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Leijon, Mats
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Publications (10 of 263) Show all publications
Parwal, A., Fregelius, M., Cardosa Silva, D., Potapenko, T., Hjalmarsson, J., Kelly, J., . . . Leijon, M. (2019). Virtual Synchronous Generator Based Current Synchronous Detection Scheme for a Virtual Inertia Emulation in SmartGrids. Energy and Power Engineering, 11(3), 99-131
Open this publication in new window or tab >>Virtual Synchronous Generator Based Current Synchronous Detection Scheme for a Virtual Inertia Emulation in SmartGrids
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2019 (English)In: Energy and Power Engineering, ISSN 1949-243X, E-ISSN 1947-3818, Vol. 11, no 3, p. 99-131Article in journal (Refereed) Published
Abstract [en]

Renewable energy sources, such as photovoltaicwind turbines, and wave power converters, use power converters to connect to the grid which causes a loss in rotational inertia. The attempt to meet the increasing energy demand means that the interest for the integration of renewable energy sources in the existing power system is growing, but such integration poses challenges to the operating stability. Power converters play a major role in the evolution of power system towards SmartGrids, by regulating as virtual synchronous ge-nerators. The concept of virtual synchronous generators requires an energy storage system with power converters to emulate virtual inertia similar to the dynamics of traditional synchronous generators. In this paper, a dynamic droop control for the estimation of fundamental reference sources is imple-mented in the control loop of the converter, including active and reactive power components acting as a mechanical input to the virtual synchronous generator and the virtual excitation controller. An inertia coefficient and a droop coefficient are implemented in the control loop. The proposed con-troller uses a current synchronous detection scheme to emulate a virtual iner-tia from the virtual synchronous generators. In this study, a wave energy converter as the power source is used and a power management of virtual synchronous generators to control the frequency deviation and the terminal voltage is implemented. The dynamic control scheme based on a current synchronous detection scheme is presented in detail with a power manage-ment control. Finally, we carried out numerical simulations and verified the scheme through the experimental results in a microgrid structure.

Place, publisher, year, edition, pages
Scientific Research Publishing, 2019
Keywords
Dynamic Droop Control, Energy Storage, Virtual Inertia, Virtual Synchronous Generator
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-379215 (URN)10.4236/epe.2019.113007 (DOI)
Funder
Swedish Research Council, 2015-03126StandUp
Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2019-03-18Bibliographically approved
Hultman, E. & Leijon, M. (2018). An updated cable feeder tool design for robotized stator cable winding. Mechatronics (Oxford), 49, 197-210
Open this publication in new window or tab >>An updated cable feeder tool design for robotized stator cable winding
2018 (English)In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 49, p. 197-210Article in journal (Refereed) Published
Abstract [en]

We have previously suggested a method for robotized stator winding of cable wound electric machines and demonstrated the method successfully in full-scale experiments. The cable feeder tool used to handle the cable during the complete winding process is an essential component of this robot cell. To take the robot winding method to the next level, into an industrial product, require further developments regarding durability, independency, flexibility and implementability. In this paper, we present an updated cable feeder tool design. This tool is designed to be used in a robot cell for cable winding of the third-generation design of the Uppsala University Wave Energy Converter generator stator. In this work, three cable feeder tool prototypes have been constructed, experimentally evaluated and validated for the intended application. Key performance parameters are presented and discussed, including suggestions for further developments. We completed a durable, compact, high performance tool design, with fully integrated control into industrial robot controllers. The experimental results presented in this article are very promising and hence, the updated cable feeder tool design represents another important step towards an industrial solution for robotized stator cable winding.

National Category
Robotics Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-334553 (URN)10.1016/j.mechatronics.2018.01.006 (DOI)
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2018-04-26Bibliographically approved
Parwal, A., Fregelius, M., Temiz, I., Göteman, M., Oliveira, J. G., Boström, C. & Leijon, M. (2018). Energy management for a grid-connected wave energy park through a hybrid energy storage system. Applied Energy, 231, 399-411
Open this publication in new window or tab >>Energy management for a grid-connected wave energy park through a hybrid energy storage system
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2018 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 231, p. 399-411Article in journal (Refereed) Published
Abstract [en]

The concern for climate change and energy consumption has increased the demand for renewable energy production considerably. Marine energy sources attract attention because of their high energy density. Wave energy is an attractive renewable energy source with large potential. Due to the nature of the ocean waves, a linear wave energy converter generates intermittent power. It is therefore crucial to regularize the power before connecting to the grid. Energy storage systems present effective ways to minimize the power fluctuations and deliver a steady power to the grid. In this paper, we present an energy management control system with a dynamic rate limiter. The method is applied to control a hybrid energy storage system, combining battery and supercapacitor, with a fully active topology controlled by the power converters. The results show that the method is able to control the charging and discharging states of the battery and the supercapacitor, and minimize the power fluctuation to the grid. The algorithm ensures low losses by shifting the required power and the stored power smoothly over the energy storage system.

