Multilevel power converter system and method

Patent metadata

Field	Value
Publication number	US-9559611-B2
Application number	US-201213629882-A
Country	US
Kind code	B2
Filing date	Sep 28, 2012
Priority date	Sep 28, 2012
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

A power converter is presented. The power converter includes at least one leg, the at least one leg includes a first string, where the first string includes a plurality of controllable semiconductor switches, a first connecting node, and a second connecting node, and where the first string is operatively coupled across a first bus and a second bus. Furthermore, the at least one leg includes a second string operatively coupled to the first string via the first connecting node and the second connecting node, where the second string includes a plurality of switching units. A method for power conversion is also presented.

First claim

The invention claimed is:

1. A power converter, comprising:
at least two legs, wherein each leg comprises:
a first string comprising a plurality of controllable semiconductor switches, a first connecting node, a second connecting node, and a third connecting node, wherein the first string is operatively coupled across a first bus and a second bus;
a second string operatively coupled to the first string via the first connecting node and the second connecting node, wherein the second string comprises:
a first portion; and
a second portion operatively coupled to the first portion via an inductor, wherein each of the first and second portions comprises a plurality of switching units having a plurality of fully controllable semiconductor switches and at least one energy storage device,

wherein the third connecting node of one leg of the at least two legs is operatively coupled to the third connecting node of the other leg to form a floating point, and wherein the third connecting nodes are not coupled to the first bus, the second bus, and a third bus of the power converter.

2. The power converter of claim 1 , wherein at least one of the plurality of fully controllable switches of the plurality of switching units is coupled in series with the at least one energy storage device to form a first limb, and the other fully controllable switches of the plurality of switching units form a second limb, and wherein the first limb is coupled in parallel with the second limb.

3. The power converter of claim 1 , wherein the plurality of fully controllable semiconductor switches comprises an insulated gate bipolar transistor, a metal oxide semiconductor field effect transistor, a field effect transistor, a gate turn-off thyristor, an insulated gate commutated thyristor, an injection enhanced gate transistor, a silicon carbide based switch, a gallium nitride based switch, a gallium arsenide based switch, or combinations thereof.

4. The power converter of claim 1 , wherein the first bus comprises a positive direct current bus and the second bus comprises a negative direct current bus.

5. The power converter of claim 1 , wherein the first string of each of the at least two legs comprises a first branch and a second branch, and wherein the second branch of the first string is operatively coupled to a corresponding first branch via a corresponding third connecting node.

6. The power converter of claim 1 , wherein the plurality of controllable semiconductor switches comprises partially controllable semiconductor switches, fully controllable semiconductor switches, or a combination thereof.

7. The power converter of claim 1 , wherein the third bus comprises a direct current bus.

8. The power converter of claim 1 , wherein the first and second portions of the second string are operatively coupled to a fourth bus.

9. The power converter of claim 8 , wherein the fourth bus comprises an alternating current phase.

10. A method for power conversion, comprising:
coupling a first string of each of at least two legs to a second string of each of the at least two legs to form a power converter, wherein the first string comprises a plurality of controllable semiconductor switches, a first connecting node, a second connecting node, and a third connecting node, and wherein the second string comprises:
a first portion;
a second portion operatively coupled to the first portion via an inductor, wherein each of the first and second portions comprises a plurality of switching units having a plurality of fully controllable semiconductor switches and at least one energy storage device;

coupling the third connecting node of one leg of the at least two legs to the third connecting node of the other leg to form a floating point such that the third connecting nodes are not coupled to a first bus, a second bus, and a third bus of the power converter;
generating a switching pattern for the plurality of controllable semiconductor switches and the plurality of switching units based on a first line parameter input at a first terminal of the power converter;
selectively switching the plurality of controllable semiconductor switches and the plurality of switching units based on the generated switching pattern; and
generating a second line parameter at a second terminal of the power converter based on the selective switching of the plurality of controllable semiconductor switches and the plurality of switching units.

11. The method of claim 10 , wherein generating the second line parameter at the second terminal of the power converter comprises generating a sinusoidal voltage with reference to the third bus.

12. The method of claim 10 , wherein selectively switching the plurality of controllable semiconductor switches comprises operatively coupling both ends of the second string to form a freewheeling path.

13. The method of claim 10 , wherein the first line parameter and the second line parameter comprise an alternating current voltage, a direct current voltage, or a combination thereof.

14. The method of claim 10 , wherein selectively switching the plurality of controllable semiconductor switches comprises operatively coupling the second string between the first bus and the third bus.

15. The method of claim 10 , wherein selectively switching the plurality of controllable semiconductor switches comprises operatively coupling the second string between the second bus and the third bus.

16. A system for power conversion, comprising:
a power source;
a load;
a first power converter, comprising:
two or more legs, wherein each of the two or more legs comprises:
a first string comprising a plurality of controllable semiconductor switches, a first connecting node, a second connecting node, and a third connecting node, wherein the first string is operatively coupled across a first bus and a second bus, wherein the third connecting node of one leg of the two or more legs is operatively coupled to the third connecting node of the other leg to form a floating point, and wherein the third connecting nodes are not coupled to the first bus, the second bus, and a third bus;
a second string operatively coupled to the first string via the first connecting node and the second connecting node, wherein the second string comprises:
a first portion;
a second portion operatively coupled to the first portion via an inductor, wherein each of the first and second portions comprises a plurality of switching units having a plurality of fully controllable semiconductor switches and at least one energy storage device; and

a controller configured to control switching of the plurality of controllable semiconductor switches and the plurality of switching units.

17. The system of claim 16 , wherein the plurality of switching units comprises a half bridge converter, a full bridge converter, or a combination thereof.

18. The system of claim 16 , wherein the controller is further configured to regulate energy stored in the second string during a line cycle.

19. The system of claim 16 , wherein the load comprises a grid, an electrical appliance, or a combination thereof.

20. The system of claim 16 , further comprising a second power converter operatively coupled to the first power converter in a back to back power converter configuration.

21. A system for power conversion, comprising:
a power source;
a load;
a first power converter, comprising:
two or more legs, wherein each of the two or more legs comprises:
a first string operatively coupled between a first b

Assignees

• Gen Electric

Inventors

• Zhang Di
• Garces Luis Jose
• Datta Rajib
• Raju Ravisekhar Nadimpalli

Classifications

• H02M7/53871

  with automatic control of output voltage or current · CPC title

• H02M7/537

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

• Y02E60/60

  Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] · CPC title

• H02M7/7575

  for high voltage direct transmission link · CPC title

• H02M3/3376

  with automatic control of output voltage or current · CPC title