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Capacitor Voltage Damping Based on Parallel Feedforward Compensation Method for LCL-Filter Grid-Connected Inverter

Active damping is a popular approach to suppress the resonance in LCL-filtered grid-connected inverter owing to lossless damping and efficient system design. In capacitor voltage (CV) damping methods, a differential compensator is essentially needed in feedback path, where the damping effectiveness depends on emulated derivative characteristics of the compensator. Such CV feedback compensation methods face design limitation at the critical resonance frequency and may require additional delay reduction to ensure stability. In this article, an alternative parallel feedforward compensation method is proposed to synthesize an almost strictly positive real plant and achieved damping with modified stability characteristics. A second-order bandpass section is employed as a compensator in damping loop based on the proposed control scheme. The main features of the proposed method are effective damping without critical resonance frequency damping limit, extended stable damping region, improved control performance, and good robustness under filter parameters and grid inductance variation conditions. The simulation and experimental results are presented to verify the effectiveness of the proposed method.