ELECTRONIC CIRCUIT SWITCH

Description

[0001] The invention relates to an electronic circuit breaker comprising two semiconductor switches, each with a switching element and a diode arranged antiparallel to the switching element. Furthermore, the invention relates to a power grid having a first and a second power sub-grid, as well as to such an electronic circuit breaker for isolating the first power sub-grid from the second power sub-grid. The invention further relates to a method for operating such a power grid.

[0002] Mechanical and electronic switches are used today to switch currents. With mechanical switches, the contact between the two terminals of the switch is made or broken mechanically. These are particularly suitable for switching alternating current because they are inexpensive to manufacture and the switching action can be easily implemented due to the zero crossing of the current. For switching direct currents, mechanical switches become more complex because an arc that occurs complicates the switching behavior. Electronic switches are often used for this purpose nowadays. These use one or more turn-off semiconductor switches as the switching element. These semiconductor switches have the advantage of being able to switch direct current easily and without an arc. However, these electronic switches have conduction losses.On the other hand, an electronic switch has the advantage of its fast switching capability and a high number of possible switching operations. This leads to a long service life of the electronic switch.

[0003] An electronic switch, also referred to as a direct current switch, is known from EP 3 379 725 A1. The document describes a method for controlling such a direct current switch, wherein the direct current switch has a first turn-off semiconductor switch and a second turn-off semiconductor switch, wherein the first and the second turn-off semiconductor switches are arranged between a first terminal and a second terminal such that a current with a first polarity can be conducted through the first turn-off semiconductor switch and the current with a polarity opposite to the first polarity can be conducted through the second turn-off semiconductor switch, wherein one of the turn-off semiconductor switches is switched off as a function of a current measurement value.

[0004] Another electronic switch for a direct current network is known from WO 2014 / 044297 A1.

[0005] Since the semiconductor switches used can usually only switch off current in one direction, an electronic switch often contains at least two semiconductor switches. The semiconductors have a switching element that can switch a current on and off in one direction. The current in the other direction is bypassed by a diode arranged parallel to the switching element. This is said to be arranged anti-parallel to the switching element. By using two semiconductor switches arranged in series between the terminals of the electronic switch, it is possible to switch, or in particular switch off, a current through the electronic switch in both directions. This arrangement of the semiconductor switches is anti-serial to one another.This means that a first semiconductor switch can switch off a current of the first polarity, i.e. in one current direction, and the second switch can switch off a current of the opposite polarity, i.e. in the opposite current direction.

[0006] For use in a DC voltage network in which a load is connected to a DC voltage source via cables or busbars, also commonly referred to as feeders or supply lines, it is sufficient to equip only one of the two feeders with an electronic switch. With this electronic switch, the power supply between the power supply network and the load can be reliably interrupted. This is because a current of the same magnitude but different polarity always flows through the two feeders between which the DC voltage is applied. Particularly in isolated DC voltage networks, the electronic switch is only installed in one feeder in order to keep costs and losses low. However, if you want to reliably detect, control and localize an earth fault, you need to install a corresponding electronic switch in both feeders.By measuring the voltage across the two electronic switches in the respective feeders, sufficient information can be obtained to detect and locate an earth fault.

[0007] An energy grid is defined as a network of interconnected energy sources and / or electrical consumers. These can be divided into individual energy subgrids. The energy grid uses direct or alternating voltage to transmit electrical energy.

[0008] The invention is based on the object of improving an electronic switch for an alternating voltage network.

[0009] This object is achieved by an electronic circuit breaker according to claim 1.

[0010] Further advantageous embodiments of the invention are specified in the dependent claims.

[0011] The invention is based on the finding that an electronic switch suitable for protecting against damage in the event of a fault, in particular an earth fault, in a power grid, in particular in a DC voltage grid, can be improved by a modified arrangement of the semiconductor switches compared to a known electronic switch. To this end, the two anti-serial semiconductor switches of a known electronic switch are now arranged distributed in the various feeds between a power supply grid, a power source or generally a first power sub-grid and a load, consumer or generally a second power sub-grid. As a result, the connections between the first grid connection and the second grid connection no longer comprise a series connection of semiconductor switches.Since there is no longer a series connection of semiconductors between the first and second grid connections, this arrangement is also referred to as semiconductor-free. The two energy subgrids can each have any number of energy sources and / or loads, such as electrical consumers.

