An improved LVRT control method of MW level DFIG-based WECS

Abstract

Doubly fed induction generator (DFIG) is widely used in wind energy conversion system (WECS). But it is difficult for DFIG to realize low voltage ride through (LVRT). According to the mathematical model of the DFIG, this paper analyzes the dynamic process of the DFIG stator flux when the grid voltage drops, and proposes an improved LVRT control method for a 5-MW DFIG-based WECS. Software algorithm of canceling stator flux DC component and negative sequence component is used when grid voltage drops a less extent. A low pass filter is used to obtain the AC component of rotor current in DQ axis. New rotor current reference value can be got by using rotor current reference value subtracting the AC component. Crowbar is used to protect rotor side converter (RSC) when the grid voltage greatly drops. In PSIM, a case study of a typical 5MW DFIGbased WECS is carried out in simulation. Simulation results prove that the proposed control strategy is effective.