Electronic protection switch

Abstract

The present invention relates to an electronic protection switch (1) having two identical semiconductor switches (2), each semiconductor switch having a switching element (21) and a diode (22) arranged in antiparallel with the switching element (21). To improve the electronic switch, it is proposed that the electronic switch also has a first power interface (3) and a second power interface (4), which have a positive potential interface (31, 41) and a negative potential interface (32, 42), respectively. The first semiconductor switch in the semiconductor switch (2) is arranged between the positive potential interface (31) of the first power interface (3) and the positive potential interface (41) of the second power interface (4) without a semiconductor series circuit, and the second semiconductor switch in the semiconductor switch (2) is arranged between the negative potential interface (32) of the first power interface (3) and the negative potential interface (42) of the second power interface (4) without a semiconductor series circuit. The switching element (21) of the corresponding semiconductor switch (2) is arranged to be able to guide and cut off the current from the first power interface (3) to the second power interface (4). The invention also relates to a power grid (5), particularly a DC voltage network (6), having a first subgrid (51) and a second subgrid (52), wherein the power grid (5) has an electronic protection switch (1) for disconnecting the first subgrid (51) and the second subgrid (52) from each other, wherein the first subgrid (51) is connected to a first power interface (3) and the second subgrid (52) is connected to a second power interface (4). The invention also relates to a method for operating such a power grid (5).

Description

Technical Field

[0001] This invention relates to an electronic protection switch having two semiconductor switches, each semiconductor switch having a switching element and a diode arranged in antiparallel with the switching element. Furthermore, this invention relates to a power grid having first and second sub-grids and an electronic protection switch for disconnecting the first sub-grid from the second sub-grid. The invention also relates to a method for operating this type of power grid. Background Technology

[0002] Today, mechanical and electronic switches are used to switch current. In the case of mechanical switches, the contact between the two interfaces of the switch is mechanically made on or off. This is particularly suitable for switching AC voltage and current because they are inexpensive to manufacture, and the switching operation can be performed in a simple way due to the zero crossing of the current. For switching DC, mechanical switches become more complex because the arcing that occurs makes the switching behavior more difficult. Electronic switches are now frequently used here. They use one or more semiconductor switches that can be turned off as switching elements. These semiconductor switches have the advantage of being able to switch DC in a simple way even without arcing. However, these electronic switches have positive losses. On the other hand, electronic switches have the advantages of fast switching capability and a large number of feasible switching operations. This results in a long service life for electronic switches.

[0003] An electronic switch, also known as a DC switch, is known from EP 3379 725A1. This document describes a method for controlling such a DC switch, wherein the DC switch has a first turn-off semiconductor switch and a second turn-off semiconductor switch, wherein the first turn-off semiconductor switch and the second turn-off semiconductor switch are arranged between a first interface and a second interface such that a current of a first polarity can be guided through the first turn-off semiconductor switch and a current of the opposite polarity can be guided through the second turn-off semiconductor switch, wherein one of the turn-off semiconductor switches is turned off based on a current measurement.

[0004] Since semiconductor switches typically only turn off current in one direction, at least two semiconductor switches are often used in an electronic switch. Here, the semiconductor has a switching element capable of turning current on and off in one direction. Current in the other direction is bypassed at the switching element by a diode arranged in parallel with it. This is called an anti-parallel arrangement of the diode and the switching element. Therefore, by using two semiconductor switches arranged in series between the interfaces of the electronic switch, it is possible to switch the current through the electronic switch in both current directions, especially to turn it off. This arrangement of the semiconductor switches is achieved by anti-series connection. This means that the first semiconductor switch can turn off current of the first polarity, i.e., in one current direction, and the second switch can turn off current of the opposite polarity, i.e., in the opposite current direction.

[0005] For use in DC voltage networks, where the load is connected to the DC voltage source via conductors or busbars (often also called leads or feeders), it is sufficient to install an electronic switch in only one of the two leads. Using such an electronic switch, the power supply between the network and the load can be reliably interrupted. This is because currents of the same magnitude but different polarities always flow through both leads, applying a DC voltage between them. Especially in isolated DC voltage networks, the electronic switch is placed in only one lead to maintain low cost and low loss. However, if a reliable identification, control, and location of ground faults is desired, a corresponding electronic switch needs to be placed in both leads. By measuring the voltage across the two electronic switches in each lead, sufficient information can be obtained to identify and locate the ground fault.

