阅读说明：本技术 用于直流电压电路的开关装置 (Switching device for DC voltage circuit ) 是由 T.贝克特 P.科伦斯伯格 H.南恩 H.希尔林 D.瓦格勒 于 2020-03-13 设计创作，主要内容包括：本发明涉及一种用于将直流电压支路耦合至直流电压总线的开关装置,其中,开关装置具有第一和第二开关模块的串联电路。第一开关模块针对第一电流方向具有可控的第一半导体开关元件,并且第二开关模块针对相反的电流方向具有可控的第二半导体开关元件。第一半导体开关元件与第一二极管并联连接,第一二极管在相反的电流方向上导通,并且第二半导体开关元件与第二二极管并联连接,第二二极管在第一电流方向上导通。两个开关模块的串联电路与第三半导体开关元件并联连接。(The invention relates to a switching device for coupling a dc voltage branch to a dc voltage bus, wherein the switching device has a series circuit of a first and a second switching module. The first switching module has a controllable first semiconductor switching element for a first current direction and the second switching module has a controllable second semiconductor switching element for an opposite current direction. The first semiconductor switching element is connected in parallel with a first diode which is conducting in the opposite current direction, and the second semiconductor switching element is connected in parallel with a second diode which is conducting in the first current direction. The series circuit of the two switching modules is connected in parallel with the third semiconductor switching element.)

1. A switching device (SCH1, SCH2) for coupling a DC voltage branch (DCA1, DCA2, DCA3) to a DC voltage bus (DCB),

wherein the switching devices (SCH1, SCH2) have a series circuit of a first switching module (SM1) and a second switching module (SM2),

wherein the first switching module (SM1) has a controllable first semiconductor switching element (Q1) for a first current direction and the second switching module (SM2) has a controllable second semiconductor switching element (Q2) for an opposite current direction,

wherein the first semiconductor switching element (Q1) is connected in parallel with a first diode (D1) which is conducting in the opposite current direction, and the second semiconductor switching element (Q2) is connected in parallel with a second diode (D2) which is conducting in the first current direction,

it is characterized in that the preparation method is characterized in that,

a series circuit of two switching modules (SM1, SM2) is connected in parallel with the semiconductor switching element (QU) which is bridged.

2. A switching device (SCH3) for coupling DC voltage branches (DCA1, DCA2, DCA3) to a DC voltage bus (DCB),

wherein the switching device (SCH3) has a parallel circuit of a third switching module (SM3) and a fourth switching module (SM4),

wherein the third switching module (SM3) has a controllable series circuit of a third semiconductor switching element (Q3) and a third diode (D3) for a first current direction, and the fourth switching module (SM4) has a controllable series circuit of a fourth semiconductor switching element (Q4) and a fourth diode (D4) for the opposite current direction,

wherein the third diode (D3) is turned off in the opposite current direction and the fourth diode (D4) is turned off in the first current direction,

it is characterized in that the preparation method is characterized in that,

the parallel circuits of the third and fourth switching modules (SM3, MS4) are connected in parallel with the bridging semiconductor switching element (QU).

3. Switching device (SCH1, SCH2) according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the semiconductor switching elements (QU) which are bridged are thyristors,

the thyristor is arranged to be switched conductive to support a current flow from the direct voltage branch to the direct voltage bus when, in a special case, the voltage on the direct voltage branch is higher than the voltage on the direct voltage bus.

4. Switching device (SCH1, SCH2) according to claim 1, 2 or 3,

it is characterized in that the preparation method is characterized in that,

the first and/or second or third and/or fourth semiconductor switching elements (Q1, Q2, Q3, Q4) are bipolar transistors, metal-oxide semiconductor field effect transistors, gallium nitride transistors or silicon carbide transistors with insulated gate electrodes.

5. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the method comprises the following steps of arranging a current sensor, wherein the current sensor can determine the magnitude and the current direction of current;

a voltage sensor is provided, which is able to determine, in particular, the magnitude of the voltage on the dc voltage bus side.

