Study on reactive power characteristics of doubly fed variable speed constant frequency wind power generators

The reactive power characteristics of doubly fed variable speed constant frequency (DFVSCF) wind power generator are important for grid´s voltage stability and generator´s low voltage ride-though (LVRT) capability. From the equivalent circuit of doubly-fed induction generator (DFIG), the balance equation of reactive power was deduced. Based on the balance equation, this paper first discussed the reactive power conversion relationship between stator and rotor whose frequencies are different, then analyzed the mechanism of DFIG´s flexible and strong capacity in reactive power regulation. It further investigated the reactive power characteristics of DFIG under different operation conditions, and summarized the influence of slip rate and stator reactive power on rotor reactive power. At last, simulation research was carried on and the results verified the validity and correctness of analysis and conclusion.