SYSTEM FOR RELIABLY SEPARATING A LOAD FROM AN ELECTRIC GRID FEEDING THE LOAD

Abstract

A system having at least two loads which are connected to a common feed line and can be switched off selectively and at least one interrupter switching element with an externally activatable ignition device is used for safely separating a load from an electric grid feeding the load.

Claims

1.-7. (canceled)

8. A system, comprising: at least two consumers which are connected to a common feed line, wherein each consumer comprised by the system is connected to the common feed line by means of its own parallel branch, wherein each consumer comprised by the system is assigned in the parallel branch leading to the respective consumer at least one interrupter switching element having an externally activatable ignition apparatus, wherein each consumer comprised by the system is assigned in the parallel branch leading to the respective consumer at least one current measuring device by means of which a current flowing in the parallel branch during operation is detectable, and wherein the ignition apparatus of the interrupter switching element in the respective parallel branch is actuated depending on the current flowing in the parallel branch, wherein the current measuring device is adapted to detect the direction of the current.

9. The system as claimed in claim 8, wherein each consumer comprised by the system is assigned in the parallel branch leading to the respective consumer the current measuring device and a voltage measuring device, wherein a voltage present in the parallel branch during operation is detectable by means of the voltage measuring device, and wherein the ignition apparatus of the interrupter switching element in the respective parallel branch is actuated depending on the current flowing in the parallel branch and depending on the voltage present in the parallel branch.

10. The system as claimed in claim 8, comprising: at least two interrupter switching elements which are connected in series and have externally activatable ignition apparatuses in each parallel branch, wherein the interrupter switching elements which are connected in series in one and the same parallel branch are actuated in parallel and at the same time.

11. The system as claimed in claim 8, wherein each consumer comprised by the system is preceded in the respective parallel branch by a series circuit composed of an actuatable semiconductor switching element and a switching element functioning as a current sink, wherein the actuatable semiconductor switching element is actuated depending on the current flowing in the parallel branch.

12. The system as claimed in claim 8, wherein each consumer comprised by the system is preceded in the respective parallel branch by a diode that permits a flow of current in the direction toward the consumer.

13. The system as claimed in claim 8, wherein each interrupter switching element is provided with a temperature color lacquer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the figures:

[0028] FIG. 1 shows a system having two consumers which are connected to a common feed line and have interrupter switching elements for the selective switch-off of each consumer by disconnecting it from the feed line,

[0029] FIG. 2 to FIG. 4 show further configurations of a system having two consumers which are connected to a common feed line and have interrupter switching elements for the selective shutdown of each consumer,

[0030] FIG. 5 shows an actuation device for actuating at least one interrupter switching element for the selective shutdown of a respective consumer,

[0031] FIG. 6 shows an activatable current sink upstream of a consumer that can be selectively switched off in order to reduce the current to be switched off, and

[0032] FIG. 7 shows an additional diode in series with the interrupter switching element for reducing the energy content to be absorbed.

DETAILED DESCRIPTION OF INVENTION

[0033] The illustration in FIG. 1 shows an example of a system 10 having at least two consumers 14 which are connected to a common feed line 12 via a respective parallel tap. The feed line 12 is, for example, a DC feed line. A DC feed line having a plurality of parallel taps is often also referred to as a DC bus. In the following text, the feed line 12 is referred to as the DC bus 12 for short, but without renouncing any further general validity. For example, converters (inverters) or a combination of a converter with a drive connected to the converter or another consumer come into consideration as consumers 14. A DC link capacitor 16 is connected upstream of such consumers 14 in a manner basically known per se.

[0034] Each consumer 14 comprised by the system 10 is connected to the DC bus 12 by means of its own parallel branch 20. Each consumer 14 comprised by the system 10 is assigned in the parallel branch 20 leading to the respective consumer 14 at least one interrupter switching element 22 having an externally activatable ignition apparatus, at least to protect the consumer 14 and/or to protect the feeding grid. An apparatus considered as an interrupter switching element 22 is known, for example, from DE 10 2014 115 397 A1 or DE 10 2016 124 176 A1.

