A power control apparatus includes a plurality of transformers configured to transform power generated by a plurality of solar cell strings, and a controller configured to control the transformers. The transformers each include a diode configured to prevent a reverse flow of power to be output from the transformer itself and a switch configured to open or close a connection between the solar cell string and an inverter. When a diode of one of the transformers has failed to prevent the reverse flow of the power to be output from the one of the transformers, the controller first opens the switches of all of the transformers and then closes the switches of the transformers other than the switch of the one of the transformers.