6. The switching device (SCH1, SCH2) of claim 5,

it is characterized in that the preparation method is characterized in that,

a control device (SE1) is provided, which is connected to the first semiconductor switching element (Q1) and the second semiconductor switching element (Q2) or the third semiconductor switching element (Q3) and the fourth semiconductor switching element (Q4) and to the control connections, in particular the gate connections, of the bridging semiconductor switching element (QU), and which is designed to detect the voltage and current,

below a first threshold value of the voltage and when a special-case current flows, the semiconductor switching element (QU) or thyristor which is bridged is switched on.

7. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the series circuit of the first switch module (SM1) and the second switch module (SM2) or the parallel circuit of the third switch module (SM3) and the fourth switch module (SM4) is connected in series, in particular on the direct-voltage branch side, with the splitter contacts (TK1, TK 3).

8. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the parallel circuit of the bridged semiconductor switching elements (QU) has an interruption device (RK1), in particular a relay contact, in particular a normally open contact.

9. Switching device (SCH1, SH2) according to claim 7 or 8,

it is characterized in that the preparation method is characterized in that,

the disconnection point (TK1, TK3) or the interruption device (RK1) can be actuated by the control device (SE1) in such a way that the current flow through the bridging semiconductor switching element (QU), in particular a thyristor, can be reset.

10. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the first threshold value of the voltage is between 10% and 50% of the nominal voltage of the dc voltage bus, in particular 30% of the nominal voltage of the dc voltage bus.

11. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the current sensor is a hall effect based sensor.

12. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

in a series circuit of the first and second switching modules (SM1, SM2), the emitters or collectors or sources or drains of the first and second semiconductor switching elements in the form of transistors (Q1, Q2) are connected to each other;

the anodes of the parallel diodes are connected to the emitter or source and the cathodes of the parallel diodes are connected to the collector or drain.

13. The switching device (SCH1, SCH2) of any of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the control device (SE1) is designed to interrupt the current flow by means of at least one switching module, in particular two switching modules, when a first threshold value of the current is exceeded, in particular when a current flows opposite to a special case.

Technical Field

The invention relates to a switching device for coupling a dc voltage branch to a dc voltage bus according to the preamble of claim 1 or 2.

Background

Dc voltage refers to a voltage of 1500 volts maximum. The dc voltage up to this level is also referred to as low voltage. More specifically, the direct current voltage particularly means a voltage greater than a low voltage having a direct current voltage of 120 volts. The DC voltage is particularly 400-800V.

Dc voltage circuit or dc circuit refers to a circuit for currents from 2 to 1000 or 5000 amperes, in particular a nominal current or a maximum current; more particularly for circuits for currents from 2 amps to 400 amps or 200 amps.

A dc voltage bus refers to at least a two-wire system having a positive conductor and a negative conductor that is supplied with a dc voltage by at least one energy source. Dc voltage devices, such as dc voltage consumers, loads, inverters, combined energy sinks (energy sources), pure (additional) energy sources, etc., are connected to the dc voltage bus via dc voltage branches. A plurality of dc voltage devices can also be connected to one dc voltage branch.

Direct voltage devices are, in particular, devices having a power of 1 kw to 500 kw.

In the meantime, dc voltage circuits, also referred to as dc voltage networks or low-voltage dc networks, which usually have a dc voltage bus with dc voltage branches, are increasingly being developed and built.

The DC voltage branch, also referred to as a load branch, is usually protected by a DC voltage switch (DC switch), referred to herein as a switching device. Such a switching device has at least one, usually two, switching modules, which have at least one controllable semiconductor switching element, also referred to as power electronic switching element, which may be connected in parallel with a diode.

The functions of the controllable semiconductor switching element and the parallel-connected diode can also be physically implemented in one semiconductor component. Such a structural element is said to be reverse-conducting.

In addition, a fuse cutout may be present.

Fig. 1 shows a switching device for coupling a dc voltage branch to a dc voltage bus according to the prior art.

Fig. 1 shows a dc voltage bus DCB, which has a positive conductor DCP and a negative conductor DCN, which are connected to a dc voltage energy source, not shown, for example, with a dc voltage of 600 volts.

