PURPOSE:To properly correct reactive power as viewed from an incoming point, by producing reactive power component generated from a dependent load, and by adding the component to the reactive power value of a main load detected by a reactive power compensator. CONSTITUTION:Current is received from a power source 1 via a power transformer 3, and is fed to a load 4. Reactive power generated from the load 4 is compensated for by an active type reactive-power compensator 5. In other words, load current IF and incoming voltage VS are detected, and by an instantaneous effective/reactive power detecting circuit 12, effective power and reactive power are found, and compensated current is found by a three-phase instantaneous-current reference arithmetic circuit 14, and via a current controlling circuit 16, a PWM controlling circuit 17 is driven. To this circuit, a reactive power correcting signal generating circuit 21 is added, ant the voltage reference VS' of an incoming point and the rectifying/smoothing value of the incoming voltage are compared with each other, and a correction value for signal according to the value of a difference between both the compared ones which is divided by a reactance in power-supply system is added to a reactive power detection value.
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