When the power is normally supplied from the commercial power supply, the storage battery is charged by reducing the DC voltage by the charge/discharge chopper. The switching unit is provided in the previous stage of the converter. When the commercial power supply is in an abnormal state, the three-phase AC converter is operated as three discharge choppers connected in parallel by supplying the power of the storage battery to the converter and boosting the power by the switching element included in the converter. The power of the storage battery is boosted by the charge/discharge chopper, and a part of the discharging power is supplied. One three-phase AC reactor is provided in the previous stage of the converter, and the three-phase AC reactor has three coils, magnetic leg iron cores having the coils winding around them, and one leg without a coil winding around it connected in parallel.