[0006] A power grid is a network of interconnected energy sources and / or electrical appliances. These can be divided into separate sub-grids. A power grid uses either direct current (DC) or alternating current (AC) voltage for transmitting electrical energy. Summary of the Invention

[0007] The purpose of this invention is to improve electronic switches used in DC voltage networks.

[0008] This objective is achieved through an electronic protective switch comprising two semiconductor switches, each having a switching element and a diode arranged in antiparallel with the switching element. It also comprises a first power interface and a second power interface, each having a positive potential interface and a negative potential interface. The first semiconductor switch is arranged between the positive potential interfaces of the first and second power interfaces without a semiconductor series circuit, and the second semiconductor switch is arranged between the negative potential interfaces of the first and second power interfaces without a semiconductor series circuit. The switching elements of the respective semiconductor switches are arranged to guide and interrupt current from the first power interface to the second power interface. Furthermore, this objective is achieved through a power grid, particularly a DC voltage network, having a first subgrid and a second subgrid. The power grid has an electronic protective switch for disconnecting the first and second subgrids from each other, wherein the first subgrid is connected to the first power interface and the second subgrid is connected to the second power interface. Additionally, this objective is achieved through a method for operating such a power grid, wherein the electronic protective switch is disconnected in the power grid in the event of a ground fault.

[0009] Other advantageous designs of the invention are given in the dependent claims.

[0010] This invention is based on the understanding that electronic switches applicable to prevent damage in the event of faults in power grids, particularly DC voltage networks, especially ground faults, are improved through a different arrangement of semiconductor switches compared to known electronic switches. To this end, the two anti-series semiconductor switches of known electronic switches are now distributed in different leads between the power supply network, power source, or typically a first subgrid, and the load, appliance, or typically a second subgrid. Thus, the connection between the first and second power interfaces no longer has a series circuit of semiconductor switches. Since there is no longer a series connection of semiconductors between the first and second power interfaces, this arrangement is also referred to as the case without a semiconductor series circuit. Here, the two subgrids can each have any number of power sources and / or loads, such as electrical appliances.

[0011] A semiconductor switch has a switching element and a diode. Here, the diode is arranged in anti-parallel relative to the switching element. While the switching element can conduct current in one current direction, the diode can only conduct current in the opposite direction and cannot switch.

[0012] Two semiconductor switches of the same type are understood to have the same structure. For example, bipolar transistors and field-effect transistors have different structures. Furthermore, individual semiconductor switches are distinguished based on their NPN or PNP type, or based on their P-channel or N-channel type. Therefore, two semiconductor switches of the same type are defined as being of the same type.

[0013] Because electronic switches are designed to prevent faults or their impact on the power grid, they are also called electronic protection switches. In an anti-parallel arrangement, a semiconductor switch is arranged such that it can guide current from a first power interface to a second power interface and turn it off, and a corresponding diode of the semiconductor switch is arranged such that it can guide current from the second power interface to the first power interface. Here, the switching element of the corresponding semiconductor switch is arranged between the first and second power interfaces, such that current in each potential interface flows from the first power interface to the second power interface through the switching element, and current in the opposite direction flows from the second power interface to the first power interface through the diode arranged in anti-parallel with the switching element. Alternatively, the switching element of the corresponding semiconductor switch can also be arranged between the first and second power interfaces, such that current in each potential interface flows from the second power interface to the first power interface through the switching element, and current in the opposite direction flows from the first power interface to the second power interface through the diode arranged in anti-parallel with the switching element.

[0014] By arranging the leads in different directions, the connection between the power supply network and the load can be disconnected, and thus the energy exchange between the power supply network and the load can be interrupted, even if only one switching element exists in the corresponding lead, because currents of the same magnitude but different directions flow through the leads respectively. The sum of the currents in one direction is equal to the sum of the currents distributed in the other direction on the different leads. Here, semiconductors are arranged in the corresponding leads such that they can turn off the current in one direction, specifically from the first power interface to the second power interface. Therefore, the connection and energy exchange between the subgrids (e.g., energy source and load) can be interrupted. The electronic protection switch thus has a total of at least four interfaces, at least two as first power interfaces for connecting to the first subgrid, such as the energy source, and at least two other interfaces as second power interfaces for connecting to the second subgrid, such as the load.

