Electric power conversion device and electric power system

Patent metadata

Field	Value
Publication number	US-10128773-B2
Application number	US-201615564402-A
Country	US
Kind code	B2
Filing date	Mar 29, 2016
Priority date	Apr 13, 2015
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

An electric power conversion device includes a first arm and a second arm each including converter cells. The converter cell of the first arm is a first converter cell having a full-bridge configuration including an energy storing element and semiconductor switching elements. The converter cell of the second arm is a second converter cell having a half-bridge configuration including an energy storing element and semiconductor switching elements. Thus, short-circuit current between DC terminals is suppressed.

First claim

The invention claimed is:

1. An electric power conversion device comprising:
a power converter including a plurality of leg circuits connected in parallel between positive and negative DC terminals, each leg circuit including a first arm and a second arm connected in series and being connected to an AC line for each phase, the first arm and the second arm each including at least one converter cell, the power converter performing power conversion between multiphase AC and DC;
a control device for controlling the power converter;
wherein each of the at least one converter cell in the first arm of each leg circuit is a first converter cell having a full-bridge configuration including an energy storing element, a first bridge having upper and lower arms both having semiconductor switching elements, and a second bridge having upper and lower arms both having semiconductor switching elements, and
each of the at least one converter cell in the second arm of each leg circuit is a second converter cell having a half-bridge configuration including an energy storing element and a first bridge having upper and lower arms both having semiconductor switching elements,
wherein in steady operation of the power converter, the control device generates voltage commands respectively for the first arm and the second arm of each leg circuit, to perform switching control for the semiconductor switching elements in the first bridges of each first converter cell in the first arm and each second converter cell in the second arm on the basis of the voltage commands, and the control device fixes one of the semiconductor switching element of the upper arm and the semiconductor switching element of the lower arm in the second bridge of each first converter cell in a ON state as an ON-fixed element, and fixes the other one in an OFF state as an OFF-fixed element;
wherein each of the first and second converter cells includes gate drive circuits for driving the corresponding semiconductor switching elements, and the gate drive circuits in the second bridge of each first converter cell have a greater gate resistance value than those of the gate drive circuits in the first bridges of the first and second converter cells.

2. The electric power conversion device according to claim 1 , wherein all the converter cells in the first arm of each leg circuit are the first converter cells, and all the converter cells in the second arm of each leg circuit are the second converter cells.

3. The electric power conversion device according to claim 1 , wherein
in each first converter cell, the upper arm and the lower arm of the first bridge each include a plurality of the semiconductor switching elements connected in parallel, one of the upper arm and the lower arm of the second bridge includes one or a plurality of the ON-fixed elements connected in parallel, and the other one includes one or a plurality of the OFF-fixed elements connected in parallel, and
a number of the parallel connected ON-fixed elements in the second bridge is not less than a number of the parallel connected OFF-fixed elements, and not greater than a number of the parallel connected semiconductor switching elements of the upper arm in the first bridge or a number of the parallel connected semiconductor switching elements of the lower arm in the first bridge, whichever is lesser.

4. The electric power conversion device according to claim 1 , wherein in each first converter cell, rated currents of the semiconductor switching elements of the second bridge are smaller than those of the semiconductor switching elements of the first bridge.

5. The electric power conversion device according to claim 1 , wherein the semiconductor switching elements of the first and second converter cells are formed from wide bandgap semiconductors having a greater bandgap than silicon.

6. The electric power conversion device according to claim 1 , wherein a connection point between the first arm and the second arm of each leg circuit is connected to an AC terminal for each phase.

7. The electric power conversion device according to claim 1 , wherein when short-circuit between the DC terminals is detected, the control device performs output control of each second converter cell of the second arm of each leg circuit so as to perform reactive power compensation operation.

8. The electric power conversion device according to claim 7 , wherein the control device controls the reactive power compensation operation using a voltage command on which common DC voltage is superimposed among all phases.

9. The electric power conversion device according to claim 7 , wherein the control device controls the reactive power compensation operation using a voltage command on which common AC voltage is superimposed among all phases.

10. The electric power conversion device according to claim 1 , wherein when short-circuit between the DC terminals is detected, the control device turns off all the semiconductor switching elements in each first converter cell of the first arm of each leg circuit.

11. The electric power conversion device according to claim 10 , wherein a sum of charge voltages of the energy storing elements of the first converter cells connected in a short-circuit current route in the power converter when the DC terminals are short-circuited is higher than voltage between the AC lines.

12. The electric power conversion device according to claim 10 , wherein when short-circuit between the DC terminals is detected, the control device performs output control of each second converter cell of the second arm of each leg circuit so as to perform reactive power compensation operation.

13. The electric power conversion device according to claim 10 , wherein at least one of the DC terminals is connected to an open/close portion, and when short-circuit between the DC terminals is detected, the control device turns off all the semiconductor switching elements in each first converter cell of the first arm of each leg circuit, and thereafter, operates the open/close portion into an opened state.

14. The electric power conversion device according to claim 13 , wherein after operating the open/close portion into an opened state, the control device performs output control of each first converter cell of the first arm of each leg circuit so as to perform reactive power compensation operation.

15. The electric power conversion device according to claim 13 , wherein after operating the open/close portion into an opened state, the control device performs output control of each first converter cell and each second converter cell of the first arm and the second arm of each leg circuit so as to perform reactive power compensation operation.

16. The electric power conversion device according to claim 13 , wherein the open/close portion is capable of interrupting current smaller than twice rated DC current of the power converter.

17. The electric power conversion device according to claim 13 , wherein when short-circuit between the DC terminals is detected, the control device performs output control of each second converter cell of the second arm of each leg circuit so as to perform reactive power compensation operation.

18. An electric power system comprising a plurality of electric power conversion devices,
each electric power conversion device comprising:
a power converter including a plurality of leg circuits connected in parallel between positive and negative DC terminals, each leg circuit including a first arm and a second arm connected in series and being connected to an AC line for each phas

Assignees

• Mitsubishi Electric Corp

Inventors

• Jimichi Takushi
• Koyanagi Kimiyuki
• Kikuchi Takeshi

Classifications

• H02J3/1857

  the bridge converters being multilevel bridge converters or modular multilevel converters · CPC title

• H02M7/49

  Combination of the output voltage waveforms of a plurality of converters · CPC title

• Y02E40/30

  Reactive power compensation · CPC title

• H02M7/483

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

• H02M7/48

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