Active Damping of LCL Resonance in Grid-Connected Inverters Through Capacitor–Voltage Feedback and the Parks–McClellan Algorithm

Abstract

This article proposes an approach to active LCL-resonance damping in grid-connected inverters, leveraging capacitor voltage feedback and the Parks-McClellan (PM) algorithm. The advantage of damping the resonance of an LCL filter through the capacitor voltage feedback offers a reduction in the number of sensors required for the signal conditioning system. However, this approach requires the use of a derivative function, which, if not designed correctly, may amplify noise components and induce instability. In this regard, a digital differentiator that exhibits minimal amplification of noise and guarantees a reduced phase delay is essential to address this issue. Therefore, a digital differentiator based on an optimized wideband finite impulse response (FIR) filter is proposed and designed using the PM algorithm. This includes an outline of the frequency response, a description of the coefficient computation procedure, and an examination of the effects of different orders. In addition, a comprehensive system description and an in-depth analysis of the current controller design are presented. Experimental results demonstrate the effectiveness of the proposed method in damping the LCL resonance of a single-phase grid-connected inverter under varying grid impedance, filter orders, and reference step conditions.