A Robust Low-Voltage-Ride-Through Strategy for Grid-Forming Converters Based on Reactive Power Synchronization

Grid-forming converters (GFMCs) prevail for their capability of providing voltage and frequency support in modern power grids with large integration of intermittent distributed power sources. As GFMCs behave as voltage sources, the current limiting of GFMCs under large disturbances requires special efforts. Furthermore, a reliable GFMC should also be capable of remaining synchronized with the grid during and after large voltage disturbances. To avoid the instability caused by phase-locked loops during low-voltage faults, GFMCs usually retain the active power synchronization under low-voltage faults when the current saturation is triggered. When voltage sags are severe, the transient stability highly depends on the fault duration. This article proposed a robust fault ride through strategy for GFMCs based on reactive power synchronization (Q-Syn) under voltage sags. The Q-Syn method ensures transient stability of GFMCs regardless of the fault duration or level. Furthermore, fast postfault recovery can be achieved with the Q-Syn method. The effectiveness of the proposed method is verified by experiments.