Medium Voltage High-Power Converter Topology for the Large Permanent Magnet Wind Generator Systems

Abstract—This paper proposes a modular, medium voltage, high-power converter topology for the large permanent magnet wind generator system, eliminating the grid-side step-up transformer, which is desirable for both onshore and offshore wind turbines. The power conversion systems for large wind turbines are facing a great challenge as today’s wind turbine power outputs approach 5 MW and above. The conventional low voltage power conversion system will suffer from a high transmission current, which significantly increases losses and cost of the cables as well as voltage drop. The converter modules are cascaded to achieve medium voltage output. Each converter module is fed by a pair of generator coils with 90 phase shift to get the stable dc-link power. At the grid-side, H-bridge inverters are connected in series to generate multilevel medium voltage output and the voltage-oriented vector control scheme is adopted to regulate th