A Unidirectional Cascaded High-Power Wind Converter With Reduced Number of Active Devices.

For large offshore wind turbines, cascaded H-bridge wind power converters can raise the wind generator voltage to a medium voltage level such as 10kV, which is favored for reducing the generator current, mitigating issues such as cable twisting in low-voltage, high-current configurations. In order to reduce the number of required active power devices, this paper presents a unidirectional-power-flow medium voltage high-power cascaded wind power converter. The proposed topology uses a unidirectional cascaded H-bridge rectifier as the generator-side converter to connect the medium-voltage permanent synchronous wind generator. The proposed topology reduces the number of active power devices and their associated gate driver circuits, control, etc. A zero deadtime modulation method is also presented for the generator side converter, which can eliminate the deadtime and improve the voltage and current waveform quality. Furthermore, the proposed topology will not increase the converter power losses as analyzed in the paper, or sacrifice dynamic control performance. Simulation and experiment results are presented, which validate the proposed unidirectional power conversion system.