ES2585840T3 - Device for switching a direct current on a pole of a direct voltage network - Google Patents

Abstract

Device (1) for switching a direct current on a pole of a direct voltage network, with two connection terminals (2, 3) for serial connection to the pole, - a main current branch (4) extending between the connection terminals (2, 3), in which two mechanical switches (6, 7) are arranged, - a secondary current branch (5) extending in parallel connection with respect to the main current branch (4) between the connection terminals (2, 3), in which two mechanical switches (8, 9) and / or two power semiconductors (20, 21) are also arranged, - a central branch (11) connecting a point of central branch potential (10) of the main current path (4), disposed between the mechanical switches (6, 7), to a central branch potential point (12) of the secondary current branch (5), arranged between mechanical switches (8, 9) or power semiconductors (20, 21), where the device (1) is expensive cterized because the central branch (11) has a power switching unit (13), which has a serial circuit formed by bipolar submodules (14) respectively with at least one semiconductor power switch (22) and means for reducing a energy (24) that is released when switching, and where the device (1) has - switching means (34) for switching the direct current in the central branch (11), such that all the direct current is conducted through the central branch (11), where the switching means (34) have at least one activatable power semiconductor (22, 36).

Description

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DESCRIPTION

Device for switching a direct current on a pole of a direct voltage network

The present invention refers to a device for switching a direct current at a pole of a branch of a direct voltage network.

The growing demand for energy throughout the world and at the same time desired reduction of CO2 emissions make so-called renewable energies more attractive. Renewable energy sources are, for example, wind installations located at sea or also photovoltaic energy installations in very sunny desert areas. To be able to use energy economically as well! The connection between renewable energy sources and a land supply network is increasingly important. Given this background, more and more debate is being held on the establishment and operation of a continuous tension grid network. However, a premise for this is that short-circuit currents can be disconnected quickly and reliably, which can occur in such a continuous mesh tension network. This requires, however, some continuous voltage switches, which until now were not available in the market. Different concepts for a continuous voltage switch of this type are known from the state of the art.

WO 2011/057675 A1 describes a continuous voltage switch, which has an operating current path with a mechanical switch as! as a disconnection branch, which is connected in parallel to the operating current path. In the disconnection branch, a series circuit of semiconductor power switches is arranged, to which a freewheel diode is connected in parallel respectively. The switching units composed of the semiconductor power switches and the free pinon diodes are connected in antiseries, where the semiconductor power switches that can be disconnected are arranged in series and for each power semiconductor switch a power semiconductor switch is provided corresponding with opposite direction of passage. In this way and way the current can be interrupted in both directions in the disconnection branch. In the operating current path, apart from the mechanical switch, an electronic auxiliary switch is also arranged in series with the mechanical switch. In normal operation the current flows through the operating current path and, thus, through the electronic auxiliary switch as! as through the closed mechanical switches, since the semiconductor power switches of the disconnection branch represent a greater resistance to the direct current. To interrupt, for example, a short-circuit current, the electronic auxiliary switch is moved to its sectioning position. This increases the resistance in the operating current path, so that the direct current is switched in the disconnection branch. The quick mechanical disconnect switch can therefore be opened without power. The short-circuit current conducted through the disconnecting branch can be interrupted by means of the semiconductor power switches. To absorb the accumulated energy in the direct voltage network and which must be reduced for switching, some arresters are provided, which are connected respectively in parallel to the semiconductor power switches of the disconnection branch.

Document DE 694 08 811 T2 describes a continuous voltage switch, in which two mechanical switches are connected in series. The series circuit formed by the two mechanical switches is protected against high surges by means of a arrester and a capacitor. Only one of the mechanical switches is connected in parallel to a power semiconductor switch that can be connected and disconnected. When the mechanical switch is opened, an electric arc is produced. The voltage that falls on the electric arc turns on the power semiconductor switch, which short-circuits the parallel open mechanical switch. The electric arc goes out. The current conducted through the power semiconductor switch can then be interrupted by a corresponding activation of the power semiconductor.

In US 5,999, 388 a continuous voltage power switch is described, which can be integrated in series in a continuous voltage line. It consists of a series circuit of semiconductor power switches that can be connected and disconnected, to which a freewheel diode is connected in parallel respectively. Likewise, a arrester, for example a varistor, is connected in parallel to each power semiconductor switch to limit the voltage. The known continuous voltage switch is made purely electronically and is therefore switched much more quickly compared to the usual mechanical switches on the market. A short circuit current flowing through the continuous voltage switch can be interrupted within a few microseconds. However, there is the disadvantage that also the operating current has to be conducted through the semiconductor power switch. This results in high transmission losses.

WO 2011/141055 discloses a DC voltage switch, which can be connected in series at a pole of a high voltage DC network. The continuous voltage switch is composed of a series mechanical switch with a semiconductor power switch, to which a freewheel diode in parallel is connected in parallel. In parallel to the series circuit formed by a semiconductor switch of

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power and a mechanical switch is connected a series circuit consisting of a coil and a capacitor, that is an LC branch, as! as a arrester that limits the voltage that falls through the LC branch. Also, a arrester is connected in parallel to the power semiconductor switch. After opening the mechanical switch, the power semiconductor switch is switched on and off with the natural frequency of the LC branch. This generates an oscillation and finally a zero current crossing in the mechanical switch, so that the electric arc produced can be turned off.

Document DE 10 2010 008 972 A1 discloses a stepped switch for a stepped transformer with two load branches, where each of the two load branches has a mechanical main contact, which conducts a constant current. In parallel to each of the load branches, a series circuit consisting of a secondary mechanical contact and a semiconductor switching unit is also provided, by means of which the true load switching is carried out.

The object of the invention is to provide a device of the aforementioned class, with which fault currents can be disconnected reliably and economically in a continuous voltage network, where in normal operation reduced losses occur at the same time .

The invention solves this object by means of a device for switching a direct current in a pole of a direct voltage network with two connection terminals for the serial connection to a pole, a main current branch that extends between the connection terminals, in which two mechanical switches are arranged, a secondary current branch that extends in parallel connection with respect to the main current branch between the connection terminals, in which two mechanical switches and / or two power semiconductors are also arranged, a central branch connecting a central branch potential point of the main current path, arranged between the mechanical switches, to a central branch potential point of the secondary current branch, arranged between the mechanical switches or the power semiconductors and which has a power switching unit, which has a series circuit consisting of bipolar sub-modules it is respectively with at least one semiconductor power switch and means for reducing an energy that is released when switching, and switching means for switching the direct current in the central branch, such that all the direct current is conducted through of the central branch, where the switching means have at least one activatable power semiconductor.

