A power conversion apparatus is provided which includes a power converter including a plurality of semiconductor switching elements which operate to perform power conversion, thereby to generate polyphase alternating current, an ac load circuit connected to an ac output side of the power converter, and a zero-phase power supply device connected to the ac load circuit. In this apparatus, the power converter, ac load circuit, and the zero-phase power supply device are connected in the form of a loop, so that voltage and current of the zero-phase power supply device provide zero-phase-sequence components when viewed from the ac output side of the power converter through the ac load circuit. The power converter performs time-sharing operations to supply and receive electric power to and from the ac load circuit, and supply and receive zero-phase-sequence power to and from the zero-phase power supply device.