Single-ended Fault Location Method for Overhead Cable Mixed Lines Connected with MMC-HVDC System

Accurate and reliable fault location technique is essential to the fault recovery of the AC overhead cable mixed lines connected with a modular multilevel converter based high-voltage direct current (MMC-HVDC) system. Control strategies for the configuration of MMC determine its output characteristics and will affect the performance of the existing fault location methods. Considering the influence of the converter control strategies on the fault compound sequence network of the mixed lines, a novel single-ended fault location method is proposed. Due to the influence of the negative-sequence current restraint strategy configurated in MMC, the negative-sequence network only contains the traditional AC side after the fault. The formed single-ended network makes the voltage set and the negative-sequence current along the mixed lines be in the same phase merely at the fault point. By using this unique boundary condition, the fault location can be realized according to the characteristic that the phase difference function is smallest at the fault point. A model of a flexible AC/DC hybrid transmission system is built in PSCAD/EMTDC. A large number of simulation results verify the effectiveness of the proposed method and its advantages in location accuracy, transition resistance and interference endurance ability. © 2020 Automation of Electric Power Systems Press.