位移过电压抑制转接地故障消弧的柔性电源控制方法

柔性电源具备中性点位移过电压抑制和接地故障消弧功能,对配电网安全稳定运行至关重要,但是位移过电压抑制在线切换到故障消弧时,存在柔性电源输出过流问题.针对切换瞬间的过流问题,提出了一种幅值差分越限主动闭锁的控制方法,实现柔性电源运行模式的可靠切换.首先,介绍柔性电源运行机理,提出一种共用电流内环的闭环控制方法.其次,建立2种运行模式下的等效电路模型,分析切换过程中的过电流原理,通过位移过电压抑制模式下电压突变量是否越限来判定切换状态,进而闭锁交流输出直至收到上层故障消弧指令,柔性电源转为接地故障消弧模式.然后,仿真分析了2种运行模式及其切换控制方法的合理性.最后,研制样机并在中国某66 kV电网得到应用,现场实测结果验证了该方法的可靠性和先进性.

Control Method of Displacement Overvoltage Suppression Switching to Ground Fault Arc-suppression for Flexible Power Source

Flexible power source has the functions of neutral point displacement overvoltage suppression and ground fault arc-suppression, which are essential for safe and stable operation of distribution networks. However, when the displacement overvoltage suppression is switched online to fault arc-suppression, the flexible power source has the problem of output overcurrent. Aiming at the overcurrent problem at the moment of switching, a control method of amplitude difference over-limit active blocking is proposed to realize the reliable switching of the flexible power source operation mode. First, the operation mechanism of flexible power source is introduced, and a closed-loop control method is proposed which shares the current inner control loop. Then, the equivalent circuit models are established in two operation modes, and the principle of overcurrent during the switching process is analyzed. The switching state is determined by whether the quantity of voltage sudden change exceeds the limit in the displacement overvoltage suppression mode. And then the AC output is blocked until the upper arc-suppression command is received, and the flexible power source switches to the ground fault arc-suppression mode. The simulation analyzes the rationality of the two operation modes and their switching control methods. Finally, a prototype is developed and applied in a 66 kV power grid of China, and the field test results verify the reliability and advancement of the proposed method.