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Power conversion device and control method thereof

  • US 8,059,434 B2
  • Filed: 07/21/2009
  • Issued: 11/15/2011
  • Est. Priority Date: 12/08/2008
  • Status: Active Grant
First Claim
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1. A power conversion device, for converting a direct-current (DC) voltage to an alternating current corresponding to an alternating-current (AC) voltage according to the AC voltage, comprising:

  • a power conversion unit, for converting the DC voltage to a high-frequency current having two envelops corresponding to the waveform of the AC voltage, the power conversion unit comprising;

    a DC to AC conversion circuit, for converting the DC voltage to a converted voltage, wherein the amplitude of the converted voltage is substantially equal to the level of the DC voltage, and the duty cycle of the converted voltage corresponds to the absolute value of the instantaneous value of the AC voltage, wherein the DC to AC conversion circuit comprises a full-bridge inverter having four active switch elements, the four active switch elements are turned on correspondingly under control of a pulse width modulation (PWM) control signal, and the four active switch elements being turned on correspondingly are for converting the DC voltage to the converted voltage; and

    an immitance conversion circuit, for converting the converted voltage to the high-frequency current by way of resonance;

    an output unit, comprising;

    an inductive circuit, for providing two induced currents according to the high-frequency current, wherein one induced current and the high-frequency current are in phase, and the other induced current and the high-frequency current are in antiphase;

    a full-wave rectifying circuit, for full-wave rectifying the two induced currents;

    an inverter circuit, for alternatively transferring the two full-wave rectified induced currents so as to output an output current; and

    a filter circuit, for filtering the output current to provide the alternating current; and

    a control unit, for providing the PWM control signal according to an instantaneous value of the AC voltage;

    wherein, the control unit obtains an alternating current command according to a product of the absolute value of the phasor of the AC voltage and a DC current command, and the alternating current command corresponds to an instantaneous value of the alternating current;

    wherein, the control unit further obtains a feed-forward signal according to a product of the alternating current command and a gain value, the feed-forward signal represents an angle, and the gain value corresponds to a ratio between effective values of the AC voltage and the alternating current; and

    wherein, the control unit further provides the PWM control signal according to an angular frequency and the angle represented by the feed-forward signal, and the angular frequency corresponds to a resonance frequency of the immitance conversion circuit.

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