[0035] To activate the at least one interrupter switching element 22, an activation apparatus 24 is provided. This generates, for example, an ignition pulse, which activates the ignition apparatus of the or each interrupter switching element 22 and causes the ignition apparatus to be ignited. Activation of the ignition apparatus of the respective interrupter switching element 22, referred to below for short as actuation of an interrupter switching element 22, causes a reliable and rapid interruption of the electrically conductive connection to the consumer 14 that previously existed via the interrupter switching element 22. After an interrupter switching element 22 has been actuated, for example due to a fault situation (short circuit or the like) in the consumer 14, the respective consumer 14 is reliably disconnected from the DC bus 12.

[0036] The illustrations in FIG. 2, FIG. 3 and FIG. 4 likewise show a system 10 having at least two consumers 14 connected in parallel with a DC bus 12. The difference from the illustration in FIG. 1 is the position and number of the interrupter switching elements 22.

[0037] In the configuration shown in FIG. 1, each consumer 14 is assigned in each of the two current paths (positive branch; negative branch) leading to a respective consumer 14 a respective interrupter switching element 22. In the configuration shown in FIG. 2, each consumer 14 is assigned in only one of the two current paths (positive branch; negative branch) leading to a respective consumer 14 a respective interrupter switching element 22.

[0038] In the configuration shown in FIG. 3, each consumer 14 is assigned in each of the two current paths (positive branch; negative branch) leading to a respective consumer 14 at least one series circuit composed of two interrupter switching elements 22, specifically a parallel circuit composed in each case of two interrupter switching elements 22 connected in series.

[0039] In the configuration shown in FIG. 4, each consumer 14 is assigned in only one of the two current paths (positive branch; negative branch) leading to a respective consumer 14 at least one series circuit composed of two interrupter switching elements 22, specifically a parallel circuit composed in each case of two interrupter switching elements 22 connected in series.

[0040] The illustration in FIG. 5 shows an interrupter switching element 22 in a current path leading to a consumer 14 (not shown). The current path starts from the DC bus 12 (likewise not shown). The illustration in FIG. 5 applies to a situation with exactly one interrupter switching element 22 in exactly one current path leading to the respective consumer 14, that is to say for configurations as shown in FIG. 2. The illustration in FIG. 5 applies in the same way to a situation with exactly one interrupter switching element 22 in each current path leading to the respective consumer 14, that is to say for configurations as shown in FIG. 1. The situation shown in FIG. 5 for only one current path then applies to both current paths. The measurement shown in FIG. 5 for only one current path then optionally takes place in both current paths, which leads to higher availability. The illustration in FIG. 5 furthermore also applies to situations with a plurality of interrupter switching elements 22 in each current path leading to the respective consumer 14 or to situations with a plurality of interrupter switching elements 22 in exactly one current path leading to the respective consumer 14, that is to say to configurations as shown in FIG. 3 or FIG. 4. The situation shown in FIG. 5 for only one interrupter switching element 22 then applies to a plurality of interrupter switching elements 22, which are actuated jointly and simultaneously, and possibly for both current paths.

[0041] In accordance with FIG. 5, each consumer 14 comprised by the system 10 is assigned in the parallel branch 20 leading to the respective consumer 14 at least one current measuring device 30. A shunt resistor, for example, functions as the current measuring device 30.

[0042] A current flowing in the parallel branch 20 during operation can be detected by means of the current measuring device 30 and the current flowing in the parallel branch 20 during operation of the respective consumer 14 is detected by means of the current measuring device 30. The current detection relates at least to a detection of the current intensity and the direction of the current flow. Optionally, the rate of increase in current is also detected as an additional tripping criterion.

