Patent ID: 8625307
Filing Date: 2014-01-07
Classification: H02M

Abstract:
1. A power converting apparatus comprising: a three-phase three-level inverter connected between positive and negative terminals of a first DC power supply, one or a plurality of single-phase inverters which are connected in series with an AC output line of each phase of said three-phase three-level inverter, and a control device, said power converting apparatus being configured such that the sums of output voltages of said three-phase three-level inverter and output voltages of said respective single-phase inverters are output to a load through a smoothing filter and a voltage of second DC power supplies, each of which is configured with a DC capacitor and which are DC input power supplies of said single-phase inverters, is lower than a one-level voltage of said three-phase three-level inverter; wherein: said control device controls said three-phase three-level inverter in such a manner that each phase of said three-phase three-level inverter outputs a voltage at a rate of one pulse per half cycle of an output voltage to a corresponding phase of said load as a primary voltage pulse, said control device controls a pulse width of the primary voltage pulse output by said three-phase three-level inverter such that an output power balance during half cycle or one cycle of said individual single-phase inverters becomes zero, and said control device controls said individual single-phase inverters by (pulse width modulation) PWM so that output voltages supplied to individual phases of said load form sine waves of which phases are offset by 2π/3 from one phase to another, the sine waves having the same peak value, and the output voltages supplied to the individual phases of said load being referenced to a point having a zero DC potential or a fixed DC potential with respect to a reference potential of said first DC power supply.