An Adaptive Restart Method for DC Transmission Line in LCC-HVDC System

DC-line fault recovery sequence (DFRS) is widely implemented in LCC-HVDC system to realize fast recovery in case of temporary fault. When permanent fault occurs, restart still happens several times as preset, resulting in repeated impacts and reducing the stability and reliability of the system. An adaptive restart for DC line fault is studied in this paper to deal with this problem. Firstly, the converter valves states and DC voltage characteristics under temporary fault and permanent fault are analyzed respectively. Then, a method based on DC voltage control is proposed to distinguish different fault states. Current DFRS strategy is improved by adding this process, through which the fault pole will only restart after the temporary fault disappearing, while directly blocked when a permanent fault is recognized. Fault handling time can be shortened and negative effects of DC line fault are minimized. The simulation results verify feasibility and effectiveness of proposed method.