A first direct-current voltage branch DCA1, a second direct-current voltage branch DCA2 and a third direct-current voltage branch DCA3 are arranged on the direct-current voltage bus DCB; additional dc voltage branches may be provided.

The first dc voltage branch DCA1 is connected to the first device G1 via a first switching device SCH1, and the second dc voltage branch DCA2 is likewise connected to the second device G2 via a second switching device SCH 2.

The first switching device SCH1 has a series circuit of a first and a second switching module SM1, SM 2. The first switching module SM1 has a controllable first semiconductor switching element Q1 for a first current direction and the second switching module SM2 has a controllable second semiconductor switching element Q2 for the opposite current direction.

A first diode D1 is connected in parallel to the first semiconductor switching element Q1, the first diode D1 is conducting in the opposite current direction to the first semiconductor switching element Q1, and a second diode D2 is connected in parallel to the second semiconductor switching element Q2, the second diode D2 being conducting in the first current direction of the first semiconductor switching element Q1.

The first switching device SCH1 is implemented with bipolar contacts (for positive and negative conductors), in this example the first and second switching modules SM1, SM2 being located in one conductor, in this example in the positive conductor of the first direct voltage branch DCA 1; the negative conductor is through and has no switch module. Alternatively, the switch modules SM1, SM2 may also be arranged in the negative conductor, or both conductors may have switch modules.

The series circuit of the two switching modules SM1, SM2 is followed by a disconnection contact on the device side or on the direct voltage branch side, wherein the first disconnection contact TK1 is provided for a positive conductor and the second disconnection contact TK2 is provided for a negative conductor, which is generally referred to as a disconnection contact, for current (galvansche) disconnection of the device or consumer.

The second switching means SCH2 is constructed in a similar manner. Further switching devices may be constructed in a similar manner.

The devices G1, G2 are typically dc voltage devices with a capacitance. In this example, the first device G1 has a first capacitance C1 and the second device G2 has a second capacitance C2. A large amount of energy is often stored in the capacitance of the (dc voltage) device.

If a fault occurs in the DC voltage circuit/DC voltage network or DC network according to fig. 1, for example a short circuit occurs at fault location F1 between second switching device SCH2 and second device G2, the short circuit there is fed from the surrounding DC voltage or DC branches and the energy source or capacitor (of the device) located therein. This results in a large current in the relevant switching device, in this example the second switching device SCH2, which triggers the switch-off.

It is important here that the other switching devices or switches are not triggered, so that a selective shutdown, known as a fault, is carried out.

In addition, the other switching devices should prevent as little as possible a current flow from the respective dc voltage branch or consumer branch to the short circuit, in order for the switching device, in this example the second switching device SCH2, to be reliably triggered. Therefore, in a switching device, a semiconductor that can be turned off, for example, a bipolar transistor having an insulated gate electrode (abbreviated as IGBT), is more obstructive because it generally has a desaturation characteristic and functions to limit a current. Furthermore, these semiconductor switches will turn off very quickly, typically in the range of single digit μ s.

If a short circuit occurs at the fault location F1, the energy of the second capacitance C2 (or the second capacitor C2) of the associated second device G2 discharges into the fault location. Additionally, the energy of the unrelated first and third dc voltage branch DCA1, the first capacitor C1 of DCA3 and possibly (not shown) the third capacitor C3 is also discharged into this fault location F1.

The first and third capacitors C1, C3 may provide a large (fault) current. For example, if the first device G1 has a small nominal current, the first switching arrangement SCH1 is dimensioned correspondingly small and the first switching arrangement SCH1 can interrupt the current flow even in the event of a fault in the other branch or not feed the other branch further before it is switched off.

The aim is to be able to carry the current in the reverse direction of the switching device (without saturation) for as long as possible.

Heretofore, this problem has been solved by significantly oversizing the switchgear, which is expensive or uneconomical.

Disclosure of Invention

The object of the present invention is to provide a solution to the above-mentioned problems, in particular to enable selective triggering of a switching device in a dc voltage branch.