According to the invention, a so-called H-circuit is provided which has two branches that run mutually in parallel, precisely a main current branch and a secondary current branch. The two parallel branches extend respectively between the two connection terminals, where each of the aforementioned branches has two mechanical switches. The potential point between the mechanical switches of the main current branch is connected, through a central branch, to the point of potential between the two mechanical switches or between the semiconductor power switches of the secondary current branch. In the central branch there is a power switching unit, which on its side comprises a series circuit formed by bipolar sub-modules. Each sub-module has at least one semiconductor power switch that can be connected and disconnected, that is to say IGBT, IGCT, GTO, etc., if necessary with parallel pinon diodes parallel respectively in the opposite direction. Instead, however, power semiconductor switches capable of driving in reverse can also be used. The number of sub-modules is based on the respective requirements. In any case, the sub-modules of the power switching unit must be able to absorb the applied voltages and disconnect safely and quickly enough even high short-circuit currents. The energy accumulated in the continuous voltage network and released when switching is reduced by means of convenient means to reduce the switching energy. In this respect it is, for example, non-linear resistors, for example arresters, varistors, etc. If the voltage that falls in them exceeds a threshold voltage, these construction pieces behave like ohmic resistors, where they transform the energy released by switching into thermal energy and deliver it to the outside atmosphere. The means for reducing switching energy are conveniently integrated in the sub-modules. Unlike this, the non-linear resistors are connected in parallel to one or more sub-modules. In addition to this, the sub-modules may also have energy accumulators in the context of the invention. The direct current to be switched can be conducted within the framework of the invention, in normal operation. Only through the main stream. Alternatively, the direct current is conducted, in normal operation, both through the main current branch and the secondary current branch. In any case, the H-circuit makes it possible to switch the direct current in such a way in the central branch that, regardless of the direction of the direct current, it is always conducted only in one direction through the central branch. The power semiconductors of the power switching unit only have to be designed to switch currents in one direction. However, in certain circumstances it is necessary to take into account countercurrents in the central branch, in the case of possible network oscillations.

In accordance with the invention, switching means are also provided which have at least one activatable power semiconductor. By means of the switching means it has become possible, within the framework of the invention, to start the switching of the direct current to be switched at least one section of the main current branch in the central branch. To do this, the semiconductor of the switching means is activated

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by means of a control signal, in such a way that either the resistance in the aforementioned section of the main current branch is increased and in the case of the secondary current branch or a circular current generated through the mentioned section or the sections is generated cited, which overlaps approximately zero with the direct current to be switched. The switching means support the mechanical switches when switching the direct current in the central branch.

Preferably, a loading branch is provided which, on the one hand, is connected to a counter-pole of the continuous voltage network polarized inversely with respect to the pole and, on the other hand, is connected or can be connected to the central branch, where the branch Load has an ohmic resistance. The loading branch is used both for commissioning and for operating the device in normal operation. If the load branch is connected, for example, to the central branch potential point of the secondary current branch, the main current branch is connected through the central branch and the load branch to the ground potential or to the backbone of the power network. continuous tension A voltage is applied to the power switching unit, which can be used, for example, for the operation of the power semiconductor switch electronics of the power switching unit. If the sub-modules in the central branch have energy accumulators, they can be charged through the load branch, where the value of the load current is determined by the design of the ohmic resistance of the load branch. The load branch is connected, within the framework of the invention, either continuously to the central branch or a mechanical switch, with which the connection between the load branch and the central branch can be established and interrupted again. Only by means of the ohmic resistance is it possible to continuously provide the connection between the load branch and the central branch in the case of a malfunction without mains. In the context of the invention, it is also not necessary to section the load branch with respect to the central branch before disconnection of a short-circuit current. The current flow is limited at all times, within the framework of the invention, by the ohmic resistance of the load branch.

If the power switching unit is ready to operate, for example, a short-circuit current can be interrupted by the device according to the invention. In normal operation a direct current flows through the main current branch, with its two mechanical switches, almost without losses. This is also valid for the branch of secondary current in the case of symmetrical conformations of the device according to the invention. In the event of a fault, the main current branch switch, located behind the potential point of the central branch in the direction of current flow, and the mechanical switch of the secondary current branch are opened, mounted if necessary in front of the potential point of central branch. By disconnecting the contacts of the switches, if no additional measures had been planned, an electric arc would be established. The switching means suppress the appearance of an electric arc, ideally completely. By opening the switches, the main current branch current in the central branch and in the lower part of the secondary current branch is switched. Then the power semiconductor switches of the power switching unit can interrupt the short-circuit current. The energy that is released is reduced by means to reduce the energy released when switching. Finally, the remaining mechanical switches of the device according to the invention are also opened. The short-circuit current is interrupted, and the central branch is galvanically sectioned with respect to the lines.

The resistance of the load branch must be designed with such a high ohmic value, that at least temporarily it can be operated at the full continuous voltage that is present and at the same with such a low ohmic value, that the load current necessary to preload can flow and permanently obtain the charge of the energy accumulators. To charge the energy accumulators of the power switching unit, a voltage of a few kilovolts is sufficient. The resistance of the load branch can therefore be designed with a high ohmic value. The maximum dissipated power and the constructive size of the ohmic resistance are therefore relatively small.

The load branch is connected or can be conveniently connected to a central branch potential point of the secondary current branch. According to this advantageous conformation of the invention, the load current flows from the main current branch through the entire central branch. All energy accumulators arranged in the central branch can be charged in this way, if the first mechanical switch of the main current branch in the direction of current flow is in its closed position.

The load branch conveniently features a mechanical switch connected in series to the ohmic resistance, which is designed to connect the load branch to the central branch. In the case of a mechanical switch, it can be a relatively slow mechanical switch because of the ohmic resistance, as already explained. The switch is for example a simple disconnector, which opens almost without current. The load branch resistance is thermally discharged through the switch, which can also be called preload resistance.

The sub-modules of the power switching unit advantageously present, at least partially, respectively a semiconductor power switch that can be connected and disconnected and a freewheel diode connected for this purpose in parallel in the opposite direction. Alternatively, each sub-module can also have a unique semiconductor power switch that can lead in reverse. As a semiconductor power switch, for example IGBTs, IGCTs, GTOs, etc. are contemplated. Normally a switch

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Power semiconductor features several power semiconductor switch chips arranged in a housing. To connect the load connections of the semiconductor power switch chips, for example, electrical connection cables are used. However, unlike this, semiconductor power switches can also be used which contact by pressure within the scope of the invention, in which the semiconductor power switch chips on the side of the load connection are connected to each other via a pressure contact These semiconductor power switches are known by the technician, however, so it is not necessary to analyze their conformation here in more detail.

The semiconductor power switches, which can be connected and disconnected from the sub-modules, are preferably designed to disconnect currents in one direction.

According to an improvement that differs from this, the submodules of the power switching unit, however, form two groups, respectively, with passages with the same orientation of their power semiconductor switches, where the power semiconductor switches of a group They are oriented against the semiconductor power switches of the other group. According to this advantageous improvement, the current can not only flow in both directions of current through the disconnection branch, but currents in both directions can also be safely disconnected. If the current flows for example due to network oscillations in the first direction, the power semiconductor switches of the first group are activated to interrupt the current in said first direction. If the current flows in the opposite direction, the power semiconductor switches of the second group are used.

In a preferred embodiment of the invention, the sub-modules of the power switching unit have at least partially respectively an electric energy accumulator and a serial circuit, connected in parallel to the electric energy accumulator, formed by two semiconductor power switches that can be connected and disconnecting respectively with a freewheel diode disposed in parallel to them, where a sub-module connection terminal is connected to a potential point between the semiconductor power switches that can be connected and disconnected and the other connection terminal It is connected to a pole of the electric energy accumulator. A sub-module topology of this type is also called a half bridge.

Naturally, in a sub-module, instead of a single power semiconductor switch, a synchronously activated serial circuit consisting of power semiconductor switches can also be used. Synchronously activated power semiconductor switches of the serial circuit then behave exactly like a single power semiconductor switch. This is also valid for the sub-modules described below, that is, also for the complete bridge circuit or the cutting controller circuit.

