基于电流信息的三端环形直流配电网保护策略

针对三端环形直流配电网发生故障时故障电流上升快且幅值大而导致的区内外故障判别困难问题,提出了一种基于电流信息的保护策略。主保护提出在故障暂态下先闭锁换流器,停止各端电源功率传输,利用此时线路中故障电流的方向判别区内外故障;为了弥补主保护在换流器出现闭锁故障时拒动的缺陷,配备以故障电流突变量变化率极性为判据的后备保护,构成三端环形直流配电网的保护策略;在PSCAD/EMTDC环境中搭建三端环形直流配电网,在发生极间短路故障工况下进行仿真,仿真结果表明:保护策略中的主保护系统能有效判断故障线路,其他线路断路器不会误动;当主保护拒动时,后备保护启动,判别区内区外故障,保证配电网安全运行,从而验证了所提保护策略的有效性。

Protection Strategy for Three-terminal Annular DC Distribution Network Based on Current Information

In view of the problems such as rapid rise and large amplitude of fault current and difficultly distinguishing the faults in and out of the region when three terminal annular DC distribution network generates faults, a protection strategy based on current information is proposed. The main protection proposes to firstly block the convertor in fault transient state, stop the transmission of each end of power supply and distinguish the faults in and out of the region based on the fault current direction in the line at this time. In order to make up the defect of resistance of the main protection in the case of blocking fault of the convertor, the backup protection based on abruptly changing rate polarity of fault current is provided, and the protection strategy of three terminal annular DC distribution network is constituted. In PSCAD/EMTDC environment, three terminal annular DC distribution network is built, and the simulation is carried out under the condition of inter electrode short circuit fault. Simulation results show that the main protection system in protection strategy can effectively judge the fault line, and the circuit breakers of other lines will not be misused. When the main protection is blocked, the backup protection is started to identify the faults in and out of the region and ensure the safe operation of the distribution network so as to verify the effectiveness of the proposed protection strategy.