Passivity Enhancement for LCL-Filtered Grid-Connected Inverter Based on Capacitor Voltage Proportional-Derivative Feedback Active Damping

Capacitor voltage feedback is a proven and cost-efficient active damping approach to alleviate the resonance hazard for the grid-connected inverter with LCL-filtered. However, the wide range variation of grid impedance has adverse effect to the damping performance under weak grid, which can even threaten the system stability. To tackle this problem, the capacitor voltage proportional-derivative feedback method is proposed based on passivity theory in this paper, so that the real-part of the inverter output admittance is ensured to be positive within the Nyquist frequency to prevent the instability. Furthermore, the controller parameters design method is presented, which achieves strong robustness and high reliability against the variable grid impedance and fluctuated filter parameters. Finally, the validity of the proposed method is confirmed by the simulation results.