Active damping of LCL-Filtered Grid-Connected inverter based on parallel feedforward compensation strategy

Abstract

Resonance related to the LCL-filter grid-connected inverter (GCI) is one of the most challenging issues in power electronics. Active damping is a widely used methodology to damp the resonance problem due to its effective control structure. In capacitor current feedback active damping methodologies, a compensator is primarily required in the feedback loop where the damping efficiency depends on the imitated features of the compensator. Such capacitor current feedback damping techniques encounter restrictions in their layout at the critical resonance frequency and may need extra amendment in the delay to assure stability. This paper proposes a different design method called parallel feedforward compensation method, which designs an almost strictly real positive plant and achieved damping with enhanced stability features. In the proposed alternative, a first-order high pass filter is used as a compensator across the LCL filter plant and filter capacitor current feedback loop. The resultant output of this augmented plant is then transmitted back at the reference point of a GCI system to attenuate the undesirable resonance peak. The key benefits of the proposed method are efficient damping without any limitation of critical resonance frequency region, better control characteristics, improved damping area, and better robustness under variations in filter parameters. The simulation and experimental outcomes based on transient response and steady-state analysis are demonstrated to validate the efficacy of the suggested method.