Power conversion device

Patent metadata

Field	Value
Publication number	US-9887539-B2
Application number	US-201514877260-A
Country	US
Kind code	B2
Filing date	Oct 7, 2015
Priority date	Oct 8, 2013
Publication date	Feb 6, 2018
Grant date	Feb 6, 2018

Abstract

A power conversion device includes an AC power source configured to output an AC voltage, a DC power source configured to output a plurality of DC voltages having different levels, an inverter configured to receive the AC voltage and the plurality of DC voltages and output an output voltage by boosting the AC voltage in a booster mode in accordance with first and second control signals, the booster mode being a mode in which a level of the AC voltage is smaller than a predetermined value, a reactor configured to smooth the output voltage of the inverter, and a control circuit configured to generate the first and second control signals using a first and second carrier signals having different frequencies, respectively, in the booster mode, and selectively output the first or second control signal in accordance with the level of the AC voltage from the AC power source.

First claim

What is claimed is:

1. A power conversion device, comprising:
a direct current (DC) power source configured to output a plurality of different DC voltages;
an alternating current (AC) power source configured to output an AC voltage;
an inverter configured to output an output voltage using the different DC voltages from the DC power source and the AC voltage from the AC power source in accordance with first and second control signals;
a reactor configured to smooth the output voltage from the inverter; and
a control circuit configured to
generate the first control signal from a first carrier signal having a first frequency and an output command voltage in a first condition,
generate the second control signal from a second carrier signal having a second frequency and said output command voltage in a second condition, the second frequency being higher than the first frequency, and
output the first and second control signals to the inverter, said first condition being a condition in which the AC voltage is smaller than the output command voltage and a voltage difference between the output command voltage and the AC voltage is smaller than a predetermined value, said second condition being a condition in which the AC voltage is smaller than the output command voltage and said voltage difference is greater than said predetermined value.

2. The power conversion device according to claim 1 , wherein the control circuit is configured to determine the first condition and second condition based on effective values of the output command voltage and the AC voltage.

3. The power conversion device according to claim 1 , wherein the control circuit is configured to determine the first condition and second condition based on instantaneous values of the output command voltage and the AC voltage.

4. The power conversion device according to claim 1 , wherein the control circuit is configured to set the first and second frequencies of the carrier signal so that maximum amplitudes of a ripple current flowing through the reactor when the inverter is operated with the first and second frequencies are substantially the same.

5. The power conversion device according to claim 1 , wherein the control circuit is configured to set the second frequency of the carrier signal in accordance with said voltage difference.

6. The power conversion device according to claim 1 , wherein the inverter is configured to operate until the AC voltage from the AC voltage source drops to 0V.

7. The power conversion device according to claim 1 , wherein the inverter configured to selectively output the AC voltage from the AC power source and one of the different DC voltages from the DC power source as the output voltage in the first and second mode.

8. The power conversion device according to claim 1 , wherein the inverter configured to output the AC voltage from the AC power source as the output voltage in a third mode.

9. The power conversion device according to claim 1 , wherein the plurality of different DC voltages include a positive-level voltage and a negative-level voltage, and the AC power source is connected to an intermediate potential point, between the positive and negative voltages, of the DC power source.

10. The power conversion device according to claim 9 , wherein
the inverter includes a switching element series circuit and a bidirectional switch having two ends,
the switching element series circuit is connected to both ends of the DC power source, and includes first and second switching elements that are connected in series, and first and second diodes that are respectively connected to the first switching element and the second switching element in reverse parallel, and
one end of the bidirectional switch is connected to a connection point of the first and second switching elements, and the other end of the bidirectional switch is connected to one end of the AC power source that has two ends, the other end of the AC power source being connected to the intermediate potential point of the DC power source.

11. The power conversion device according to claim 10 , wherein the first and second switching elements includes metal-oxide-semiconductor field-effect transistors (MOSFETs) each formed of a wide band gap semiconductor with either silicon carbide or gallium nitride as a material.

12. The power conversion device according to claim 10 , wherein the first and second diodes are each formed of a wide band gap semiconductor with either silicon carbide or gallium nitride as a material.

13. The power conversion device according to claim 10 , wherein the bidirectional switch is configured by connecting metal-oxide-semiconductor field-effect transistors (MOSFETs), each formed of a wide band gap semiconductor with either silicon carbide or gallium nitride as a material, in reverse parallel.

14. The power conversion device according to claim 10 , wherein the bidirectional switch includes diodes each formed of a wide band gap semiconductor with either silicon carbide or gallium nitride as a material.

15. A power conversion device, comprising:
an alternating current (AC) power source configured to output an AC voltage;
a direct current (DC) power source configured to output a plurality of DC voltages having different levels;
an inverter configured to receive the AC voltage from the AC power source and the plurality of DC voltages from the DC power source and output an output voltage by boosting the AC voltage from the AC power source in a booster mode in accordance with first and second control signals, said booster mode being a mode in which a level of the AC voltage from the AC power source is smaller than a predetermined value;
a reactor configured to smooth the output voltage from the inverter; and
a control circuit configured to
generate the first control signal using a first carrier signal having a first frequency and the second control signal using a second carrier signal having a second frequency that is different from the first frequency in said booster mode and
selectively output the first or second control signal in accordance with the level of the AC voltage from the AC power source.

16. The power conversion device according to claim 15 , wherein the inverter includes a plurality of switching elements configured to be switched by the first or second control signals in accordance with the level of the AC voltage from the AC power source in said booster mode.

17. The power conversion device according to claim 15 , wherein
the second frequency is higher than the first frequency, and
the control circuit is configured to generate the first control signal when a voltage difference between the AC voltage from the AC power source and the predetermined value is smaller than an other predetermined value, and generate the second control signal when said voltage difference is greater than the other predetermined value.

Assignees

• Fuji Electric Co Ltd

Inventors

• Wang Qichen
• Fujita Satoru

Classifications

• H02M7/537

  using semiconductor devices only, e.g. single switched pulse inverters · CPC title

• H02M5/4585

  having a rectifier with controlled elements · CPC title

• H02M2001/0093

  Electricity · mapped topic

• H02J3/00 Primary

  Circuit arrangements for AC mains or AC distribution networks · CPC title

• H02M7/487

  Neutral point clamped inverters · CPC title