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Publications (10 of 35) Show all publications
Ayob, M. N., Castellucci, V., Abrahamsson, J. & Waters, R. (2019). A remotely controlled sea level compensation system for wave energy converters. Energies, 12(10), Article ID 1946.
Open this publication in new window or tab >>A remotely controlled sea level compensation system for wave energy converters
2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 10, article id 1946Article in journal (Refereed) Published
Abstract [en]

The working principle of the wave energy converter (WEC) developed at Uppsala University (UU) is based on a heaving point absorber with a linear generator. The generator is placed on the seafloor and is connected via a steel wire to a buoy floating on the surface of the sea. The generator produces optimal power when the translator's oscillations are centered with respect to the stator. However, due to the tides or other changes in sea level, the translator's oscillations may shift towards the upper or lower limit of the generator's stroke length, resulting in a limited stroke and a consequent reduction in power production. A compensator has been designed and developed in order to keep the generator's translator centered, thus compensating for sea level variations. This paper presents experimental tests of the compensator in a lab environment. The wire adjustments are based on online sea level data obtained from the Swedish Meteorological and Hydrological Institute (SMHI). The objective of the study was to evaluate and optimize the control and communication system of the device. As the device will be self-powered with solar and wave energy, the paper also includes estimations of the power consumption and a control strategy to minimize the energy requirements of the whole system. The application of the device in a location with high tides, such as Wave Hub, was analyzed based on offline tidal data. The results show that the compensator can minimize the negative effects of sea level variations on the power production at the WEC. Although the wave energy concept of UU is used in this study, the developed system is also applicable to other WECs for which the line length between seabed and surface needs to be adjusted.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
wave energy converter, tidal compensation, control system, tides, Wave Hub
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-381166 (URN)10.3390/en12101946 (DOI)000471016700125 ()
Funder
Swedish Energy Agency, 2016-002062
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-08-06Bibliographically approved
Felicetti, R., Abrahamsson, C. J. & Lundin, U. (2019). Experimentally validated model of a fast switched salient pole rotor winding. In: 2019 IEEE Workshop on Electrical Machines Design, Control and Diagnosis (WEMDCD): . Paper presented at 2019 IEEE International Workshop on Electrical Machines Design, Control, and Diagnosis (WEMDCD 2019), Athens, Greece, 22–23 April 2019 (pp. 150-156). IEEE
Open this publication in new window or tab >>Experimentally validated model of a fast switched salient pole rotor winding
2019 (English)In: 2019 IEEE Workshop on Electrical Machines Design, Control and Diagnosis (WEMDCD), IEEE, 2019, p. 150-156Conference paper, Published paper (Refereed)
Abstract [en]

The article proposes a model of a salient pole synchronous machine field winding based on a single transmission line model. An experimental method to derive the parameters is also presented and validated. Finally, the measured voltage distribution in the winding is compared to the model voltage distribution and the results match, demonstrating the model capabilities. The model describes the intrinsic resonance phenomena and accurately determines the voltage amplification factor.

Place, publisher, year, edition, pages
IEEE, 2019
Keywords
Distributed parameter circuits, eddy currents, parasitic capacitance, resonance, skin effect, stray inductance
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity; Engineering Science; Electrical Engineering with specialization in Systems Analysis
Identifiers
urn:nbn:se:uu:diva-386188 (URN)10.1109/WEMDCD.2019.8887777 (DOI)978-1-5386-8107-7 (ISBN)
Conference
2019 IEEE International Workshop on Electrical Machines Design, Control, and Diagnosis (WEMDCD 2019), Athens, Greece, 22–23 April 2019
Projects
This research has been carried out within the HydroFlex project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 764011.
Funder
EU, Horizon 2020, 764011
Available from: 2019-06-19 Created: 2019-06-19 Last updated: 2020-01-09Bibliographically approved
Kristiansen Nøland, J., Evestedt, F., Pérez-Loya, J. J., Abrahamsson, J. & Lundin, U. (2018). Comparison of Thyristor Rectifier Configurations for a Six-Phase Rotating Brushless Outer Pole PM Exciter. IEEE transactions on industrial electronics (1982. Print), 65(2), 968-976
Open this publication in new window or tab >>Comparison of Thyristor Rectifier Configurations for a Six-Phase Rotating Brushless Outer Pole PM Exciter
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2018 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, no 2, p. 968-976Article in journal (Refereed) Published
Abstract [en]

