Quasi proportional-resonant control of single-phase photovoltaic grid-connected system with LCL filter

The grid-connected photovoltaic (PV) power generation is expected to be more widespread and paid more attention. In order to suppress the high-frequency harmonic current of PV grid-connected inverters, LCL filter is utilized to lower the current total harmonic distortion rate. On the basis of LCL filter, double-loop current control scheme with the quasi proportional-resonant method is designed. The proposed control method can reduce the steady-state error of the current, and eliminate the impact of the grid frequency offset on the net current. And the system oscillation caused by the resonance frequency can be decreased, too. Therefore, the stability and robustness of the grid-connected system are improved. Simulation is implemented, and the simulation results confirm the effectiveness of the proposed control method.