[0012] The semiconductor switch comprises a switching element and a diode. The diode is arranged antiparallel to the switching element. While the switching element can conduct current in one direction, the diode can only conduct current in the opposite direction, but cannot switch.

[0013] Two semiconductor switches of the same type are defined as having the same semiconductor switch structure. For example, bipolar transistors and field-effect transistors have different structures. Individual semiconductor switches are further differentiated by their NPN or PNP types, or by their P-channel or N-channel types. Thus, two semiconductor switches of the same type are defined by their being of the same type.

[0014] Since the electronic switch is intended to protect against a fault or the effects of a fault in the power grid, it is also referred to as an electronic circuit breaker. In the anti-parallel arrangement, the semiconductor switch is arranged in such a way that it can conduct a current from the first grid connection to the second grid connection and switch it off, and the diode of the respective semiconductor switch is arranged in such a way that it can conduct a current from the second grid connection to the first grid connection. The switching element of the respective semiconductor switch is arranged between the first and second grid connections in such a way that a current flows in the individual potential connections from the first to the second grid connection through the switching element, and a current flows in the opposite direction, i.e. from the second to the first grid connection, through the diode arranged anti-parallel to the switching element.Alternatively, it is also possible to arrange the switching element of the respective semiconductor switch between the first and second mains connection in such a way that a current flows in the individual potential connections, from the second to the first mains connection through the switching element and a current flows in the opposite direction, i.e. from the first to the second mains connection through the diode arranged antiparallel to the switching element.

[0015] By arranging them in different feeders, it is possible to separate the connection between the power supply network and the load, and thus also the energy exchange between the power supply network and the load, even if there is only one switching element in each feeder, because a current of the same magnitude but in a different direction flows through each feeder. The sum of the currents in one direction is equal to the sum of the currents in the other direction, which are distributed across the different feeders. The semiconductors are arranged in the respective feeders in such a way that they can switch off this current in one direction, in particular from the first network connection to the second network connection. This makes it possible to interrupt the connection and the energy exchange between the energy sub-networks, for example a power source and a load.The electronic circuit breaker thus has a total of at least four connections, at least two as the first mains connection for connection to a first energy sub-network, such as an energy source, and at least two further connections as the second mains connection for connection to a second energy sub-network, such as a load.

[0016] In a DC voltage network, the electronic circuit breaker advantageously has exactly two potential connections as the first network connection and exactly two potential connections as the second network connection, since for these applications there are exactly two feeds between the energy source and the load, between which the supply voltage, the DC voltage, is applied. The two potential connections of the respective network connections are then intended to be connected in this DC voltage network, on the one hand, to the positive potential of the load or energy source and to the negative potential of the energy source or load. In general, instead of an energy source and a load, there can be a first energy sub-network, i.e. a first DC voltage sub-network, and a second energy sub-network, i.e. a second DC voltage sub-network. These potential connections are therefore also referred to as the positive potential connection or the negative potential connection.negative potential connection. The current through the two leads is equal in magnitude during fault-free operation, but differs in sign. In other words, the current has a different polarity in the two leads. This represents the forward current and the return current between the power source and the load.

[0017] In general, such an electronic circuit breaker is also suitable for use in a single-phase AC network. This also has two supply lines to which the semiconductor switches can be distributed. The electronic circuit breaker then also has two potential connections per network connection, with the positive potential connection connected to the phase conductor, for example, and the negative network connection to the neutral conductor.

[0018] Use in a three-phase power grid is also possible. Depending on the design, this will have three or four feeds (three phases and possibly a neutral conductor). The electronic circuit breaker for such a grid then has three or four potential connections. Here, too, the switching elements are all arranged between the individual potential connections of the first and second grid connection so that they can conduct a current from the first grid connection to the second grid connection and switch it off. Here, too, the semiconductors are arranged between the first and second grid connection without using a series connection of two semiconductor switches. In this arrangement, the diodes of the semiconductor switch are also arranged anti-parallel to the switching element.

