In the present invention, when configuring a control system of an inverter performing power conversion between AC and DC, a frequency computation is performed based on biaxial voltage amounts obtained through two current regulators in such a way that each of biaxial component currents obtained by detecting an AC circuit current and performing a rotational coordinate transformation matches each respective command value and phase information in synchronization with an electromotive force power supply of the AC circuit is obtained by integrating the frequency to perform the rotational coordinate transformation of the AC current and also the inverter is caused to operate by generating a PWM switching signal from the biaxial voltage amounts to perform necessary power conversion control.