A SVC control section detects a bus voltage from an instrument transformer, and adjusts reactive power generated by a SVC according to the detected bus voltage. A cooperative control section generates a control command for controlling the interconnection and parallel-off of a phase lead capacitor and a phase lag reactor on the basis of the amount of reactive power generated by the SVC and the bus voltage detected by the instrument transformer and a voltage sensor. A voltage comparator compares the bus voltage with a predetermined threshold voltage set to a voltage lower than a lower limit value of a steady state fluctuation range of the bus voltage and outputs the comparison result to a circuit breaker control section. When the bus voltage is lower than the threshold voltage, the circuit breaker control section locks the control command from the cooperative control section.