To reduce an energy that is released when switching, which is accumulated in the continuous voltage network, it is provided for each sub-module of the power switching unit at least one non-linear resistance for example in the form of a arrester and / or a varistor . The non-linear resistance is connected in parallel, for example, to the entire sub-module.

The sub-modules of the power switching unit, which are configured as bridging means, can interrupt the current in only one direction. If you want to interrupt the flow of current in two directions, you also need to configure two groups of sub-modules, where the sub-modules of one group are used to interrupt the current in a first direction and the sub-modules of the other group for interruption of the current in a second sense, as opposed to the first sense.

According to a preferred embodiment of the invention, however, the sub-modules of the power switching unit are at least partially configured as a complete bridge circuit and therefore have an electric energy accumulator and two serial circuits, connected in parallel to the accumulator. of electric energy, respectively with two power semiconductor switches that can be connected and disconnected with parallel pinon diodes parallel respectively in contrasense, where a first connection terminal is connected to the potential point between the two power semiconductor switches of the first series circuit and a second sub-module connection terminal to the potential point between the two power semiconductor switches of the second serial circuit. A complete bridge circuit of this type is capable of interrupting currents in both directions, that is, in other words, disconnecting them.

As already explained, each sub-module of the power switching unit conveniently presents a arrester and / or a varistor, either connected in parallel to a single semiconductor power switch that can be connected and disconnected or connected in parallel to the energy accumulator electric sub module.

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The submodules of the power switching unit advantageously have a series circuit formed by a semiconductor power switch that can be connected and disconnected with free pinon diodes and a diode, which has the same direction of passage as the freewheel diode. , where the serial circuit is connected in parallel to an electric energy accumulator and a first terminal block of sub-module is connected to the potential point between the semiconductor power switch that can be connected and disconnected, and the diode and the other terminal of Sub-module connection are connected to a pole of the electric energy accumulator, and the semiconductor power switch that can be connected and disconnected is arranged between the sub-module connection terminals. A sub-module of this type can be called semipuente with a single semiconductor of controllable power. A corresponding conformation of the complete bridge circuit may also be advantageous in the context of the invention. A complete bridge circuit will then be presented by two controllable power semiconductor switches.

In contrast to this, the sub-modules of the power switching unit are at least partially configured as cutting control modules. These cutting control modules have an electric energy accumulator, to which a first series circuit is connected in parallel. The first series circuit consists of a semiconductor power switch that can be connected and disconnected with a parallel freewheel diode in the opposite direction and a diode oriented in the same direction as the freewheel diode. In addition to this, a second series circuit is planned, which is also connected in parallel to the electric energy accumulator. The second series circuit consists of a semiconductor power switch that can be connected and disconnected with a parallel freewheel diode in the opposite direction and another diode oriented in the same direction as the freewheel diode. The diode of the second series circuit bridges an ohmic resistance. The first sub-module connection terminal is connected to a pole of the electric energy accumulator and the second sub-module connection terminal to the potential point between the disconnectable power semiconductor switch and the diode of the first series circuit. These control modules of cutting can transform particularly well the energy accumulated in the network and that must be reduced when switching into thermal energy and evacuating it to the outside atmosphere.

According to a preferred conformation, the switching means are arranged in the central branch in series with respect to the power switching unit and designed to generate a circular current, which flows through at least one of the mechanical switches of the main current branch and is opposed to the direct current to commute. A circular current of this type can be generated in both meshes to the left and to the right of the central branch, where each mesh is configured by the central branch, a section of the main current route and a section of the secondary current route. In a mesh it is directed against the main current to be switched in the main current branch. Both currents add zero in an ideal case, in such a way that the mechanical switch can then be opened without current in the said section of the main current branch. In the other mesh, however, the circular current and the direct current to be commuted flow in the main current branch in the same direction and are therefore reinforced. In the case of a symmetrical configuration of the device according to the invention, the corresponding to the secondary current branch is applied, such that a mechanical switch is also opened without current in the secondary current branch. In this regard, the two switches that open without current are arranged in the direction of the direct current, in the secondary current branch and in the main current branch, after the respective point of potential central branch. Only one external current can be influenced, that is, a current flowing outside the continuous voltage switch according to the invention, if at least one mechanical switch of the main current branch is open and a flow of the direct current to commute through the branch of secondary current, either by means of a mechanical switch also open or a diode. In this regard, the switching means are shaped in such a way that they generate such a high counter-voltage in the time window needed in said mesh, that the current flow in the main current branch can be suppressed and the mechanical switch opened without current , arranged behind the central branch potential point of the main current branch in the direction of direct current flow.

The switching means conveniently have a current sensor, which is arranged in the main current branch. The current sensor is connected to a control and regulation unit of the device according to the invention. The current sensor detects the current flowing through the main current branch and provides current measurement values for the regulation unit. The regulation unit checks whether the current measurement values received have an intervention criterion. An intervention criterion of this type is, for example, an excessive current increase, di / dt, or occurs when the measured current values exceed a current threshold value beyond a predetermined time window. However, basically any combination with other measurement values of protective devices, etc. is possible. or another criterion within the framework of the invention. If an intervention criterion of this type is presented, the current in the central branch is switched and the mechanical switch (s) is opened. As soon as the mechanical switches can absorb tension, the current flowing through the central branch is limited or disconnected. If you only want to limit the current in the central branch, but not disconnect it, only some sub-modules of the power switching unit are disconnected. If, in parallel to the disconnected sub-modules, a non-linear resistor is connected, such as a arrester, this action is taken to increase the electrical resistance of the central branch. Therefore, the current flowing through the branch is limited

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central. If the limitation has become unnecessary, for example after the rapid repair of a fault, the mechanical switches of the main current branch can be closed again, so that the current flows again almost without losses through the current branch main and, where appropriate, the branch of secondary current.

In a convenient development in relation to this the load branch is connected to the potential point between the power switching unit and the switching means. Such a connection of the load branch between the switching means and the power switching unit makes it possible, to charge the energy accumulators of the switching means, also to take advantage of parts of the secondary current branch for the charging current. This is particularly advantageous if the switching means have sub-modules that are shaped as so-called bridging means.

According to a preferred embodiment of the invention, the switching means form a series circuit of bipolar sub-modules, in which each sub-module has an electric energy accumulator and a semiconductor power switch connected in parallel to the electric energy accumulator. With the help of the power semiconductor circuit, the voltage of the bipolar sub-module that falls on the sub-module connection terminals can be adjusted. The voltage that falls on the electric energy accumulator or a zero voltage, that is, no voltage, is applied to the sub-module connection terminals. Because of the series circuit, the voltage that falls in the entire series circuit of the sub-modules of the communication means can be adjusted step by step, where the height of the steps corresponds to the voltage that falls on the electric energy accumulator of a sub module. The higher the voltage generated in said mesh by means of switching, the greater the circular current driven by this voltage.

The conformation of the power semiconductor circuit of the switching means may be a half-bridge or full-bridge circuit, as already described in relation to the sub-modules of the power switching unit. If the power semiconductor circuit is a half-bridge circuit, only a series circuit of two disconnectable power semiconductor switches with parallel pin-free diodes respectively is provided in the opposite direction, where a first sub-module connection terminal is connected to the point of potential between the semiconductor power switches that can be connected and disconnected and another sub-module connection terminal to a pole of the electric energy accumulator. The sub-modules configured as a half-bridge circuit of the switching means must be oriented in such a way that a counter voltage can be generated with the desired polarity in the operating current path. This is normally the case if the half-bridge circuits of the switching means are oriented in the opposite direction to the half-bridge circuits of the sub-modules of the power switching unit.

