基于波形相关性的直流配电网主动式接地故障选线

采用小电流接地方式的直流配电网发生单极接地故障时故障特征较弱，为准确可靠选出故障线路，文中提出基于注入信号波形相关性的接地故障选线方法。所提方法首先将预先设计的附加控制策略施加于直流配电网的模块化多电平换流器(modular multilevel converter，MMC)上，实现探测信号注入。然后结合零模网络，得出故障特征为：各条健全馈线首端计算的特定频率零模电流流向相同、而其与故障馈线首端计算的零模电流流向相反。最后，基于该故障特征设计选线判据，引入皮尔森相关性系数比较各条馈线的归一化零模电流和总归一化零模电流的相关性，根据健全馈线相关性系数接近于1、故障馈线相关性系数接近于-1的特征完成故障选线。仿真结果表明，所提方法在高阻接地故障下能可靠识别发生在母线或各条馈线任意位置的单极接地故障。

An active grounding fault line selection method for DC distribution network based on waveform correlation

The fault characteristics of direct current (DC) distribution network with small current grounding mode are inconspicuous when single-pole grounding fault occurs. In order to accurately and reliably select the fault line,a grounding fault selection method based on the injected signal waveform correlation is proposed. Firstly,a predesigned additional control strategy is applied to the modular multilevel converter (MMC) of the DC distribution network to achieve the detection signal injection. Then,in combination with the zero-mode network,the fault characteristics are as follows. The specific frequency zero-mode current flow at the beginning of each sound feeder are same,which are opposite to zero-mode current flow at the beginning of the faulty feeder. Finally,based on this fault characteristic,the fault selection criterion is designed,and the Pearson correlation coefficient is introduced to compare the correlation between the normalized zero-mode current of each feeder and the total normalized zero-mode current. The fault selection is completed based on the characteristics that the correlation coefficient of the sound feeder is close to 1 and the correlation coefficient of the faulty feeder is close to -1. The simulation results show that the proposed method can reliably identify single-pole grounding fault occurring at any location on the bus or each feeder under high-resistance grounding fault.