PURPOSE: To achieve an optimal design with respect to the capacity and the response of device by providing a current command means which weight the positive phase reactive component and negative phase component of a basic wave detected through a current detecting means and operating a current command for a power converter.

CONSTITUTION: A PLL circuit 30A is synchronized in phase with the positive fundamental component of system voltage Vs while a PLL circuit 30B is synchronized in phase with the negative fundamental component of the system voltage Vs. With respect to the negative phase of the fundamental component, load current Ih is fed to 3-phase/2-phase converting section 21. The proportional gains ka, kb at amplifying sections 25A, 25B are set such that 1>=ka>kb. When the compensation degree of the reactive fundamental component is increased while that of the negative fundamental component is decreased, fluctuation of actual instantaneous power caused by the negative phase component is suppressed and the capacity of energy storing element in a power converter can be reduced resulting in the achievement of economic design of the entire compensator.