Thyristor based voltage source converter

• US 9,762,136 B2
• Filed: 11/27/2012
• Issued: 09/12/2017
• Est. Priority Date: 11/27/2012
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited (Hitachi, Ltd.)
• Original Assignee: ABB Schweiz AG (ABB Limited)
• Inventors: Barupati, Praveen Kumar, Jonsson, Tomas, Subramanian, Sasitharan
• Primary Examiner(s): Behm, Harry
• Assistant Examiner(s): NOVAK, PETER MICHAEL
• Application Number:
  US14/434,646
• Publication Number:
  US 20150295507A1
• Time in Patent Office: 1,750 Days
• 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 5/443 using devices of a thyratron or thyristor type requiring extinguishing means
• CPC Class Codes: H02M 7/4811 having auxiliary actively switched resonant commutation circuits connected to intermediate DC voltage or between two push-pull branches
• CPC Class Codes: H02M 7/4835 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 Class Codes: H02M 7/487 Neutral point clamped inverters

Abstract

A voltage source converter includes a number of valves, the valves including switching elements with anti-parallel diodes provided in a bridge for switching between two states. The bridge is provided in at least one phase leg that stretches between two direct current poles and has at least one midpoint, which is connected to an alternating current terminal. The switching element of at least one valve is a thyristor. The converter further includes a commutation cell associated with the valve, where the commutation cell is controllable to reverse-bias the valve if it is to stop conducting current.

Claims

1. A voltage source converter, comprising:

a number of valves, the valves comprising switching elements with anti-parallel diodes and being provided in a bridge for switching between two states, said bridge being provided in at least one phase leg that stretches between two direct current poles and having at least one midpoint, which is connected to an alternating current terminal, where the switching element of at least one valve is a thyristor;

a commutation cell associated with the valve, wherein said commutation cell is controllable to reverse-bias said valve if it is to stop conducting current; and

at least one string of multilevel cells, said cells being configured to provide voltage contributions to a state of the bridge for assisting in the forming of an AC waveform,

wherein the commutation cell is included in the string of multilevel cells, in a phase leg or in an intermediate branch connected between a midpoint of the phase leg and a midpoint of the string of multilevel cells,

wherein the string of multilevel cells is connected between the two direct current poles,

wherein the intermediate branch comprises a bidirectional switch, and

wherein the commutation cell is controllable to reverse-bias the thyristor of said valve if it is to stop conducting current and the bidirectional switch comprises at least one pair of anti-parallel thyristors, where a thyristor of the bidirectional switch having the same direction of conduction as the thyristor of said valve in relation to the AC terminal is fireable when the thyristor stops to conduct.

2. The voltage source converter according claim 1, further comprising a control unit configured to control the switching of the commutation cell for stopping the valve from conducting current.

3. The voltage source converter according to claim 2, wherein the control unit is further configured to check that the voltage of the string shared by the valve and a following entity that is to start conducting is zero.

4. The voltage source converter according to claim 2, wherein the string of multilevel cells is connected in series to at least one of the valves such that the string of multilevel cells and the at least one of the valves as a whole are connected between the midpoint of the phase leg and one of the two direct current poles.

5. The voltage source converter according to claim 2, wherein the string of multilevel cells is directly connected between the two direct current poles.

6. The voltage source converter according to claim 1, wherein the string of multilevel cells is connected in series to at least one of the valves such that the string of multilevel cells and the at least one of the valves as a whole are directly connected between the midpoint of the phase leg and one of the two direct current poles.

7. The voltage source converter according to claim 1, wherein the string of multilevel cells is directly connected between the two direct current poles.

8. The voltage source converter according to claim 1, wherein the commutation cell is a full-bridge cell.

9. The voltage source converter according to claim 1, wherein the commutation cell is a half-bridge cell.

10. The voltage source converter according to claim 1, wherein each of said multilevel cells is a half-bridge cell having an energy storage element, and is configured to provide either a voltage contribution corresponding to a voltage across the energy storage element or a zero voltage to the state of the bridge for assisting in the forming of the AC waveform.

11. A voltage source converter, comprising:

a number of valves, the valves comprising switching elements with anti-parallel diodes and being provided in a bridge for switching between two states, said bridge being provided in at least one phase leg that stretches between two direct current poles and having at least one midpoint, which is connected to an alternating current terminal, where the switching element of at least one valve is a thyristor;

a commutation cell associated with the valve, wherein said commutation cell is controllable to reverse-bias said valve if it is to stop conducting current; and

at least one string of multilevel cells, said cells being configured to provide voltage contributions to a state of the bridge for assisting in the forming of an AC waveform,

wherein the commutation cell is included in the string of multilevel cells, in a phase leg or in an intermediate branch connected between a midpoint of the phase leg and a midpoint of the string of multilevel cells,

wherein the string of multilevel cells is connected between the two direct current poles,

wherein the intermediate branch comprises a bidirectional switch, and

wherein the commutation cell is controllable to reverse-bias the anti-parallel diode of said valve, if it is to stop conducting current and the bidirectional switch comprises at least one pair of anti-parallel thyristors, where a thyristor of the bidirectional switch having the same direction of conduction as the diode of said valve in relation to the AC terminal is fireable when the anti-parallel diode stops to conduct.

12. The voltage source converter according claim 11, further comprising a control unit configured to control the switching of the commutation cell for stopping the valve from conducting current.

13. The voltage source converter according to claim 12, wherein the control unit is further configured to check that the voltage of the string shared by the valve and a following entity that is to start conducting is zero.

14. The voltage source converter according to claim 12, wherein the string of multilevel cells is connected in series to at least one of the valves such that the string of multilevel cells and the at least one of the valves as a whole are connected between the midpoint of the phase leg and one of the two direct current poles.

15. The voltage source converter according to claim 12, wherein the string of multilevel cells is directly connected between the two direct current poles.

16. The voltage source converter according to claim 11, wherein the string of multilevel cells is connected in series to at least one of the valves such that the string of multilevel cells and the at least one of the valves as a whole are directly connected between the midpoint of the phase leg and one of the two direct current poles.

17. The voltage source converter according to claim 11, wherein the string of multilevel cells is directly connected between the two direct current poles.

18. The voltage source converter according to claim 11, wherein the commutation cell is a full-bridge cell.

19. The voltage source converter according to claim 11, wherein the commutation cell is a half-bridge cell.

20. The voltage source converter according to claim 11, wherein each of said multilevel cells is a half-bridge cell having an energy storage element, and is configured to provide either a voltage contribution corresponding to a voltage across the energy storage element or a zero voltage to the state of the bridge for assisting in the forming of the AC waveform.