[0019] To reliably locate a fault such as a ground fault, it is not possible to install an electronic switch in just one feeder. Therefore, two electronic switches, each with two semiconductors, have been used to connect the power supply network to the load. In this case, however, the conduction losses of the individual switches result in a total of four times the conduction losses across the respective semiconductor conductors. The proposed electronic circuit breaker, which uses only two semiconductors, halves the conduction losses. It is also significantly cheaper to manufacture, as only half the semiconductors are required, thus eliminating the need for expensive semiconductor switches.

[0020] Due to the arrangement of the semiconductor switches, the first semiconductor switch can conduct and interrupt a current from the positive potential terminal of the first power supply connection to the positive potential terminal of the second power supply connection, and the second semiconductor switch can conduct and interrupt a current from the negative potential terminal of the first power supply connection to the negative potential terminal of the second power supply connection. This allows a current between the two energy sub-networks to be interrupted regardless of the direction of energy flow.

[0021] In an advantageous embodiment of the invention, the electronic circuit breaker has a voltage detector for measuring a voltage between the positive potential terminal of the first mains connection and an earth potential and / or a voltage between the negative potential terminal of the first mains connection and the earth potential and / or a voltage between the positive potential terminal of the second mains connection and the earth potential and / or a voltage between the negative potential terminal of the second mains connection and the earth potential.

[0022] Compared to an electronic switch that is only located in one feed, the electronic circuit breaker with a semiconductor in each feed has the advantage of also being able to obtain information about the status of the second feed. In a DC voltage network, the two semiconductor switches are distributed across the two feeds. Different values ​​can be measured between the first mains connection and earth potential and the second mains connection and earth potential using the respective voltage detection based on the forward voltage across the corresponding semiconductor switch or, if a current flows through the diodes, the forward voltage of the diodes. This information is helpful in detecting and locating faults such as earth faults in the DC voltage network.In other words, by distributing the semiconductors of the electronic switch from one supply to the two supplies, a degree of freedom in the measurement can be gained from which information on faults, in particular earth faults in the DC voltage network, can be determined. In contrast to an arrangement in which there is only one electronic switch in one of the two supplies, if a current occurs through the semiconductor switch or the diode in the other supply line, an earth fault can be reliably located based on the different potentials of the two terminals of the semiconductor switch compared to earth potential due to the forward voltage. At the same time, the electronic circuit breaker does not have any higher losses because it is designed for use in a DC voltage network with exactly two semiconductor switches in the current path to be switched.Since in the event of an earth fault only exactly one potential of a semiconductor terminal is equal to the earth potential, this information can be used to identify this terminal as the location of the earth fault.

[0023] By locating the ground fault, it is possible to transmit this information to a higher-level or further control or protective device, which then safely shuts down the area where the fault occurs. This also enables safe operation of the electronic circuit breaker. The affected area can then be shut down, for example, using its associated semiconductor switch or a mechanical switch, which generates virtually no losses during normal operation and only needs to be designed for a small number of switching operations.

[0024] In a further advantageous embodiment of the invention, the two identical semiconductor switches are each formed by an IGBT semiconductor switch. Due to its current-carrying capacity and blocking capacity, the IGBT is particularly suitable for the implementation of the proposed circuit breaker. Its design is based on an NPN transistor. This allows the circuit to be constructed symmetrically and behaves the same for both the positive and negative potential connections. Furthermore, an IGBT reacts sufficiently quickly to be able to separate the sub-networks from one another quickly, even in the event of a ground fault. Furthermore, its blocking capacity and overload capacity are sufficient to safely separate the networks from one another, especially when using inductive loads.

[0025] The invention is described and explained in more detail below with reference to the exemplary embodiments illustrated in the figures. They show: FIG 1 shows a power supply to a load via a known electronic switch, FIG 2 shows an electronic circuit breaker and FIG 3 shows a DC voltage system.

[0026] The FIG 1 shows a known arrangement in which an energy source 55 is connected to a load 56 via two known electronic switches 7. The electronic switches 7 are arranged in the individual leads 57, which electrically connect the energy source 55 to the load 56. This is, for example, a direct current network in which the energy source 55 and load 56 are connected to one another via two leads 57, and in which a direct voltage is applied between the two leads 57. In order to be able to disconnect the load 56 from the energy supply network 55, an electronic switch 7 is present in each of the two leads 57. By means of the electronic switch 7 in both leads 57, a current in just one of the two leads 57, as can occur, for example, in the event of an earth fault, can be reliably switched off.

