Full Feedforward Control Strategy with Pre-Filter of LCL Grid-Connected Inverter in Weak Grid

Abstract

With the large number of wind, photovoltaic and other new energy distributed generation connected to the grid, the weak impedance of the grid is more prominent. The full feed-forward control has a good suppression effect on the power grid background harmonic and has been widely used, but the traditional full feedforward control cannot adapt to the change of grid impedance. In this paper, a full feedforward control strategy with pre-filter is proposed. By setting a reasonable depth factor and passband width, the system can perform full feedforward only at the selected frequency and attenuate at other frequencies, so a good characteristic of grid voltage harmonic rejection is also maintained. The simulation in MATLAB/Simulink shows that the output still maintains high power factor and good sinusoidal characteristics under rich grid voltage harmonics and a certain grid inductive reactance, which verifies that the improved full feedforward strategy has good weak grid adaptability and robustness.