[0043] A signal that encodes the current intensity that can be detected by means of the current measuring device 30 and that is detected during operation (current measurement value) can be fed to the two inputs of a comparator—first comparator—32 (or another comparison apparatus; referred to in the following text as comparator for short) and is fed to the comparator 32 during operation, in a manner basically known per se, together with a signal encoding a current limit value.

[0044] The activation apparatus 24 can be actuated by means of an output signal of the comparator 32 and is actuated during operation by means of the output signal of the comparator 32. The output signal of the comparator 32 can be generated depending on the result of the comparison of the signals present at its two inputs, and is generated during operation depending on the result of the comparison of the signals present at its two inputs. In the event of an overcurrent situation, that is to say a current measurement value exceeding the current limit value, the activation apparatus 24 is actuated and the interrupter switching element 22 (FIG. 2) or a plurality of interrupter switching elements 22 (FIG. 1, FIG. 3, FIG. 4) is or are actuated by means of the actuation of the activation apparatus 24. In the event of an overcurrent situation, the consumer 14 affected by the overcurrent situation is thus reliably disconnected from the DC bus 12.

[0045] In the embodiment shown in FIG. 5, a voltage measuring device 34 is provided in addition to the current measuring device, in a basically optional manner. A series circuit composed of two ohmic resistors connected to ground, for example, functions as the voltage measuring device 34. A signal that can be obtained by the voltage measuring device 34, for example the potential present at the center tap of the series circuit, or generally a signal (voltage measurement value) that encodes the electrical voltage in the parallel branch 20 can be fed to the two inputs of a comparator—second comparator—36 (or another comparison apparatus; referred to in the following text as comparator for short) and during operation is fed to the comparator 36, in a manner basically known per se, together with a signal that encodes a voltage limit value.

[0046] The activation apparatus 24 can be actuated by means of an output signal of the comparator 36 and is actuated during operation by means of the output signal of the comparator 36. The output signal of the comparator 36 can be generated depending on the result of the comparison of the signals present at its two inputs, and is generated during operation depending on the result of the comparison of the signals present at its two inputs. In the event of an overvoltage situation, that is to say a voltage measurement value exceeding the voltage limit value, the activation apparatus 24 is actuated and the interrupter switching element 22 (FIG. 2) or a plurality of interrupter switching elements 22 (FIG. 1, FIG. 3, FIG. 4) is or are actuated by means of the actuation of the activation apparatus 24. In the event of an undervoltage situation, the consumer 14 affected by the overcurrent situation is reliably disconnected from the DC bus 12.

[0047] In the case of a current measuring device 30 connected upstream of the activation apparatus 24 and a voltage measuring device 34 also connected upstream of the activation apparatus 24, the activation apparatus 24 can be activated both by means of the current measuring device 30 and by means of the voltage measuring device 34. The activation apparatus 24 can therefore be activated by means of the current measuring device 30 and by means of the voltage measuring device 34. To activate the activation apparatus 24, however, a corresponding signal from the current measuring device 30 or the voltage measuring device 34 is sufficient. The activation apparatus 24 is accordingly activated when there is an overcurrent situation or a brief undervoltage situation present or when there is an overcurrent situation and an undervoltage situation present.

[0048] The current limit value as an input signal for the comparator 32 is generated and provided by means of a logic circuit 40 (for example a logic circuit 40 in the form of a basically known microcontroller, ASIC, FPGA or the like). In the case of a (fundamentally optional, additional) voltage measurement, the voltage limit value is generated and provided as an input signal for the comparator 36 by means of a logic circuit 40, advantageously by means of the same logic circuit 40. The current limit value is specified or can be specified, in particular can be parameterized. In the case of a (fundamentally optional, additional) voltage measurement, the current limit value and the voltage limit value are specified independently of one another or can be specified independently of one another, in particular can be parameterized independently of one another.

[0049] The logic circuit 40 also determines the current direction and outputs an enable signal based on the determined current direction via an enable line 41. The enable signal may prevent activation of the activation apparatus 24. An enable signal with a first status blocks the activation apparatus 24 and prevents activation of the activation apparatus 24. An enable signal with a second status, which is complementary to the first status, does not cause the activation apparatus 24 to be blocked, and activation of the activation apparatus 24 is possible.

