Converter and a method for controlling a converter

• US 20040240240A1
• Filed: 03/02/2004
• Published: 12/02/2004
• Est. Priority Date: 09/21/2001
• Status: Active Grant

• Current Assignee: ABB AB (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Ramezani, Esie, Jonsson, Tomas, Lundberg, Peter, Bijlenga, Bo, Johansson, Nicklas
• Granted Patent: US 6,995,994 B2
• Time in Patent Office: Days
• US Class Current: 363/56.12
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/4826 operating from a resonant DC source, i.e. the DC input voltage varies periodically, e.g. resonant DC-link inverters

Abstract

The invention relates to a converter provided with a resonant circuit (16), which converter comprises a device (31) for measuring the derivative (dI/dt) of the current through the current valves 82, 3) and a detection device (32) co-operating with said measuring device (31) for detecting a short-circuit in the converter, the detection device (32) being adapted to detect a short-circuit current when the current derivative (dI/dt) measured by the measuring device (31) is equal to or exceeds a stipulated current derivative limit value (dI/dt_lim) during a length of time exceeding a stipulated time limit value (t_lim). The invention also relates to a method for controlling such a converter.

Claims

1. A converter comprising:

a series connection of at least two current valves (2, 3) arranged between two poles (4, 5), a positive and a negative, of a direct voltage side of the converter, each of which current valves comprising at least one circuit (12) provided with a semiconductor component (13a, 13b) of turn-off type and a rectifying component (14a, 14b) connected in anti-parallel therewith, an alternating voltage phase line (11) being connected to a mid-point (10), denominated phase output, of the series connection between two current valves while dividing the series connection into two equal parts (1a, 1b),

a resonant circuit (16) comprising snubber capacitors (15), which are connected in parallel with a respective one of the semiconductor components (13a, 13b) of turn-off type of the current valves, and at least one inductor (17) and an auxiliary valve (18) provided with semiconductor components (20a, 20b) of turn-off type for recharging said snubber capacitors (15) in connection with a commutation of the phase current, and

a control device (24) for controlling the turn-on and turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves, wherein the converter comprises a device (31) for measuring the derivative (dI/dt) of the current through the current valves (2, 3), and a detection device (32) co-operating with said measuring device (31) for detecting a short-circuit in the converter, the detection device (32) being adapted to detect a short-circuit current when the current derivative (dI/dt) measured by the measuring device (31) is equal to or exceeds a stipulated current derivative limit value (dI/dt_lim) during a length of time exceeding a stipulated time limit value (t_lim).

2. A converter according to claim 1, wherein the respective current valve (2, 3) is provided with means (40) for limiting the size of the current derivative (dI/dt) of the current valve (2, 3) to a maximum value (dI/dt_max).

3. A converter according to claim 2, wherein the means (40) of the respective current valve (2, 3) for limiting the size of the current derivative (dI/dt) of the current valve (2, 3) to a maximum value (dI/dt_max) comprises a capacitor (41) in each one of the semiconductor components (13a, 13b) of turn-off type of the current valve arranged between the gate (G) and the emitter (E) of the respective semiconductor component (13a, 13b) of turn-off type.

4. A converter according to claim 3, wherein the means (40) further comprises a zener-diode (42) in each one of the semiconductor components (13a, 13b) of turn-off type of the current valve arranged between the gate (G) and the emitter (E) of the respective semiconductor component (13a, 13b) of turn-off type in series with the capacitor (41) arranged between the gate and the emitter.

5. A converter according to, claim 1, wherein the measuring device (31) is adapted, when the current derivative (dI/dt) measured by the measuring device (31) is equal to or exceeds the current derivative limit value (dI/dt_lim), to send signals indicating this to the detection device (32).

6. A converter according to, claim 1, wherein the measuring device (31) is adapted to send measuring signals to the measuring device (32) indicating the value of the measured current derivative (dI/dt).

7. A converter according to claim 1, wherein the measuring device (31) comprises a first measuring member (31a) for measuring the current derivative (dI/dt) in a first one (1a) of said two parts of the series connection of current valves (2, 3), and a second measuring member (31b) for measuring the current derivative (dI/dt) in a second one (1b) of said two parts of the series connection of current valves (2, 3).

8. A converter according to claim 1, wherein at least one of the circuits (12) with a semiconductor component (13a, 13b) of turn-off type and a rectifying component (14a, 14b) connected in anti-parallel therewith included in the current valves is provided with a measuring member (31a, 31b) for measuring the current derivative (dI/dt) connected in series with the semiconductor component (13a, 13b) of turn-off type included in the circuit (12) and in parallel with the snubber capacitor (15) belonging to the circuit (12).

9. A converter according to claim 1, wherein the control device (24) is adapted to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when the detection device (32) detects a short-circuit current as a consequence of the measured current derivative (dI/dt) being equal to or exceeding the current derivative limit value (dI/dt_lim) during a length of time exceeding the stipulated time limit value (t_lim).

