electrical network

Abstract

The invention relates to an electrical network (1000) equipped with feeders (1010 . . . 1013), consumers (1050 . . . 1053) and a distribution network (2000) arranged therebetween, and having at least one semiconductor switch (2010; 2011) and at least one electromechanical switch (2020 . . 2027) for isolating a feeder or a consumer in the event of a fault, wherein the feeders and consumers are arranged in groups and are connected to one another by means of busbars (200) and associated semiconductor switches, wherein in the event of a fault the respective feeder and consumer can each be isolated from the network (1000) by means of the electromechanical switch, and in the event of a fault, the feeders and consumers of the respective groups can be isolated from one another by means of the semiconductor switches in order to prevent crosscurrents on the busbars.

Description

Technical Field

[0001] The present invention relates to an electrical network. Background Art

[0002] A DC network, also known as a DC (Direct Current) network, consists of feeders and consumers. For example, Figure 1 Figure 1 shows such a DC network, which has feeders 1010, 1011, 1012, 1013 and consumers 1050, 1051, 1052, 1053. This type of DC network is becoming increasingly popular because it minimizes conversion losses. Energy efficiency is improved because the AC-to-DC conversion only needs to be performed once for all motors, rather than individually for each motor.

[0003] Furthermore, DC power distribution networks have the advantage of being very low-loss, as the frequency is zero and there are no impedance losses, only resistance losses. A further advantage of DC networks is that, due to the zero frequency, there is no skin effect, so, for example, cables with smaller cross-sections can be used, resulting in lower costs.

[0004] Any type of feeder can be used in a typical DC network. For example, renewable energy sources such as photovoltaics or wind turbines can be used as feeders, while batteries or flywheels and an AC network connection with an AC-DC converter can be used as backup resources. Each feeder uses a converter, which can be an AC-DC converter or a DC-DC converter for different DC voltages. To achieve a nearly constant DC current without fluctuations, DC link capacitors are often used directly after conversion to the DC side. Therefore, each converter is typically connected to a DC link capacitor. This system is called a DC link.

[0005] The AC-DC converter in the DC network can be constructed as a unidirectional (rectifier) ​​or bidirectional (e.g. active front-end technology). The uncontrolled rectifier in unidirectional mode usually consists of a diode and an active front end (AFE), which consists of an IGBT and a diode. When the active front end (AFE) is disconnected, the current cannot flow from the DC side to the AC side, which is blocked by the freewheeling diode. When the voltage on the DC side is lower than the voltage on the AC side, the current flowing from the AC side to the DC side is not blocked by the diode arrangement. Therefore, when the active front end (AFE) is in the disconnected state, this is equivalent to a three-phase uncontrolled rectifier.

[0006] Corresponding to Figure 1 As shown in FIG, feeders are usually connected to a busbar 200. Consumers receive power from the feeders via a common busbar.

[0007] Electric motors that require an AC power supply are generally considered electrical consumers. Therefore, an additional DC-AC converter is required for each electric motor on the consumer side. Each converter is in turn connected to a DC intermediate circuit capacitor to achieve a constant voltage. Therefore, additional capacitors are located upstream of the DC-AC converter (inverter).

[0008] As shown, DC networks contain numerous capacitors, located both on the feeder side and the consumer side. To start up a DC network, these capacitors must be charged to the network's distribution voltage, as otherwise, large currents would flow, such as in the event of a short circuit. Resistors are typically used to limit the current in order to charge the capacitors, which in turn increases the charging time. During normal operation, capacitors act as filters and present no problems. However, if a fault occurs in the DC network, the capacitors discharge, releasing their entire energy within milliseconds. The resulting currents, in the order of hundreds of kA (kiloamperes), can cause damage to the DC network.

[0009] Another problem is so-called LCR oscillations, which are caused by inductive, capacitive, and ohmic components in the network. In the event of a fault, the voltage typically drops suddenly and the current rises sharply, but due to the LCR oscillations, negative voltages are observed in the DC system for a short period of time. The oscillations are caused by the leakage inductance of the cables. Inductance and ohmic resistance are usually introduced into the system via the cables, while capacitance is usually introduced into the system via the capacitors of the DC intermediate circuit (DC-Link). In the event of a fault, the capacitors are discharged, and the voltage across them becomes negative due to the LCR oscillations. This results in a situation where, after the capacitors have discharged, the voltage on the AC side of the AC-DC converter is approximately zero volts, while a negative voltage appears on the DC side due to the LCR oscillations. As a result, large currents flow through the converter diodes to recharge the capacitors, which can damage these diodes.

