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Coordinated control of series-connected offshore wind park based on matrix converters


A. Garcés, Department of Electric Power Engineering, Norwegian University of Science and Technology, NO 7491 Trondheim, Norway.



Optimization and reliability are two important aspects in design and operation of wind parks either for offshore as for onland emplacements. However, offshore locations demand conscientious effort in optimizing the size and the weight of each component in the energy conversion system because of the high investment and maintenance costs related with the supporting structures and transportation respectively. Achieving these two objectives requires the combination of different optimization stages, which consider a suitable design of the entire conversion system with innovative and more efficient power electronic devices, optimized topology of the offshore grid and customized control strategies for optimizing the operation of the park.

This paper presents an energy conversion concept for wind turbines on the basis of a reduced matrix converter (RMC) that will enable series direct current architecture in offshore wind parks thus preventing the need for offshore platforms. The RMC is built with bidirectional semiconductors that give reduced losses because of both superior topology and more efficient semiconductors. The proposed conversion topology is tested in stationary state and transient operation. In addition to operational features of the concept, control and operation of a wind park with several turbines are presented.

Dynamic operation of the turbine as well as the high-voltage direct current transmission line effects are considered. Three types of models are therefore developed. First, an accurate and detailed model for analyzing one single turbine with the converter operated at high-frequency switching is presented. This model considers a new modulation for the RMC. A second and simplified model is used for small signal analysis. This model permits to simulate several series-connected cluster during transient. Finally, an optimal direct current load flow model is used for evaluating stationary state operation.

Results show the technical feasibility of the proposed concept and their advantages over conventional topologies. The paper also discusses the technological challenges that this type of offshore grid architecture will bring. Copyright © 2011 John Wiley & Sons, Ltd.