Robust Loop Correction Scheme Based on Reference Model for Inverters in Weak Grids

Grid-connected inverters are widely used to interface renewable energy and energy storage resources into power grids. However, the impedance of the power transmission line is relatively large in weak grids, which can affect the stability of grid-connected inverters. In order to improve the stability of inverters in weak grids, a robust loop correction method is proposed in this article. First, a reference model with good stability is designed. Then, a high-pass filter is used to obtain the high-frequency components of the reference model response, and a low-pass filter is used to obtain the low-frequency components of the actual system response. The outputs of the two filters are added together to form the actual feedback current. Consequently, this method can correct the frequency characteristics of an inverter in high-frequency range, so that the inverter still has a good stability margin in a weak grid. The effectiveness of the proposed method is verified by both simulation and experimental results.