[0010] Therefore, in Figure 1 In the example, protective devices 2020, 2021, 2022, 2023, 2024, 2025, 2026, and 2027 are arranged between feeders 1010, 1011, 1012, and 1013 and consumers 1050, 1051, 1052, and 1053 and busbar 200. These protective devices can be a combination of fuses and electrical switches. In a DC network with different sources, typical protective devices cannot trigger quickly enough in the event of a fault. Despite conventional fuses and electrical switches, capacitors discharge, often damaging the converter's diodes.

[0011] Furthermore, if a fault occurs in a small consumer with a cable of a small cross-section, this cable can also be damaged. However, the biggest problem is that in the event of a fault, discharge currents flow simultaneously from different capacitors. The large combined current can cause permanent damage to the cable. Summary of the Invention

[0012] Therefore, the object of the present invention is to provide an electrical network which avoids the problems of known DC networks in the event of a fault.

[0013] According to the invention, this object is achieved by an electrical network according to claim 1. Advantageous embodiments of the electrical network according to the invention are given in the dependent claims.

[0014] An electrical network according to claim 1, comprising a feeder, a consumer and a distribution network arranged between them, and comprising at least one semiconductor switch and at least one electromechanical switch for isolating the feeder or the consumer in the event of a fault, wherein the feeders and the consumers are arranged in groups which are connected to one another by means of busbars and associated semiconductor switches, wherein in the event of a fault the respective feeder and the consumer can each be isolated from the network by means of the electromechanical switch, and in the event of a fault, the groups of feeders and consumers can be isolated from one another by means of the semiconductor switches in order to prevent crosscurrents on the busbars.

[0015] Advantageously, groups of feeders and consumers can achieve a highly reliable system. In the event of a fault, it can be isolated from the network, while the remaining network can continue to operate. Discharging of the DC link capacitors of other feeders can also be prevented. Costs are also reduced due to the relatively small number of semiconductor switches arranged on the busbars. While the capacitors of disconnected groups are being recharged, the semiconductor switches can act as current limiters. In this case, the semiconductor switches can be operated as controlled resistors or in a pulsed manner for short periods within the effective range.

[0016] In a further embodiment, a group of a power feeder and a power consumer consists of one power feeder and one power consumer.

[0017] In a further embodiment, a group of power feeders and power consumers consists of two power feeders and two power consumers.

[0018] In one embodiment, in the event of a fault, after the electromechanical switch has been triggered, the group in which the fault occurred and the electromechanical switch was triggered is recharged by the group without the fault by switching a semiconductor switch arranged between the two groups.

[0019] In another embodiment, a semiconductor switch arranged between the two groups functions as a current limiter during the recharging process. Here, the semiconductor switch can be operated briefly as a controlled resistor within the effective range or in a pulsed mode. Alternatively, a resistor arranged between the two groups functions as a current limiter during the recharging process.

[0020] In a further embodiment, the feeders and consumers are distributed into groups in such a way that each group can supply its consumers with sufficient energy via its feeders.

[0021] In a further embodiment, the feeders and consumers are distributed into the groups in such a way that each group can provide sufficient energy via its feeder to supply an adjacent group.

[0022] In a further embodiment, the feeders and consumers are allocated to the groups in such a way that consumers with high availability are arranged in a group having two adjacent groups.

[0023] In one embodiment, the feeders and consumers are divided into groups in such a way that sensitive consumers are arranged in an additional group which is in turn designed as a subgroup within a further group.

[0024] In a further embodiment, the additional group is electrically connected as a subgroup to the further group by means of semiconductor switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The characteristics, features, and advantages of the present invention described above and their implementation methods will be more clearly understood with reference to the following description of the embodiments described in detail with reference to the accompanying drawings.