Keywords
Wave energy converter, Hybrid energy storage system, Energy management control system, Dynamic rate limiter, State of charge
National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-361207 (URN)10.1016/j.apenergy.2018.09.146 (DOI)000452345400030 ()
Funder
StandUpSwedish Research Council, 2015-03126Carl Tryggers foundation
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2019-01-22Bibliographically approved
Parwal, A., Fregelius, M., Leijon, J., Chatzigiannakou, M., Svensson, O., Temiz, I., . . . Leijon, M. (2018). Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System. In: 2018 5TH INTERNATIONAL CONFERENCE ON ELECTRIC POWER AND ENERGY CONVERSION SYSTEMS (EPECS).: . Paper presented at 5th International Conference on Electric Power and Energy Conversion Systems (EPECS), APR 23-25, 2018, Kitakyushu, JAPAN..
Open this publication in new window or tab >>Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
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2018 (English)In: 2018 5TH INTERNATIONAL CONFERENCE ON ELECTRIC POWER AND ENERGY CONVERSION SYSTEMS (EPECS)., 2018Conference paper, Published paper (Refereed)
Abstract [en]

This paper provides an overview of electric power conversion system installed at the Lysekil research site, located at the west coast of Sweden. The electric power conversion system consists of rectifiers, rectifying the power from the wave energy converters, a DC-link and a grid-tied inverter. The paper focuses on the performance of the inverter and the filter and presents experimental results obtained during the grid integration.

Series
International Conference on Electric Power and Energy Conversion Systems, ISSN 2325-2677
Keywords
wave energy converter (WEC), wave energy havesting, grid integration, LCL filter response
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-373349 (URN)10.1109/EPECS.2018.8443488 (DOI)000450072100010 ()978-1-5386-6457-5 (ISBN)
Conference
5th International Conference on Electric Power and Energy Conversion Systems (EPECS), APR 23-25, 2018, Kitakyushu, JAPAN.
Funder
Swedish Research Council, 2015-03126Swedish Energy AgencyStandUp
Available from: 2019-01-15 Created: 2019-01-15 Last updated: 2019-01-22Bibliographically approved
Parwal, A., Fregelius, M., Leijon, J., Chatzigiannakou, M. A., Svensson, O., Temiz, I., . . . Leijon, M. (2018). Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System. In: : . Paper presented at Fifth International Conference on Electric Power and Energy Conversion Systems (EPECS 2018), Kitakyushu, Japan : April 23-25, 2018.
Open this publication in new window or tab >>Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
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2018 (English)Conference paper, Published paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-361208 (URN)
Conference
Fifth International Conference on Electric Power and Energy Conversion Systems (EPECS 2018), Kitakyushu, Japan : April 23-25, 2018
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2019-04-01Bibliographically approved
Potapenko, T., Temiz, I. & Leijon, M. (2018). Optimization of Resistive Load for a Wave Energy Converter with a Linear Generator Power Take Off. In: The 4th Asian Wave and Tidal Energy Conference in Taiper, Taiwan, September 9-13, 2018.: . Paper presented at 4th AWTEC2018, 9-13 September, 2018, Taipei, Taiwan.
Open this publication in new window or tab >>Optimization of Resistive Load for a Wave Energy Converter with a Linear Generator Power Take Off
2018 (English)In: The 4th Asian Wave and Tidal Energy Conference in Taiper, Taiwan, September 9-13, 2018., 2018Conference paper, Oral presentation with published abstract (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-362233 (URN)
Conference
4th AWTEC2018, 9-13 September, 2018, Taipei, Taiwan
Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2019-01-09Bibliographically approved
Hultman, E. & Leijon, M. (2018). Robotized stator cable winding. Robotics and Computer-Integrated Manufacturing, 53, 197-214
Open this publication in new window or tab >>Robotized stator cable winding
2018 (English)In: Robotics and Computer-Integrated Manufacturing, ISSN 0736-5845, E-ISSN 1879-2537, Vol. 53, p. 197-214Article in journal (Refereed) Published
Abstract [en]

Automated stator winding assembly has been available for small and medium sized conventional electric machines for a long time. Cable winding is an alternative technology developed for medium and large sized machines in particular. In this paper we present, evaluate and validate the first fully automated stator cable winding assembly equipment in detail. A full-scale prototype stator cable winding robot cell has been constructed, based on extensive previous work and experience, and used in the experiments. While the prototype robot cell is adapted for the third design generation of the Uppsala University Wave Energy Converter generator stator, the winding method can be adapted for other stator designs. The presented robot cell is highly flexible and well prepared for future integration in a smart production line. Potential cost savings are indicated compared to manual winding, which is a backbreaking task. However, further work is needed to improve the reliability of the robot cell, especially when it comes to preventing the kinking of the winding cable during the assembly.