[0015] In a DC voltage network, an electronic protection switch advantageously has exactly two potential interfaces as a first power supply interface and exactly two potential interfaces as a second power supply interface because, for these applications, there are exactly two leads between the energy source and the load, through which a power supply voltage, i.e., a DC voltage, is applied. The two potential interfaces of the corresponding power supply interface are then configured to, in the case of a DC voltage network, connect to the positive potential of the load or energy source on one hand and to the negative potential of the energy source or load on the other. Typically, instead of the energy source and the load, it can be a first sub-grid, i.e., a first DC voltage sub-grid, and a second sub-grid, i.e., a second DC voltage sub-grid. Therefore, these potential interfaces are respectively called positive potential interfaces or negative potential interfaces. The current through the two leads is the same in error-free operation, but with different signs. In other words, the current has different polarities in the two leads. Here, it is the forward current and the reverse current between the energy source and the load.

[0016] Typically, this type of electronic protection switch is also suitable for applications in single-phase AC voltage networks. It also has two leads, allowing the semiconductor switch to be distributed across these feeds. Furthermore, each power interface of the electronic protection switch also has two potential interfaces, where, for example, the positive potential interface is connected to the phase conductor, and the negative power interface is connected to the neutral conductor.

[0017] Application in three-phase power grids is also feasible. Depending on the design, it has three or four leads (three phases and, if necessary, a neutral conductor). The electronic protection switch for this network then has three or four potential interfaces. Here, the switching elements are also arranged between the respective potential interfaces of the first and second power interfaces, enabling current to be directed from the first power interface to the second power interface and then switched off. Here, the semiconductors are also arranged between the first and second power interfaces without a semiconductor series circuit; that is, a series connection of two semiconductor switches is not used. The diodes of the semiconductor switches are also correspondingly located in anti-parallel with the switching elements in this arrangement.

[0018] To reliably locate faults such as ground faults, it's impractical to place an electronic switch in only a single lead. Currently, two electronic switches, each with two semiconductors, are used to connect the power supply network to the load. However, this results in a total of four times the forward losses across the respective semiconductor conductors due to the forward losses of each switch. The proposed electronic protection switch, with only two semiconductors in total, halves these forward losses. It is also cheaper to manufacture, requiring only half the semiconductors and thus saving on expensive semiconductor switches.

[0019] By arranging semiconductor switches, the first semiconductor switch can guide and interrupt the current from the positive potential interface of the first power interface to the positive potential interface of the second power interface, and the second semiconductor switch can guide and interrupt the current from the negative potential interface of the first power interface to the negative potential interface of the second power interface. Therefore, the current between the two sub-grids can be interrupted regardless of the direction of energy flow.

[0020] In an advantageous embodiment of the invention, the electronic protection switch has a voltage detector for measuring the voltage between the positive potential interface of the first power interface and the ground potential and / or the voltage between the negative potential interface of the first power interface and the ground potential and / or the voltage between the positive potential interface of the second power interface and the ground potential and / or the voltage between the negative potential interface of the second power interface and the ground potential.

[0021] Compared to an electronic switch with only one lead, an electronic protection switch having a semiconductor in each of the corresponding leads has the advantage of also being able to obtain status information about the second lead. In a DC voltage network, two semiconductor switches are distributed on two leads. Here, between the first power interface and ground potential and between the second power interface and ground potential, different values ​​are measured by means of corresponding voltage detectors based on the forward voltage on the corresponding semiconductor switch or the forward voltage on the diode when current flows through the diode. This information is helpful in identifying and locating faults, such as ground faults in a DC voltage network. In other words, by splitting the semiconductor of the electronic switch from one lead to two leads, degrees of freedom in measurement can be obtained, from which information about the fault can be determined, especially ground faults in a DC voltage network. Conversely, in the case of an arrangement with only one electronic switch in one of the two leads, when current is generated through the semiconductor switch or the diode in the corresponding other feed line, the ground fault can be reliably located based on the forward voltages of the two interfaces of the semiconductor switch relative to the ground potential. Meanwhile, the electronic protection switch does not have any higher losses because it is constructed for applications in DC voltage networks using exactly two semiconductor switches in the current path to be switched. Since, in the case of a ground fault, the potential of only exactly one semiconductor interface is equal to the ground potential, this interface can be identified as the location of the ground fault from this information.

[0022] By locating grounding faults, this information can be transmitted to higher-level or other control or protection devices, allowing for the safe shutdown of the faulty area. Therefore, safe operation can also be achieved through electronic protective switches. The affected area can then be shut off, for example, by means of its associated semiconductor or mechanical switches, which incurs almost no losses during normal operation and requires only design for a small number of switching operations.

