In a power conversion apparatus that boosts a solar light voltage, converts it to AC and supplies AC power to a load or system, a second inverter is connected in series to one of two terminals on the AC side of a first inverter that uses, as its DC source, a DC voltage boosted from a solar light voltage by a chopper circuit. A third inverter is connected in series to the other terminal. Then, output voltages of the second and third inverters are controlled to be equal, and an output voltage is provided by using the sum of the generated voltages of the first, second, and third inverters. Thus, a mid-point potential of the DC power source is made equivalent to an intermediate potential of the output voltage of the power conversion apparatus, that is, the mid-point potential (ground potential) of a system.