To reduce the impact of traveling wave velocity, wave head recognition, and LMD (Local Mean Decomposition) end effect and mode mixing on location accuracy, this paper presents a fault location method based on improved LMD for hybrid three-terminal HVDC transmission lines, which is not affected by wave velocity. Firstly, the improved LMD is used to get the time when the fault traveling wave first arrives at the four measuring terminals. Then the fault branch is identified according to the ratio of the time of the fault traveling wave arriving at the measuring terminal. Finally, the equation is listed according to the principle of traveling wave location and the measurement equation which is not affected by the wave velocity is deduced. A hybrid three-terminal HVDC transmission system model is built by PSCAD to simulate various faults and output fault data under various fault conditions. MATLAB is used to process the fault data and verify the location algorithm. The simulation results show that the location method proposed in this paper is not affected by fault distances, fault types, infeed levels and transition resistances. In addition, it has higher accuracy than LMD based on CSI (Cubic Spline Interpolation) algorithm, wavelet packet location algorithm and double-ended location method of using wave velocity calculation.

为降低行波速度、波头识别、LMD（Local Mean Decomposition）端部效应和模式混合对定位精度的影响，本文提出了一种基于改进LMD的混合三端高压直流输电线路故障定位方法。不受波速影响。首先，利用改进的LMD得到故障行波最先到达四个测量端的时间。然后根据故障行波到达测量端的时间比确定故障支路。最后根据行波定位原理列出方程，推导出不受波速影响的测量方程。利用PSCAD建立混合三端高压直流输电系统模型，模拟各种故障，输出各种故障条件下的故障数据。利用MATLAB对故障数据进行处理并验证定位算法。仿真结果表明，本文提出的定位方法不受故障距离、故障类型、馈电电平和过渡电阻的影响。此外，基于CSI（三次样条插值）算法、小波包定位算法和使用波速计算的双端定位方法，它比LMD具有更高的精度。进料水平和过渡阻力。此外，基于CSI（三次样条插值）算法、小波包定位算法和使用波速计算的双端定位方法，它比LMD具有更高的精度。进料水平和过渡阻力。此外，基于CSI（三次样条插值）算法、小波包定位算法和使用波速计算的双端定位方法，它比LMD具有更高的精度。