An object of the invention is to provide a control technique capable of connecting a storage battery to a DC bus via a DC/DC converter and controlling charging and discharging of the storage battery by the DC/DC converter. A DC grid system according to the invention calculates a voltage command value of a DC bus using a present voltage of a storage battery and a target voltage of the storage battery, and provides the voltage command value as a command value for each of an AC/DC converter and a DC/DC converter (see FIG. 1).