Analysis of Switching Mechanisms and Transient Stability of Virtual Synchronous Generators Considering Current Limiting

Aiming at the transient stability analysis of Virtual Synchronous Generators considering current limitation, this paper primarily constructs a switching dynamic model for single-converter grid-connected systems based on state variables, identifying that the switch between converter control modes occurs at particular phase angles. Further, employing the Segmental Equal Area Criteria, we investigate the transient stability of the proposed model and derive the analytical expressions for the system's critical clearing angle, unveiling the influence mechanism of the saturation current angle on the system's transient stability. Additionally, recognizing that grid-forming converters under limitation constraints may stabilize in current limiting control mode, we propose a method for configuring the saturation current angle to enhance the transient stability margin of the system. This method not only prevents the system from being locked in current limiting mode after fault clearance but also maximizes the critical clearing angle. Finally, simulations based on MATLAB/Simulink are conducted to validate the accuracy of the stability analysis results and the effectiveness of the saturation current angle setting method.