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Power converting apparatus

  • US 7,577,007 B2
  • Filed: 11/29/2006
  • Issued: 08/18/2009
  • Est. Priority Date: 12/27/2005
  • Status: Active Grant
First Claim
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1. A power converting apparatus comprising:

  • a single-phase multiplex converter connected to a load via a reactor to provide electric power to the load, said single-phase multiplex converter including a first single-phase inverter to which a maximum DC source voltage is supplied and at least one second single-phase inverter, said first single-phase inverter outputting voltage pulses at a rate of one pulse per half period of a reference AC voltage, said first and at least one second single-phase inverters being connected in series at AC output sides of said single-phase inverters, wherein said first and at least one second single-phase inverters convert DC power fed from a DC power supply into AC power; and

    a control unit for controlling said single-phase multiplex converter to produce an output voltage having a quasi-sinusoidal waveform simulated by the sum of output voltages of respective single-phase inverters, said control unit including a current controller for regulating an output current of said single-phase multiplex converter to follow a target current which is determined in accordance with the load, whereinsaid current controller drives said at least one second single-phase inverter such that the output current of said single-phase multiplex converter follows the target current,said control unit includesa central processing unit having a mathematical processing capability, anda control circuit including a digital signal processing circuit and an analog circuit including a hysteresis comparator circuit having an ordinary range of hysteresis,said central processing unit outputs a current signal corresponding to the target current,said current controller regulates the output current using said control circuit,said current controller generates a control signal which is supplied to said at least one second single-phase inverter so that the output current of said single-phase multiplex converter increases and decreases within the ordinary range of hysteresis, andsaid hysteresis comparator circuit has a marginal range of hysteresis encompassing the ordinary range of hysteresis and, if the output current of said single-phase multiplex converter goes out of the ordinary range of hysteresis, said control unit makes a correction so that output current of said single-phase multiplex converter varies within the ordinary range of hysteresis.

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