Unlike this, the semiconductor power circuit of the sub-modules of the switching means is configured together with the electric energy accumulator as a complete bridge circuit, where two series circuits are provided as already described above. The two series circuits are switched in parallel to the electric energy accumulator and have two power semiconductor switches that can be connected and disconnected respectively, with parallel pinon diodes parallel respectively in the opposite direction. Instead of power semiconductor switches with free pinon diodes, power semiconductor switches with reverse conduction capability can also be used. The potential point between the two power semiconductor switches is connected respectively to a sub-module connection terminal, in such a way that the voltage that falls on the electric energy accumulator, a zero or zero voltage, can be generated in the sub-module connection terminals. even the inverse voltage of the electric energy accumulator. The complete bridge circuit can thus generate voltages that have different polarities. These are particularly advantageous if it is intended to generate counter voltages for currents in both directions.

As the electric energy accumulator of the sub-modules, both of the switching means and of the power switching unit, a capacitor is provided, for example.

According to a conformation of the invention that differs from this the switching means are configured as semiconductor switching switches, which are arranged in the main current branch. The semiconductor switching switches can be switched on and off like the other power semiconductor switches and, if necessary, have a parallel freewheel diode in the opposite direction. Instead of the parallel connection between the power semiconductor circuit and the freewheel diode, power semiconductor switches with reverse conduction capability can be used. To reduce an energy that is released when switching, a arrester, a varistor or other non-linear resistor can be connected in parallel to the power semiconductor switches. Energy accumulators can also be used as capacitors, etc. To reduce energy. In this respect, the semiconductor switching switches are arranged between the potential point of the central branch, that is the central branch potential point of the main current branch and one of the mechanical switches of the main current branch. In this way two semiconductor switching switches with parallel freewheel diode are provided in

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contradiction and, if necessary, some arresters as means to reduce an energy that is released when switching. However, a non-linear resistance is not always essential and can be dispensed with within the framework of the invention as requested. To switch a current that flows through the main current branch in the central branch, the switching switch, located behind the point of potential of the central branch in the direction of the direct current flow, is moved to its interruption position where A current flow is interrupted through the switching switch. If the resistance through the main current branch becomes too large, the direct current in the central branch is switched and it can be interrupted there! specifically after the opening of the mechanical switches. At the same time that the activation of the semiconductor switching switch also opens the mechanical switch, arranged behind the switching semiconductor switch in the direction of current flow. The direction of passage of the switching semiconductor switch has been chosen in such a way that, by means of the switching semiconductor switch, a current flowing from the point of central branch potential to the respective associated mechanical switch can be interrupted. In order to interrupt both directions of current, the two semiconductor switching switches are mutually oriented in the opposite direction, in accordance with this example of realization.

If the secondary current branch does not have any semiconductor switching switch, the mechanical switches are open in normal operation, since otherwise the flow of current will flow through the secondary current branch because of the high resistance in the branch of mainstream. The secondary current branch must therefore have mechanical quick-closing switches, to ensure a switching in the central branch.

According to a preferred conformation of the invention, the secondary current branch also has two semiconductor switching switches, which are arranged and oriented as the main current branch switching switches. In normal operation the current can flow in this way both through the main current branch and through the secondary current branch. For switching the current in the central branch, the switching switch, arranged behind the central branch potential point of the main current branch in the main current branch, is thus moved once! as the switching switch, mounted in front of the central branch potential point of the secondary current branch in the direction of the current, to its respective sectioning position.

The secondary current branch can also have power semiconductors instead of two mechanical switches, where the center branch potential point is arranged between the mentioned power semiconductors. The power semiconductors mentioned have a direction of passage oriented in the opposite direction and are formed for example as diodes or thyristors. They prevent a flow of current through the branch of secondary current in normal operation.

The main circuit branch mechanical switches are configured as fast switches and designed to open within a range of 1 ms to 10 ms. The mechanical switches of the secondary current branch, however, are for example relatively slow mechanical switches, which open within a range of 10 ms to 60 ms. These fast switches have a reduced switching mass, which must be moved when switching. In addition to this, some drives are required that respond quickly, for example electrodynamic drives. The commercially available power semiconductor switches normally switch in an order of magnitude between 10 ms and 50 ms. These commercial switches are arranged for example in the branch of secondary current. They open before the appearance of a fault case, where the direction of the direct current to be switched is known. Obviously mechanical switches are also known that open within a range of milliseconds.

According to another variant of the invention it is convenient that the device according to the invention is also used modularly and, thus, be used as a bipolar or two-pole construction part in a series circuit.

Finally, it should be noted that it is true that the semiconductor power switches that can be connected and disconnected are revealed here always in relation to parallel pinon diodes in the opposite direction or as power semiconductors with reverse conduction capability. However, this is mainly due to the fact that disconnectable power semiconductors such as IGBTs. IGCTs, GTOs, etc. They are usually distributed on the market always with a parallel freewheel diode in contradiction. A counterwheel-free diode of this type is used to protect the power semiconductor switch which, in relation to a voltage opposed to its direction of passage, is extremely sensitive. The aforementioned freewheel diode, however, is not essential in all the cases shown here. These cases are clearly visible to the technician, so that no explicit reference is made to this in an isolated case. However, within the scope of protection, the embodiments of the invention must be included, in which the freewheel diode arranged in parallel in the opposite direction to the power semiconductor switch can be dispensed with.

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Convenient conformations and advantages of the invention are the subject of the following description of embodiments, with reference to the drawing figures, where the same reference symbols refer to construction pieces with the same effect, and where they show

Figure 1 a first example of embodiment of the device according to the invention,

Figures 2 and 3 the embodiment according to Figure 1 in different positions, to clearly show step by step the loading of the device according to Figure 1,

Figure 4 another example of embodiment of the device according to the invention,

Figures 5 to 8 some examples of realization of the sub-modules for use in the device according to the invention, and

Figures 9 to 14 other examples of embodiment of the device according to the invention.

Figure 1 shows an example of embodiment of the device 1 according to the invention, which has two connection terminals 2 and 3 with which the device 1 can be switched in series on a pole, that is to say a line of a continuous voltage network. The device 1 is used to interrupt a current flow at the pole of the direct voltage network and, thus, can be called a continuous voltage switch.

The device 1 has a current branch 4 as well as a secondary current branch 5. In the exemplary embodiment shown in Figure 1 both current paths have the same validity and have, in other words, approximately the same electrical resistance. A direct current flowing between the connection terminals 2 and 3 thus flows both through the main current branch 4 and through the secondary current branch 5. Both the main current branch 4 and the secondary current branch 5 they have two mechanical switches 6, 7, 8 and 9. respectively. Between the mechanical switches 6 and 7 of the main current branch 4, a central branch potential point 10 is configured. The central branch potential point 10 is connected through a central branch 11 to a point of central branch potential 12 of the secondary current branch 5. The central branch 11 has a power switching unit 13, which has a serial circuit formed by sub-modules 14, whose conformation will be treated in more detail later. Here it is already said that each of the sub-modules 14 has at least one semiconductor power switch that can be connected and disconnected, whose direction of passage is oriented from the center branch potential point 10 of the main current branch 4 to the point of central branch potential 12 of the secondary current branch 5. In this way, the currents that flow in this direction through the power switching unit 13 can be interrupted specifically by means of the semiconductor power switches that can be switched on and off. absorbing the energy that is released here uses energy absorbing means that is released when switching, that is, for example, non-linear resistors such as arresters or varistors. These arresters are either part of the sub-modules, as shown, or are connected in parallel to one or more sub-modules.

