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Coordinated Control of Wave Energy Converters Subject to Motion Constraints
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Wave Energy)ORCID iD: 0000-0002-4842-1029
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2016 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, no 6, 475Article in journal (Refereed) Published
Abstract [en]

In this paper, a generic coordinated control method for wave energy converters is proposed, and the constraints on motion amplitudes and the hydrodynamic interaction between converters are considered. The objective of the control problem is to maximize the energy converted from ocean waves, and this is achieved by coordinating the power take-off (PTO) damping of each wave energy converter in the frequency domain in each sea state. In a case study, a wave energy farm consisting of four converters based on the concept developed by Uppsala University is studied. In the solution, motion constraints, including constraints on the amplitudes of displacement and velocity, are included. Twelve months of sea states, based on measured wave data at the Lysekil test site on the Swedish west coast, are used in the simulation to evaluate the performance of the wave energy farm using the new method. Results from the new coordinated control method and traditional control method are compared, indicating that the coordinated control of wave energy converters is an effective way to improve the energy production of wave energy farm in harmonic waves.

Place, publisher, year, edition, pages
MDPI, 2016. Vol. 9, no 6, 475
Keyword [en]
wave energy farm; coordinated control; optimal damping; motion constraints; frequency domain
National Category
Ocean and River Engineering
Identifiers
URN: urn:nbn:se:uu:diva-297187DOI: 10.3390/en9060475ISI: 000378854400088OAI: oai:DiVA.org:uu-297187DiVA: diva2:941091
Funder
Swedish Energy AgencyStandUpSwedish National Infrastructure for Computing (SNIC)
Available from: 2016-06-21 Created: 2016-06-21 Last updated: 2017-11-28Bibliographically approved
In thesis
1. Modelling and Advanced Control of Fully Coupled Wave Energy Converters Subject to Constraints: the Wave-to-wire Approach
Open this publication in new window or tab >>Modelling and Advanced Control of Fully Coupled Wave Energy Converters Subject to Constraints: the Wave-to-wire Approach
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ocean wave energy is a promising renewable source to contribute to supplying the world’s energy demand. The Division of Electricity at Uppsala University is developing a technology to capture energy from ocean waves with a wave energy converter (WEC) consisting of a linear permanent magnet generator and a point absorber. The linear generator is placed on sea bed and is driven directly by the floating absorber. Since March 2006, multiple wave energy converters have been deployed on the Swedish west coast outside the town of Lysekil. The technology is verified by long-term operation during at sea and satisfactory reliability of the electricity generation.

This thesis focuses on developing advanced control strategies for fully coupled wave energy converters subject to constraints. A nonlinear control strategy is studied in detail for a single WEC subject to constraints under regular and irregular waves. Besides, two coordinated control strategies are developed to investigate the performance of a wave energy farm subject to constraints. The performance of the WECs using these control strategies are investigated in case studies, and optimal PTO damping coefficients are found to maximize the output power. The results show that these control strategies can significantly improve the performance of the WECs, in terms of mean power, compared to a conventional control.

Besides these control strategies, a wave-to-wire simulation platform is built to study the power generation control of the WEC subject to constraints.  The wave-to-wire simulation platform allows both nonlinear and linear control force. The results show that there is a good agreement between the desired value and the actual value after advanced control.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 116 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1528
Keyword
Ocean wave energy, marine energy converter, wave energy converter, wave energy farm, potential flow theory, linear permanent magnet generator, control strategy, wave-to-wire approach, physical constraints, power generation control.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-320906 (URN)978-91-554-9934-1 (ISBN)
Public defence
2017-09-01, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-06-01 Created: 2017-04-26 Last updated: 2017-06-08

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Wang, LiguoEngström, JensLeijon, MatsIsberg, Jan

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