Station-building power supply device

The station-building power supply device includes a capacitor unit that stores therein surplus regenerative power, a first power conversion unit that performs DC/DC power conversion, and a second power conversion unit that converts DC power. A first voltage threshold for detecting the occurrence of surplus regenerative power is set and a first SOC threshold for detecting whether the capacitor unit can discharge is set. The first power conversion unit is controlled such that power is supplied from the feeder to the capacitor unit to charge the capacitor unit when the feeding voltage exceeds the first voltage threshold, and the second power conversion unit is controlled such that power is supplied from the capacitor unit to the station loads when the SOC of the capacitor unit exceeds the first SOC threshold.