10. A converter according to claim 1, wherein the converter comprises a device (33) co-operating with the detection device (32) for measuring the current strength (I) in the current valves (2, 3), the detection device (32) being adapted to detect a short-circuit current when the measured current strength exceeds a stipulated current strength limit value (I_lim).

11. A converter according to claim 10, wherein the device (33) for measuring of current strength (I) comprises a first measuring member (33a) for measuring the current strength (I) in a first one (1a) of said two parts of the series connection of current valves (2, 3), and a second measuring member (33b) for measuring the current strength (I) in a second one (1b) of said two party of the series connection of current valves (2, 3).

12. A converter according to claim 10, wherein, the control device (24) is adapted to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when the detection device (32) detects a short-circuit current as a consequence of the measured current strength (I) exceeding the stipulated current strength limit value (I_lim).

13. A converter according to claim 12, wherein the control device (24) is adapted, when the measured current strength (I) exceeds the stipulated current strength limit value (I_lim) in one (1a, 1b) of said two parts of the series connection of current valves (2, 3), to firstly initiate a turn-off of the semiconductor components (13b, 13a) of turn-off type of the current valves in the other part (1b, 1a) of the series connection and thereafter initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves in the part (1a, 1b) of the series connection where the measured current strength (I) exceeded the stipulated current strength limit value (I_lim).

14. A converter according to claim 13, wherein the control device (24) is adapted to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves in the part (1a, 1b) of the series connection where the measured current strength (I) exceeded the stipulated current strength limit value (I_lim) with a stipulated time delay (t_d) after the initiation of the turn-off of the semiconductor components (13b, 13a) of turn-off type of the current valves in the other part (1b, 1a) of the series connection.

15. A converter according to claim 1, wherein each semiconductor component (13a, 13b) of turn-off type of the current valves (2, 3) is provided with a control unit (25) adapted to execute a turn-on and turn-off of the associated semiconductor component (13a, 13b) of turn-off type guided by control signals received from the control device (24), the respective control unit (25) being adapted to send back to the control device (24) a confirmation in connection with the receipt of a control signal, and that the control device (24) is adapted to allow a turn-on of a semiconductor component (13a, 13b) of turn-off type of a current valve in one of the parts of the series connection of current valves (2, 3) only if it has received from all the control units (25) in the other part of the series connection of current valves (2, 3) a confirmation of received control signal concerning the turn-off of the associated semiconductor component (13b, 13a) of turn-off type.

16. A converter according to claim 1, wherein the respective current valve (2, 3) comprises members (25) for detecting a blocking voltage in the rectifying component/components (14a, 14b) of the current valve, and that the control device (24) is adapted to allow a turn-on of a semiconductor component (13a, 13b) of turn-off type in one of the parts (1a, 1b) of the series connection of current valves (2, 3) only if it has received from each current valve in the other part (1b, 1a) of the series connection of current valves (2, 3) a signal indicating that, a blocking voltage has been detected in the rectifying component/components (14b, 14a) of the current valve.

17. A converter according to claim 1, the respective current valve (2, 3) comprises members (25) for detecting a blocking voltage in the rectifying component/components (14a, 14b) of the current valve, and that the control device (24) is adapted to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) if no blocking voltage has been detected in a current valve within a predetermined period of time after the moment a turn-on signal has been sent to a current valve arranged in opposite polarity.

18. A converter according to claim 1, wherein the converter is an ARCP-converter, which comprises a series connection of at least two intermediate link capacitors (7, 8) arranged between the two poles (4, 5) of the direct voltage side of the converter, the resonant circuit (16) comprising a series connection of an inductor (17) and an auxiliary valve (18) arranged between the phase output (10) and a midpoint (9) of said series connection of intermediate link capacitors (7, 8), which auxiliary valve (18) comprises at least two semiconductor components (20a, 20b) of turn-off type arranged in opposite polarity in relation to each other.

30. A converter according to claim 11, wherein the control device (24) is adapted to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when the detection device (32) detects a short-circuit current as a consequence of the measured current strength (I) exceeding the stipulated current strength limit value (I_lim).

19. A method for controlling a converter, which converter comprises:

a series connection of at least two current valves (2, 3) arranged between two poles (4, 5), a positive and a negative, of a direct voltage side of the converter, each of which current valves comprising at least one circuit (12) provided with a semiconductor component (13a, 13b) of turn-off type and a rectifying component (14a, 14b) connected in anti-parallel therewith, an alternating voltage phase line (11) being connected to a mid-point (10), denominated phase output, of the series connection between two current valves while dividing the series connection into two equal parts (1a, 1b),

a resonant circuit (16) comprising snubber capacitors (15), which are connected in parallel with a respective one of the semiconductor components (13a, 13b) of turn-off type of the current valves, and at least one inductor (17) and an auxiliary valve (18) provided with semiconductor components (20a, 20b) of turn-off type for recharging said snubber capacitors (15) in connection with a commutation of the phase current, and

a control device (24) for controlling the turn-on and turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves, wherein the derivative (dI/dt) of the current through the current valves (2, 3) is measured and compared with a current derivative limit value (dI/dt_lim), a short-circuit current being detected when the measured current derivative (dI/dt) is equal to or exceeds the current derivative limit value (dI/dt_lim) during a length of time exceeding a stipulated time limit value (t_lim).

