Ground fault identification method for LVDC distribution networks based on active signal injection and phase feature analysis

To accurately and reliably identify ground faults in low-voltage DC (LVDC) distribution networks and address the limitations of existing transient-based methods in terms of sensitivity and reliability, this paper proposes a ground fault identification method based on active signal injection. By introducing an auxiliary control strategy in the voltage source converter (VSC), a specific-frequency probing signal is actively injected after protection is triggered to enhance fault characteristics. Zero-sequence currents from each feeder are then compared with the system's total zero-sequence current using cross-correlation to determine the optimal alignment delay. At this delay point, the phase difference cosine is calculated and used as the fault identification criterion. Simulation results confirm that the proposed method is highly reliable and effective.