Recovery Overcurrent Analysis for Grid Forming Converter Under Symmetrical Fault with the Impact of Power Synchronization Dynamics

Due to the inherent self-synchronous voltage source characteristics of the grid forming (GFM) converter, its output current is significantly affected by power angle swing dynamics. Since the power angle swing is dominated by active power control, the transient current behavior during fault and recovery stage is closely related to the power synchronization dynamics, which needs detailed investigation. This paper proposed a transient current model of grid-connected GFM converter, which depicts the relationship between the current behavior and power angle motion. Moreover, the recovery overcurrent (ROC) boundary is quantitively characterized through the energy function to identify whether the ROC phenomenon occurs. On this basis, the impact of power synchronization dynamics on the ROC behavior is evaluated. It reveals that the reduction of active power control reference, the decrease of inertia constant, and the enhancement of damping coefficient in the active power control loop can help GFM converter avoid ROC phenomenon. The above analysis and discussion are well-validated in simulation platform.