To enable a generator power source and a solar generation system to be operated in parallel when a commercial power source is cut off and to contrive the space saving.

For a commercial power source 11 and a generator power source 17, the circuit is switched over to the side of the generator power source 17 at power failure of the commercial power source 11 by a switch 18, and a load 31 is supplied with power at all times from the generator power source 17 and a photovoltaic generation system 10. When a switch signal receiving circuit 33 receives the signal of the switch 18 at a power failure, contacts 33a1-33a5 are closed individually in response to conditions. For example, the signal from a generator linked voltage/frequency synchronized operation range signal generator 35 is used to control an inverter 32a via the contact 33a2.