An Intelligent and Precise Grid Impedance Identification Scheme

This article proposes an intelligent grid impedance identification method based on harmonic current of characteristic order(s), aiming at different grid-following (GFL) control methods. The general model of GFL grid-connected inverter system is first established. Based on different control methods, the corresponding characteristic harmonics in current, that can be the indicators for grid impedance identification, are then extracted. Finally, the experimental results verify the correctness of proposed method. The proposed characteristic harmonics-based identification method can precisely predict the real-time grid impedance with enough accuracy and much less data necessary, which completes and improves the intelligent identification method under different circumstances.