Fault location of DC grid is one of the crucial techniques for safe and reliable operation of power systems. This paper presents a single-ended fault location method for DC lines in bipolar high-voltage direct current transmission based on modular multi-level converter (MMC-HVDC) system, which focuses on short-distance DC lines. Firstly, the fault path after tripping is considered to be equivalent to a two-order RLC series circuit, and the initial voltage of the fault path is provided by the residual voltage of MMC submodule capacitors. Then, the differential equation of the fault path is established in time domain. Finally, by sampling the voltage and current signal of single-end MMC submodule capacitor and the voltage signal of the MMC bridge arm inductor, the fault distance, as well as the fault resistance, is obtained. A bipolar MMC-HVDC model is built by PSCAD/EMTDC, and the proposed method is verified by MATLAB. The simulation results show that the proposed method can accurately locate the fault position and is almost immune to the fault resistance.

中文翻译：

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双极MMC-HVDC系统直流线路单端故障定位方法

直流电网故障定位是电力系统安全可靠运行的关键技术之一。本文提出了一种基于模块化多电平转换器（MMC-HVDC）系统的双极高压直流输电直流线路单端故障定位方法，主要针对短距离直流线路。首先，将跳闸后的故障路径视为等效于一个二阶RLC串联电路，故障路径的初始电压由MMC子模块电容器的剩余电压提供。然后，建立故障路径的时域微分方程。最后，通过对单端MMC子模块电容的电压电流信号和MMC桥臂电感的电压信号进行采样，得到故障距离，以及故障电阻。用PSCAD/EMTDC建立了双极MMC-HVDC模型，并通过MATLAB验证了所提出的方法。仿真结果表明，该方法能够准确定位故障位置，并且几乎不受故障电阻的影响。