AUXILIARY POWER SUPPLY DEVICE FOR STATION BUILDINGS

A station building auxiliary power unit includes a start-of-operation determination unit 21 that determines, based on a first signal that represents information on a power flow direction indicating a direction of flow of electrical power between an AC distribution line electrically connecting to an electric vehicle and a substation for supplying AC power to the AC distribution line, whether first AC power on an AC distribution line side is to be transformed into second AC power usable by a load, and if it is determined that transformation is to be performed, generates and outputs a second signal, a voltage instruction value calculator 22 that calculates and outputs a voltage instruction value corresponding to the second signal, and a PWM signal generator 23 that generates, based on the voltage instruction value, a control signal for a power converter circuit operated upon transformation of the first AC power into the second AC power, and outputs the control signal.