Hybrid Active Damping Combining Capacitor Current Feedback and Point of Common Coupling Voltage Feedforward for LCL-Type Grid-Connected Inverter

Both the capacitor-current-feedback (CCF) active damping and the point of common coupling (PCC) voltage feedforward can provide damping for the LCL-type grid-connected inverter. They are usually individually adopted, and negative damping will occur in a certain frequency range due to the digital control delay, leading to a nonminimum phase behavior. In this article, a hybrid active damping that combines the CCF and unit PCC voltage feedforward is studied. With properly designing the CCF gain, the positive damping range could sweep the entire frequency range with the variation of grid impedance. As a reward, the maximum profit of damping cooperation can be harvested, ensuring high robustness against both grid impedance variation and filter parameter fluctuation. The simulation and experimental results are provided to verify the effectiveness of the hybrid active damping.