Area-based stability analysis method of grid-connected converter under wide operating conditions

Grid-connected converters (GCCs) exhibit diverse stability characteristics at different operating points. However, traditional stability analysis methods usually study the stability of GCC at a specific operating point. To analyze the stability under time-varying operation conditions, this paper proposes an area-based stability analysis method. Firstly, operating point variables are introduced by the coordinate transformation relationship in phase-locked loop (PLL). Secondly, the small-signal model of GCC considering the coupling between PLL and current control is built. Based on the built model, the stable operation domain can be obtained. The stability of the system can be quickly determined by the relative position of the operating point to the stable boundary. Then, the mechanisms of impedance parameters and control parameters on the stable domain are analyzed to improve the stability of GCC. Finally, the effectiveness and correctness of the proposed area-based stability analysis method are verified by simulation and experiment.