This problem is solved by a switching device having the features of claim 1 or 2.

According to the invention, this is achieved in that a series circuit or a parallel circuit of two (electronic or semiconductor-based) switching modules is connected in parallel with the bridging semiconductor switching element. The bridged semiconductor switching element serves to conduct the current for special situations in which the voltage on the dc voltage branch is higher than the voltage on the dc voltage bus, in particular when the difference in voltage exceeds a threshold value of the voltage.

Normally, current flows from the dc voltage bus to the device via the switching means or the dc voltage branch, for example, in the positive conductor.

In a special case, on the positive conductor, the current flows from the device to the direct voltage bus through the switching means, which is also referred to as the reverse direction.

In a similar manner, in the normal case, on the negative conductor, the current flows from the device via the direct-voltage branch, the switching means, to the direct-voltage bus. In a special case, the current flows from the dc voltage bus, via the switching device or the dc voltage branch to the device via the negative conductor, i.e. in the reverse direction. The special case here refers to a current flow in the reverse direction, which may also be an allowed operating case.

The semiconductor switching element which is designed to be able to carry a greater current in one direction and the current in the reverse direction of the switching device for as long as possible is carried by the bridging semiconductor switching element, so that the switching device in the other direct voltage branch can be triggered. In this case, the semiconductor switching element that is bridging is activated.

Advantageous embodiments of the invention are specified in the dependent claims.

In an advantageous embodiment of the invention, the semiconductor switching element which is bridged is a thyristor which is arranged such that it can be switched on, for example, to enable a current in the positive conductor to flow from the device to the direct-current voltage bus. In a similar manner, if the switch module is arranged in the negative conductor, the thyristor is arranged in the negative conductor.

When current flows from the anode side connector of the thyristor to the cathode side connector of the thyristor through the switch module, the thyristor can be switched to be conducted; and the thyristors are arranged accordingly.

This has the particular advantage that, for the semiconductor switching elements which are bridged, a particularly simple and cost-effective solution is provided which can easily conduct large currents, in particular in one direction.

In an advantageous embodiment of the invention, the first and/or second or third and/or fourth semiconductor switching elements are bipolar transistors, metal-oxide semiconductor field effect transistors, gallium nitride transistors or silicon carbide transistors (SiC transistors for short) with insulated gate electrodes.

This has the particular advantage that a simple solution is given for the semiconductor switching elements of the switching module.

In an advantageous embodiment of the invention, a current sensor is provided, which can determine the magnitude and direction of the current. Furthermore, a voltage sensor is provided, which can determine, in particular, the magnitude of the voltage on the dc voltage bus side.

This has the particular advantage that for the switching device an integrated and compact solution is given which does not require external sensors.

In an advantageous embodiment of the invention, a control device is provided, which is connected to the first and second or third and fourth semiconductor switching elements and to the control connections of the bridged semiconductor switching elements, in particular to the respective gate connection, voltage sensor and current sensor, and which is designed to switch the bridged semiconductor switching element or thyristor into conduction when a first threshold value of the voltage is undershot and when a special case current flows, i.e. in the case of a thyristor, when a current flows from the anode-side connection of the thyristor through the switching module to the cathode-side connection of the thyristor.

This has the particular advantage that a compact solution with integrated control is given for the switching device.

In an advantageous embodiment of the invention, the series circuit or the parallel circuit of the two switching modules is connected in series with the disconnection point on the side of the dc voltage branch.

This has the particular advantage that a galvanic separation of the dc voltage branch (galvanosche) can be achieved.

In an advantageous embodiment of the invention, the parallel circuit of the bridged semiconductor switching elements has an interruption device, in particular a relay contact, in particular a normally open contact.

This has the particular advantage that, in the case of thyristors or similar semiconductor switching elements, the current flow can be reset (rackstellung) or reset (racksetzung).

In an advantageous embodiment of the invention, the disconnection point or the interruption device can be actuated by a control device in such a way that the current flow through the semiconductor switching element, in particular the thyristor, which is bridged, is resettable or resettable.

