Power converter for converting DC voltage into AC phase voltage having three levels of positive, zero and negative voltage
First Claim
Patent Images
1. A power converter comprising:
- capacitors connected in series so as to divide a DC voltage;
a DC/AC converter for converting said DC voltage charged on said capacitors into an AC output phase voltage having positive, zero and negative levels, which said output phase voltage is supplied to a load; and
a modulation means for supplying said DC/AC converter with a signal so as to generate a sequence of alternating output pulses with interleaving zero-level pulses between a half cycle of a fundamental wave of said output phase voltage of said DC/AC converter and adjusting a width of only either one of the positive and negative output pulses in said half cycle of the fundamental wave of said output phase voltage depending upon a DC component of a difference between voltages on said capacitors.
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Abstract
An apparatus for a three-level DC/AC converter, in which the width of output pulse having the same polarity as the fundamental wave of the converter output phase voltage is adjusted depending upon the DC component of a differential voltage between two DC voltages in a dipolar modulation system of the converter. Whereby, the imbalance of DC components between the two DC voltages is easily and effectively suppressed.
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Citations
18 Claims
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1. A power converter comprising:
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capacitors connected in series so as to divide a DC voltage; a DC/AC converter for converting said DC voltage charged on said capacitors into an AC output phase voltage having positive, zero and negative levels, which said output phase voltage is supplied to a load; and a modulation means for supplying said DC/AC converter with a signal so as to generate a sequence of alternating output pulses with interleaving zero-level pulses between a half cycle of a fundamental wave of said output phase voltage of said DC/AC converter and adjusting a width of only either one of the positive and negative output pulses in said half cycle of the fundamental wave of said output phase voltage depending upon a DC component of a difference between voltages on said capacitors. - View Dependent Claims (2)
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3. A power converter comprising:
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capacitors connected in series so as to divide a DC voltage; a DC/AC converter for converting said DC voltage charged on said capacitors into an AC output phase voltage having positive, zero and negative levels, which said output phase voltage is supplied to a load; and a modulation means for supplying said DC/AC converter with a signal so as to generate a sequence of alternating output pulses with interleaving zero-level pulses between a half cycle of a fundamental wave of said output phase voltage of said DC/AC converter and adjusting a width of only said output pulses having a same polarity as said fundamental wave of said output phase voltage depending upon a DC component of a difference between voltages on said capacitors. - View Dependent Claims (4, 5, 6)
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7. A power converter comprising;
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capacitors connected in series so as to divide a DC voltage; and a DC/AC converter for converting said DC voltage charged on said capacitors into an AC output phase voltage having positive, zero and negative levels, which output phase voltage is supplied to a load; and a modulation means for supplying said DC/AC converter with a signal so as to generate a sequence of alternating output pulses with interleaving zero-level pulses between a half cycle of a fundamental wave of said output phase voltage of said DC/AC converter and adjusting a width of only said output pulses having a polarity opposite to said fundamental wave of said output phase voltage depending upon a DC component of a difference between a divided said DC voltage on said capacitors. - View Dependent Claims (8, 9, 10)
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11. A power converter comprising:
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capacitors connected in series to divide a DC voltage; a DC/AC converter for converting direct current fed from said capacitors into an AC output phase voltage having positive, zero and negative levels; and a modulation means which divides a fundamental wave voltage instruction formed based on an amplitude instruction of a voltage and a frequency instruction output to said DC/AC converter into a positive-side voltage instruction for generating positive output pulses on a phase of said DC/AC converter and a negative-side voltage instruction for generating negative output pulses, and then forms a signal based on said positive-side and said negative-side voltage instructions to turn on or off switching elements that constitute said DC/AC converter, distributes distribution signals corresponding to DC components of a difference between voltages on said capacitors depending upon a polarity of said fundamental wave voltage instruction, and superposes said distribution signals on one of said positive-side voltage instruction and said negative-side voltage instruction. - View Dependent Claims (12, 13, 14)
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15. An apparatus for controlling an electric car comprising:
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capacitors connected in series to divide a DC voltage; a DC/AC converter for converting direct current fed from said capacitors into an AC output phase voltage having positive, zero and negative levels; an AC motor driven by said output phase voltage from said DC/AC converter; and a modulation means which has a first modulation mode in which said DC/AC converter is supplied with a signal for generating a sequence of alternating output pulses with interleaving zero-level pulses in response to a voltage instruction and a frequency instruction fed to said DC/AC converter, a sequence of pulses corresponding to half a cycle of a fundamental wave of said output phase voltage of said DC/AC converter, and a second modulation mode in which said DC/AC converter is supplied with a signal for generating a sequence of output pulses different from a sequence of output pulses of said first modulation mode and adjusting a width of only either one of a positive and negative output pulse in a half cycle of said fundamental wave of said output phase voltage depending upon an imbalance of DC components between a divided said DC voltages in said first modulation mode and in said second modulation mode. - View Dependent Claims (16, 18)
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17. An apparatus for controlling an electric car comprising;
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capacitors connected in series to divide a DC voltage; a DC/AC converter for converting direct current fed from said capacitors into an AC output phase voltage having positive, zero and negative levels; an AC motor driven by said output phase voltage from said DC/AC converter; and a modulation means which has a first modulation mode in which said DC/AC converter is supplied with a signal for generating a sequence of alternating output pulses with interleaving zero-level pulses in response to a voltage instruction and a frequency instruction fed to said DC/AC converter, said sequence corresponding to half a cycle of a fundamental wave of said output phase voltage of said DC/AC converter, and a second modulation mode in which said DC/AC converter is supplied with a signal for generating a second sequence of output pulses different from said sequence of said first modulation mode and adjusting only a width of an output pulse which has a same polarity as said fundamental wave of said output phase voltage of said DC/AC converter depending upon a DC component of a difference between a divided said DC voltage.
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Specification