基于主动探测式的柔性直流电网纵联保护

Pilot Protection of Flexible DC Grid Based on Active Detection

为了提高柔性直流线路保护的可靠性和灵敏度,确保直流电网故障区域的准确甄别。文中考虑传统模型识别思想的优势和局限性,结合主动探测式策略,提出基于主动探测式的直流电网纵联保护原理。利用混合式MMC的直流故障穿越控制策略,将换流站端口故障电流进行限制,在此基础上利用MMC的高可控性,分别在各个换流站端口注入相同频率的正弦式故障探测信号。利用模型识别思想,根据两端探测信号在区外故障时满足电容模型而区内不满足的特点,引入斯皮尔曼相关性系数,构造电容模型相关性判别式,实现直流电网故障区域判别。仿真结果表明,文中提出的主动探测式保护方案能够准确地识别出直流电网故障区域,具备较高耐受过渡电阻性能,且对采样率要求低。

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.