To minimize voltage fluctuation and flicker of an receiving end without enlarging device capacity particularly.

A compensation current value I* synthesizing a reactive current, a reversed phase current, and a harmonic current separated from a load current IL is multiplied by a compensation gain KALL to obtain a compensation current command I1*. By changing the compensation gain KALL like KALL-K and KALL+K at this time, voltage fluctuation of each case is calculated via simulated system impedances 19a-19c. Compensation gain is determined to perform control by repeating the operation that the compensation gain by which the obtained voltage fluctuation becomes the smallest is used as the next time compensation gain.