直流配电网单极接地故障定位方法

Method of locating single-pole-to-ground fault in DC distribution system

本文首先分析了换流器直流侧经钳位电阻中点接地的优势。在此基础上,建立了直流配电网单极接地故障的模型,分析了故障电流的特征,发现故障暂态电流为线路分布电容充、放电电流,距离故障点越近,流过的暂态电容电流越大。利用快速傅里叶变换提取暂态电容电流特征频段的总能量,通过比较各分支的总能量确定故障点方向,并利用树状图搜索确定故障区间。进而在故障区间上利用负荷电流和故障区间端点的残余电压计算故障距离。在Simulink/Matlab中搭建了数字仿真模型,仿真结果验证了该方法的有效性。在实验室进行了物理模拟实验,对本文方法进行了验证。

The paper presents a proposal to ground the dc side of converter through the midpoint of clamping resistors and discusses its advantages. By establishing the fault model,the characteristics of fault current are analyzed,which imply that the fault current is formed by the stray capacitor current. The nearer the node is to the fault point,the larger the transient fault current is. Fast Fourier transform（ FFT） is applied to obtain the overall energy of transient capacitor current in the characteristic frequency band at each branch. By comparing the overall energy,the fault section can be identified with the assistance of tree graph. Finally,the fault distance in fault section is calculated with the load current and the residual voltage at one terminal of the fault section. Simulations in the Simulink /Matlab verify the effectiveness of the algorithm. Physical simulation experiments are carried out,which verify the algorithm further.