Stability study of grid-forming energy storage converters considering frequency coupling characteristics

With the massive integration of power electronics into the grid, the time-varying characteristics of grid line impedance have significantly increased the dynamic interaction between energy storage converters employing Virtual Synchronous Generator (VSG) control algorithms and the system impedance. This interaction heightens the peril of instability in the control system. Establishing a sequence resistance model for the VSG control algorithm can effectively analyze the stability of the control algorithm. However, existing studies lack a detailed sequence impedance model of the VSG dual-loop control algorithm that accounts for frequency coupling characteristics. This paper develops a sequence opposition model of the VSG control algorithm taking into account frequency interaction characteristics and analyzes the dynamic interaction between the VSG control algorithm and various grid impedances, ensuring stable operation under different line impedance conditions.