Electrical apparatus and a limiting method

• US 20050063124A1
• Filed: 07/04/2002
• Published: 03/24/2005
• Est. Priority Date: 08/09/2001
• Status: Abandoned Application

• Current Assignee: ABB Power Grids Switzerland AG (ABB Limited)
• Original Assignee: ABB Power Grids Switzerland AG (ABB Limited)
• Inventors: Al-Hosini, Falah, Lundberg, Peter, Bijlenga, Bo, Johansson, Nicklas
• Application Number:
  US10/485,965
• Publication Number:
  US 20050063124A1
• Time in Patent Office: Days
• US Class Current: 361/111
• 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: H03K 17/0828 in composite switches

Abstract

An electrical apparatus for limiting the peak voltage across a recttifying member (23) of a current valve arranged in a circuit having a substantial inductance (24) and having at least one controllable semiconductor device (22) and at least one said rectifying member (23) connected in anti-parallel therewith when the rectifying member is turning off, comprises means (28, 29) adapted to control the semiconductor device so as to increase the conductivity thereof during turning off of the rectifying member.

Claims

1. An electrical apparatus for limiting the peak voltage across a rectifying member of a current valve arranged in a circuit having a substantial inductance and having at least one controllable semiconductor device and at least one said rectifying member connected in anti-parallel therewith when turning off the rectifying member, characterized in that it comprises means adapted to control the semiconductor device so that the conductivity thereof is increased during the turning off of the rectifying member.

2. An apparatus according to claim 1, wherein said means are adapted to control the degree of conductivity of the semiconductor device when the rectifying member is turning off in dependence of the instantaneous magnitude of the voltage across the rectifying member.

3. An apparatus according to claim 2, wherein means are adapted to control the voltage across the rectifying member according to a predetermined reference voltage wave shape through controlling the degree of conductivity of the semiconductor device when the rectifying member is turning off.

4. An apparatus according to claim 2, wherein it comprises members adapted to measure the voltage across the rectifying member and said means are adapted to consider voltage values so measured when controlling the semiconductor device.

5. An apparatus according to claim 4, wherein it comprises members adapted to compare the voltage measured across the rectifying member with a reference voltage, and that said means are adapted to control the semiconductor device in dependence of the result of this comparison.

6. An apparatus according to claim 5, wherein said means are adapted to control the semiconductor device towards an increasing conductivity when the voltage measured is higher than the reference voltage and control the semiconductor device towards a lower conductivity when the voltage measured is lower than the reference voltage.

7. An apparatus according to claim 1, wherein it is designed to limit the peak voltage across a rectifying member of a current valve having an IGBT (Insulated Gate Bipolar Transistor) as semiconductor device.

8. An apparatus according to claim 7, wherein said means comprise a series connection of a capacitive and a resistive member between the gate and the collector of the IGBT and a negative current source connected to the gate and adapted to drain a predetermined current as soon as the voltage between the gate and the emitter of the IGBT exceeds a determined value and when this value is exceeded divert the share of the current above this predetermined current to the gate of the IGBT so as to increase this gate-emitter voltage and bring the IGBT towards a state of a higher conductivity.

9. An apparatus according to claim 8, wherein the current source is controllable, and that the apparatus comprises members adapted to control said predetermined level of the current drained by the current source so as to control the time derivative of the voltage increase across the IGBT when the rectifying member is turning off.

10. An apparatus according to claim 9, wherein said members for controlling the predetermined current level of the current source is adapted to achieve such controlling between at least two discrete values and at voltages across the rectifying member below a predetermined level to have a first higher current value of the current source and when exceeding the predetermined level of the voltage across the rectifying member change to a second lower value of the current which the current source is adapted to drain.

11. An apparatus according to claim 10, wherein the first higher current value is substantially higher than the second lower current value, preferably at least five times higher.

12. An apparatus according to claim 9, wherein the current control members comprise a transistor adapted to be controlled for controlling the current of the current source.

13. An apparatus according to claim 9, wherein the current control members comprise a resistor with a variable resistance and members adapted to vary the resistance of the resistor for varying the current of the current source.