In FIG. 1, switching means 34 can also be recognized, which conformation is also discussed in more detail later. The switching means 34 have in any case at least one semiconductor power switch that can be connected and disconnected, which has not been shown in Figure 1. The switching means 34 produces, in the case of a corresponding activation of the or of the semiconductor power switches, a switching of the direct current to be disconnected at the central branch 11.

To start the electronics, if necessary to charge the electric energy accumulator of the power switching unit 13 and if necessary the switching means, a charging branch 15 is provided that has an ohmic resistance 16 as a preload resistor so as a mechanical switch 17, which is configured here as a disconnector. The loading branch 15 is connected to the ground potential in the exemplary embodiment shown in Figure 1. Unlike this, the loading branch 15 is connected to the counter pole, that is, for example, to a negative pole of a network of Continuous voltage, while connection terminals 2 and 3 are connected to the positive pole of the continuous voltage network. In both variants there would be the possibility, after applying the pole voltage to the connection terminal 2 and closing the switch 17 with the mechanical switch 6 closed, to take a voltage that falls on the semiconductor power switches that are connected and disconnected to supply power to the electronics of the semiconductor power switches and, thus, prepare for its operation the power switching unit 13. In addition there is the possibility of charging in a controlled manner the energy accumulators arranged in sub-modules 14, where the value of the load current is set by the value of the ohmic resistance 16. The ohmic resistance is designed in such a way that it can be operated at least temporarily with all the voltage that falls between the pole and the ground potential, respectively the counter polo. The switch 17 can remain basically closed.

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permanent with a sufficiently high design of the resistance 16. Unlike this, it can be used to discharge the ohmic resistance 16, which occurs when the switch 17 is opened.

Figures 2 and 3 clearly show the charge of energy accumulators of the sub-modules 14 of the power switching unit 13 and, if necessary, the sub-modules not shown of the switching means 34. To do this first only mechanical switches 6 and 17 are closed. The current load I then flows from the connection terminal 2 through the switch 6, through the central branch 11 and the load branch 15, to ground. First, electronic power controllers of the semiconductor power switches are loaded, then the high voltage energy accumulators of the sub-modules 14. If the power switching unit 13 is ready for operation, switch 7 closes. main current now flows through the mechanical switches 6 and 7 to the connection terminal 3. The load current flowing through the central branch 11 is maintained, however, while the switches 8 and 9 of the current branch are open secondary 5.

Figure 4 shows another example of embodiment of the device 1 according to the invention, which corresponds to a great extent with the example of embodiment according to Figure 1, where however switches 8 and 9 have moved between the terminal of connection 2 and a branch point 18 between the main current branch 4 and the secondary current branch 5, respectively between the branch point 19 and the connection terminal. Instead of them, power semiconductors 20 and 21 in the form of diodes are provided in the secondary current branch, which prevent a current from flowing from the connection terminal 2 or 3 through the secondary current branch 5 directly to the branch of load 15, without being conducted through the central branch 11. Basically, switches 8 and 9 between connection terminals 2 and 3 and branch points 18 or 19 can be dispensed with. However, they make possible the controlled connection of a section of the continuous tension network and the galvanic section of the unit with respect to the continuous tension network.

Examples of possible sub-modules 14 for device 1 according to the invention have been shown in Figures 5, 6, 7 and 8. Sub-module 14 shown in Figure 5 has only a single power semiconductor switch 22 that can be connected and disconnected with a freewheel diode 23 connected in parallel in the opposite direction. A sub-module 14 of this type can only be used, in the embodiments of the invention according to figures 1 to 4, forming part of the power switching unit 13, but not being part of the switching means 34, since these in the case of an arrangement in the central branch 11 have to present an electric energy accumulator to generate a circular current. To the parallel circuit formed by the semiconductor power switch 23 and the freewheel diode a arrester 24 is connected in parallel, which absorbs the energy that is released when switching. In the case of the arrester 24, this is a means to absorb the energy that is released when switching. Instead of a single power semiconductor switch that can be connected and disconnected it is also possible, within the framework of the invention to use a power semiconductor switch that can be connected and disconnected and can simultaneously activate a serial circuit, where a single arrester It is connected in parallel to the entire series circuit.

The number of sub-modules 14 in the power switching unit 13 depends on the blocking capacity of the power semiconductor switches 22, in this case IGBTs. It is currently within a range of up to 6.5 kV. The voltage in the high voltage DC networks, which are currently almost exclusively formed as point-to-point connections, is normally between 300 and 500 kV. 800 kV transmission lines are also known. The arresters 24 are sized in such a way that they together block with an applied operating voltage, that is, they are non-conductive. However, if the voltage that falls on them exceeds a maximum voltage, these become conductors, in such a way that a controlled current flow is made possible, where the arresters 24 are heated and deliver the electrical energy as thermal energy to The outside atmosphere The number of arresters 24 connected in series corresponds to the number of non-conductive sub-modules, that is, interrupted. If, therefore, sub-modules 14 are not transferred to their interruption position, a controlled current flow of magnitude can be set through the arresters. This is used for example for the controlled connection of a network section.

Figure 6 shows a sub-module 14, which configures a so-called half bridge. The half bridge is composed of an electric energy accumulator 25, here a high voltage capacitor, as well as a series 26 circuit that is connected in parallel to the electric energy accumulator 25. The series 26 circuit has two semiconductor power switches that can connect and disconnect connected to each other in parallel in the form of IGBTs 22, to which a freewheel diode 23 is connected in parallel respectively. A first connection terminal 27 is connected to the potential point between the two power semiconductor switches 22 of the series circuit 26. The second connection terminal 28 is at the potential of one of the poles of the electric energy accumulator 25. Between the terminals of connection 27 and 28 a bridging switch 29 is provided, with which sub-module 14 can be bridged in case of failure. If a single sub-module fails, the entire power switching unit 13 continues to have operating capacity. For the absorption of high short-circuit currents, a diode 30 is arranged between the sub-module connection terminals 27 and 28. This supports the free-wheel diode 23, also arranged between the sub-module connection terminals 27 and 28, in the case of high currents flowing through sub-module 14. Instead of a

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diode 30 a thyristor can also be used. A bridging switch 29 and a diode 30 or a thyristor 30 between the terminals are not always essential. If sub-module 14 is used, for example, in a power switching unit 13 to disconnect the current flowing through the central branch 11, it can be dispensed with without replacing a diode 30 or a thyristor used instead of the diode. In addition, semiconductor switches of pressure contact power can also be used in the context of the invention with a characteristic called "conduction in case of failure" (in English "conduction on fail"), which are also made conductors in case of failure. This would normally mean that diode 30 could be dispensed with. Finally, it should be noted that, instead of two isolated power semiconductor switches, a total of two series circuits of power semiconductor switches can be used respectively. The bridge means also has again a arrester 24, which is connected in parallel to the electric energy accumulator 25. This arrester 24 is also used again to absorb the energy that is released when switching. The arrester 24 is arranged, in the case of an exemplary embodiment that differs from Figure 6, between the sub-module terminals 27 and 28. Obviously the circuit in half a bridge according to Figure 6 can only interrupt the flow of current from the first sub-module connection terminal 27 in the direction of the second sub-module connection terminal 28. In the opposite direction the current flows without impediments and without control through the freewheel diode 23 and, if necessary, through the short-circuit diode 30. By means of the circuit in H, chosen in the context of the invention, the current to be disconnected flows, however, basically only in one direction through the central branch 11, in such a way that it is particularly preferred as a sub-module 14 in the central branch 11 a half bridge that switches the current. At this point, it is to be noted that to switch or limit the current, the upper power semiconductor switch 22 can also be dispensed with in Figure 6, which is therefore not arranged between the sub-module connection terminals 28, 29. The series circuit 26 according to figure 6, it will then correspond to the series circuit 26 according to figure 8. A sub-module of half-bridge 14 of this type is, however, not suitable for generating circular currents and, thus, also not being part of the means of switching 34 in the central branch 11, which will be discussed in more detail later.

