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Power converter

  • US 5,621,628 A
  • Filed: 06/06/1996
  • Issued: 04/15/1997
  • Est. Priority Date: 06/13/1995
  • Status: Expired due to Fees
First Claim
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1. A power converter, comprising:

  • a converter;

    a three-level DC voltage source, composed of a series connected capacitors connected between outputs of said converter, to generate a positive potential, a neutral potential and a negative potential;

    a three-level NPC inverter connected to said three-level DC voltage source;

    a chopper circuit; and

    chopper control means for controlling said chopper circuit;

    said chopper circuit including,a series circuit of a first switching device and a second switching device connected between a positive potential point and a negative potential point of said three-level DC voltage source,a first diode connected in antiparallel with said first switching device,a second diode connected in antiparallel with said second switching device, anda reactor,an anode of said first switching device being connected to said positive side potential point of said three-level DC voltage source,a cathode of said first switching device being connected to an anode of said second switching device,a cathode of said second switching device being connected to said negative side potential point of said three-level DC voltage source,said reactor being connected between a neutral potential point of said three-level DC voltage source and a connecting point of said first and second switching devices;

    said chopper control means including,first voltage detecting means for detecting a first voltage between one of said capacitors,second voltage detecting means for detecting a second voltage between the other of said capacitors,voltage control means connected to receive said first voltage and said second voltage for comparing said first voltage with said second voltage to generate a voltage difference and for generating a voltage control output signal so that said voltage difference becomes zero, andcontrol means connected to receive said voltage control output signal for driving said first and second switching devices based on said voltage control output signal;

    whereby to suppress the fluctuation of said neutral potential of said three-level DC power source.

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