The Performance of Current Differential Protection in a Distribution Network Containing Grid-Forming Distributed Generators

This paper addresses the misoperation and refusal issues of current differential protection caused by grid-forming distributed generation integration into active distribution networks. Through establishing a virtual synchronous machine control model for grid-forming distributed generation and conducting fault sequence network analysis, the mechanism of output current phase shift during low-voltage ride-through (LVRT) affecting differential protection criteria is revealed. The study demonstrates that during external faults, grid-forming distributed generation injects reverse short-circuit currents causing virtual increases in differential currents, significantly elevating traditional criteria misoperation rates. During internal faults, controlled current outputs reduce protection sensitivity. The theoretical analysis is ultimately validated through simulation verification.