Power conversion device

Patent metadata

Field	Value
Publication number	US-9712070-B2
Application number	US-201314359649-A
Country	US
Kind code	B2
Filing date	Jun 4, 2013
Priority date	Jun 4, 2013
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A power conversion device includes transformers provided with primary windings connected to input terminals and secondary windings including pluralities of single-phase open windings that are insulated to each other; a plurality of converter cells connected to the secondary windings of the transformers; and a control circuit for controlling ON/OFF of switching elements. The converter cells are each include a converter and the inverter that are provided with the switching elements, in which their input ends are connected to the respective single-phase open windings, so that the input ends are connected in mutually parallel fashion, through the transformers, to the input terminal of each phase, and in which their output ends are connected in mutually serial fashion to an output terminal of each phase, to thereby perform three or more-level power conversion.

First claim

The invention claimed is:

1. A power conversion device which performs power conversion between input terminals of multi-phase AC and output terminals of multi-phase AC, comprising:
a voltage-transformer device including primary windings connected to the input terminals and secondary windings comprising pluralities of single-phase open windings that are insulated to each other;
a plurality of converter cells including switching elements, each converter cell of which input ends are connected to both ends of each single-phase open winding, the converter cells' respective input ends are connected in mutually parallel fashion to the input terminal of each phase through the voltage-transformer device, and the converter cells' respective output ends are connected in mutually serial fashion to the output terminal of each phase, said converter cells each performing conversion between a single-phase AC and another single-phase AC; and
a control circuit for controlling ON/OFF of the switching elements, the control circuit being configured to control a DC bus voltage in each of the converter cells to be evenly balanced to each other;
wherein the converter cells each comprise: a capacitor series connection; a converter that converts a single-phase AC voltage from the input ends into a three or more-level DC voltage and outputs it to the capacitor series connection; and an inverter that converts a DC voltage from the capacitor series connection into a single-phase AC voltage and outputs it to the output ends;
wherein the control circuit is configured to:
control a DC bus voltage that is a voltage of the capacitor series connection in each of the converter cells, to have a predetermined bus-voltage command value,
control an average value of the DC bus voltages of the converter cells connected to mutually different phases of the output terminals, and
control an input-current active component of the primary windings of the voltage-transformer device so that the average value becomes the predetermined bus-voltage command value.

2. The power conversion device of claim 1 , wherein the control circuit is further configured to take a balance among the DC bus voltages of the converter cells connected to mutually different phases of the output terminals, and control voltage command values of the inverters in the converter cells so that the plural DC bus voltages are evenly balanced to each other.

3. The power conversion device of claim 1 , wherein the control circuit is further configured to take a balance among the DC bus voltages of a plural number of the converter cells connected in mutually serial fashion in each phase of the output terminals, and control voltage command values of the inverters in the plural number of the converter cells so that the plural DC bus voltages are evenly balanced to each other.

4. The power conversion device of claim 1 , wherein the capacitor serial connection is configured with a positive-side capacitor and a negative-side capacitor which are serially connected to each other, and the DC bus voltage of the converter cell is established by a positive-side DC bus voltage applied to the positive-side capacitor and a negative-side DC bus voltage applied to the negative-side capacitor; and
wherein the control circuit is further configured to take a balance between the positive-side DC bus voltage and the negative-side DC bus voltage in each of the converter cells, and control voltage command values of the switching elements that constitute at least one of the converter and the inverter so that the positive-side DC bus voltage and the negative-side DC bus voltage are evenly balanced to each other.

5. The power conversion device of claim 1 , wherein the control circuit controls switching-timings of the switching elements that constitutes at least one of the converter and the inverter in each of a plural number of the converter cells connected in mutually serial fashion in each phase of the output terminals, to shift among the plural number of the converter cells so as to reduce a harmonic component that is contained in at least one of an input current to the input terminals and an output voltage from the output terminals.

6. The power conversion device of claim 1 , wherein the voltage-transformer device is configured by a plurality of transformers whose respective ones of the primary windings are connected in parallel to the input terminals.

7. The power conversion device of claim 1 , wherein the voltage-transformer device is configured by a single transformer including second wirings, a plural number of which are given per one of the primary windings in one phase.

8. The power conversion device of claim 1 , wherein numbers of phases of the multi-phase AC of the input terminals and the multi-phase AC of the output terminals are equal to each other, and
wherein the input ends of a plural number of the converter cells whose output ends are connected in mutually serial fashion to the output terminal, are connected in mutually parallel fashion, through the voltage-transformer device, to the input terminal whose phase is the same as the phase of the output terminal to which said input ends are connected.

9. The power conversion device of claim 1 , wherein the multi-phase AC is a three-phase current, and the primary windings of the voltage-transformer device are provided in three-phase star connection.

10. The power conversion device of claim 1 , wherein at least one of the switching elements and diodes which constitute at least one of circuits of the converter and the inverter in each of the converter cells, are formed of a wide bandgap semiconductor material that is wider in bandgap than silicon.

11. The power conversion device of claim 5 , wherein the control circuit is configured to perform a PWM control using a carrier signal, and control the switching-timings of the switching elements to shift among the plural number of the converter cells, by shifting a phase of the carrier signal among the plural number of the converter cells.

12. The power conversion device of claim 9 , wherein a core of the voltage-transformer device is configured with more than three-leg cores.

13. The power conversion device of claim 10 , wherein the wide bandgap semiconductor material is a silicon carbide, a gallium nitride family material or diamond.

14. A power conversion device which performs power conversion between input terminals of multi-phase AC and output terminals of multi-phase AC, comprising:
a voltage-transformer device including primary windings connected to the input terminals and secondary windings comprising pluralities of single-phase open windings that are insulated to each other;
a plurality of converter cells including switching elements, in which their input ends are connected to the respective single-phase open windings, and their output ends are connected in mutually serial fashion to the output terminal of each phase, said converter cells each performing conversion between a single-phase AC and another single-phase AC; and
a control circuit configured to control a DC bus voltage that is a voltage of a capacitor series connection in each of the converter cells, to have a predetermined bus-voltage command value, take a balance among DC bus voltages of the converter cells connected to mutually different phases of the output terminals, and control voltage command values of inverters in said converter cells so that the DC bus voltages are evenly balanced to each other for controlling ON/OFF of the switching elements, the control circuit including a bus-voltage control unit which controls the DC bus voltage that is the voltage of the capacitor se

Assignees

• Toshiba Mitsubishi Electric Industrial Systems Corp

Inventors

• Jimichi Takushi
• Azuma Satoshi
• Koyanagi Kimiyuki
• Nakamura Ritaka
• Shimomura Yasuhito
• Kato Yoshihito

Classifications

• H02M5/293 Primary

  using semiconductor devices only · CPC title

• H02M5/458

  using semiconductor devices only · CPC title

• H02M1/14

  Arrangements for reducing ripples from DC input or output · CPC title

• H02M1/12

  Arrangements for reducing harmonics from AC input or output · CPC title

• H02M7/4833 Primary

  Capacitor voltage balancing · CPC title