Patent ID: 7692415

Claim:
A reactive power control apparatus for an AC power system, wherein a reactive power compensation device, and a compensation capacitor device including at least one compensation capacitor are connected to a system bus of the AC power system, and reactive power is controlled in accordance with a fluctuation of an AC voltage of the system bus, comprising: a compensation capacitor control device which controls a connection status of the compensation capacitor with respect to the system bus; wherein said compensation capacitor control device includes: a voltage drop abnormality clearing decision circuit which outputs a voltage drop abnormality clearing signal having one level after a voltage drop abnormality state of the AC power system has been cleared; and a bus detection voltage output means for receiving the voltage drop abnormality clearing signal and for outputting a bus detection voltage after clearing of a voltage drop abnormality as corresponds to the AC voltage of the system bus on the basis of the voltage drop abnormality clearing signal having the one level, wherein the bus detection voltage, after clearing of the voltage drop abnormality, is varied according to the AC voltage of the system bus after that the voltage drop abnormality state of the AC power system has been cleared; and a compensation capacitor control circuit which controls the connection status of the compensation capacitor with respect to the system bus on the basis of a voltage level of the bus detection voltage after the clearing of the voltage drop abnormality.