VOLTAGE SOURCE CONVERTER (VSC) WITH NEUTRAL-POINT-CLAMPED (NPC) TOPOLOGY AND METHOD FOR OPERATING SUCH VOLTAGE SOURCE CONVERTER

• US 20130272045A1
• Filed: 11/05/2012
• Published: 10/17/2013
• Est. Priority Date: 11/04/2011
• Status: Active Grant

• Current Assignee: General Electric Technology GmbH (General Electric Company)
• Original Assignee: Alstom Technology Ltd. (Alstom SA)
• Inventors: Soeiro, Thiago Batista, Kolar, Johann Walter, Ranstad, Per, Linner, Jrgen
• Granted Patent: US 9,543,855 B2
• Time in Patent Office: Days
• US Class Current: 363/131
• CPC Class Codes: H02M 1/0054 Transistor switching losses periodically suspending operation of switching converter in low power mode H02M1/0035
• CPC Class Codes: H02M 1/0095 Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A Voltage Source Converter (VSC) (10) with Neutral-Point-Clamped (NPC) topology with one or more phases, comprises an intermediate DC circuit having at least a first and a second capacitance connected in series between a positive terminal and a negative terminal, providing a central tap terminal between both capacitances, and at least one sub-circuit for generating one phase of an alternating voltage, each sub-circuit comprising an AC terminal for supplying a pulsed voltage; a circuit arrangement of the form of a conventional NPC converter, with a first series connection of at least two switches between said AC terminal and said positive terminal, a second series connection of at least two switches between said AC terminal said negative terminal, and switchable connections from said central tap terminal to the centers of both two-switch series connections; and additional first and second auxiliary switches assigned to said two-switch series connections.

Claims

1. Voltage Source Converter (VSC) with Neutral-Point-Clamped (NPC) topology with one or more phases, comprising:

an intermediate DC circuit having at least a first and a second capacitance connected in series between a positive terminal and a negative terminal, providing a central tap terminal between both capacitances, and

at least one sub-circuit for generating one phase of an alternating voltage, each sub-circuit comprising;

an AC terminal for supplying a pulsed voltage;

a circuit arrangement of the form of a conventional NPC converter, with a first series connection of at least two switches between said AC terminal and said positive terminal, a second series connection of at least two switches between said AC terminal said negative terminal, and switchable connections from said central tap terminal to the centers of both two-switch series connections; and

additional first and second auxiliary switches assigned to said two-switch series connections.

2. The voltage source converter according to claim 1, wherein the first and second two-switch series connections each comprise two active switches in series connection, the switchable connections from said central tap terminal to the centers of both two-switch series connections each comprise a diode as a passive switch, and the additional first and second auxiliary switches are connected between said AC terminal and said positive and negative terminals, respectively.

3. The voltage source converter according to claim 2, wherein the first and/or second of said additional auxiliary switches have diodes or active switches connected in parallel.

4. The voltage source converter according to claim 2, wherein one or more active switches are connected from said first and second two-switch series connections to said central tap terminal.

5. The voltage source converter according to claim 1, wherein the first and second two-switch series connections each comprise an active switch and a diode in series connection, the switchable connections from said central tap terminal to the centers of both two-switch series connections each comprise a diode as a passive switch, and the additional first and second auxiliary switches are connected between said AC terminal and said positive and negative terminals, respectively.

6. The voltage source converter according to claim 5, wherein the first and/or second of said additional auxiliary switches have diodes or active switches connected in parallel.

7. The voltage source converter according to claim 5, wherein one or more active switches are connected from said first and second two-switch series connections to said central tap terminal.

8. The voltage source converter according to claim 1, wherein

the intermediate DC circuit has four capacitances connected in series between the positive terminal and the negative terminal, providing the central tap terminal between said capacitances,

the at least one sub-circuit for generating one phase of an alternating voltage comprises:

within said first series connection at least four switches between said AC terminal and said positive terminal;

within said second series connection of at least four switches between said AC terminal said negative terminal;

four additional auxiliary switches connected in series between said positive and negative terminals, with connection of the AC terminal to the middle point of the series connection of the four additional auxiliary switches; and

one or more diode(s) connected between each series connection of said four capacitances and the series connections of said sub-circuit switches.

9. The voltage source converter according to claim 8, wherein any of the four additional auxiliary switches have diodes or active switches connected in parallel.

10. The voltage source converter according to claim 8, wherein one or more active switches are connected between each series connection of said four capacitances and the series connections of said sub-circuit switches.

11. The voltage source converter according to claim 1, wherein

the intermediate DC circuit has six capacitances connected in series between the positive terminal and the negative terminal, providing the central tap terminal between said capacitances,

the at least one sub-circuit for generating one phase of an alternating voltage comprises:

within said first series connection at least six switches between said AC terminal and said positive terminal;

within said second series connection of at least six switches between said AC terminal said negative terminal;

six additional auxiliary switches connected in series between said positive and negative terminals, with connection of the AC terminal to the middle point of the series connection of the six additional auxiliary switches; and

one or more diode(s) connected between each series connection of said six capacitances and the series connections of said sub-circuit switches.

12. The voltage source converter according to claim 11, wherein any of the six additional auxiliary switches has diodes or active switches connected in parallel.

13. The voltage source converter according to claim 11, wherein one or more active switches are connected between each series connection of said six capacitances and the series connections of said sub-circuit switches.

14. The voltage source converter according to claim 1, wherein said first and second two-switch series connections each consist of two active switches in series connection.

15. The voltage source converter according to claim 1, wherein said first and second two-switch series connections each consist of two active switches in series connection, and said switches have diodes and/or active switches connected in parallel.

16. The voltage source converter according to claim 1, wherein the capacitances have all the same value.

17. The voltage source converter according to claim 1, wherein three sub-circuits are provided for feeding the output into a three-phase grid.

18. Method for operating a voltage source converter according to claim 1, wherein each sub-circuit generates a pulse-modulated voltage signal at the respective AC terminal in order to generate an AC voltage.