[0023] In another advantageous embodiment of the invention, two identical semiconductor switches are each formed from an insulated-gate bipolar transistor (IGBT) semiconductor switch. IGBTs are particularly suitable for implementing the proposed protective switch due to their current-carrying and blocking capabilities. Their structure is based on an NPN transistor. Therefore, the circuit can be constructed symmetrically, and the characteristics are identical for both positive and negative potential interfaces. Furthermore, the IGBT's response speed is fast enough to disconnect the subnetworks from each other quickly enough, even in the event of a ground fault. Moreover, its blocking and overload capabilities are sufficient, especially when using inductive loads, to safely disconnect the networks from each other. Attached Figure Description

[0024] The invention will be described and explained in more detail below with reference to the embodiments shown in the accompanying drawings. The drawings show:

[0025] Figure 1 This illustrates the energy supply to the load via a known electronic switch.

[0026] Figure 2 Electronic protection switch and

[0027] Figure 3 A DC voltage system is shown. Detailed Implementation

[0028] Figure 1 A known arrangement is shown, 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 respective leads 57 that electrically connect the energy source 55 and the load 56. Here, for example, this is a DC voltage network, in which the energy source 55 and the load 56 are connected to each other via two leads 57, and in which a DC voltage is applied between the two leads 57. To enable the isolation of the load 56 from the energy supply network 55, an electronic switch 7 is present in each of the two leads 57. The electronic switches 7 in the two leads 57 can reliably shut off the current in only one of the two leads 57, for example, the current that may occur in a ground fault.

[0029] The electronic switch 7 has two semiconductor switches 2 connected in series. Each semiconductor switch 2 has a switching element 21 that can conduct and turn off current in one direction. A diode 22 is connected in parallel with the switching element 21, but the diode cannot turn off current in the opposite direction. Therefore, the diode 22 is arranged in anti-parallel with the switching element 21. The semiconductor switches 2 are thus arranged in anti-series. Anti-series means that the electronic switch 7 can turn off current in one direction by means of one of the two semiconductor switches 2, and can turn off current in the opposite direction by means of the other semiconductor switch 2.

[0030] Figure 2 An electronic protective switch 1 is shown. It has two semiconductor switches 2, with diodes 22 and switching elements 21 connected in anti-parallel. Compared to a known electronic switch 7, it has a total of four phase interfaces 31, 32, 41, and 42. Two of these phase interfaces 31 and 32 form a first power interface 3, and the other two phase interfaces 41 and 42 form a second power interface 4. Two leads are connected to the first and second power interfaces 3 and 4, where a DC voltage is applied in the case of a DC voltage network 6. Therefore, the phase interfaces 31, 32, 41, and 42 at the first and second power interfaces have positive and negative potentials of the DC voltage, respectively. To distinguish the interfaces of the power interfaces, these interfaces are referred to as positive potential interfaces 31 and 41 and negative potential interfaces 32 and 42. If the electronic protective switch is used in an AC voltage network and this involves phase interfaces and neutral conductor interfaces, this designation is also retained below.

[0031] Semiconductor switch 2 is arranged in the leads to interrupt the energy flow between the first power interface 3 and the second power interface 4. This interruption ensures energy flow in both directions because the same current flows between the positive potential interface 31 of the first power interface and the positive potential interface 41 of the second power interface 4, as does between the negative potential interface 32 of the first power interface 3 and the negative potential interface 42 of the second power interface 4. The currents differ only in their directions. This current is, in this case, the forward current from the energy source to the load and the reverse current. To interrupt the energy flow regardless of the energy flow direction, the current flows once through the switching element 21 and once through the diode 22. Therefore, the current can be interrupted regardless of the energy flow direction.

[0032] According to Figure 1 Compared to using two electronic switches 7, in the case of an electronic protection switch, the forward loss of semiconductor switch 2 occurs only twice for both forward and reverse currents throughout the circuit, whereas it occurs four times when using two electronic switches 7. Therefore, compared to known solutions, electronic protection switch 1 can halve the losses.

[0033] By arranging the semiconductor switches 2, the first semiconductor switch can guide and interrupt the current from the positive potential interface 31 of the first power interface 3 to the positive potential interface 41 of the second power interface 4, and the second semiconductor switch can guide and interrupt the current from the negative potential interface 32 of the first power interface 3 to the negative potential interface 42 of the second power interface 4. Therefore, the current between the two sub-grids can be interrupted regardless of the direction of energy flow.

