Patent ID: 9712070
Date: 2017-07-18
CPC Classifications: H02M

Claim:
1. A power conversion device which performs power conversion between input terminals of multi-phase AC and output terminals of multi-phase AC, comprising: a voltage-transformer device including primary windings connected to the input terminals and secondary windings comprising pluralities of single-phase open windings that are insulated to each other; a plurality of converter cells including switching elements, each converter cell of which input ends are connected to both ends of each single-phase open winding, the converter cells' respective input ends are connected in mutually parallel fashion to the input terminal of each phase through the voltage-transformer device, and the converter cells' respective output ends are connected in mutually serial fashion to the output terminal of each phase, said converter cells each performing conversion between a single-phase AC and another single-phase AC; and a control circuit for controlling ON/OFF of the switching elements, the control circuit being configured to control a DC bus voltage in each of the converter cells to be evenly balanced to each other; wherein the converter cells each comprise: a capacitor series connection; a converter that converts a single-phase AC voltage from the input ends into a three or more-level DC voltage and outputs it to the capacitor series connection; and an inverter that converts a DC voltage from the capacitor series connection into a single-phase AC voltage and outputs it to the output ends; wherein the control circuit is configured to: control a DC bus voltage that is a voltage of the capacitor series connection in each of the converter cells, to have a predetermined bus-voltage command value, control an average value of the DC bus voltages of the converter cells connected to mutually different phases of the output terminals, and control an input-current active component of the primary windings of the voltage-transformer device so that the average value becomes the predetermined bus-voltage command value.