一种基于电压反馈控制的配电网短路故障柔性限流方法

在短路故障发生初期快速检测出故障并对短路电流进行限制,有利于电力系统安全稳定运行。采用电流半周波曲线与时间轴围成的面积作为判据进行短路故障早期检测,结合配电网短路故障特征与级联H桥变流器输出特性,提出了将3个单相级联H桥多电平变流器应用于配电网短路故障柔性限流。所提限流装置采用电容耦合的方式实现并网。选取电压信号作为反馈量,采用适当的控制方法使装置输出合适的电压以达到限制故障电流的目的。仿真结果表明,在短路故障早期检测的基础上,所提方法能实现对故障电流首个峰值的抑制,减小危害,减轻断路器的开断负担,且投入限流时无需进行故障选相。

A Flexible Current Limiting Method of Distribution Network Short Circuit Fault Based on the Voltage Feedback Control

The short circuit current can be limited quickly after being detected in the incipient stage of short circuit fault,in this case,the operation safety of power system can be ensured.In this paper,the area surrounded by current half-cycle curve and the time axis is taken as the criterion of early detection on short circuit fault.Combining the characteristics of distribution network short circuit fault with the output features of cascaded H-bridge converter,a method based on three single-phase cascaded H-bridge multi-level converters is proposed in flexible short-current limiting.These converters are connected to the grid via coupled capacitors.The voltage signal is selected as the feedback so that the converters can generate output voltage to achieve the goal of limiting fault current using an appropriate control method.The simulation results show that based on the early detection,the proposed method can suppress the first peak value of the fault current to mitigate the harms and relieve the burden of circuit breaker.In addition,the selection of faulty phases is unnecessary.