This has the particular advantage that, in particular when further feeding of the dc voltage bus through the dc voltage branch is to be inhibited, a controlled resetting of the current flow, in particular through the thyristor, is enabled by the control device.

In an advantageous embodiment of the invention, the first threshold value of the voltage is between 10% and 50% of the nominal voltage of the dc voltage bus, in particular 30% of the nominal voltage of the dc voltage bus.

Alternatively, the difference between the magnitude of the voltage of the dc voltage bus and the magnitude of the voltage of the dc voltage branch may be determined with a second voltage sensor, which is compared to a voltage threshold or a threshold value of the voltage.

This has the particular advantage that the criterion for the threshold value of the voltage is simple.

In an advantageous embodiment of the invention, the current sensor is a hall-effect sensor.

This has the particular advantage that a simple solution is given for the determination of the magnitude and direction of the current.

In an advantageous embodiment of the invention, in the series circuit of the first and second switching modules, the emitters or collectors or the sources or drains of the first and second semiconductor switching elements in the form of transistors are connected to one another. The anodes of the parallel diodes are connected to the emitter or source and the cathodes of the parallel diodes are connected to the collector or drain.

This has the particular advantage that, in accordance with the invention, a simple implementation of the switching module is provided.

In an advantageous embodiment of the invention, the control device is designed to interrupt the current flow by means of at least one, in particular two, switching modules, in particular in the normal case, if a first threshold value of the current is exceeded.

This has the particular advantage that the control device not only provides an overcurrent protection function, but also a function according to the invention.

All embodiments, which are dependent not only on claims 1 or 2 but also on individual features or combinations of features of the claims, allow the switching device to be improved, so that the selectivity in the dc voltage network is improved. In particular, devices of different power classes can thereby be operated on a common direct voltage bus.

Drawings

The described features, characteristics and advantages of the present invention, as well as the manner of attaining them, will become more apparent and be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings.

In the associated drawings:

fig. 1 shows a schematic diagram of a dc voltage branch with a switching device on a dc voltage bus according to the prior art;

fig. 2 shows a schematic diagram of a dc voltage branch with a switching device on a dc voltage bus according to the invention;

FIG. 3 shows a first schematic of the present invention;

FIG. 4 shows a second schematic of the invention;

FIG. 5 shows a portion of another switching device;

fig. 6 shows a further switching device according to the invention.

Detailed Description

Fig. 1 shows a schematic diagram of a dc voltage branch with a switching device on a dc voltage bus according to the prior art, which has already been described above.

Fig. 2 shows a schematic diagram according to fig. 1 with the difference that according to the invention a series circuit of a first and a second switching module SM1, SM2 is connected in parallel with a bridging semiconductor switching element QU (a thyristor in the example according to fig. 2). Here, a series circuit of two switching modules is arranged in the positive conductor of the first direct voltage branch DCA 1. The thyristor is connected with its cathode to a connection on the dc voltage bus side of the series circuit of the switching modules, which also forms a connection on the dc voltage bus side of the switching device, and with its anode to a connection on the installation side of the series circuit of the switching modules.

In this example, the first and/or second semiconductor switching elements Q1, Q2 are bipolar transistors (abbreviated as IGBTs) having insulated gate electrodes. However, it may also be a metal-oxide semiconductor field effect transistor or a gallium nitride transistor.

Furthermore, at least one current sensor, not shown, is provided, which can determine the magnitude and direction of the current in the direct voltage branch. Furthermore, at least one voltage sensor, not shown, is provided, which can determine the magnitude of the voltage in the dc voltage branch, in particular on the dc voltage bus side.

A control device SE1 is provided, which is connected to the control connections, in particular the gate connections, of the first, second and bridging semiconductor switching elements Q1, Q2, QU. Furthermore, control unit SE1 is connected to a voltage sensor (not shown) and a current sensor (not shown).

The control device SE1 is designed to switch the thyristor into conduction when the voltage is below a first threshold value and when a current flows from the anode-side terminal of the thyristor through the switching module to the cathode-side terminal of the thyristor.