Figure 7 clearly shows a sub-module 14, which has been carried out as a complete bridge circuit. Also the complete bridge circuit according to Figure 7 has an electric energy accumulator 25 and a first series circuit 26, formed by two IGBTs 22 with parallel freewheel diode 23 in counter direction. In addition, a second series circuit 31 is also provided, which is also connected in parallel to the electric energy accumulator 25 and which also has two IGBTs 22, in series with respect to each other, with a parallel freewheel diode 23 parallel respectively in contradiction. The first sub-module connection terminal 27 is connected to the potential point between the IGBTS 22 of the first serial circuit, while the second sub-module connection terminal 28 is connected to the potential point between the IGBTs 22 of the second serial circuit 31. The half-bridge circuit according to figure 6 is able, according to the activation of the IGBTs 22, to generate in the connection terminals of sub-module 27 and 28 or the capacitor voltage Uc that falls on the capacitor 25 or a zero voltage, that is to say a zero tension. In the connection terminals of sub-module 27 and 28, the capacitor voltage Uc that falls in the electric energy accumulator 25 or a zero voltage cannot be generated, but also the reverse capacitor voltage -Uc. In this way the sub-module connection terminals 27, 28 of the complete bridge circuit can be polarized differently. Here we want to emphasize again that in each 26 and / 31 series circuit, one of the IGBTs 22 can be dispensed with without being replaced, for example of the IGBT 22 represented respectively above in Figure 7. A complete bridge sub-module 14 of this type with in total two or three power semiconductors 22 that can be connected and disconnected is certainly suitable for switching or limiting the current in the central branch 11, forming part of the power switching unit 13. However, with such a sub module 14 It is possible to generate a circular current. A complete bridge sub-module 14 with two or three power semiconductor switches 22 that can be connected and disconnected is therefore not suitable for forming part of the switching means 34 in the central branch 11, the configuration of which will be discussed in more detail later.

Figure 8 shows a sub-module 14, which here is called the cutting controller module. Also the cutting controller module 14 has an electric energy accumulator 25 as! as a first series 26 circuit, which is connected in parallel to the electric energy accumulator 25. The series 26 circuit, however, has only a semiconductor power switch 22 with a freewheel diode 23 parallel in the opposite direction. In series with the semiconductor power switch 22, here an IGBT, another diode 32 is connected that is oriented in the same direction as the freewheel diode 23 of the first series circuit 26. In addition to this a second series circuit is again provided. 31, which is also connected in parallel to the electric energy accumulator 25 and also has only one IGBT 22 with a freewheel diode 23 in contradiction and, in series with it, another diode 32. In parallel to diode 32 of the second series circuit 31, an ohmic resistance 33 is provided. The second series circuit 31 is used to limit the voltage that falls on the electric energy accumulator 25. If it becomes excessively large, the IGBT 22 is connected, so that a flow of current through the ohmic resistance 33 as! as a discharge of the electric energy accumulator 25. The first sub-module connection terminal 27 is connected to the potential point between diode 32 and IGBT 22 of the first series circuit 26, while the second sub-module connection terminal 28 is located to the potential of the pole of the electric energy accumulator 25. Because of this connection it is not possible to apply the voltage of the electric energy accumulator between the connection terminals of sub-module 27 and 28. Only one current flow can be switched from the connection terminal from sub-module 27 to the sub-terminal connection terminal 28. The electric energy accumulator 25

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It is primarily used to supply power to the electronics of the IGBTs. The capacitor is also responsible for switching no voltage spikes when switching, because of which the semiconductors could be destroyed. With regard to this, it is to be noted that, instead of a second series 31 circuit, a arrester can also be used that is connected in parallel to the electric energy accumulator 25. In other words, the cutting controller module will then correspond to the circuit in half bridge shown in figure 6, where the IGBT 22 not disposed between the two sub-module connection terminals 27 and 28 can be dispensed with.

In the context of the invention, it can be advantageous, in the case of sub-module 14, both according to figure 7 and according to figure 8, that a semiconductor power switch, for example, is arranged between the sub-module connection terminals 27 and 28, for example a thyristor, or a mechanical switch 29, as shown in Figure 6 in relation to the half bridge. Mechanical switch 29 is used to bypass sub-module 14 if necessary.

Figure 9 shows another example of embodiment of the device 1 according to the invention, which corresponds to a great extent with the example of embodiment shown in Figure 1, where however the switching means 34 arranged in more detail have been represented in series with respect to the power switching unit 13. The switching means 34 are also composed of a series circuit consisting of sub-modules 14, of which only one is shown in Figure 9, where however, by means of the lines to strokes and points of the central branch 11, the serial circuit of these identical sub-modules 14 has been indicated in the figure. In accordance with the exemplary embodiment shown in FIG. 9, the sub-modules 14 of the switching means 34 are configured as a complete bridge circuit with the arrester 24 according to FIG. 7. The sub-modules 14 of the switching means 34 are provided for actuation. two mutually opposed circular currents in the meshes formed by the main current branch, the secondary current branch and the central branch. The device shown in Figure 9 is symmetrically shaped. In other words, the direct current to be disconnected flows in normal operation for example from the connection terminal 2 to the connection terminal 3, both through the main current branch 4 and through the secondary current branch 5. Each of the two circular currents generated by the switching means 34 are in contradiction with respect to the direct current to be switched in one of the mechanical switches, here 7 and 8, such that a current resulting from approximately zero is obtained in the respective mechanical switches 7 and 8. The mechanical switches 7 and 8 are therefore opened without current. The total current is switched to the central branch 11 and flows through the power switching unit 13 and the mechanical switches 6 and 9 to the connection terminal 3. Sub-modules 14 of the power switching unit 13 can disconnect or limit the direct current now. Then the remaining mechanical switches 6 and 9 can be opened.

By means of the sub-modules 14 of the switching means 34, two circular currents are actuated as described above through the two meshes formed by the central, secondary and main branches. One of the circular currents flows clockwise, while the other circular current flows counterclockwise through the respective mesh. This ensures that, regardless of the direction of the direct current to be disconnected, the direct current to be switched and one of the circulating currents always overlap in one of the mechanical switches 6, 7 of the main current branch and in a switch mechanical of the branch of secondary current 8 or 9 until forming zero. In this regard, the switches, in which a resulting current of approximately zero is set, are arranged on different sides of the central branch, that is to say in the direction of the direct current to be switched in front of or behind the center branch potential point of its respective branch. The said mechanical switches, eg 7 and 8, can then be opened, so that the current flows through the power switching unit 13, whose sub-modules 14 can then interrupt or limit the current flow. The sub-modules 14 of the switching means 34 shown in FIG. 9 also have a arrester 24, such that they can also act as sub-modules of the power switching unit 13. If the sub-modules 14 of the switching unit of Power 13 are also configured as full-bridge circuits according to Figure 7, one can also speak of only one serial circuit, where only the activation of the sub-modules by means of a control and regulation unit not shown makes a distinction, of whether the sub-modules 14 act as part of the switching means 34 or of the power switching unit 13. Naturally, a complete bridge sub-module 14 can also perform both actions displaced in time. Naturally, the sub-modules 14 of the switching means 34, which are configured according to FIG. 7 as a complete bridge circuit with arrester 24, can also be used to disconnect or limit the current.

