Coordinated Optimization of DFIG Rotor Crowbar and DC-chopper Resistances Based on NSGA-II

Abstract

Abstract Low voltage ride-through (LVRT) scheme of doubly-fed induction generator (DFIG) will affect the transient stability of power system since it will change the operation state of wind turbine. The LVRT scheme combining rotor crowbar circuit and Direct Current chopper (DC-chopper) circuit is effective, but the resistances of crowbar and DC-chopper are set separately and the impact on the system transient stability is usually ignored, which makes it difficult to gain optimum control effect. In this paper, the relation between rotor crowbar and DC-chopper in LVRT duration is analyzed in theory, which shows the effect of DC-chopper circuit can be considered as the variation of crowbar in equivalent circuit. Furthermore, by analyzing the effect of crowbar on the LVRT performance and power system transient stability, a coordinated resistance optimization method of crowbar and DC-chopper is proposed. Based on this method, a multi-objective optimization model for crowbar and DC-chopper resistance considering both LVRT performance and system transient stability is established, and the non-dominated sorting genetic algorithms-II (NSGA-II) is applied to solve this multi-objective optimization problem. The simulation results verify that the coordinated optimization scheme will not only achieve better LVRT characteristics, but also improve the transient stability of power system.