[0027] The electronic switch 7 comprises a series circuit of two semiconductor switches 2 arranged in series. The semiconductor switches 2 have a switching element 21 which can conduct a current in one direction and switch it off. Arranged parallel to this switching element 21 is a diode 22 which can conduct a current in the opposite direction but cannot switch it off. The diode 22 is thus arranged anti-parallel to the switching element 21. The semiconductor switches 2 are arranged anti-serially. Anti-serial means that a current in one direction can be switched off by the electronic switch 7 using one of the two semiconductor switches 2 and a current in the opposite direction can be switched off by the other of the two semiconductor switches 2.

[0028] The FIG 2 shows an electronic circuit breaker 1.This has two semiconductor switches 2, in each of which the diode 22 is arranged anti-parallel to the switching element 21. In contrast to the already known electronic switch 7, this has a total of four phase connections 31, 32, 41, 42. Two of these phase connections 31, 32 form the first mains connection 3, and a further two of these phase connections 41, 42 form the second mains connection 4. The two leads to which the DC voltage is applied when used in a DC voltage network 6 are connected to both the first and second mains connections 3, 4. Thus, the phase connections 31, 32, 41, 42 at the first mains connection 3 and at the second mains connection each have a positive potential and a negative potential of this DC voltage. In order to be able to differentiate the connections of the mains connections from one another, they are referred to as the positive potential connection 31, 41 and the negative potential connection 32, 42.This designation will also be retained in the following if the electronic circuit breaker is used in an AC network and this involves a phase connection and a neutral conductor connection.

[0029] The semiconductor switches 2 are arranged in the leads in such a way as to interrupt the flow of energy between the first mains connection 3 and the second mains connection 4. This interruption can be ensured for both energy flow directions because the same current flows between the positive potential connection 31 of the first mains connection and the positive potential connection 41 of the second mains connection 4 as between the negative potential connection 32 of the first mains connection 3 and the negative potential connection 42 of the second mains connection 4. The currents only differ in their direction. This is a forward current and a return current from the energy source to the load. In order to be able to interrupt the flow of energy regardless of the direction of energy flow, the current flows once through the switching element 21 and once through the diode 22. The current can thus be interrupted regardless of the direction of energy flow.

[0030] In contrast to the use of two electronic switches 7 according to FIG 1 With the electronic circuit breaker, the forward and reverse current losses of the semiconductor switches 2 only occur twice in the entire circuit, whereas they occur four times when two electronic switches 7 are used. Thus, the electronic circuit breaker 1 can halve the losses compared to the known solution.

[0031] Due to the arrangement of the semiconductor switches 2, the first semiconductor switch can conduct and interrupt a current from the positive potential terminal 31 of the first network connection 3 to the positive potential terminal 41 of the second network connection 4, and the second semiconductor switch can conduct and interrupt a current from the negative potential terminal 32 of the first network connection 3 to the negative potential terminal 42 of the second network connection 4. This allows a current between the two energy sub-networks to be interrupted regardless of the energy flow direction.

[0032] The FIG 3shows an energy network 5. Due to the two feeds between, this can be a direct current network 6, for example. Alternatively, it can also be designed as an alternating current network. This energy network 5 generally has a first energy sub-network 51 and a second energy sub-network 52. These are connected to one another via two feeds 57, with the electronic circuit breaker 1 being incorporated into these feeds 57 in order to be able to separate the two sub-networks from one another or connect them to one another. The energy sub-networks 51, 52 can have one or more energy sources (not shown in detail) and / or one or more loads (not shown in detail), such as electrical consumers. It is possible for the energy sub-networks to have a combination of energy sources and loads.In the simplest case, one energy sub-network 51 is an energy source configured as a DC voltage source, and the second energy sub-network is a load supplied with a DC voltage. With the aid of the electronic circuit breaker 1, the energy flow between the two sub-networks can be interrupted regardless of the energy flow direction. Furthermore, this arrangement can be used to detect and localize an occurring fault, in particular a ground fault, by measuring and evaluating the voltage present at the respective potentials 31, 32, 41, 42 relative to ground potential. This is particularly advantageous for use in an isolated DC voltage network.

