Location Method of Pole-to-pole Short-circuit Fault for Flexible DC Grid Based on Simplified Model of Overhead Line; [基于架空线路简化模型的柔性直流电网双极短路故障定位法]

Accurately locating pole-to-pole short-circuit faults on DC side of multi-terminal flexible DC transmission system with modular multilevel converters (MMCs) is a key measure to ensure fast power recovery. In view of the problems of distance measurement for fault location and difficulties in obtaining the parameters of overhead lines, this paper proposes a location method of pole-to-pole short-circuit fault for the flexible DC grid based on a simplified R-L model of overhead lines. The unit resistance and inductance values in the fault state of overhead lines can be deduced through the presetting pole-to-pole short-circuit fault tests, so the R-L line model is obtained. Based on the model, the fault location formulas are derived, and the fault location can be calculated more accurately by using the measured voltage and current data from both ends of the short-circuit line. A four-terminal flexible DC system based on PSCAD/EMTDC is used to verify the effectiveness of the proposed location algorithm. The simulation results show that the proposed location algorithm has high precision and reliability, which is almost immune to the transition resistance and the transmission power of the system. At the same time, it also proves that the simplified R-L model has high precision. © 2020 Automation of Electric Power Systems Press.