Method for controlling a direct current switch, direct current switch, and DC voltage system

Abstract

In a method for controlling a direct current switch having first and second semiconductor switches capable of being switched off, the first and second semiconductor switches are arranged between first and second terminals to enable conduction of a current with a first polarity through the first semiconductor switch and conduction of the current with a second polarity that is opposite to the first polarity through the second semiconductor switch. One of the first and second semiconductor switches is switched off as a function of a current measurement value.

Claims

1. A method for controlling direct current switch, in particular a fault current switch or a circuit-breaker, with the direct current switch having first and second semiconductor switches capable of being switched off, said method comprising: arranging the first and second semiconductor switches between first and second terminals to enable conduction of a current with a first polarity through the first semiconductor switch and conduction of the current with a second polarity that is opposite to the first polarity through the second switch; switching off one of the first and second semiconductor switches as a function of a current measurement value; registering a further current measurement value at a point at which a return current associated with the current measurement value is assumed; forming a difference between the current measurement value and the further current measurement value; and switching off the one of the first and second semiconductor switches, when an amount of the difference is exceeded.

2. The method of claim 1, wherein the first and second semiconductor switches are arranged antiserially.

3. The method of claim 1, wherein the first and second semiconductor switches are arranged in an antiparallel circuit and are each embodied in particular as a reverse-blocking IGBT.

4. The method of claim 1, further comprising switching off one of the first and second semiconductor switches in a fault situation.

5. The method of claim 4, further comprising detecting the fault situation as a function of a time derivation of the current measurement value to switch off the one of the first and second semiconductor switches.

6. The method of claim 1, wherein precisely one of the first and second semiconductor switches is switched off.

7. The method of claim 1, wherein switching off the one of the first and second semiconductor switches is selected as a function of a polarity of the current measurement value of the current.

8. The method of claim 1, wherein switching off the one of the first and second semiconductor switches is implemented at a first limit value of the first polarity and at a second limit value of the second polarity, with the first limit value being greater than the second limit value by at least 25%.

9. The method of claim 1, further comprising: detecting a short circuit by U.sub.CE monitoring; and switching off the short circuit by a local control device configured to trigger the first and second semiconductor switches, in particular independently of a superordinate controller.

10. The method of claim 1, further comprising: determining a of the first and second semiconductor switches by formation of an i*t value or i.sup.2*t value; and switching off the one of the first and second semiconductor switches, when a load limit value is exceeded.

11. The method of claim 1, wherein the difference is formed frequency-selectively, in particular for frequencies below 1 kHz.

12. A direct current switch, comprising: first and second terminals; first and second semiconductor switches capable of being switched off and arranged between the first and second terminals to enable conduction of a current with a first polarity through the first semiconductor switch and conduction of the current with a second polarity that is opposite to the first polarity through the second semiconductor switch; a local control device configured to switch off the current through the direct current switch as a function of a current measurement value by switching off one of the first and second semiconductor switches; and a current measurement device configured to register a further current measurement value at a point at which a return current associated with the current measurement value is assumed, wherein the local control device is configured to form a difference between the current measurement value and the further current measurement value end to switch off the one of the first and second semiconductor switches, when an amount of the difference is exceeded.

13. The direct current switch of claim 12, further comprising a comparator configured to detect a polarity of the current.

14. The direct current switch of claim 12, wherein each of the first and second semiconductor switches has U.sub.CE monitoring.

15. The direct current switch of claim 12, further comprising a protection element between one of the first and second terminals and one of the first and second semiconductor switches.

16. The direct current switch of claim 15, wherein the protection element is at least one of a switch-disconnector and a fuse.

17. The direct current switch of claim 12, further comprising a current measurement device and/or a voltage measurement device.

18. The direct current switch of claim 12, further comprising a superordinate controller configured to switch on and off the first and second semiconductor switches, said local control device including an interface to the superordinate controller.

19. A DC voltage system, comprising: an energy source having a DC voltage; an electric load having a DC voltage connection; and a direct current switch connected to the energy source and the electric load, said direct current switch comprising first and second terminals, first and second semiconductor switches capable of being switched off and arranged between the first and second terminals to enable conduction of a current with a first polarity through the first semiconductor switch and conduction of the current with a second polarity that is opposite to the first polarity through the second semiconductor switch, and a local control device configured to switch off the current through the direct current switch as a function of a current measurement value by switching off one of the first and second semiconductor switches, and a current measurement device configured to register a further current measurement value at a point at which a return current associated with the current measurement value is assumed, wherein the local control device is configured to form a difference between the current measurement value and the further current measurement value and, to switch off the one of the first and second semiconductor switches, when an amount of the difference is exceeded.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is described and explained in more detail below on the basis of the exemplary embodiments shown in the figures. In the drawings:

(2) FIG. 1 shows a direct current switch, connected to an electric load and an energy source, and

(3) FIG. 2 shows an energy supply system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) FIG 1 shows a direct current switch 1 which is connected to an energy source 5 and an electric load 6. The energy source 5 can be a generator, a photovoltaic system, an energy supply system or else an energy store, such as a battery for example. The direct current switch 1 serves to disconnect the electric load 6 from the energy source 5 and to switch off a current i. A current measurement device 4 is used to measure the current i and can be arranged inside the direct current switch 1 or outside the direct current switch 1. The semiconductor switches 2a, 2b which can be switched off are arranged antiserially between the first terminal 21 of the direct current switch 1 and the second terminal 22. This means that a current flow through the first semiconductor switch 2a flows through the diode which is antiparallel to the second semiconductor switch 2b. In the case of opposite polarity, i.e. a reverse current flow direction, the current flows through the second semiconductor switch 2b and through the diode which is antiparallel to the first semiconductor switch 2a. An antiparallel circuit of the two semiconductor switches 2a, 2b is not illustrated here. In this case diodes can be dispensed with, but the semiconductor switches must then be reverse-blockable.

(5) The local control device 3, which is connected to the control terminals of the semiconductor switches 2a, 2b, serves to trigger the semiconductor switches 2a, 2b. The open-loop logic and/or closed-loop logic uses the signal from the current measurement device 4 as an input variable in this case. The interface 11 to the superordinate controller 8 serves here for the connection to a superordinate controller 8 (not shown here).

(6) A fuse 9 can be integrated into the load branch as a further protection element and in the case of a high current load ensures the protection of the electric load 6, independently of the direct current switch 1, in particular independently of the local control device 3.

(7) FIG. 2 shows a DC voltage system 50 which has a plurality of energy sources 5 and electric loads 6. For the avoidance of repetition, reference is made to the description relating to FIG. 1 and the reference characters therein. These components are connected to one another via a busbar 7. The busbar 7 in this case comprises an outward conductor and a return conductor, which serves to conduct the current to the electric load 6 (outward conductor) and back (return conductor) to the energy source 5. The individual energy sources 5 and the electric loads 6 are in each case disconnectably connected to the busbar 7 via one or, not shown here, multiple direct current switches 1. The energy transmission within the DC voltage system between the components takes place by means of DC voltage on the busbar 7. A DC voltage is present between the two conductors in this case.

(8) At the lower electric load the option of fault current protection is to be explained in greater detail, so that some important components of the direct current switch 1 are illustrated more precisely. To create fault current protection another current measurement device 41 is present in the corresponding load path. The current measurement device 41 is arranged in one of the two conductors of the bulbar 7 and the corresponding other current measurement device 41 is arranged in the other conductor. Thus the outward current to the electric load 6 and the return current from said electric load 6 can be measured. If these currents are not identical, i.e. the difference is not equal to zero, it can be assumed that a fault current is present and the direct current switch opens its connection by means of at least one of the two semiconductor switches 2a, 2b which can be switched off. To this end the further current measurement device 41 can transmit the measured signal to the direct current switch 1. The local control device 3 (not shown here) evaluates this signal, for example by forming a difference with the signal of the current measurement device 4, and if required initiates the protection response, by setting said semiconductor switch into the blocking state by triggering at least one of the semiconductor switches 2a, 2b which can be switched off.

(9) Likewise it is possible to carry out the fault current protection using a superordinate controller 8. In this case the signal of the further current measurement device 41 is also transmitted to the superordinate controller 8 in addition to the signal from the current measurement device 4, which takes place for example via a corresponding interface 11. The superordinate controller 8 can additionally monitor the operating state of the individual components (energy sources 5 and electric loads 6) from the signals from the individual direct current switches 1 and if required trigger a single direct current switch 1 or multiple direct current switches 1. Likewise it is possible to determine information from these about the status of the individual components in the direct current system 50.

(10) To summarize, the invention relates to a method for controlling a direct current switch, wherein the direct current switch has a first semiconductor switch and a second semiconductor switch which can be switched off, wherein the first and the second semiconductor switches are arranged between a first terminal and a second terminal such that a current with a first polarity can be conducted through the first semiconductor switch and the current with a polarity that is opposite to the first polarity can be conducted through the second semiconductor switch, wherein one of the semiconductor switches is switched off as a function of a current measurement value. The invention further relates to a direct current switch having a first and a second semiconductor switch which can be switched off and a local control device for the performance of such a method. In addition the invention relates to a DC voltage system having at least one energy source with a DC voltage and at least one electric load with a DC voltage terminal and at least one such direct current switch