Study on the fault ride through critical elements and coordinated control of DFIG's converters

Abstract

The increasing of large-scale wind power integration capacity brings great challenges to the safe operation and management of power grid. Modern grid codes put forward the requirements of fault ride through (FRT) capability: (i) to remain continuous operation at a given time; (ii) to contribute to support the voltage stability during FRT by providing reactive current. Aiming at the FRT problem of doubly fed induction generator (DFIG), critical elements of the rotor side converter (RSC) and the grid side converter (GSC) to FRT are analysed, and the improving RSC control scheme, adding extra hardware equipment, and improving reactive current control scheme are studied. Matlab/Simulink simulation studies are conducted to verify the effectiveness of the proposed strategies. The results show that when the grid fault is light, the improving RSC control strategy can effectively control the rotor winding overcurrent, when the grid fault is serious, it needs additional hardware equipment; the coordinated control strategy of the RSC and the GSC providing reactive current support is identified as the most advantageous approach because it not only provides enhanced reactive support for the grid, but also avoids over-speed risk of DFIG based wind turbine shaft.