基于新型柔性故障限流器的多端直流配电网故障隔离策略

Fault isolation strategy for multi-terminal DC distribution network based on novel flexible fault current limiter

针对多端直流系统故障电流峰值高、上升速度快以及无法保证非故障区域供电可靠性的问题,提出一种适用于中高压配电网的级联式新型柔性故障限流器与机械式直流断路器协同作用的故障隔离策略。首先通过微分欠压保护触发柔性故障限流器,实现极间电压箝位效果,抑制故障电流,提高直流系统故障隔离后的动态恢复特性。其次依据直流断路器的分断速度,实现故障限流器动作时间的灵活设置。利用断路器方向纵联保护信号保证故障区域换流站侧故障限流器的持续作用,直至直流断路器动作隔离故障。该策略还可避免换流站闭锁,降低断路器分断速度与开断容量要求,延长断路器使用寿命,提高系统供电可靠性。最后,在MATLAB/Simulink中搭建四端中压配电网模型,并通过仿真验证故障限流器的效果以及所提策略的可行性。

Aiming at the problems of high peak value of fault current,fast rising speed and unable to ensure the reliability of power supply in non-fault area in multi-terminal DC system,a fault isolation strategy based on the cooperation of a cascaded novel flexible current limiter and a mechanical DC circuit breaker is proposed,which is suitable for the medium and high voltage distribution network.Firstly,the flexible current limiter is triggered by differential undervoltage protection to achieve the effect of inter-pole voltage clamping,suppress the fault current and improve the dynamic recovery characteristics of DC system after fault isolation.Secondly,according to the breaking speed of DC circuit breaker,the action time of current limiter can be set flexibly.The directional pilot protection signal of the circuit breaker is used to ensure the continuous action of the current limiter at the converter station side in the fault area until the circuit breaker acts to isolate the fault.This strategy can also avoid the blocking of converter station,reduce the requirements of breaking speed and breaking capacity of circuit breaker,prolong the service life of circuit breaker and improve the reliability of system power supply.Finally,a four-terminal medium voltage distribution network model is built in MATLAB/Simulink,and the effect of current limiter and the feasibility of the proposed strategy are verified by simulation.