[0050] The activation apparatus 24 is blocked by means of the enable signal if the detected current direction shows that the current flows from the parallel branch 20 in the direction of the DC bus 12. This is the case when there is a short circuit present in a consumer 14 and the short circuit is fed, for example, from the DC link capacitor 16 of at least one further consumer 14 connected to the same DC bus 12. Such a consumer 14 is only indirectly affected by the short circuit and does not need to be switched off. The consumer 14 in which the short circuit is present should, of course, be switched off. The short-circuit current flows into this consumer 14 (current direction from the DC bus 12 in the direction of the consumer 14). In this current direction, the activation apparatus 24 is not blocked. The activation apparatus 24 can be activated on the basis of the current measurement and/or the voltage measurement and, in the event of a short circuit, is activated at least on the basis of the current measurement.

[0051] The current measuring device 30, the comparator 32 and the logic circuit 40 that supplies the current limit value together form an actuation device 42, namely an actuation device 42 connected upstream of the activation apparatus 24. Actuation of the activation apparatus 24 is possible by means of an output signal of the actuation device 42, that is to say for example an output signal of the comparator 32, and the activation apparatus 24 is actuated during operation in the event of an overcurrent situation. In the basically optional configuration shown in FIG. 5, the actuation device 42 additionally comprises the voltage measuring device 34 and the comparator 36. Actuation of the activation apparatus 24 is possible by means of an output signal of such an actuation device 42, that is to say for example an output signal of the comparator 32 or an output signal of the comparator 36, and the activation apparatus 24 is actuated during operation in the event of an overcurrent situation or an overvoltage situation.

[0052] An actuation device 42 by means of which at least the exceeding of a current limit value can be identified by a current measurement value recorded during operation, that is to say an overcurrent situation can be identified, as well as an actuation device 42 by means of which the activation apparatus 24 can be blocked or enabled depending on the current direction, is shown conceptually in the illustrations in FIG. 1 to FIG. 4 in each parallel branch 20 on the input side of the activation apparatus 24 shown there. The actuation device 42 is optionally a device as shown in FIG. 5, that is to say a device by means of which the exceeding of a current limit value by a current measurement value recorded during operation and the exceeding of a voltage limit value by a voltage measurement value recorded during operation can be identified, that is to say an overcurrent situation and an undervoltage situation can be identified, and such an actuation device 42 is also to be taken into account in the conceptual addition to the illustrations in FIG. 1 to FIG. 4 and represents an advantageous embodiment of the innovation proposed here.

[0053] The illustration in FIG. 6 shows a further fundamentally optional embodiment of a circuit in a parallel branch 20 outgoing from the DC bus 12 and leading to a consumer 14. FIG. 6 shows a configuration having in each case one interrupter switching element 22 in each current path of the parallel branch 20 (as in FIG. 1). The special feature of the embodiment shown in FIG. 6 also applies in the same way to the configuration in accordance with FIG. 2 (exactly one interrupter switching element 22 in exactly one current path), the configuration in accordance with FIG. 3 (a plurality of interrupter switching elements 22 in each current path) and the configuration in accordance with FIG. 4 (a plurality of interrupter switching elements 22 in exactly one current path). In the illustration in FIG. 6, the actuation device 42 shown as a block also comprises the activation apparatus 24, which is not illustrated separately for reasons of clarity.

[0054] The special feature of the embodiment shown in FIG. 6 consists in a current sink 44 that can be activated on the input side. In the exemplary embodiment shown, a capacitor 44 functions as the current sink 44. The current sink 44 can be activated in that an electronically actuatable semiconductor switching element 46, in the embodiment shown a thyristor 46, is connected upstream of said current sink in a series circuit. The series circuit composed of the semiconductor switching element 46 and the current sink 44 is connected between the two current paths of the parallel branch 20 and thus connected in parallel with the consumer 14 connected to the parallel branch 20.