The series circuit of the two switching modules SM1, SM2 is connected in series with the disconnection contacts on the direct voltage branch side, i.e. on the first device G1 side. In this example, the two conductors, i.e. the positive and negative conductor, of the direct voltage branch have separate contacts TK1, TK 2. The separating contact has a separating function, in particular according to a standard, i.e. a reliable galvanic separation with a standard-compliant spacing distance and/or creepage or air distance is given.

The disconnection contacts TK1, TK2 can be embodied as relay contacts which are actuated by the control device SE 1.

The bridged semiconductor switching element QU, in this example a parallel circuit of thyristors, has an interruption device RK1, in particular a relay contact, which in this example is designed as a normally open contact

The parallel circuit of the bridged semiconductor switching elements QU is connected in particular only in parallel with the switching module. As shown in fig. 2, the first and/or second split contacts TK1, TK2 are not comprised within the parallel circuit.

The first and second disconnection contacts TK1, TK2 or the interrupt device RK1 can be actuated by the control device SE1, so that the current flowing through the bridging semiconductor switching element, in particular the thyristor QU, can be reset.

The series-connected first and second switching modules SM1, SM2 may be designed such that the emitters or collectors or sources or drains of the first and second semiconductor switching elements Q1, Q2 are connected to one another, depending on the semiconductor switching elements used. In the example according to fig. 2, the collectors of the IGBTs are connected to each other. The emitters form respective external connections of a series circuit of switching modules SM1, SM2, a first external connection being connected to the dc voltage bus, if appropriate by means of a fuse, and a second external connection being connected to the device, if appropriate by means of the disconnection contacts TK1, TK 2.

As shown, the anodes of the parallel diodes are connected to the emitter or source and the cathodes of the parallel diodes are connected to the collector or drain.

The control device is also designed to interrupt the current flow by means of at least one, in particular two, switching modules when the current exceeds a first threshold value, in particular when a current flows in a normal case (as opposed to a special case).

Fig. 3 shows a schematic diagram of the present invention with a first semiconductor switching element Q1, a second semiconductor switching element Q2 and a first device or consumer load 1.

A bridging semiconductor switching element QU in the form of a thyristor is connected in parallel with the series circuit of the first and second semiconductor switching elements Q1, Q2.

Fig. 4 shows the schematic diagram according to fig. 3 with the difference that the first series circuit of the first and second semiconductor switching elements Q1, Q2 is connected to the dc voltage bus DCB via a first fuse Si1, the second series circuit with the fifth and sixth semiconductor switching elements Q5, Q6 in a similar manner is connected to the dc voltage bus DCB via a second fuse Si2, the bridging second semiconductor switching element QU in the form of a thyristor is connected in parallel with the fifth and sixth semiconductor switching elements Q5, Q6, and the second device or consumer load2 is connected to the bridging second semiconductor switching element QU.

Fig. 5 shows a third switching device SCH3 for coupling a dc voltage branch to a dc voltage bus according to fig. 1 or fig. 2, with the difference that the third switching device SCH3 has a parallel circuit of a third switching module SM3 and a fourth switching module SM4, wherein the third switching module SM3 has a controllable series circuit of a third semiconductor switching element Q3 and a third diode D3 for a first current direction, and the fourth switching module SM4 has a controllable series circuit of a fourth semiconductor switching element Q4 and a fourth diode D4 for an opposite current direction, wherein the third diode D3 is blocked in the opposite current direction and the fourth diode D4 is blocked in the first current direction.

The functions of the controllable semiconductor switching elements (Q3, Q4) and the series-connected diodes (D3, D4) can also be physically implemented in one semiconductor component. Such a structural element is said to be capable of reverse blocking.

In this example, the parallel circuit is arranged in the positive conductor. The parallel circuit has a third split contact TK3 in the positive conductor and a fourth split contact TK4 in the negative conductor.

Fig. 6 shows an arrangement according to fig. 5, with the difference that the parallel circuit of the third and fourth switching modules SM3, SM4 is connected in parallel with a bridging semiconductor switching element QU.