14. An apparatus according to claim 9, wherein said control member is adapted to control the current of the current source to have a high level until the voltage across the rectifying member has exceeded a value above which it will effect a reduction of the current through said inductance.

15. An apparatus according to claim 9, wherein a capacitor is arranged between the collector and the gate of the IGBT and in series with the collector and the current source.

16. An apparatus according to claim 1, wherein a RC-snubber member is connected in parallel with the rectifying member of the current valve.

17. An apparatus according to claim 1, wherein it is adapted to limit the peak voltage across the rectifying member of a current valve having a series connection of semiconductor devices and rectifying members connected in anti-parallel therewith, and that the apparatus comprises said means adapted to individually control the semiconductor device belonging to each individual rectifying member to turn on at least slightly when the rectifying member is turning off.

18. An apparatus according to claim 1, wherein it is adapted to limit the peak voltage across a rectifying member in the form of a diode when the latter is turned off.

19. An apparatus according to claim 1, wherein it is adapted to limit the peak voltage across a rectifying member of a said current valve included in a converter.

20. An apparatus according to claim 19, wherein the current valve is a part of a voltage stiff converter adapted to convert alternating voltage into direct voltage and conversely.

21. An apparatus according to claim 20, wherein said converter is a part of a plant for transmitting electric power in the form of high voltage direct current (HVDC).

22. An apparatus according to claim 20, wherein said current valve is a part of a resonance circuit for recharging snubber capacitors of other main current valves located on both sides of a phase output of the converter so as to thereby enable turning on of semiconductor devices of turn-off type of the main current valves at a low voltage thereacross.

23. An apparatus according to claim 22, wherein the resonance circuit is constituted by an ARCP-circuit (Auxiliary Resonant Commutation Pole).

24. An apparatus according to claim 23, wherein said current valve, in which the peak voltage across a rectifying member shall be limited when the rectifying member is turning off, is a part of a so called auxiliary valve circuit in the ARCP-circuit.

25. An apparatus according to claim 24, wherein the converter has an auxiliary valve comprising at least one set of two said auxiliary valve circuits connected in series, each of which comprises a semiconductor device of turn-off type and a rectifying member connected in anti-parallel therewith, said semiconductor devices of turn-off type of the two auxiliary valve circuits being arranged in opposite polarity with respect to each other, and that the ARCP-circuit also comprises an inductor connected in series with said set of auxiliary valve circuits.

26. An apparatus according to claim 19, wherein it is adapted to limit the peak voltage across a rectifying member of a said current valve being a part of a converter belonging to an arrangement for driving an electric motor.

27. A method for limiting the peak voltage across a rectifying member of a current valve arranged in a circuit having a substantial inductance and having at least one controllable semiconductor device and at least one said rectifying member connected in anti-parallel therewith when turning off the rectifying member, characterized in that the semiconductor device is during the turning off of the rectifying member controlled towards an increased conductivity for limiting the voltage increase across the rectifying member.

28. A method according to claim 27, wherein the degree of turning on of the semiconductor device at turning off of the rectifying member is controlled in dependence of the instantaneous magnitude of the voltage across the rectifying member.

29. A method according to claim 28, wherein the voltage across the rectifying member of the current valve is controlled according to a predetermined reference voltage wave shape when the rectifying member is turning off.

30. A method according to claim 27, wherein it is the peak voltage across a rectifying member of a current valve having an IGBT as semiconductor device that is limited, and that the current limitation takes place by diverting a current from the collector of the IGBT until a predetermined level has been reached for the current and when this level is exceeded the share of the current above this level is diverted to the gate of the IGBT so as to increase the gate-emitter voltage thereof and influence the IGBT towards an increased conductivity.

31. A method according to claim 30, wherein said predetermined level of the current is controlled so as to control the time derivative of the voltage increase across the IGBT when the rectifying member is turning off.

32. A computer program product adapted to be loaded directly into the internal memory of a computer and comprising software code portions for instructing a processor to carry out the steps according to claim 27, when the product is run on a computer.

33. A computer program product according to claim 32, provided at least partially over a network as the Internet.

34. A computer readable medium having a program recorded thereon adapted to make a computer control the steps according to claim 27.