Hybrid Generator for Wind Generation Systems

This paper proposes a new high voltage hybrid generator (HG) employed in a proposed off-shore wind generation system with HVDC interconnection and transmission. The proposed system is compared with an existing commercial wind generation system and shown to be more efficient, to have lower mass, hence potentially lower cost. The system in this paper offers a much simplified power conversion for wind turbines, in particular the gearbox (GB), low voltage generator, back-to-back voltage source converters (VSC) and turbine transformer typical of existing commercial systems are replaced with a high voltage direct drive HG and a passive rectifier. The proposed HG uses two rotor field excitations, permanent magnet (PM) and wound field (WF). Voltage and power control of the HG is facilitated via the machine WF energized by a brushless exciter. Further, the HG employs a multiphase stator winding that yields improved power density while essentially eliminating the smoothing devices that would otherwise be required. A prototype HG is built and tested to validate the effectiveness of the design.