Multilevel power converter

Patent metadata

Field	Value
Publication number	US-11095231-B2
Application number	US-201716627887-A
Country	US
Kind code	B2
Filing date	Jul 5, 2017
Priority date	Jul 5, 2017
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A multilevel power converter has at least one phase module with a plurality of modules connected between positive and negative DC voltage connections. The phase module has a first phase module branch connected to the positive DC voltage connection, and a second phase module branch connected to the negative DC voltage connection. Each of the modules has at least two electronic switching elements and an electric energy storage unit. A third phase module branch connects the first phase module branch to the second phase module branch. A switching device connects an AC voltage connection of the multilevel power converter to a first connection node between the first phase module branch and the third phase module branch in a first switch position and connects the AC voltage connection to a second connection node between the third phase module branch and the second phase module branch in a second switch position.

First claim

The invention claimed is:

1. A multilevel power converter, comprising:
a first DC voltage terminal, a second DC voltage terminal, an AC voltage terminal, and at least one phase module connected between said first and second DC voltage terminals;
said at least one phase module including a plurality of modules, each of said plurality of modules including at least two electronic switching elements and an electrical energy storage device;
said at least one phase module including a first phase module branch connected to said first DC voltage terminal, a second phase module branch connected to said second DC voltage terminal, and a third phase module branch connecting said first phase module branch to said second phase module branch;
a switching device configured, in a first switch position, to connect said AC voltage terminal to a first connection point between said first phase module branch and said third phase module branch and, in a second switch position, to connect said AC voltage terminal to a second connection point between said third phase module branch and said second phase module branch;
said switching device including a first power electronics switch having antiparallel-connected thyristors; and said switching device including a second power electronics switch having antiparallel-connected thyristors.

2. The multilevel power converter according to claim 1 , wherein said switching device, in the second switch position, isolates said AC voltage terminal of the multilevel power converter from said first connection point and, in the first switch position, isolates said AC voltage terminal from said second connection point.

3. The multilevel power converter according to claim 1 , wherein each of said first phase module branch, said second phase module branch, and said third phase module branch respectively comprises at least two of said plurality of modules in a series-connected circuit.

4. The multilevel power converter according to claim 1 , wherein each of said first, second, and third phase module branches comprises at least five of said plurality of modules connected in series.

5. The multilevel power converter according to claim 1 , wherein:
said switching device comprises a first power electronics switch which, in the first switch position of said switching device, connects said AC voltage terminal to said first connection point and, in the second switch position of said switching device, isolates said AC voltage terminal from said first connection point; and
said switching device comprises a second power electronics switch which, in the second switch position of said switching device, connects said AC voltage terminal to said second connection point and, in the first switch position of said switching device, isolates said AC voltage terminal from said second connection point.

6. The multilevel power converter according to claim 1 , wherein at least one module of said third phase module branch is configured to deliver a voltage output with a positive or a negative polarity.

7. The multilevel power converter according to claim 1 , wherein at least one module of said third phase module branch comprises a full-bridge circuit.

8. The multilevel power converter according to claim 7 , wherein said full-bridge circuit comprises four electronic switching elements and an electrical energy storage device.

9. The multilevel power converter according to claim 1 , wherein said third phase module branch comprises a plurality of electrically series-connected sub-branches, and said switching device has a third switch position, wherein said AC voltage terminal is connected to a third connection point of two said sub-branches.

10. The multilevel power converter according to claim 1 , wherein said switching device is configured to assume the switch positions in accordance with an instantaneous value of a voltage that is present at said AC voltage terminal.

11. The multilevel power converter according to claim 10 , wherein:
said switching device assumes the first switch position when the instantaneous value of the voltage at said AC voltage terminal is greater than zero, and said switching device assumes the second switch position when the instantaneous value of the voltage at said AC voltage terminal is lower than zero, or
said switching device assumes the first switch position when the instantaneous value of the voltage at said AC voltage terminal lies within a first preselected voltage range, and said switching device assumes the second switch position when the instantaneous value of the voltage at said AC voltage terminal lies within a second preselected voltage range.

12. A high-voltage direct current transmission installation, comprising a multilevel power converter according to claim 1 .

13. A method of operating the multilevel power converter according to claim 1 , the method comprising:
measuring an instantaneous value of a voltage that is present on the AC voltage terminal of the multilevel power converter; and
depending on the measured instantaneous value, connecting the AC voltage terminal to the first connection point between the first phase module branch and the third phase module branch, or connecting the AC voltage terminal to the second connection point between the third phase module branch and the second phase module branch.

14. The method according to claim 13 , which comprises:
placing the switching device into the first switch position to connect the AC voltage terminal to the first connection point and to isolate the AC voltage terminal from the second connection point; or
placing the switching device into the second switch position to connect the AC voltage terminal to the second connection point and to isolate the AC voltage terminal from the first connection point.

15. The method according to claim 13 , which comprises:
connecting the AC voltage terminal to the first connection point when the instantaneous value of the voltage at the AC voltage terminal is greater than zero, and connecting the AC voltage terminal to the second connection point when the instantaneous value of the voltage at the AC voltage terminal is lower than zero; or
connecting the AC voltage terminal to the first connection point when the instantaneous value of the voltage at the AC voltage terminal lies within a first preselected voltage range, and connecting the AC voltage terminal to the second connection point when the instantaneous value of the voltage at the AC voltage terminal lies within a second preselected voltage range.

16. The method according to claim 13 , wherein the third phase module branch comprises a plurality of electrically series-connected sub-branches, between which at least one further connection point is provided, and the method further comprises connecting the AC voltage terminal to the first connection point, to the second connection point, or to the further connection point in dependence on the measured instantaneous value.

17. The method according to claim 13 , which comprises, in the event of an occurrence of a fault, isolating the AC voltage terminal from the phase module by way of the switching device.

Assignees

• Siemens Ag

Inventors

• Gambach Herbert
• Hussennether Volker
• Schuster Roland
• Westerweller Thomas
• Chaudhry Adnan

Classifications

• H02M7/483 Primary

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

• H02M7/4835

  comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage · CPC title

• H02M1/0095

  Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M2007/4835

  Electricity · mapped topic