Synthesis of active damping for grid-connected inverters with an LCL filter

LCL filter characterized with high harmonic current attenuating performance and low cost are suitable for medium and high power grid-connected inverters. But, the resonance poles endanger the safety of operation, and the active damping (AD) is an effective means to increase the system security. This paper focus on the theoretical exercise of possible strategies to damp the resonance of grid-connected inverter with LCL-filter, the systematical synthesis method for AD is presented, and a unified analytical model for AD is proposed. The AD structures are listed based on single-state variable and single-compensator, and the effective AD strategies are distinguished by root locus. And then, the published AD approaches can be involved in derived AD structures, and the novel AD approach is successfully proposed. The characteristics and performance of the proposed AD approach is analyzed, and its validity is verified by experiment results to demonstrate the success of the theoretical exercise of active damping strategies.