抑制电压过冲的新型SVC低电压保护控制策略

New SVC Low-voltage Protection Control Strategy to Suppress Voltage Overshoot

针对含静止无功补偿器SVC的电力系统在故障清除后的暂态过程中出现高电压的问题,在理论分析SVC引发电压过冲机理和常规低电压保护控制策略不足的基础上,提出抑制电压过冲的新型SVC低电压保护控制策略,即系统正常运行时先延时记录PI控制器输出电纳参考值与转换的触发角,在故障后将其锁定并屏蔽PI控制器的原输入与输出,然后输入锁定的触发角至触发控制环节准备脉冲信号,控制TCR输出感性无功功率,抵消故障清除后突增的容性无功功率以抑制电压过冲;同时根据锁定的电纳参考值计算出等效误差输入PI控制器,改变其输出,当退出SVC低电压保护控制时等于故障前的值,避免切换至恒压控制的过程中发生振荡。在PSCAD/EMTDC中的仿真结果表明,上述控制策略具有可行性和有效性。

Aiming at the problem of high voltage in the transient process after the fault clearance in the power system with static var compensator(SVC),based on theoretical analysis of the mechanism of SVC inducing voltage overshoot and the deficiency of conventional low-voltage protection control strategies,a new SVC low-voltage protection control strategy was proposed to suppress voltage overshoot.That is,when the system was running normally,the reference value of susceptance output by PI controller and the trigger angle of conversion were firstly recorded with delay,after the fault,they were locked and the original input and output of the PI controller were also shielded.Then the locked trigger angle was input into the trigger control link to prepare the pulse signal to control TCR to output inductive reactive power for offsetting the capacitive reactive power that increased suddenly after the fault clearance to suppress voltage overshoot.At the same time,the equivalent error was calculated according to the locked susceptance reference value,and it was input to the PI controller to change its output,which was equal to the value before the fault when exiting the SVC low-voltage protection control,to avoid oscillation during switching to constant voltage control.The simulation results in PSCAD/EMTDC show that the above control strategy is feasible and effective.