Patent ID: 7733069

Claim:
A power converting apparatus which is connected to an electric power system, said apparatus comprising: a converting circuit, arranged to convert direct current power to alternating current power; a transforming circuit, arranged to transform voltage outputted from said converting circuit; a switch, arranged to make/break connection between said transforming circuit and the electric power system; a detector, arranged to detect a line voltage of the electric power system; and a controller, arranged to control operation of said converting circuit and transforming circuit, and to control connection of said switch, based on the detected line voltage of the electric power system and a connection state between said apparatus and the electric power system, wherein the transforming circuit comprises a relay and a plurality of secondary windings, and wherein the controller sends a first signal to the relay to connect the plurality of secondary windings in parallel when the detected line voltage has a first predetermined value, and sends a second signal to the relay to connect the plurality of secondary windings in series when the detected line voltage has a second predetermined value.