Passivity Enhancement for LCL-Filtered Inverter With Grid Current Control and Capacitor Current Active Damping

This article takes a deep insight into the passivity-based design of LCL-filtered inverter with grid current control and capacitor current active damping. It reveals that although an optimal damping gain can theoretically ensure the passivity, it is susceptible to both the lagging phase of the current regulator and the fluctuations of filter parameters. After thoroughly assessing the impacts of these two factors, proper phase compensations are proposed to enhance the passivity. It is found that a phase-lead or phase-lag compensator is needed, depending on the relation of the one-sixth of the sampling frequency to the resonance frequency of inverter-side inductor and filter capacitor. The guidelines on the compensation selection and parameter design are provided. Simulation and experimental results are conducted to verify the theoretical analysis.