At this point it is to be noted that in the context of the invention the sub-modules 14 of the power switching unit 13 do not always have to be identically shaped. In this way, a part of the sub-modules 14 can be formed, for example, according to figure 5, another part according to figure 6, another part according to figure 7 and a last part according to figure 8. The sub-modules 14 of the switching means 34, however, must have an electric energy accumulator 25 with which it is first possible to generate a circular current in the mesh. In addition to this, sub-module 14 must be able to generate the voltage that falls on the electric energy accumulator 25 at the sub-module connection terminals 27, 28.

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Figure 10 shows a conformation according to Figure 9, where however the switching means 34 are formed as circuits in half a bridge according to Figure 6, where however, no diode 30 and no bridge switch are provided. Also in figure 10 several sub-modules 14 of the switching means 34 are connected in series, where also this serial connection is clarified by the dashed and dotted lines. Unlike the complete bridge circuit according to figure 9, the half bridge circuit according to figure 19 can only generate a voltage polarity at the sub-module connection terminals 27 and 28. However, due to the current through the central branch 11 always flows only in one direction, this unique voltage polarity is totally sufficient to switch or limit a direct current in both directions. In addition to this, the sub-modules 14 of the switching means 34 cannot interrupt a current flowing from the main current branch 4 to the secondary current branch 5 through the central branch 11, since it flows through the diodes of free pin 23 between the sub-module connection terminals 27 and 28. After switching the current in the central branch 11 it may therefore be convenient to close the switch 29 that bridges the sub-modules 14 of the switching means 34, which is not shown in figures 9 and 10. If the sub-modules 14 of the power switching unit 13 also have a half-bridge circuit, the IGBTs or in relation to the IGBTs of the sub-modules 14 of the switching means 34 have an opposite orientation. . In the conformation of the device 1 shown in Figure 10, the switching means 34 generates circular currents that flow in one direction opposite to the other, that is to say in a clockwise direction or against the clockwise direction, such that two of the switches mechanics can be opened without current and the current is switched on the central branch 11. Because of the different polarization of the power semiconductor switches 22 of the sub-modules 14 of the switching means 34, compared to the sub-modules 14 of the power unit Power switching 13, the load branch 15 is no longer connected to the central branch potential point of the secondary current branch 5, but connected to the potential point between the power switching unit 13 and the switching means 34. The charging current to charge the electric energy accumulator 25 of the sub-modules 14 of the switching means 34 then flows from the connection terminal 3 through s of the switch 9, through the switching means 34 and finally through the loading branch 15, to ground or to the counter pole.

Figure 11 shows another embodiment of the invention, where not connected to each other in series is not an isolated device, but several bipolar devices 1. The mode of operation of the isolated devices corresponds to the mode of operation that has been explained in relation to the figures cited so far. The device 1 may also be structured in accordance with the other conformations of the invention represented or realized above. The number of devices 1 connected in series is completely voluntary. The series circuit has the advantage that the complete continuous voltage switch formed by it can be scaled better, to interrupt the current, and can be better designed for different voltage levels. Comparatively minor devices can be produced and handled more economically. The voltage that falls on the isolated switches is lower, so that the switching speed of the mechanical switches is accelerated. However, there is the disadvantage of the necessary synchronization of the isolated devices. In addition to this, it is possible, as already indicated in Figure 1, to equip the device 1 with an inductivity in the form of a coil or a choke. A coil or throttle of this type is also in the conformation according to figure 11, where the throttle is arranged distributed by the isolated devices. In this way the choke can also be scaled more easily.

Figure 12 shows another example of embodiment of the device 1 according to the invention, wherein the switching means 34 are no longer arranged in the central branch 11. Rather it is arranged between the center branch potential point of the main current branch 4 and each mechanical switch 6 and 7 of the main current row 4 a switching semiconductor switch 36 and 37, with a parallel freewheel diode 23 parallel respectively. In parallel to the semiconductor switching switch 36 and with this also a free arrester 24 is connected to each freewheel diode 23, which is used as a means to reduce an energy that is released when switching. The switching means 34 thus comprise the semiconductor switching switches 36, 37, the respective freewheel diode 23 as! as the respective non-linear resistance 24. The switching semiconductor switches 36 and 37 are mutually oriented in such a way that a current flow in both directions can be interrupted or limited. In comparison with figure 1, the semiconductor switching switches 36 or 37 support the mechanical switches 6 and 7, to switch the current in the central branch 11. If for example the current flows from the connection terminal 2 to the connection terminal 3 through the main current branch 4, with the mechanical switch 8 open, to switch off the current, the semiconductor switching switch 37 is activated and at the same time the mechanical switch 7. due to the resistance that increases so rapidly the flow is switched of current in the central branch 11, such that the power switching unit 13 can interrupt it. Then all the mechanical switches are opened.

Figure 13 shows another example of embodiment of the device 1 according to the invention, which corresponds to a great extent with the example of embodiment shown in Figure 12, where however two semiconductor switching switches 38 and 39 are also arranged in form of IGBTs in the branch of secondary currents 5. In accordance with this advantageous improvement in normal operation all mechanical switches 6, 7, 8 and 9 are closed. Semiconductor switching switches 36, 37, 38 and 39 have been

moved to its passage position, so that a current can flow from the connection terminal 2 to the connection terminal 3, both through the main current branch 4 and through the secondary current branch 5. To disconnect the current is transferred simultaneously to its sectioning position or the semiconductor switching switches 37 and 38 are opened! as mechanical switches 7 and 8. Then the current 5 flows from the connection terminal 2 to the central branch 11 and only through the main current branch 4, the mechanical switch 6, the freewheel diode 23 and then to through the freewheel diode 23 and the mechanical switch 9 closed, to the connection terminal 3. The power switching unit 13 can then interrupt the current.

Figure 14 clearly shows another conformation of the switch according to the invention, in which the 10 switching semiconductor switches 38 and 39 of the secondary current branch 5 are expendable with respect to the exemplary embodiment according to Figure 13. Instead they are two diodes 20 and 21 arranged in the secondary current branch 5, as in the example of embodiment according to figure 5. The diodes 20 and 21 prevent a current flow through the secondary current branch 5, without this being conducted previously through the central branch 11. Switches 8 and 9 support diodes 20 and 21, but are also expendable with a corresponding design of diodes 20 and 21.