National Category
Robotics
Identifiers
urn:nbn:se:uu:diva-334554 (URN)10.1016/j.rcim.2018.04.009 (DOI)000437037900017 ()
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2018-09-13Bibliographically approved
Savin, A., Temiz, I., Strömstedt, E. & Leijon, M. (2018). Statistical analysis of power output from a single heaving buoy WEC for different sea states. Marine Systems & Ocean Technology, 2-4, 103-110
Open this publication in new window or tab >>Statistical analysis of power output from a single heaving buoy WEC for different sea states
2018 (English)In: Marine Systems & Ocean Technology, ISSN 1679-396X, Vol. 2-4, p. 103-110Article in journal (Refereed) Published
Abstract [en]

Output power fluctuations from a wave energy converter (WEC) utilizing the principle of an oscillating body are unavoidable due to the reciprocating movement of the translator inside the generator. Moreover, the wave energy flux largely varies with time and propagates with the wave group velocity. Making use of the oscillating output power is a challenge for many wave energy conversion concepts. Therefore, estimation of the output power from a WEC solely by the mean power does not fully reflect the process of energy conversion, especially, by a direct drive linear generator. In the present paper, the output power from the WEC with a linear generator power take-off (PTO) is considered as a stochastic process, and the WEC performance is evaluated from the statistical point of view and related to the linear generator’s (LG) stroke length. Statistics as mean, standard deviation, relative standard deviation, maximum, and mode are found for different sea states. All statistics have shown an expected overall tendency with a rising significant wave height of incoming waves. As the significant wave height increases, statistics of the power output such as mean, standard deviation, maximum, and quantile are increasing, and the mode is decreasing beside the mode for the sea state C. It has been noted that for a significant wave height equal to the LG’s stroke length, the mode is greater than the same values for sea states of other significant wave heights. The results are based on a full-scale offshore experiment and may be used for the design of energy conversion systems based on a linear generator PTO.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-368743 (URN)10.1007/s40868-018-0050-x (DOI)
Available from: 2018-12-07 Created: 2018-12-07 Last updated: 2019-02-14Bibliographically approved
Leijon, J., Sjölund, J., Ekergard, B., Boström, C., Eriksson, S., Temiz, I. & Leijon, M. (2018). Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power. Energies, 11(1), Article ID 84.
Open this publication in new window or tab >>Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power
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2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 1, article id 84Article in journal (Refereed) Published
Abstract [en]

The wave energy converter (WEC) studied and developed at Uppsala University in Sweden is a point absorbing buoy connected to a linear generator (LG) on the seabed. Previous studies have improved the sustainability of the generator, changing its magnets from Nd2Fe14B-magnets to ferrites. In this paper, the magnetic circuit of the linear generator is further studied. Ferrite magnets of two different types (Y30 and Y40) are studied along with different shapes of pole shoes for the system. The finite element method (FEM) simulations in a program called Ace are performed. The results show that a linear generator including both Y30 and Y40 magnets and shortened T-shaped pole shoes can generate a similar magnetic energy in the airgap as a linear generator only containing Y40 magnets and rectangular pole shoes. This shows that the magnetic circuit can be altered, opening up sizes and strengths of magnets for different retailers, and thereby possibly lowering magnet cost and transportation. This work was previously presented as a conference at the European Wave and Tidal Energy Conference (EWTEC) 2017 in Cork, Ireland; this manuscript has been carefully revised and some discussions, on magnet costs for example, have been added to this paper.

Keywords
wave energy converter (WEC), linear generator (LG), ferrite permanent magnets (PMs), renewable energy sources
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-348930 (URN)10.3390/en11010084 (DOI)000424397600084 ()
Funder
Swedish Research Council, 2015-03126Swedish Energy Agency, P42243-1
Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2019-03-04Bibliographically approved
Hettiarachchi, P., Lobato, A., Cooray, V. & Leijon, M. (2018). Time Domain Analysis of the Lightning Interaction with Wave Energy Converters. In: : . Paper presented at 34th International Conference on Lightning Protection, 2-7 Sept, 2018,Rzeszow, Poland.
Open this publication in new window or tab >>Time Domain Analysis of the Lightning Interaction with Wave Energy Converters
2018 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-368794 (URN)
Conference
34th International Conference on Lightning Protection, 2-7 Sept, 2018,Rzeszow, Poland
Available from: 2018-12-07 Created: 2018-12-07 Last updated: 2019-03-14Bibliographically approved
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