An Improved Frequency Modulation Method for Fault Ride Through of MMC-HVDC Systems Connected DFIG Wind Farms

In order to improve the transient characteristics and Fault Ride Through (FRT) capabilities of MMC-HVDC systems connected DFIG wind farms, their dynamic behaviors during the FRT are analyzed in detail. An improved frequency modulation method is proposed to suppress the oscillation of the DC voltage of the MMC-HVDC system caused by DFIG stator current's DC component. An auxiliary power reduction control strategy is designed for wind farms to increase the FRT performance of the whole system. Simulation results show that the proposed schemes can significantly suppress the oscillations of the DC voltage of the MMC-HVDC and improve the FRT capability of the system.