[0034] Figure 3A power grid 5 is shown. Through two leads, the power grid can be, for example, a DC voltage network 6. Alternatively, it can also be designed as an AC voltage network. This power grid 5 typically has a first sub-grid 51 and a second sub-grid 52. They are interconnected by two leads 57, through which an electronic protection switch 1 is introduced to allow the two sub-grids to be isolated from or connected to each other. Sub-grids 51 and 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 equipment. Here, the sub-grids may have a combination of energy sources and loads. In a simple case, one sub-grid 51 is an energy source configured as a DC voltage source, and the second sub-grid is a load supplied with DC voltage. With the aid of the electronic protection switch 1, the energy flow between the two sub-grids can be interrupted regardless of the direction of energy flow. Furthermore, this arrangement allows for the identification and location of faults, particularly ground faults, by measuring and evaluating the voltages applied relative to the ground potential at the corresponding potentials 31, 32, 41, 42. This is particularly advantageous for use in isolated DC voltage networks.

[0035] In summary, this invention relates to an electronic protective switch having two semiconductor switches, each having a switching element and a diode arranged in anti-parallel with that switching element. To improve the electronic switch, particularly regarding losses during operation and fault location, the electronic switch also has a first power interface and a second power interface, each having a positive potential interface and a negative potential interface. The first semiconductor switch is arranged between the positive potential interfaces of the first and second power interfaces without a semiconductor series circuit, and the second semiconductor switch is arranged between the negative potential interfaces of the first and second power interfaces without a semiconductor series circuit. The switching elements of the respective semiconductor switches are arranged such that current can be directed and interrupted from the first power interface to the second power interface. The invention also relates to a power grid, particularly a DC voltage network, having a first subgrid and a second subgrid, wherein the power grid has an electronic protective switch for disconnecting the first and second subgrids from each other, wherein the first subgrid is connected to the first power interface and the second subgrid is connected to the second power interface. Furthermore, the invention relates to a method for operating such a power grid.

Claims

1. An electronic protection switch (1), comprising: - Two identical semiconductor switches (2), each having a switching element (21) and a diode (22) arranged in antiparallel to the switching element (21); and - A first power interface (3) and a second power interface (4), wherein the first power interface and the second power interface have a positive potential interface (31, 41) and a negative potential interface (32, 42), respectively. in, Two identical semiconductor switches, one of which is a first semiconductor switch (2), is arranged between the positive potential interface (31) of the first power interface (3) and the positive potential interface (41) of the second power interface (4) without a semiconductor series circuit. The other two identical semiconductor switches, one of which is a second semiconductor switch (2), is arranged between the negative potential interface (32) of the first power interface (3) and the negative potential interface (42) of the second power interface (4) without a semiconductor series circuit. The switching element (21) of each semiconductor switch (2) is arranged to guide and cut off current from the first power interface (3) to the second power interface (4). The electronic protection switch (1) has a voltage detector, which is used to measure the voltage between the positive potential interface (31) of the first power interface (3) and the ground potential, and / or measure the voltage between the negative potential interface (32) of the first power interface (3) and the ground potential, and / or measure the voltage between the positive potential interface (41) of the second power interface (4) and the ground potential, and / or measure the voltage between the negative potential interface (42) of the second power interface (4) and the ground potential.

2. The electronic protection switch (1) according to claim 1, wherein, The electronic protection switch (1) has exactly two semiconductor switches (2) for connecting current between power interfaces (3, 4) in a DC voltage network.

3. The electronic protection switch (1) according to any one of claims 1 or 2, wherein, The two identical semiconductor switches are each formed from IGBT semiconductor switches.

4. A power grid (5) having a first sub-grid (51) and a second sub-grid (52), wherein, The power grid (5) has an electronic protection switch (1) according to any one of claims 1 to 3, the electronic protection switch being used to disconnect the first sub-power grid (51) and the second sub-power grid (52) from each other, wherein the first sub-power grid (51) is connected to the first power interface (3) and the second sub-power grid (52) is connected to the second power interface (4).

5. The power grid (5) according to claim 4, wherein, The power grid is a DC voltage network (6).

6. The power grid (5) according to any one of claims 4 or 5, wherein, Subgrids (51, 52) have one or more inductive loads.

7. A method for operating a power grid (5) according to any one of claims 4 to 6, wherein, When a ground fault occurs in the power grid (5), the electronic protection switch (1) is disconnected.

8. The method according to claim 7, wherein, The location of the fault is determined by measuring the voltage between the positive potential interface (31) of the first power interface (3) and the ground potential, and / or measuring the voltage between the negative potential interface (32) of the first power interface (3) and the ground potential, and / or measuring the voltage between the positive potential interface (41) of the second power interface (4) and the ground potential, and / or measuring the voltage between the negative potential interface (42) of the second power interface (4) and the ground potential.

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