Further, for example, in the positive conductor, a current sensor SI is provided. Furthermore, a voltage sensor SU is provided, which is connected to the positive and negative conductors and is arranged in particular on the dc voltage bus DCB side for determining the magnitude of the voltage on the dc voltage bus DCB side.

The current and voltage sensors SI, SU are connected to the control device according to fig. 2. The control device is in turn connected to the third and fourth switching modules SM3, SM4, in particular to the control connections thereof, in particular to the gate connections of the third and fourth semiconductor switching elements Q3, Q4 (preferably bipolar transistors with insulated gate electrodes), etc.

The control device SE1 is connected to the control connection of the bridging semiconductor switching element QU, in particular to the gate connection of the thyristor.

The bridged parallel circuit of the semiconductor switching elements QU, in particular thyristors, has an interrupt device RK1, the interrupt device RK1 being connected in particular to the switching device SE 1.

In one embodiment, the third and fourth disconnection contacts TK3, TK4 can be connected to the control device SE1, as shown in fig. 6.

On the side of the dc voltage branch, i.e. on the side of the device, a further dc voltage sensor may be provided to determine the magnitude of the voltage on the side of the device, i.e. on the side of the dc voltage branch. The further dc voltage sensor may be connected to control unit SE 1.

The switching means according to fig. 6 may be used instead of the first and second switching means SCH1, SCH 2. Furthermore, a dc voltage branch with a first, second or third switching device SCH1, SCH2, SCH3 may be provided.

The present invention will be briefly described below.

An electronic bidirectional switching device having a semiconductor switch with a freewheeling diode is designed for operating currents, which can carry a saturation current only for a short time in the μ s range in the event of a short circuit.

Selective disconnection of the faulty branch becomes difficult when disconnecting the feedback current from the other branches. The aim is to carry the current in the reverse direction from the branch as long as possible without saturation.

For this reason, the size of the switching device needs to be designed to be excessively large. This is an expensive solution.

According to the invention, a further semiconductor switching element, in particular advantageously a thyristor, is provided in order to enable the branch to be discharged quickly via the dc voltage bus into the dc voltage branch which is defective.

The bridged thyristors QU act "in the reverse direction" as a bypass in parallel with the series circuit or parallel circuit of the switching modules or semiconductor switching elements or semiconductor switches. The thyristor QU is switched on or fired when a voltage limit value on the direct voltage bus (for example 30% of the nominal voltage of the direct voltage bus) is undershot and a (large) current flows from the device into the direct voltage bus (i.e. in the reverse direction) through the positive conductor of the direct voltage branch.

Thus, the switching modules SM1, SM2 or SM3, SM4 or the semiconductor switching elements Q1, Q2/Q3, Q4 do not need to conduct a full (short-circuit) current in the reverse direction, which is taken over by the (bypass) thyristor QU which is bridged. The thyristor conducts a (large) (short-circuit) current, which therefore provides the faulty direct-current voltage branch with sufficient energy for the disconnection to take place.

After the fault (short circuit) is removed, the switching device is reset. In particular, the bridged thyristors QU are turned off. This is mandatory if, after the short circuit has been eliminated, the voltage on the dc voltage bus side is greater than the voltage on the dc voltage branch side, or it can be done by opening the interruption device/relay contact RK1 in the line branch of the thyristor or by opening the disconnection contacts TK1, TK2 or TK3, TK 4.

Therefore, the switching devices SCH1, SCH3 are ready to be turned on again.

With the invention, improved selectivity can be achieved in a direct voltage distribution or direct voltage network with a plurality of branches and distributed capacitors. The switching device of the faulty branch is thus intensified for opening.

In the application case, the (additional) thyristor QU which is bridged is switched when the return (short-circuit) current is formed by the connected device or its capacitance.

With the invention, the switching modules SM1, SM2, SM3, SM4 or the semiconductor switching elements Q1, Q2, Q3, Q4 can be designed with smaller dimensions, with thyristors a robust overall structure being possible.

Although the invention has been illustrated and described in more detail in the details by means of embodiments, the invention is not limited to the examples disclosed, from which other variants can be derived by the person skilled in the art without departing from the scope of protection of the invention.