We Claim:
1. A power conversion device (100) comprising:
a power conversion main circuit (11;21) for converting power supplied from an AC power supply to a direct current; and
a control unit (200a;200b) that generates and outputs a PWM signal, the PWM signal being an on/off signal of a semiconductor switch that constitutes the power conversion main circuit (11;21), wherein
the control unit (200a;200b) includes
a carrier-wave generation unit (402) that generates and outputs a carrier wave having changes from a lower limit to an upper limit and from the upper limit to the lower limit for an integral number of times per one cycle of the AC power supply,
a modulation-wave command generation unit (401) that generates and outputs a modulation wave command based on an input voltage waveform command of the power conversion main circuit (11;21), and
a comparison unit (403) that compares the carrier wave with the modulation wave command to generate the PWM signal, wherein
the carrier wave has characteristics such that one change time from the lower limit to the upper limit and then returning to the lower limit is constant, and a time ratio between a change time from the lower limit to the upper limit and a change time from the upper limit to the lower limit changes periodically, and wherein
the carrier-wave generation unit (402) generates a periodical change of the time ratio for an odd number of times in one cycle of the AC power supply.
2. A power conversion device (100) comprising:
a power conversion main circuit (11;21) for converting power supplied from an AC power supply to a direct current; and
a control unit (200a;200b) that generates and outputs a PWM signal, the PWM signal being an on/off signal of a semiconductor switch that constitutes the power conversion main circuit (11;21), wherein
the control unit (200a;200b) includes
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a carrier-wave generation unit (402) that generates and outputs a carrier wave having changes from a lower limit to an upper limit and from the upper limit to the lower limit for an integral number of times per one cycle of the AC power supply,
a modulation-wave command generation unit (401) that generates and outputs a modulation wave command based on an input voltage waveform command of the power conversion main circuit (11;21), and
a comparison unit (403) that compares the carrier wave with the modulation wave command to generate the PWM signal, wherein
the carrier wave has characteristics such that one change time from the lower limit to the upper limit and then returning to the lower limit is constant, and a time ratio between a change time from the lower limit to the upper limit and a change time from the upper limit to the lower limit changes periodically, and wherein
the carrier-wave generation unit (402) generates a carrier wave in which a change from the lower limit to the upper limit and a change from the upper limit to the lower limit occur for an odd number of times per one cycle of the AC power supply.
3. The power conversion device (100) according to claim 1 or 2, wherein the carrier-wave
generation unit (402) generates a carrier wave in which a waveform thereof becomes
symmetrical before and after in a time axis direction, in one cycle of a periodical change of the
time ratio.
4. The power conversion device (100) according to any one of claims 1 to 3, wherein
the carrier-wave generation unit (402) includes
a spread-spectrum carrier-wave generation unit (407) that generates a carrier wave in which the time ratio changes periodically, and
a fixed-carrier-wave generation unit (408) that generates a carrier wave in which the time ratio is constant and does not change, and wherein
the carrier-wave generation unit (402) selects any of outputs from the spread-spectrum carrier-wave generation unit (407) and the fixed-carrier-wave generation unit (408), based on a signal obtained by monitoring a formation operating condition of the power conversion device (100) input from a formation control device provided outside of the control unit (200a;200b) or a control signal determined by the formation control device based on the formation operating
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condition of the power conversion device (100), and then outputs a selected output to the comparison unit (403).
5. The power conversion device (100) according to claim 4, wherein when number of power conversion devices (100a; 100b) connected to each of the main transformers (MTr1;Mtr2) to be operated is different, only the power conversion device (100a; 100b) connected to any one of the main transformers (MTr1;Mtr2) selects, as a carrier wave, an output of the spread-spectrum carrier-wave generation unit (407), and the remaining power conversion device (100a; 100b) selects an output of the fixed-carrier-wave generation unit (408) as a carrier wave.
6. An AC electric-vehicle drive system including a plurality of main transformers (MTr1;Mtr2) that output AC power from an AC overhead wire as an AC power supply to a plurality of output windings, the system comprising:
a power conversion main circuit (11;21) for converting power supplied from an AC power supply to a direct current; and
a control unit (200a;200b) that generates and outputs a PWM signal, which an on/off signal of a semiconductor switch that constitutes the power conversion main circuit (11;21), wherein
the control unit (200a;200b) includes
a carrier-wave generation unit (402) that generates and outputs a carrier wave having changes from a lower limit to an upper limit and from the upper limit to the lower limit for an integral number of times per one cycle of the AC power supply,
a modulation-wave command generation unit (401) that generates and outputs a modulation wave command based on an input voltage waveform command of the power conversion main circuit (11;21), and
a comparison unit (403) that compares the carrier wave with the modulation wave command to generate the PWM signal, and wherein
in power conversion device (100) that is at least connected to the power conversion main circuit (11;21),
the carrier wave has characteristics such that one change time from the lower limit to the upper limit and then returning to the lower limit is constant, and a time ratio between a change
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time from the lower limit to the upper limit and a change time from the upper limit to the lower limit changes periodically.
7. The AC electric-vehicle drive system according to claim 6, wherein the carrier-wave generation unit (402) generates a carrier wave in which a waveform thereof becomes symmetrical before and after in a time axis direction, in one cycle of a periodical change of the time ratio.
8. The AC electric-vehicle drive system according to claim 6 or 7, wherein the carrier-wave generation unit (402) includes
a spread-spectrum carrier-wave generation unit (407) that generates a carrier wave in which the time ratio changes periodically, and
a fixed-carrier-wave generation unit (408) that generates a carrier wave in which the time ratio is constant and does not change, and wherein
the carrier-wave generation unit (402) selects any of outputs from the spread-spectrum carrier-wave generation unit (407) and the fixed-carrier-wave generation unit (408), based on a signal obtained by monitoring a formation operating condition of the power conversion device (100) input from a formation control device provided outside of the control unit (200a;200b) or a control signal determined by the formation control device based on the formation operating condition of the power conversion device (100), and then outputs a selected output to the comparison unit (403).
9. The AC electric-vehicle drive system according to claim 8, wherein when number of
power conversion devices (100a; 100b) connected to each of the main transformers (MTr1;Mtr2)
to be operated is different, only the power conversion device (100a; 100b) connected to any one
of the main transformers (MTr1;Mtr2) selects, as a carrier wave, an output of the spread-
spectrum carrier-wave generation unit (407), and the remaining power conversion device (100a;
100b) selects an output of the fixed-carrier-wave generation unit (408) as a carrier wave.
Dated this 12 day of May 2016
DIGITALLY SIGNED
(D. Jayaseelan Solomon)
REG. No: IN/PA-324
of De Penning & De Penning
Agent for the Applicants
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