Recent technological developments have caused a renewed interest in the brushless excitation system. With the application of wireless communication, the conventional diode bridge has been replaced with fully controllable thyristors on the shaft. It offers the same dynamic performance as the conventional static excitation system. The thyristor bridge of the conventional three-phase exciter needs to be controlled with a high firing angle in normal operation in order to fulfill a requirement of both a high ceiling voltage and a high ceiling current. A high firing angle causes high torque ripple to be absorbed by the exciter stator and a low power factor results in a low utilization of the designed exciter. In this contribution, we present a strategy that solves this problem by looking into combinations of thyristor configurations of a double-star six-phase connection of the exciter. Experimental results are used to verify the circuit models implemented for this investigation. A hybrid-mode 12-pulse thyristor bridge configuration seems to be a good solution for implementations in commercial apparatus. An additional switch interconnects two separate thyristor bridges from parallel- to series connection at the rectifier output, and utilizes the advantages of both topologies.

Keywords
Bridge circuits, Generators, Shafts, Thyristors, Topology, Torque, Windings, 12-pulse thyristor rectifiers, Fast-response exciters, active rectification, brushless exciters, hybrid-mode operation, multiphase machines, outer-pole PM machines, rotating exciters, synchronous generators
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-328391 (URN)10.1109/TIE.2017.2726963 (DOI)000418415200002 ()
Available from: 2017-08-22 Created: 2017-08-22 Last updated: 2018-01-25Bibliographically approved
Ayob, M. N., Castellucci, V., Abrahamsson, J., Svensson, O. & Waters, R. (2018). Control Strategy for a Tidal Compensation System for Wave Energy Converter Device. In: : . Paper presented at The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan.
Open this publication in new window or tab >>Control Strategy for a Tidal Compensation System for Wave Energy Converter Device
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2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Ocean and River Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-363349 (URN)978-1-880653-87-6 (ISBN)
Conference
The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
Available from: 2018-10-17 Created: 2018-10-17 Last updated: 2019-04-05Bibliographically approved
Perez-Loya, J. J., Abrahamsson, J., Evestedt, F. & Lundin, U. (2018). Demonstration of Synchronous Motor Start by Rotor Polarity Inversion. IEEE transactions on industrial electronics (1982. Print), 65(10), 8271-8273
Open this publication in new window or tab >>Demonstration of Synchronous Motor Start by Rotor Polarity Inversion
2018 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, no 10, p. 8271-8273Article in journal (Refereed) Published
Abstract [en]

Synchronous motors are reliable and efficient, but it is relatively difficult to start them. In some cases, a variable frequency drive is utilized. In some other, asynchronous start is achieved by virtue of induced currents in a solid rotor, or a rotor damper cage installed for this purpose. In this contribution, a method to start a synchronous machine without a damper cage is presented. The starting was achieved by inverting the polarity of the rotor field winding in a timely manner with respect to the rotating stator field. The technique was verified with experiments performed on a 200 kVA experimental test rig and also simulated on a 20 MVA machine.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018
Keywords
Magnetic fields, starting, synchronous motors
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-362093 (URN)10.1109/TIE.2017.2784342 (DOI)000441990000012 ()
Funder
StandUpSweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Available from: 2018-10-01 Created: 2018-10-01 Last updated: 2018-10-09Bibliographically approved
Pérez-Loya, J. J., Abrahamsson, J. & Lundin, U. (2018). Electromagnetic losses in synchronous machines during active compensation of unbalanced magnetic pull. IEEE transactions on industrial electronics (1982. Print), 66(1), 124-131
Open this publication in new window or tab >>Electromagnetic losses in synchronous machines during active compensation of unbalanced magnetic pull
2018 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 66, no 1, p. 124-131Article in journal (Refereed) Published
Abstract [en]

Unbalanced magnetic pull (UMP) is typically caused by rotor or stator shape defects, electrical short circuits, eccentric rotor/stator bores, as well as unreasonable pole-slot combinations. It leads to vibration and increases noise and energy losses of the machine. By actively controlling the magnetic fields and forces that arise between the rotor and stator by regulating the rotor field current of separated pole groups, it is possible to cancel it. In this paper, we measure and calculate the currents induced in the damper bars for a synchronous machine test rig under 20% static eccentricity with and without active compensation of UMP. This is done to validate our finite-element calculations. Afterward, we perform loss calculations for a 74-MVA synchronous generator with and without stator parallel circuits. We find that, with active compensation of UMP for an eccentric machine, the damper bar currents and stator parallel circuit circulating currents can be eliminated and the electromagnetic efficiency of the machine that has a static eccentricity fault increases.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-328080 (URN)10.1109/TIE.2018.2827991 (DOI)000443894700012 ()
Funder
StandUp
Note

