Power conversion device for reliable control of circulating current

Patent metadata

Field	Value
Publication number	US-10637343-B2
Application number	US-201515758922-A
Country	US
Kind code	B2
Filing date	Sep 17, 2015
Priority date	Sep 17, 2015
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

A power conversion device includes a plurality of leg circuits and a control device. The plurality of leg circuits correspond to respective phases of an AC circuit and connected in parallel between common first and second DC terminals. Each leg circuit includes a plurality of chopper cells each including an energy storage and cascaded to one another and at least one inductance connected in series to the plurality of chopper cells. The control device controls an operation of only at least one chopper cell included in each leg circuit based on a circulating current which circulates through the leg circuits.

First claim

The invention claimed is:

1. A power conversion device which converts power between a DC circuit and an AC circuit, the power conversion device comprising:
a plurality of leg circuits which correspond to respective phases of the AC circuit and are connected in parallel between common first and second DC terminals, each leg circuit including:
a plurality of converter cells each including an energy storage and cascaded to one another; and
at least one inductance connected in series to the plurality of converter cells; and

a control device which controls operations of the plurality of converter cells,
the control device controlling an operation of at least one converter cell included in each leg circuit based on a circulating current which circulates among the leg circuits, and controlling an operation of at least another converter cell not based on the circulating current,
each leg circuit being divided into a first arm and a second arm with a connection portion electrically connected to a corresponding phase of the AC circuit being interposed,
the first arm of each leg circuit including:
a plurality of first converter cells controlled not based on the circulating current;
a plurality of second converter cells controlled based on the circulating current; and
a first inductance,

the second arm of each leg circuit including a plurality of third converter cells controlled not based on the circulating current,
the control device generating a first voltage command value for controlling output voltages from the plurality of first converter cells for each leg circuit based on a DC current and a DC voltage from the DC circuit and an AC current and an AC voltage of each phase from the AC circuit,
the control device generating a second voltage command value for controlling output voltages from the plurality of second converter cells by linearly combining a first value based on a difference between the circulating current and a circulating current command value with the first voltage command value for each leg circuit.

2. The power conversion device according to claim 1 , wherein:
the energy storage is a capacitor;
each second converter cell further includes a voltage detector which detects a voltage of the capacitor; and
the control device generates the second voltage command value by further linearly combining a second value based on a difference between the voltage of the capacitor and a command value for the voltage of the capacitor with the first value and the first voltage command value.

3. The power conversion device according to claim 2 , wherein:
the second value is corrected based on the DC current from the DC circuit; and
the second voltage command value is generated with the corrected second value.

4. The power conversion device according to claim 2 , wherein:
the second value is corrected based on the AC current from the AC circuit; and
the second voltage command value is generated with the corrected second value.

5. A power conversion device which converts power between a DC circuit and an AC circuit, the power conversion device comprising:
a plurality of leg circuits which correspond to respective phases of the AC circuit and are connected in parallel between common first and second DC terminals, each leg circuit including:
a plurality of converter cells each including an energy storage and cascaded to one another; and
at least one inductance connected in series to the plurality of converter cells; and

a control device which controls operations of the plurality of converter cells,
the control device controlling an operation of at least one converter cell included in each leg circuit based on a circulating current which circulates among the leg circuits, and controlling an operation of at least another converter cell not based on the circulating current,
each leg circuit being divided into a first arm and a second arm with a connection portion electrically connected to a corresponding phase of the AC circuit being interposed,
the first arm of each leg circuit including:
a plurality of first converter cells controlled not based on the circulating current;
a plurality of second converter cells controlled based on the circulating current; and
a first inductance,

the second arm of each leg circuit including a plurality of third converter cells controlled not based on the circulating current,
the energy storage being a capacitor,
each second converter cell further including a voltage detector which detects a voltage of the capacitor;
the control device generating a first voltage command value for controlling output voltages from the plurality of first converter cells for each leg circuit based on a DC current and a DC voltage from the DC circuit and an AC current and an AC voltage of each phase from the AC circuit; and
the control device generating a second voltage command value for controlling output voltages from the plurality of second converter cells by linearly combining a first value based on a difference between the circulating current and a circulating current command value, a second value resulting from correction of a difference between the voltage of the capacitor and a command value for the voltage of the capacitor based on the AC current from the AC circuit, and a bias value set in advance with one another for each leg circuit.

6. The power conversion device according to claim 1 , wherein each second converter cell is of a half bridge type.

7. A power conversion device which converts power between a DC circuit and an AC circuit, the power conversion device comprising:
a plurality of leg circuits which correspond to respective phases of the AC circuit and are connected in parallel between common first and second DC terminals, each leg circuit including:
a plurality of converter cells of a half bridge type each including an energy storage and cascaded to one another; and
at least one inductance connected in series to the plurality of converter cells; and

a control device which controls operations of the plurality of converter cells of each leg circuit,
the control device configured to:
control at least one converter cell included in a leg circuit to control a circulating current which flows through the leg circuit; and
control another converter cell included in the leg circuit not to control the circulating current which flows through the leg circuit and to control a current other than the circulating current which flows through the leg circuit, wherein:

the control device includes:
a first control unit configured to control at least one converter cell included in a leg circuit to control a circulating current which flows through the leg circuit; and
a second control unit separate from the first control unit and configured to control another converter cell included in the leg circuit not to control the circulating current which flows through the leg circuit and to control a current other than the circulating current which flows through the leg circuit.

8. A power conversion device which converts power between a DC circuit and an AC circuit, the power conversion device comprising:
a plurality of leg circuits which correspond to respective phases of the AC circuit and are connected in parallel between common first and second DC terminals, each leg circuit including:
a plurality of converter cells of a single half bridge type each including an energy storage and cascaded to one another; and
at least one inductance connected in series to the plurality of converter cells; and

a control device which controls operations of the plurality of converter cells,
the control device controlling an operation of at least one converter cell included in each leg circuit based on a circulating c

Assignees

• Mitsubishi Electric Corp

Inventors

• Fujii Toshiyuki
• Jimichi Takushi
• Uda Ryosuke

Classifications

• H02M7/797

  using semiconductor devices only · CPC title

• H02M7/48

  using discharge tubes with control electrode or semiconductor devices with control electrode · CPC title

• H02M7/483 Primary

  Converters with outputs that each can have more than two voltages levels · CPC title

• H02M2007/4835

  Electricity · mapped topic

• H02M2001/0003

  Electricity · mapped topic