基于主动探测式的柔性直流电网纵联保护

In order to improve the sensitivity and speed of flexible DC line protection, and to ensure the accurate identification of the fault areas in DC grid, this paper proposes a principle of DC grid pilot protection based on the active detection strategy so as to overcome the limitations of traditional identification method. By using the DC fault ride-through control strategy of the hybrid MMC sub-module, the fault current at the converter station port is limited. Based on the high controllability of MMC, the sinusoidal fault detection signals with the same frequency are injected into the line at each converter station port. With the idea of model recognition, according to the fact that the capacitance model condition is satisfied with the detected signals at both ends when the external faults occur while not when the internal faults occur, the spearman correlation coefficients is introduced. The correlation discriminant of capacitance model is constructed to realize the fault area discrimination of DC power grid. The simulation results show that the active detection protection schemes proposed in this paper can accurately identify the fault area of DC grid with higher fault resistance and lower sampling rate.