[0026] In the attached figure:

[0027] Figure 1 A conventional DC electrical network with feeders and consumers is shown;

[0028] Figure 2 A DC network with feeders and consumers and semiconductor switches is shown; and

[0029] Figure 3 An electrical network according to the invention is shown having feeders and consumers, wherein the feeders and consumers are arranged in groups. DETAILED DESCRIPTION

[0030] Figure 3FIG. 1 shows an electrical network 1000 according to the present invention. Electrical network 1000 includes feeders 1010, 1011, 1012, 1013, consumers 1050, 1051, 1052, 1053, and a distribution network 2000 arranged therebetween. Distribution network 2000 further includes electromechanical switches 2020, 2021, 2022, 2023, 2024, 2025, 2026, 2027. Electromechanical switches 2020, 2021, 2022, 2023, 2024, 2025, 2026, 2027 are arranged so that, in the event of a fault, feeders 1010, 1011, 1012, 1013 or consumers 1050, 1051, 1052, 1053 can be disconnected from busbar 200. The different power feeders 1010 ; 1011 ; 1012 ; 1013 and power consumers 1050 ; 1051 ; 1052 ; 1053 are electrically connected to one another via a busbar 200 .

[0031] Feeders 1010, 1011, 1012, 1013 and consumers 1050, 1051, 1052, 1053 are arranged in groups, for example, feeder 1010 and consumer 1050 form group 1. Feeder 1010 is connected to busbar 200 via electromechanical switch 2020, and consumer 1050 is connected to busbar 200 via electromechanical switch 2021.

[0032] The second group is formed by feeders 1011 and 1012 and consumers 1051 and 1052. Feeder 1011 is electrically connected to busbar 200 via electromechanical switch 2022, feeder 1012 is electrically connected to busbar 200 via electromechanical switch 2024, consumer 1051 is electrically connected to busbar 200 via electromechanical switch 2023, and consumer 1052 is electrically connected to busbar 200 via electromechanical switch 2025. Group 1, formed by feeder 1010 and consumer 1050, is connected to group 2, formed by feeders 1011 and 1012 and consumers 1051 and 1052, via semiconductor switch 2010.

[0033] Figure 3 , a third group is shown consisting of feeder 1013 and consumer 1053. Feeder 1013 is connected to busbar 200 via electromechanical switch 2026, and consumer 1053 is connected to busbar 200 via electromechanical switch 2027. The third group consisting of feeder 1013 and consumer 1053 is electrically connected to group 2 consisting of feeders 1011, 1012 and consumers 1051, 1052 via semiconductor switch 2011.

[0034] The function of the electromechanical switches is to disconnect the respectively associated feeders 1010; 1011; 1012; 1013 and consumers 1050; 1051; 1052; 1053 from the network 1000 in the event of a fault. In order to prevent transverse currents on the busbar 200 in the event of a fault, the feeders 1010; 1011; 1012; 1013 and consumers 1050; 1051; 1052; 1053 of the respective groups can also be disconnected from one another by means of semiconductor switches 2010; 2011.

[0035] The semiconductor switches 2010 ; 2011 used in the electrical network 1000 according to the invention can be produced on the basis of silicon (Si), silicon carbide (SiC) or gallium nitride (GaN).

[0036] The electrical network 1000 according to the present invention may comprise groups with different numbers of feeders and consumers. For example, a group may consist of one feeder and one consumer, e.g. Figure 3 Group 1 is formed by the feeder 1010 and the consumer 1050 , and group 3 is formed by the feeder 1013 and the consumer 1053 .

[0037] A group can also consist of two feeders and two consumers, e.g. Figure 3 The group 2 shown in FIG. 1 is formed by power feeders 1011 ; 1012 and power consumers 1051 ; 1052 .

[0038] It is conceivable that a group is formed from more than two feeders and consumers, as well as from a different number of feeders or consumers.

[0039] In the event of a fault on the feeder or consumer side, the associated electromechanical switch is triggered. Similarly, a group is separated from the other groups by means of semiconductor switches 2010 and 2011. This prevents crosscurrents from flowing on busbar 200, while allowing the group unaffected by the fault to continue operating normally. Once the fault is resolved, the group can be returned to the network. To do this, the capacitors on the feeder or consumer side must be charged. This can be accomplished by the group without the fault by re-switching the semiconductor switches 2010 and 2011 arranged between the two groups. The semiconductor switches 2010 and 2011 arranged between the two groups act as current limiters during the recharging process. In this case, the semiconductor switches can be operated briefly within the effective range as controlled resistors or in a pulsed mode. Additionally, resistors can be placed at the semiconductor switches 2010 and 2011 to act as current limiters during the recharging process.

