ALTERNATING-CURRENT POWER SWITCH AND METHOD FOR SWITCHING AN ALTERNATING CURRENT

Abstract

An alternating current circuit breaker has a series circuit of bipolar switching modules which are inserted in series into a phase line of an alternating current line. Each switching module has an energy storage device and actuatable power semiconductors that can be activated and deactivated. Each switching module can be driven such that a switching module voltage that corresponds to a positive or negative energy storage device voltage or a zero voltage can be generated at the poles of the switching module. A controller is configured to actuate the switching modules based on a polarity change of a phase current such that the switching module voltage switches polarity, wherein a switching module voltage opposite the phase voltage can be generated. A method for switching alternating currents is effected with the alternating current circuit breaker.

Claims

1-9. (canceled)

10. An alternating-current circuit breaker, comprising: a series circuit of bipolar switching modules to be inserted in series into a phase line of an alternating-voltage line; each said switching module having poles for carrying a switching module voltage, an energy-storage device and drivable power semiconductors capable of being switched on and off; each said switching module being configured to be driven such that said poles carry a switching-module voltage that corresponds to a positive or negative energy-storage voltage or to a voltage having a zero value; a control device connected to said switching modules, said control device being configured to drive said switching modules in dependence on a reversal of polarity of a phase current to cause the switching-module voltage to change a polarity thereof, enabling a switching-module voltage to be generated that is opposed to a phase voltage.

11. The alternating-current circuit breaker according to claim 10, wherein at least some of said switching modules are full-bridge circuits.

12. The alternating-current circuit breaker according to claim 10, wherein a sum of energy-storage voltages of said switching modules is greater than a product of a square root of two and a nominal voltage of the phase line.

13. The alternating-current circuit breaker according to claim 10, further comprising a monitoring device for monitoring energy-storage voltages of said switching modules, to enable a balancing of the energy-storage voltages.

14. A method for switching an alternating current, the method comprising: providing an alternating-current circuit breaker with a series circuit of bipolar switching modules inserted in series into a phase line of an alternating-voltage line, each switching module having an energy-storage device and drivable power semiconductors that are capable of being switched on and off, and each switching module being enabled to be driven such that poles thereof generate a switching-module voltage that corresponds to a positive or negative energy-storage voltage or to a voltage having a value of zero; using a control device for driving the switching modules; and driving the switching modules in dependence on a reversal of polarity of a phase current such that the switching-module voltage changes a polarity and a switching-module voltage opposed to a phase voltage is generated.

15. The method according to claim 14, which comprises driving the switching modules concurrently upon a reversal of the polarity of the phase current, to cause the switching-module voltage to change polarity.

16. The method according to claim 14, which comprises driving the switching modules in a time-shifted manner upon a reversal of the polarity of the phase current, to cause the switching-module voltages to change polarity in time-shifted manner.

17. The method according to claim 14, which comprises providing switching modules being full-bridge circuits.

18. The method according to claim 14, which comprises monitoring the energy-storage voltages with a monitoring device for balancing the energy-storage voltages.

Description

[0025] The invention will be elucidated further in the following on the basis of an embodiment example represented in FIGS. 1 and 2.

[0026] FIG. 1 shows an embodiment example of an alternating-current power switch according to the invention in schematic representation;

[0027] FIG. 2 shows a switching module for the alternating-current power switch according to the embodiment example shown in FIG. 1.

[0028] In detail, an embodiment example of an alternating-current power switch 1 is represented in FIG. 1. The alternating-current power switch 1 includes a first series connection 11 of bipolar switching modules 21, 22 and 23. The first series connection 11 has been serially inserted into a first phase line 31 of a three-phase alternating-voltage line 3.

[0029] Furthermore, the alternating-current power switch 1 includes a second series connection 12 of switching modules 24 to 26, which is arranged in a second phase line 32 of the alternating-voltage line 3, and a third series connection 13 of switching modules 27 to 29, which is arranged in a third phase line 33.

[0030] In the embodiment example represented in FIG. 1, all three series connections 11, 12 and 13 are of similar structure. All the switching modules 21-29 also exhibit the same structure. They are realized as full-bridge circuits.

[0031] At the connecting terminals of each switching module 21-29 a switching-module voltage Us1-Us9 falls. The switching-module voltages Us1-Us9 generally have differing values with differing polarities at a given time.

[0032] The sum of the switching-module voltages Us1-Us3 yields a total voltage Ug1 of the first series connection 11: Ug1=Us1+Us2+Us3.

[0033] Correspondingly, for a total voltage Ug2 of the second series connection and for a total voltage Ug3 of the third series connection it holds that Ug2=Us4+Us5+Us6 and Ug3=Us7+Us8+Us9.

[0034] By means of the switching-module voltages, a counter-voltage with respect to a phase voltage obtaining in the respective phase line 11-13 can consequently be generated, in order to switch off a current in the phase line. According to the embodiment example represented in FIG. 1, three switching modules are provided in each series connection. In general, the number of switching modules may be arbitrary and may have been adapted to the respective application. With a suitable number of switching modules that employ commercially available power semiconductors, voltages of up to 5 kV, for instance, can be switched off.

[0035] The alternating-current power switch 1 further includes a control device 4. The control device 4 is connected on the output side to each power-semiconductor switch of each switching module 21-29. The control device 4 is capable of switching each of the power-semiconductor switches on and off independently of one another. Hence the control device 4 is capable of driving the switching modules 21-29 in such a manner that predetermined switching-module voltages Us1-Us9, and hence also predetermined total voltages Ug1-Ug3, are generated at any time in each of the phase lines 31-33.

[0036] FIG. 2 shows the switching module 21 of the alternating-current power switch 1 shown in FIG. 1. The remaining switching modules 22-29 are of similar construction to switching module 21. Switching module 21 comprises four power-semiconductor switching units 41-44 and also an energy-storage device in the form of a power capacitor 40. Each power-semiconductor switching unit 41-44 exhibits a respective power semiconductor in the form of an IGBT 51-54 and a diode 61-64 antiparallel thereto.

[0037] Switching module 21 takes the form of a full-bridge circuit. By an appropriate drive of the individual power semiconductors 51-54, energy can be supplied to or withdrawn from the power capacitor 40. At the connectors or poles 71 and 72 of switching module 21 the voltage falling at the energy-storage device, also designated as the energy-storage voltage Ue, an oppositely-directed voltage Ue or even a zero voltage can be set by suitable switching of the power semiconductors 51-54 on and/or off in a manner known to a person skilled in the art. With respect to further details of the structure and mode of operation of the converter 3 and of the full-bridge circuit, reference is hereby made, incidentally, to printed publication WO 2015/003737 A1.

[0038] The reversal of polarity of the voltage falling at the connectors 71, 72 can be obtained by alternating switching of the power-semiconductor pairs 51, 54 and 52, 53 on and off.

[0039] By suitable switching of the power semiconductors 51-54 on and off, over and above this the power capacitor 40 can be recharged in a manner known to a person skilled in the art prior to or in the course of a fall in voltage.

[0040] In normal operation of the alternating-current power switch 1 the power capacitor 40 is generally bypassed. This is done, for instance, by switching power semiconductor 51 or power semiconductor 52 on, depending on the direction of the operating current.