Passivity-Based Design for LCL-Filtered Grid-Connected Inverters with Inverter Current Control and Capacitor-Current Active Damping

Passivity-based design gains much popularity in grid-connected inverters (GCIs) since it enables system stability regardless of the uncertain grid impedance. This paper devotes to a systematic passivity-based design guidance for the LCL-filtered GCI with inverter current control and capacitor-current active damping. It is found that the passivity can be guaranteed with an optimal damping gain of the capacitor-current active damping, but it suffers from both the filter parameter drift and the lagging phase of the current regulator, especially at the one-sixth sampling frequency. To address this issue, a phase-lead compensation is introduced in series with the current regulator, which helps to enhance the full-band passivity and high robustness against the aforementioned challenge. Experiments are conducted to confirm the theoretical expectation.