[0040] In order to ensure that the separation or division of feeders and consumers into groups in the event of a fault results in autonomous groups, feeders and consumers should be allocated to the groups in such a way that each group can supply its consumers with sufficient energy via its feeders.

[0041] In order to recharge a group that is isolated from the grid by means of semiconductor switches 2010 ; 2011 in the event of a fault, the feeders and consumers should be distributed among the groups in such a way that each group can provide sufficient energy via its feeder to supply adjacent groups.

[0042] For high-availability consumers that cannot possibly be separated from the network, these consumers should be allocated to groups in such a way that they are arranged in a group with two adjacent groups. Thus, high-availability consumers can be fed by possibly different sources.

[0043] Sensitive electrical consumers, such as welding robots, can be arranged in additional groups, which are in turn designed as subgroups within other groups. These additional groups can in turn be electrically connected to other groups as subgroups by means of semiconductor switches 2010 ; 2011 .

[0044] Corresponding to Figure 3 In the diagram, semiconductor switches 2010 and 2011 divide busbar 200 into three groups. Each cable connection via busbar 200 is secured using an electromechanical switch, which is less expensive than semiconductor switches, for example. The switching or reaction time of an electromechanical switch is typically around 10 ms (milliseconds). Thus, the DC network is divided into small, independent groups, which are interconnected using semiconductor switches 2010 and 2011.

[0045] The electrical network 1000 according to the present invention can be configured to generate groups with different protection levels. Each group is connected to one or more other groups via semiconductor switches 2010 and 2011. In the event of a fault in one group, semiconductor switches 2010 and 2011 are responsible for rapidly isolating that group from the rest of the electrical network 1000 within 10 μs (microseconds), allowing the majority of the electrical network 1000 to continue operating despite the fault.

[0046] In the event of a fault, electromagnetic switches are used to isolate the fault within the group. After isolating the fault with the electromagnetic switch, the consumers can be reconnected and the faulty group can be recharged with the help of the power management system. To recharge the capacitors, semiconductor switches 2010 and 2011 can be used as current limiters, or additional resistors can be used as current limiters.

[0047] The division of the groups should be carried out under the following boundary conditions. Each group should be supplied with as much energy as possible by its feeder so that at least its own consumers can be operated, so that the group is independent of other feeders. In addition, the feeder should provide sufficient backup energy to supply power to the faulty group after the fault is isolated. The consumers should also be prioritized according to their importance in the separated state. Consumers with less demanding requirements should be connected to feeders with small DC intermediate circuit capacitors (DC-Link). High-availability consumers should be arranged between the two groups in order to have higher redundancy in the electrical network 1000 according to the present invention. Sensitive consumers should be arranged in an additional group within the group, where the additional group is electrically connected to the group as a subgroup by means of semiconductor switches. Other groups can be connected using other semiconductor switches.

[0048] The electrical network 1000 according to the present invention also reduces LCR oscillations. The busbar 200 should be connected directly to the AC-DC converter, so that there is little inductance in the event of a fault. This configuration also means that negative voltages only occur in exceptional circumstances. Finally, during capacitor discharge, negative voltages can be prevented by connecting a resistor or inductor in series to protect the converter diodes. Alternatively, surge diodes can be connected in parallel with the DC link capacitors (DC-Link).

[0049] The electrical network according to the present invention achieves high system availability due to the formation of groups that can operate independently in the event of a fault. Discharge of the DC link of other feeders is also prevented, which reduces the load on the cables in the event of a fault. Discharge of the DC link of consumers from adjacent groups is also prevented, as discharge into the fault is no longer possible. During the operation of electrical network 1000, low energy losses occur due to the use of only a small number of semiconductor switches 2010 , 2011 . After a fault occurs, semiconductor switches 2010 , 2011 act as current limiters when recharging the capacitors of the disconnected group. In this case, the semiconductor switches can briefly operate as controlled resistors or in a pulsed manner within the effective range.

