Studies on fault ride-through and its control of doubly-fed induction generators in wind farms

The low voltage ride-through ability of a wind farm has an important effect on the transient stability of a power system.The excitation control principle of a doubly-fed induction generator(DFIG) was analyzed and the vector control strategy of a wind generator was established based on the current decoupling method.Crowbar hysteresis loop protection of the rotor side converter(RSC) and voltage support technology of the grid side converter(GSC) during the fault were also presented.The transient responses of two types of generators of traditional synchronous generators and DFIGs in short-and long-time short-circuit faults were studied and parameters of the converter,which affect performances of a wind generator,were discussed by using PSCAD / EMTDC simulation tool.The results show that the emergency countermeasures for the converter can quickly restore the control ability of the wind turbine,then the voltage can be reconstructed rapidly by adjusting the magnitude and phase angle of the rotor flux vector.In addition,the selection of suitable DC capacitance capacity will enhance the ability of resisting negative sequence current of a GSC during an imbalance fault.