A system of an interconnected inverter includes an inverter that converts DC power from a DC power supply into AC power and provides AC power to an AC power line, an RDC that converts a voltage value obtained by a voltage sensor into electrical angle information that shows a phase angle of an output voltage, the voltage sensor obtaining a voltage value of an output voltage from the inverter to a power grid, and an ECU that controls the inverter to provide an alternating current in synchronization with an alternating current that flows through the AC power line by using timing at which an angle shown in the electrical angle information given from the RDC attains to a prescribed angle. Extra cost for diversion can be reduced.