[0055] The semiconductor switching element 46 is actuated by means of the actuation device 42, in particular by means of a signal output by the comparator 32 in the event of an overcurrent situation and thus depending on the current flowing in the parallel branch 20, that is to say for example a short-circuit current I.sub.K. The activation of the semiconductor switching element 46 and the activation of an interrupter switching element 22 or a plurality of interrupter switching elements 22 by means of the actuation device 42 take place simultaneously, in particular due to one and the same output signal routed to the semiconductor switching element 46 and to the or each interrupter switching element 22.

[0056] The semiconductor switching element 46 becomes conducting due to the actuation and the current sink 44 is thus connected between the two current paths of the parallel branch 20 (the current sink 44 is activated). When the current sink 44 is activated in this way, at least some of the current flowing in the parallel branch 20 flows—in the illustration of FIG. 6 as part I.sub.K1 of the short-circuit current I.sub.K shown—in the current sink 44 (a capacitor 44 acting as a current sink 44 is charged). By rapidly activating the current sink 44, at least some of the current I.sub.K flowing in the parallel branch 20, that is to say for example a short-circuit current, is routed into the current sink 44 within the first microseconds after an overcurrent situation has been identified. As a result, the current to be switched off by means of an interrupter switching element 22 or a plurality of interrupter switching elements 22 is reduced. The remaining current to be switched off is shown in the illustration in FIG. 6 as part I.sub.K2 of the short-circuit current I.sub.K; I.sub.K=I.sub.K1 I.sub.K2.

[0057] The illustration in FIG. 7 finally shows a further fundamentally optional embodiment of a circuit in a parallel branch 20 outgoing from the DC bus 12 and leading to a consumer 14. FIG. 7 shows—just as in FIG. 6—a configuration having in each case one interrupter switching element 22 in each current path of the parallel branch 20 (as in FIG. 1). The special feature of the embodiment shown in FIG. 7 also applies in the same way to the configuration in accordance with FIG. 2 (exactly one interrupter switching element 22 in exactly one current path), the configuration in accordance with FIG. 3 (a plurality of interrupter switching elements 22 in each current path) and the configuration in accordance with FIG. 4 (a plurality of interrupter switching elements 22 in exactly one current path). In the illustration in FIG. 7, the actuation device 42 shown as a block also—just as in FIG. 6—comprises the activation apparatus 24, which is not illustrated separately for reasons of clarity.

[0058] The special feature of the embodiment shown in FIG. 7 consists in at least one diode 48 connected in series with the at least one interrupter switching element 22. The diode 48 is connected in such a way that it is conducting for current flowing from the DC bus 12 into the consumer 14 and blocks a current flow in the opposite direction, that is to say for example a current flow due to the charge of the DC link capacitor 16 in the direction of the DC bus 12. This results in the current to be switched off being reduced for an interrupter switching element 22 to be switched off. This results from the fact that in the event of a short-circuit situation of a consumer 14, for example, no charge can flow away from the DC link capacitors 16 of other consumers 14 and the short-circuit current can increase.

[0059] The embodiments in accordance with FIG. 6 and FIG. 7 can optionally be combined and a combination of the embodiments in accordance with FIG. 6 and FIG. 7 is a partial aspect of the innovation proposed here.

[0060] Although the invention has been described and illustrated in detail by way of the exemplary embodiment, the invention is not restricted by the disclosed example or examples and other variations can be derived herefrom by a person skilled in the art without departing from the scope of protection of the invention.

[0061] Individual aspects of the description submitted here that are in the foreground can thus be briefly summarized as follows: A system 10 having at least two consumers 14 which are connected to a common feed line 12 and can be switched off selectively and the use of at least one interrupter switching element 22 having an externally activatable ignition apparatus for reliably disconnecting a consumer 14 from a feeding electric grid are specified.