Highly robust LCL three-phase grid-connected inverter under non-ideal grid

A current-voltage dual-loop grid-connected control strategy for a conventional grid-connected inverter that is susceptible to instability under a non-ideal grid is designed. The effects of grid impedance and fluctuations in this strategy are considered. The influence of power network impedance change on LCL filter is analysed, the small signal model of phase-locked loop is established, and the design methods of system parameters and controller parameters to improve the robustness of the system are given. Finally, through MATLAB/Simulink simulation, current and voltage output of grid-connected inverters and grid-connected current quality parameters are obtained under different working conditions, verifying the correctness and feasibility of theoretical derivation.