Abstract: Under the condition of weak grid, the normal operation of the grid-connected inverter will be affected by the background harmonics of the grid and the dynamic changes of the grid impedance, resulting harmonic resonance occurring in the grid-connected current. Therefore, a new resonant suppression strategy for LLCL grid-connected inverters is proposed. Based on the weighted average current control and grid voltage feedforward control, the strategy introduces the capacitive current feedback link, which preserves the advantages of eliminating the influence of grid voltage on the grid-connected current in the traditional grid voltage feedforward control method.By setting the feedback coefficient in the new feedback link, the resonance peak can be effectively suppressed, and at the same time, the stability of the grid-connected inverter is not affected by the grid impedance, which improves the stability of the LLCL grid-connected inverter and reduces the harmonic content of the grid-connected current. Finally, the effectiveness of the new strategy of resonance suppression is verified by building the simulation and experimental platform.

Key words: LLCL grid-connected inverter, weak grid, capacitive current feedback, resonance suppression, grid voltage feed forward