A double closed-loop PID controller, consisting of voltage regulating loop ( internal loop) and power factor correction loop ( external loop), was used to both correct the power factor and regulate the voltage fluctuation. 采用双闭环PID控制结构,内环为电压调节,外环为功率因数校正,使SVC装置能同时达到功率因数校正和改善电压的目的。