Claims (21)

5 10 fifteen twenty 25 30 35 40 Four. Five 1. Device (1) for switching a direct current on a pole of a direct voltage network, with - two connection terminals (2, 3) for serial connection to the pole, - a main current branch (4) extending between the connection terminals (2, 3), in which two mechanical switches (6, 7) are arranged, - a secondary current branch (5) that extends in parallel connection with respect to the main current branch (4) between the connection terminals (2, 3), in which two mechanical switches (8, 9) are also arranged and / or two power semiconductors (20, 21), - a central branch (11) connecting a central branch potential point (10) of the main current path (4), arranged between the mechanical switches (6, 7), to a central branch potential point (12 ) of the secondary current branch (5), arranged between the mechanical switches (8, 9) or the power semiconductors (20, 21), where the device (1) is characterized in that the central branch (11) has a unit of power switching (13), which has a series circuit formed by bipolar sub-modules (14) respectively with at least one semiconductor power switch (22) and means for reducing an energy (24) that is released when switching, and where the device (1) presents - switching means (34) for switching the direct current in the central branch (11), in such a way that all the direct current is conducted through the central branch (11), where the switching means (34) have at least one activatable power semiconductor (22, 36). 2. Device (1) according to claim 1, characterized in that a load branch (15) is provided which, on the one hand, is connected to the ground potential or to a counter-pole of the continuous voltage network polarized inversely with respect to the pole and, on the other hand, it is connected or can be connected to the central branch (11), where the load branch (15) has an ohmic resistance (16). 3. Device (1) according to claim 2, characterized in that the load branch (15) is connected or can be connected to the center branch potential point (12) of the secondary current branch (5). Device (1) according to claim 2 or 3, characterized in that the load branch (15) has a mechanical switch (17) connected in series to the ohmic resistance (16), which is designed to connect the load branch ( 15) to the central branch (11). Device (1) according to one of the preceding claims, characterized in that the sub-modules (14) of the power switching unit (13) have, at least partially, respectively a semiconductor power switch (22) that can be connected and disconnected and a freewheel diode (23) connected for this in parallel in the opposite direction. Device (1) according to one of the preceding claims, characterized in that the power switching unit (13) is designed to disconnect currents in only one direction. Device (1) according to one of the preceding claims, characterized in that the sub-modules (14) of the power switching unit (13) have at least partially respectively an electric energy accumulator (25) and a serial circuit (26) , connected in parallel to the electric energy accumulator (25), formed by two semiconductor power switches (22) that can be connected and disconnected respectively with a freewheel diode (23) arranged in parallel in parallel, where a connection terminal of sub module (27) is connected to a potential point between the semiconductor power switches (22) that can be connected and disconnected and the other connection terminal (28) is connected to a pole of the electric energy accumulator (25). Device (1) according to one of the preceding claims, characterized in that the sub-modules (14) of the power switching unit (13) have at least partially an electric energy accumulator (25) and two series circuits (26, 31 ), connected in parallel to the electric energy accumulator (25), respectively with two semiconductor power switches that can be connected and disconnected with parallel pin-free diodes in the opposite direction, where a first connection terminal (27) is connected to a point of potential between the two power semiconductor switches (22) of the first series circuit (26) and a second sub-module connection terminal (28) to the potential point between the two power semiconductor switches (22) of the second series circuit (31) ). 5 10 fifteen twenty 25 30 35 40 Four. Five fifty 9. Device (1) according to one of the preceding claims, characterized in that the means for reducing the energy released when switching are varistors and / or arresters (24). 10. Device (1) according to claim 9, characterized in that the varistors and / or arresters are connected at least partially in parallel to an electric energy accumulator (25). Device (1) according to one of the preceding claims, characterized in that the sub-modules (14) of the power switching unit (13) are configured at least partially as control modules for cutting and have an electric energy accumulator (25) , to which a first series circuit (26) formed by a power semiconductor switch (22) is connected in parallel that can be connected and disconnected with a parallel freewheeling diode (23) in parallel and a diode (32) oriented in the same direction with respect to the freewheel diode (23), and a second series circuit (31) formed by a semiconductor power switch (28) that can be connected and disconnected with a freewheel diode (23) parallel in the opposite direction and another diode ( 32) oriented in the same direction with respect to the freewheel diode (23), where the diode (32) of the second series circuit (31) bypasses an ohmic resistor (33), and the first sub-module connection terminal (27) is connected to a pole of the electric energy accumulator (25) and the second sub-module connection terminal (28) to the potential point between the disconnectable power semiconductor switch (22) and the diode (32) of the first series circuit (26) . Device (1) according to one of the preceding claims, characterized in that the switching means (34) are arranged in the central branch (11) in series with respect to the power switching unit (13) and designed to generate a current circular, which is opposed to the direct current to commute. 13. Device (1) according to claim 12, characterized in that the load branch (15) is connected or can be connected to the potential point between the power switching unit (13) and the switching means (34). 14. Device (1) according to claim 12 or 13, characterized in that the switching means (34) form a serial circuit formed by bipolar sub-modules (14), wherein each sub-module (14) has an electric energy accumulator (25) and a semiconductor power switch (26, 31) connected in parallel to the electric energy accumulator (25). 15. Device (1) according to claim 14, characterized in that the power semiconductor circuit configures a serial circuit (26) formed by two disconnectable power semiconductor switches (22) with parallel pinon diodes (23) parallel respectively in the opposite direction, wherein a first sub-module connection terminal (27) is connected to the potential point between the semiconductor power switches (22) that can be connected and disconnected and another sub-module connection terminal (28) to a pole of the electric energy accumulator (25). 16. Device (1) according to claim 14, characterized in that the power semiconductor circuit configures two series circuits (26, 31) formed respectively by two power semiconductor switches (22) that can be connected and disconnected with free pinon diodes ( 23) parallel respectively in contrasense, where the potential point between the semiconductor power switches (22) that can be connected and disconnected from the first serial circuit (26) is connected to the first sub-module connection terminal (27) and the point of potential between the semiconductor power switches (22) that can be connected and disconnected from the second serial circuit (31) is connected to the second sub-module connection terminal (28). 17. Device (1) according to one of claims 1 to 11, characterized in that the switching means (34) are arranged in the main current branch (4) and have semiconductor switching switches (31, 37), at that means are connected in parallel to reduce an energy (24) that is released when switching, where each semiconductor switching switch (36, 37) is arranged between the potential central branch point (10) of the main current branch ( 4) and one of the mechanical switches (6, 7) of the main current branch (4). 18. Device (1) according to claim 17, characterized in that a semiconductor switching switch is arranged between each mechanical switch (6, 7) and the central branch potential point (10) of the main current branch (4). where the two semiconductor switching switches (36, 37) of the main current branch (4) are mutually oriented against each other. 19. Device (1) according to one of claims 17 or 18, characterized in that the secondary current branch (5) has switching semiconductor switches (38, 39), and connected in parallel to the switching semiconductor switches (38) , 38) means are provided for evacuating an energy (24) that is released when switching. 20. Device (1) according to claim 19, characterized in that between each mechanical switch (8, 9) or between each power semiconductor (20, 21) of the secondary current branch (5) and the center branch potential point ( 12) of the secondary current branch (5), a switching semiconductor switch (38, 39) is respectively arranged, wherein the two switching semiconductor switches (38, 39) are oriented 5 mutually inconsistent. 21. Device (1) according to one of the preceding claims, characterized in that the mechanical switches (6, 7) of the main current branch (4) are quick switches and are designed to open in a range of 1 ms to 10 ms, in where the mechanical switches (8, 9) of the secondary current branch (5) are comparatively slow mechanical switches, which open in a time range of 10 to 50 ms. 10 22. Installation for switching direct currents on a pole of a direct voltage network, with a serial circuit formed by devices (1) according to one of the preceding claims.