Research on dynamic current limiting control strategy of grid converter under power grid voltage sag fault

Compared with conventional control strategies, grid-forming converters based on virtual synchronous generator (VSG) control inherently provide virtual inertia and damping characteristics, offering superior stability and flexibility when coping with variations in system impedance. However, following a grid fault, such converters may still experience overcurrent and transient instability. To enhance the converter's current limiting capability, this paper proposes a transient current suppression scheme that combines a current limiter with a time-varying virtual impedance. This approach effectively mitigates both transient and steady state overcurrent events. Moreover, by adjusting the power reference according to the extent of grid-side voltage sag, the proposed strategy ensures that the grid-forming converter continues to support the grid voltage during faults, thereby improving the converter's transient stability under large disturbances. Finally, a single-VSG, grid-connected model is implemented in MATLAB/Simulink to compare and analyze the transient current suppression effects of the limiter and virtual impedance control; simulation results validate the effectiveness of the proposed current limiting control strategy.