An electric power conversion system includes: an inverter; a voltage converter including a high-voltage end connected to a direct-current power source and a low-voltage end connected to the inverter; and a controller. The controller is configured to control switching elements such that a voltage of the low-voltage end becomes lower than a voltage of the high-voltage end in a first state. The controller is configured to control the switching elements such that the voltage of the low-voltage end becomes equal to the voltage of the high-voltage end in a second state.