A switch circuit includes n switching elements (n≥2) connected in series between an input node and an output node. A control device is configured to convert DC power in a power storage device into AC power synchronized with AC power supplied from an AC power supply during a normal state and supply the AC power to the output node, by controlling a power converter, when an abnormality of at least one of the AC power supply and the switch circuit is sensed in a state where the control device outputs conduction commands for the n switching elements. The control device is further configured to produce cutoff commands for cutting off the n switching elements during execution of power conversion in the power converter, and sense a cutoff abnormality of the switch circuit based on terminal-to-terminal voltages of the n switching elements during production of the cutoff commands.