To suppress a startup current to start a plurality of loads whose current is to be suppressed, using a power convertor.

The output power of a power storage battery equipment 3 is converted into an AC power with an AC-DC converter 4. To perform self-sustaining operation of a motor 7 and its auxiliary transformer 9, the AC-DC converter firstly starts the auxiliary transformer by soft-start control. It keeps the auxiliary transformer to a voltage V1 which can keep normal operation of the auxiliary equipment and can start with the start current of the motor suppressed, being lower than a nominal voltage V2 of a system. To start the motor, the voltage V1 is raised to the nominal voltage V2.