell ämneskategori
    Meteorologi och atmosfärforskning Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-190902 (URN)
    Tillgänglig från: 2013-01-09 Skapad: 2013-01-09 Senast uppdaterad: 2016-02-03
    7. Interference from cloud-to-ground and cloud flashes in wireless communication system
    Öppna denna publikation i ny flik eller fönster >>Interference from cloud-to-ground and cloud flashes in wireless communication system
    2014 (Engelska)Ingår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, s. 237-246Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.

    Nyckelord
    Bit error rate, Cloud flash, Cloud-to-ground flash, Interference, Microwave radiation, Wireless system
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:uu:diva-228679 (URN)10.1016/j.epsr.2014.03.022 (DOI)000337554200032 ()
    Tillgänglig från: 2014-07-22 Skapad: 2014-07-21 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
  • 20.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Narrow bipolar pulses and associated microwave radiation2013Konferensbidrag (Refereegranskat)
  • 21.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, Eryk
    Interference from cloud-to-ground and cloud flashes in wireless communication system2014Ingår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, s. 237-246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.

  • 22.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, Eryk
    Performance analysis of audio streaming over lightning-interfered MIMO channels2012Konferensbidrag (Refereegranskat)
  • 23.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, E.
    Wireless Communications and Networking Lab, Macquarie University, Sydney, Australien.
    Lightning interference in multiple antennas wireless communication systems2012Ingår i: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, s. 155-165Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

  • 24.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza Binti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hettiarachchi, Pasan
    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 Observations of Lightning Signature At 2400 MHz in Sweden Thunderstorm2012Ingår i: / [ed] BinSulaiman, HA; Jaafar, A, NEW YORK: IEEE , 2012, s. 88-91Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a preliminary observation of lightning signature at 2400 MHz. We believe this is the first time such observation was made in such frequency band. One positive ground discharge and one cloud discharge waveforms have been selected from a collection of waveforms recorded using fast and slow broadband antenna systems. In addition, waveforms recorded directly from 2400 MHz whip antenna associated with the selected ground and cloud discharges waveforms were observed. The measurements were carried out in Uppsala, Sweden in July 2012. We discovered a possible lightning signature at 2400 MHz with the existence of bursts of pulses happened to occur simultaneously with preliminary breakdown, negative return stroke and cloud pulses. These bursts of pulses possibly interfered in some ways with the transmitted bits leading to higher recorded error bits during the thunderstorm.

  • 25.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Occurrence of Narrow Bipolar Event as Part of Cloud-to-Ground Flash in Tropical Thunderstorms2014Konferensbidrag (Refereegranskat)
  • 26.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses2014Ingår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, s. 810-813Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

  • 27.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri Abadi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Universiti Teknikal Malaysia Melaka.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Latitude Dependence of Narrow Bipolar Pulse Emissions2015Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, s. 40-45Artikel i tidskrift (Refereegranskat)
  • 28.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri Abadi
    Universiti Teknikal Malaysia Melaka.
    Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden2014Ingår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikel i tidskrift (Refereegranskat)
  • 29.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Johari, Dalina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ismail, Mohd Muzafar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Chaotic Pulse Train in Cloud-to-Ground and Cloud Flashes of Tropical Thunderstorms2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we report for the first time the observation of chaotic pulse train (CPT) preceding natural subsequent negative return strokes and also CPT occurrence in IC flashes from tropical thunderstorms in South Malaysia. In CG flashes, all CPTs were occurred in between return strokes with 41.1% have occurred between the first and second return strokes. The maximum number of CPT in one sequence is 3, which can be observed between the first and third return strokes only. In IC flashes, all CPTs were observed to occur in between IC flash pulses.

  • 30.
    Ahmad, Mohd Riduan
    et al.
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Periannan, Dinesh
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Sabri, Muhammad Haziq Mohammad
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Abd Aziz, Mohamad Zoinol Abidin
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Esa, Mona Riza Mohd
    UTM, Inst Voltan Tinggi & Arus Tinggi IVAT, Johor Bharu, Malaysia.
    Lu, Gaopeng
    Chinese Acad Sci, Beijing, Peoples R China.
    Zhang, Hongbo
    Chinese Acad Sci, Beijing, Peoples R China.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Emission Heights of Narrow Bipolar Events in a Tropical Storm over the Malacca Strait2017Ingår i: 2017 International Conference On Electrical Engineering And Computer Science (Icecos), IEEE , 2017, s. 305-309Konferensbidrag (Refereegranskat)
    Abstract [en]

    Emission heights for narrow bipolar events (NBEs) have been reported mostly from observations at mid latitudes but none have been reported from tropical regions. In this paper, we are reporting for the first time the heights of NBE emissions from a tropical storm over the Malacca Strait, a narrow water passage between the Malay Peninsula and Sumatra Island. A total of 49 positive NBEs (+NBEs) were detected from the storm. The NBE activity can be divided into two stages according to the emission heights and radar reflectivity data. The first stage (or S1) lasted for only 6 minutes, started with the first detected NBE, and produced 20 NBEs (41%). The emission heights ranged between 12.0 and 16.7 km. Radar reflectivity data showed that the storm reached maximum values at 55 dBZ within the period S1. In contrast, the second stage (S2) lasted longer (32 minutes) and produced 29 NBEs (59%). The emission heights were lower and ranged from 8.5 to 13.7 km. Radar reflectivity data showed that the storm reached maximum values at 50 dBZ within the period S2.

  • 31.
    Ahmad, M.R.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rashid, M.
    Aziz, M.H.A.
    Esa, M.R.M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, E.
    Analysis of Lightning-induced Transient in 2.4 GHz Wireless Communication System2011Ingår i: Proceeding of IEEE International Conference on Space Science and Communication (IconSpace), Penang, Malaysia, pp225-230, 2011Konferensbidrag (Refereegranskat)
  • 32.
    Ahmad, Noor Azlinda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknis