Grid Disturbance and Internal Voltage Source Saturation Impact on Power-Angle Curves of GFM

This paper investigates the effect of current limit constraints imposed by grid forming converter (GFM) on grid synchronization during and after the recovery from three-phase symmetrical faults. Saturation effects in GFM control due to factors such as internal voltage source, current reference and voltage sag on the power-angle curves significantly deviates from sinusoidal-based relationship and influences the transient stability studies. The approximation of internal voltage source to grid voltage is not valid for the case of grid disturbance in the case of symmetrical faults. The theoretical analysis includes these effects and provide a generalized expression for the case of prioritizing angle in current saturation algorithm. Simulation results validate the theoretical model for various system disturbances for stable and unstable cases.