Title in dissertation reference list: Electromagnetic losses in synchronous machines during active compensation of unbalanced magnetic pull due to static eccentricity

Available from: 2017-08-16 Created: 2017-08-16 Last updated: 2019-12-06Bibliographically approved
Abrahamsson, C. J., Pérez-Loya, J. J., Fregelius, M., Evestedt, F., Bladh, J. & Lundin, U. (2018). Magnetic thrust bearing for a 10 MW hydropower generator with a Kaplan turbine. In: : . Paper presented at Hydro 2018, Oct 15 - Oct 17, Gdansk, Poland 2018,.
Open this publication in new window or tab >>Magnetic thrust bearing for a 10 MW hydropower generator with a Kaplan turbine
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2018 (English)Conference paper, Published paper (Refereed)
National Category
Energy Systems
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-363975 (URN)
Conference
Hydro 2018, Oct 15 - Oct 17, Gdansk, Poland 2018,
Available from: 2018-10-22 Created: 2018-10-22 Last updated: 2019-03-13Bibliographically approved
Ayob, M. N., Castellucci, V., Göteman, M., Widén, J., Abrahamsson, J., Engström, J. & Waters, R. (2018). Small-Scale Renewable Energy Converters for Battery Charging. Journal of Marine Science and Engineering, 6(1), Article ID 26.
Open this publication in new window or tab >>Small-Scale Renewable Energy Converters for Battery Charging
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2018 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter).

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
small wave energy converter, oscillating water column, heaving point absorber
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-357765 (URN)10.3390/jmse6010026 (DOI)000428558900025 ()
Funder
Swedish Energy AgencySwedish Research Council, 2015-04657ÅForsk (Ångpanneföreningen's Foundation for Research and Development)StandUpCarl Tryggers foundation
Available from: 2018-08-22 Created: 2018-08-22 Last updated: 2019-04-05Bibliographically approved
Nøland, J. K., Evestedt, F., Pérez-Loya, J. J., Abrahamsson, J. & Lundin, U. (2018). Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter. IEEE transactions on energy conversion, 33(1), 59-67
Open this publication in new window or tab >>Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter
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2018 (English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 33, no 1, p. 59-67Article in journal (Refereed) Published
Abstract [en]

The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this paper, a six-phase outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A fast-response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents possible, improving the transient behavior of the synchronous generator. In this paper we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage and reduce the steady state torque ripple. Experimental results are given for validating the models implemented for the analysis.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-328396 (URN)10.1109/TEC.2017.2746559 (DOI)000425623700007 ()
Available from: 2017-08-22 Created: 2017-08-22 Last updated: 2018-04-25Bibliographically approved
Nøland, J. K., Evestedt, F., Pérez-Loya, J. J., Abrahamsson, J. & Lundin, U. (2017). Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator. IEEE transactions on industry applications, 53(3), 2016-2027
Open this publication in new window or tab >>Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator
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2017 (English)In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 53, no 3, p. 2016-2027Article in journal (Refereed) Published
Abstract [en]

Generally, PM machines are used as PMG pre-exciters in 3-stage brushless excitations systems. This paperpresents the design, characterization and prototyping of a rotatingbrushless PM exciter used in a proposed 2-stage excitation systemfor a synchronous generator. The proposed design reduces thenumber of components compared with conventional systems.A comparison with the state-of-the-art conventional excitationsystems is given. The design of a fast-response, or high initialresponse, brushless exciter requires active rectification on therotating frame, replacing the non-controllable diode bridge. Theobjective was to construct an exciter with the capability of a50 Aoutput field current as well as a high value of the available ceilingvoltage and ceiling current. The final exciter was constructed to befitted into an in-house synchronous generator test setup. A finiteelement model of the exciter was validated with experimentalmeasurements. The exciter prototype is also compared with analternative armature design with non-overlapping single-layerconcentrated windings but with the same main dimensions.The paper includes a general design procedure suitable foroptimization of PM brushless exciters that fulfill the requirementsof their synchronous generators and the grid.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-315594 (URN)10.1109/TIA.2017.2669890 (DOI)000402062600031 ()
Available from: 2017-02-15 Created: 2017-02-15 Last updated: 2018-09-17Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2698-2941

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