Power matching based current limitation method for grid forming converter under large disturbances

Abstract

Grid forming (GFM) converter mimics the operational characteristics of the synchronous generator, serves as a voltage source that provides voltage and frequency support to the power system. However, due to its voltage source nature, the current of the GFM converter is highly determined by the external system, increasing the risk of overcurrent under large disturbances and potential damage to the converter. The conventional current reference limitation suffers from synchronization instability, which causes the converter to lose synchronization. To address this issue, this paper proposes a novel power matching based current limitation method, which maintains the synchronization of the GFM converter and also avoids overcurrent issues. Specifically, when a large disturbance occurs, considering the maximum output power of the GFM converter, the reference power of the converter is corrected using the frequency to match the output power in real time. Therefore, the output power of the converter is always its maximum value, with the current constrained to the maximum level allowed, avoiding overcurrent and instability. Finally, the superiority of the proposed method is verified by experiment and simulation.