Abstract:Study the understanding of the phase-locked accuracy of the coupled dual-synchronous reference frame phase-locked loop (Decoupling dual synchronous reference system phase-locked loop,DDSRF-PLL) under grid voltage imbalance. In order to eliminate the influence of DC offset, a DDSRF-PLL structure combining hybrid second-order and third-order generalized integrators (Mixed second- and third-order generalized integrator, MSTOGI) is proposed, and a nonlinear function is introduced to control its PI controller. First, harmonics can be effectively attenuated and the effects of DC offset are reduced through the MSTOGI's filtering capabilities. Secondly, the nonlinear function can adjust the PI parameters according to the size of the system deviation, which improves the accuracy and speed of phase locking. Through Matlab/Simulink to simulate the effectiveness and reliability of the proposed method.