[0033] In summary, the invention relates to an electronic circuit breaker comprising two semiconductor switches, each with a switching element and a diode arranged antiparallel to the switching element.In order to improve the electronic switch, in particular with regard to the losses occurring during operation and with regard to fault localization, it is proposed that the electronic switch further comprise a first mains connection and a second mains connection, each with a positive potential connection and a negative potential connection, wherein a first of the semiconductor switches is arranged without a semiconductor series connection between the positive potential connection of the first mains connection and the positive potential connection of the second mains connection and a second of the semiconductor switches is arranged without a semiconductor series connection between the negative potential connection of the first mains connection and the negative potential connection of the second mains connection, wherein the switching element of the respective semiconductor switch is arranged in such a way as to be able to conduct a current from the first mains connection to the second mains connection and to switch it off.The invention further relates to an energy network, in particular a direct current network, comprising a first energy sub-network and a second energy sub-network, wherein the energy network comprises such an electronic circuit breaker for isolating the first energy sub-network and the second energy sub-network from one another, wherein the first energy sub-network is connected to the first grid connection and the second energy sub-network is connected to the second grid connection. Furthermore, the invention relates to a method for operating such an energy network.

Claims

1. Electronic protection switch (1) for a single-phase or three-phase AC voltage network, having - two semiconductor switches (2) of the same kind, each with a switching element (21) and a diode (22) arranged antiparallel to the switching element (21), and - a first network terminal (3) and a second network terminal (4), each with a positive potential terminal (31,41) and a negative potential terminal (32,42), wherein the semiconductor switches of the same kind are of an identical type, wherein a first of the two semiconductor switches (2) of the same kind is arranged without a semiconductor series connection between the positive potential terminal (31) of the first network terminal (3) and the positive potential terminal (41) of the second network terminal (4) and a second of the two semiconductor switches (2) of the same kind is arranged without a semiconductor series connection between the negative potential terminal (32) of the first network terminal (3) and the negative potential terminal (42) of the second network terminal (4), wherein the switching element (21) of the respective semiconductor switch (2) is arranged so as to be able to conduct and switch off a current from the first network terminal (3) to the second network terminal (4), wherein the two semiconductor switches (2) of the same kind are each formed by an IGBT semiconductor switch.

2. Electronic protection switch (1) according to claim 1, wherein the electronic protection switch (1) has precisely two semiconductor switches (2) for switching a current between the network terminals (3,4) in an AC voltage network, wherein the positive potential terminal (31) is connected to the phase and the negative potential terminal (32) to the neutral conductor.

3. Electronic protection switch (1) according to one of claims 1 or 2, wherein the electronic protection switch (1) in each case has a voltage detection for measuring a voltage between the positive potential terminal (31) of the first network terminal (3) and a ground potential and / or a voltage between the negative potential terminal (32) of the first network terminal (3) and the ground potential and / or a voltage between the positive potential terminal (41) of the second network terminal (4) and the ground potential and / or a voltage between the negative potential terminal (42) of the second network terminal (4) and the ground potential.

4. Electronic protection switch (1) according to one of claims 1 to 3, wherein the two semiconductor switches of the same kind each have a design based on an NPN-type transistor.

5. Energy network (5) with a first energy subnetwork (51) and a second energy subnetwork (52), wherein the energy network (5) has an electronic protection switch (1) according to one of claims 1 to 4 for disconnecting the first energy subnetwork (51) and the second energy subnetwork (52) from one another, wherein the first energy subnetwork (51) is connected to the first network terminal (3) and the second energy subnetwork (52) is connected to the second network terminal (4).

6. Energy network (5) according to claim 5, wherein the energy subnetworks (51,52) have one or more inductive loads.

7. Method for operating an energy network (5) according to one of claims 5 or 6, wherein the electronic protection switch (1) is opened when a ground fault occurs in the energy network (5).

8. Method according to claim 7, wherein the location of the fault is ascertained from the measurement of a voltage between the positive potential terminal (31) of the first network terminal (3) and a ground potential and / or a voltage between the negative potential terminal (32) of the first network terminal (3) and the ground potential and / or a voltage between the positive potential terminal (41) of the second network terminal (4) and the ground potential and / or a voltage between the negative potential terminal (42) of the second network terminal (4) and the ground potential.

9. Use of an electronic protection switch according to one of claims 1 to 4 in a single-phase or three-phase AC voltage network.