Review of Generator Systems for Direct-Drive Wind Turbines
Review of Generator Systems for Direct-Drive Wind Turbines D. Bang, H. Polinder, G. Shrestha, J.A. Ferreira Electrical Power Processing / DUWIND Delft University of Technology Mekelweg 4, 2628 CD Delft The Netherlands Phone: +31 (0)15 27 85791, Fax: +31 (0)15 27 82968 D.J.Bang@tudelft.nl, H.Polinder@tudelft.nl, G.Shrestha@tudelft.nl, J.A.Ferreira@tudelft.nl Abstract- The objective of this paper is to review direct-drive and geared generator systems and to identify suitable generator concepts for direct-drive wind turbines. The comparison of different generator systems in literature is discussed with the criteria based on the energy yield, cost, and weight. Different promising permanent-magnet (PM) machines proposed in literature are also discussed to find suitable generator type, because direct-drive PM machines are more superior in terms of the energy yield, reliability and maintenance problem. Finally, suitable concepts to overcome the disadvantages of direct-drive are suggested considering both electromagnetic and mechanical structure. I. INTRODUCTION Various wind turbine concepts have been developed and built to maximize the energy harnessed, to minimize the cost, and to improve the power quality during the last two decades. Such turbine concepts can be classified with a view to the rotational speed, the power regulation, and the generator system. When considering the construction of the generator system, the turbines can be classified into the direct-drive and the geared concepts. When focusing on the generator type, the generator system can be classified into the electrically excited (EE) machine and the permanent magnet (PM) machine. The comparisons of different generator systems for wind turbines have been proposed in a number of literatures.
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