Claims

1. An electrical network (1000) comprising a feeder (1010; 1011; 1012; 1013), a consumer (1050; 1051; 1052; 1053) and a power distribution network (2000) arranged between the feeder and the consumer and comprising at least one semiconductor switch (2010; 2011) and at least one electromechanical switch (2020; 2021; 2022; 2023; 2024; 2025; 2026; 2027), wherein The electromechanical switch is used to disconnect a feeder (1010; 1011; 1012; 1013) or a consumer (1050; 1051; 1052; 1053) in the event of a fault, wherein the feeders (1010; 1011; 1012; 1013) and the consumers (1050; 1051; 1052; 1053) are arranged in groups and are connected to one another by means of a busbar (200) and associated semiconductor switches (2010; 2011). It is characterized by: In the event of a fault, the respective feeders (1010; 1011; 1012; 1013) and consumers (1050; 1051; 1052; 1053) can each be disconnected from the network (1000) by means of an electromechanical switch (2020; 2021; 2022; 2023; 2024; 2025; 2026; 2027), and in the event of a fault, the feeders (1010; 1011; 1012; 1013) and consumers (1050; 1051; 1052; 1053) of the respective groups can be disconnected from one another by means of the semiconductor switches (2010; 2011) in order to prevent transverse currents on the busbar (200), wherein in the event of a fault, In this case, after the electromechanical switch (2020; 2021; 2022; 2023; 2024; 2025; 2026; 2027) has been triggered, the group in which a fault has occurred and in which the electromechanical switch (2020; 2021; 2022; 2023; 2024; 2025; 2026; 2027) has been triggered is recharged by the group in which no fault has occurred by switching a semiconductor switch (2010; 2011), which is arranged between the two groups, wherein the feeders (1010; 1011; 1012; 1013) and the consumers (1050; 1051; 1052; 1053) are distributed among the groups in the following manner: That is, the high-availability consumers are arranged in a group with two adjacent groups, so that the high-availability consumers are fed by different sources.

2. The electrical network (1000) according to claim 1, wherein One group of power feeders (1010; 1011; 1012; 1013) and power consumers (1050; 1051; 1052; 1053) consists of one power feeder (1010; 1013) and one power consumer (1050; 1053).

3. The electrical network (1000) according to claim 1, wherein One group of power feeders (1010; 1011; 1012; 1013) and power consumers (1050; 1051; 1052; 1053) consists of two power feeders (1011; 1012) and two power consumers (1051; 1052).

4. The electrical network (1000) according to any one of claims 1 to 3, wherein: A semiconductor switch (2010; 2011) arranged between the two groups acts as a current limiter during the recharging process.

5. The electrical network (1000) according to claim 4, wherein A resistor is arranged at the semiconductor switch (2010; 2011) arranged between the two groups, said resistor serving as a current limiter during the recharging process.

6. The electrical network (1000) according to any one of claims 1 to 3, wherein: The feeders (1010; 1011; 1012; 1013) and the consumers (1050; 1051; 1052; 1053) are allocated to groups in the following manner: - That is, each group is able to provide sufficient energy for its consumers (1050; 1051; 1052; 1053) via its feeders (1010; 1011; 1012; 1013).

7. The electrical network (1000) according to any one of claims 1 to 3, wherein: The feeders (1010; 1011; 1012; 1013) and the consumers (1050; 1051; 1052; 1053) are allocated to groups in the following manner: - That is, each group is able to provide enough energy through its feeder (1010; 1011; 1012; 1013) to supply the adjacent groups.

8. The electrical network (1000) according to any one of claims 1 to 3, wherein: The feeders (1010; 1011; 1012; 1013) and the consumers (1050; 1051; 1052; 1053) are allocated to groups in the following manner: That is, the sensitive electrical consumers ( 1050 ; 1051 ; 1052 ; 1053 ) are arranged in an additional group, which in turn is designed as a subgroup within another group.

9. The electrical network (1000) according to claim 8, wherein The additional group is electrically connected to the other group as a subgroup by means of semiconductor switches (2010; 2011).

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