Patent ID: 7485987

Claim:
A power converting device comprising: a plurality of single-phase inverters, each single-phase inverter receiving DC power from a respective DC power supply and producing AC power at an AC-output side, the AC-output sides of the single-phase inverters being connected in series; and a control device for controlling each of the single-phase inverters to deliver an output current corresponding to a predefined output current, the plurality of single-phase inverters producing an output voltage that is the sum of respective output voltages generated by the single-phase inverters in response to control by the control device, wherein the control device includes: a basic gradational level calculator for calculating a basic gradational level of the output voltage of the plurality of single-phase inverters based on a reference voltage, a gradational level correction value calculator for calculating a gradational level correction value for correcting the basic gradational level so that the output current of the plurality single-phase inverters follows the predefined output current, a gradational output voltage level calculator for calculating a gradational output voltage level for the plurality of single-phase inverters by correcting the basic gradational level using the gradational level correction value, and an inverter control processor for outputting control signals to the plurality of single-phase inverters in accordance with the gradational output voltage level.