20. A method according to claim 19, wherein the size of the current derivative (dl/dt) of the respective current valve (2, 3) is limited to a maximum value (dI/dt_max).

21. A method according to claim 19, wherein the size of the current derivative (dI/dt) of the respective current valve (2, 3) is limited to a maximum value (dI/dt_max) with the aid of a capacitor (41) in each one of the semiconductor components (13a, 13b) of turn-off type of the current valve arranged between the gate (G) and the emitter (E) of the respective semiconductor component (13a, 13b) of turn-off type, preferably ire series with a zener-diode (42).

22. A method according to claim 19, the control device (24) is made to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when a short-circuit current has been detected as a consequence of the measured current derivative (dI/dt) being equal to or exceeding the current derivative limit value (dI/dt_lim) during a length of time exceeding the stipulated time limit value (t_lim).

23. A method according to claim 19, wherein the current strength (I) in the current valves (2, 3) is measured, a short-circuit current being detected when the measured current strength exceeds a stipulated current strength limit value (I_lim).

24. A method according to claim 23, wherein the control device (24) is made to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when a short-circuit current has been detected as a consequence of the measured current strength (I) exceeding the stipulated current strength limit value (I_lim).

25. A method according to claim 24, wherein the control device (24) is made, when the measured current strength (I) exceeds the stipulated current strength limit value (I_lim) in one (1a, 1b) of said two parts of the series connection of current valves (2, 3), to firstly initiate a turn-off of the semiconductor components (13b, 13a) of turn-off type of the current valves in the other part (1b, 1a) of the series connection and thereafter initiate a turn-off of the semiconductor components (13) of turn-off type of the current valves in the part (1a, 1b) of the series connection where the measured current strength (I) exceeded the stipulated current strength limit value (I_lim).

26. A method according to claim 25, wherein the control device (24) is made to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves in the part (1a, 1b) of the series connection where the measured current strength (I) exceeded the stipulated current strength limit value (I_lim) with a stipulated time delay after the initiation of the turn-off of the semiconductor components (13b, 13a) of turn-off type of the current valves in the other part (1b, 1a) of the series connection.

27. A method according to claim 19, wherein a turn-on and turn-off of the respective semiconductor component (13a, 13b) of turn-off type of the current valves (2, 3) is executed with the aid of a control unit (25) guided by control signals received from the control device (24), the respective control unit (25) sending back a confirmation to the control device (24) in connection with the receipt of a control signal, and that the control device (24) is made to allow a turn-on of a semiconductor component (13a, 13b) of turn-off type of a current valve in one of the parts of the series connection of current valves (2, 3) only if it has received from all the control units (25) in the other part of the series connection of current valves (2, 3) a confirmation of received control signal concerning the turn-off of the associated semiconductor component (13b, 13a) of turn-off type.

28. A method according to claim 19, wherein a blocking voltage in the rectifying component/components (14a, 14b) of the current valve is detected, and that the control device (24) is made to allow a turn-on of a semiconductor component (13a, 13b) of turn-off type of a current valve in one of the parts (1a, 1b) of the series connection of current valves (2, 3) only if it has received from each current valve in the other part (1b, 1a) of the series connection of current valves (2, 3) a signal indicating that a blocking voltage has been detected in the rectifying component/components (14b, 14a) of the current valve.

29. A method according to claim 19, wherein a blocking voltage of the rectifying component/components (14a, 14b) of the converter is detected, and that the control device (24) is made to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) if no blocking voltage is detected in a current valve within a predetermined period of time after the moment a turn-on signal has been sent to a current valve arranged in opposite polarity.

31. A method according to claim 20, wherein the size of the current derivative (dI/dt) of the respective current valve (2, 3) is limited to a maximum value (dI/dt_max) with the aid of a capacitor (41) in each one of the semiconductor components (13a, 13b) of turn-off type of the current valve arranged between the gate (G) and the emitter (E) of the respective semiconductor component (13a, 13b) of turn-off type, preferably in series with a zener-diode (42).

32. A method according to claim 20, the control device (24) is made to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when a short-circuit current has been detected as a consequence of the measured current derivative (dl/dt) being equal to or exceeding the current derivative limit value (dI/dt_lim) during a length of time exceeding the stipulated time limit value (t_lim).

33. A method according to claim 21, the control device (24) is made to initiate a turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves (2, 3) when a short-circuit current has been detected as a consequence of the measured current derivative (dI/dt) being equal to or exceeding the current derivative limit value (dI/dt_lim) during a length of time exceeding the stipulated time limit value (t_lim).