Control delay compensation scheme based on non-instantaneous loading and pulse-width equivalence for active damping of LCL-type inverters

Active damping (generally by the feedback of capacitor current) is an effective solution to the resonance peak of LCL-type grid-connected inverters. However, the damping performance is significantly affected by the computation and pulse-width modulation delays in the digital control system, which results in poor system robustness. Moreover, the phase lag would be introduced by these control delays, leading to the constrained bandwidth and low-frequency gain of control loop. In this study, a novel compensation method based on non-instantaneous loading and pulse-width equivalence is proposed to completely eliminate the computation delay without any reliability problem. Moreover, compared to the traditional strategies, the proposal can be extended to most two-level converters because of its simplicity. Finally, the validity of the proposed method is confirmed by the experimental results from a 3 kW single-phase grid-connected inverter with an LCL filter.