VSG Control with Adaptive Virtual Impedance Compensation for Enhanced Small-Signal Stability Under Varying Grid SCRs

The virtual synchronous generator (VSG) controlled grid-forming (GFM) voltage source converters (VSCs) can operate stably with designed control parameters when connected with weak grids. However, variations in grid short-circuit ratio (SCR), particularly when the SCR increases, significantly affect the small-signal stability of VSG-controlled VSCs. To address this issue, this work proposes an adaptive virtual impedance (VI) compensation strategy based on a passive grid-impedance identification method for VSG-controlled VSCs. Firstly, the influence of grid impedance on the VSG control power loop is analyzed, deriving its impact on the small-signal stability. Then, an accurate passive equivalent grid impedance identification method is proposed. Furthermore, an adaptive VI-based VSG control strategy is proposed, ensuring the VSG-controlled VSC system’s stability and enhancing the control performance under varying grid SCRs. Finally, simulation results validate the feasibility and practicability of the proposed method.