Positive and Negative Sequence Components Separation Control Method for PV Inverters Based on Second-order Generalized Integrator

The negative sequence components generated by the grid during asymmetric faults cause deviations and fluctuations of the output frequency from phase-locked loop and the output current and power from grid-connected PV inverter. To solve these problems, a phase-locked loop based on the second-order generalized integrator quadrature signal generator (SOGI-QSG) is designed to achieve the phase locking of the grid-connected inverter. A positive and negative sequence separation method is proposed to eliminate the influence of its DC component using a single SOGI-QSG unit, and then a control strategy is designed to suppress the negative sequence current. Finally, a grid-connected PV generation system simulation model is built in PSCAD/EMTDC to verify the rapidity of phase locking and negative sequence current suppression. The proposed control strategy can achieve the separation of positive and negative sequence current components rapidly and accurately, and improve the accuracy of output power of the grid-connected inverter.