Switching device, emergency power system and procedure for operating the emergency power system

Abstract

The patent right relates to a switching device (10) for supplying a load (50) optionally in grid operation or in island operation, comprising: - a mains connection (14) with a first phase conductor connection (14p) and a first neutral conductor connection (14n), - an inverter connection (18) with at least two connection terminals (18p, 18p2, 18n) for connecting a bidirectional inverter (30), and - a load connection (15) with a second phase conductor connection (15p) and a second neutral conductor connection (15n), - a network monitoring switch (11) with a monostable contact (11.2) that can be actuated by an actuating coil (11.1), - an electromechanical switching unit (12) with an actuator (12.1), a first switching contact (12.2) and a positively guided auxiliary contact (12.6), wherein the first switching contact (12.2) is arranged in a connecting line between the first phase conductor terminal (14p) and a connection terminal (18p) of the inverter terminal (18) associated with the first phase conductor terminal (14p), and - a status terminal (16) with a connected electrical circuit (13) for signaling a state of the switching device (10). The patent right also relates to an emergency power system (100) with such a switching device (10) and a method for operating the emergency power system (100).

Description

Technical field

[0001] The application relates to a switching device for an emergency power system, an emergency power system with such a switching device, and a method for operating an emergency power system. State of the art

[0002] An emergency power system, also called a backup power system, is designed to ensure a continuous power supply to loads even when the main power grid (MSG) that normally supplies them fails. The emergency power system typically uses a battery as its energy source, which is charged via a bidirectional inverter when the MSG is operating normally. The loads are usually connected to the MSG and the emergency power system via a local distribution network. When the MSG fails, the local distribution network is disconnected from the main MSG. After this disconnection, the loads connected to the local distribution network operate in island mode, powered by the energy previously stored in the battery, which is then supplied to the local distribution network via the bidirectional inverter.It is also possible for the emergency power system to have additional energy sources besides the battery. This is particularly advantageous if the power outage is expected to last for an extended period. Additional energy sources could include, for example, a diesel generator, a wind turbine, and / or a photovoltaic (PV) system, all of which are also connected to the emergency power system.

[0003] During a transition from grid operation to island operation of the emergency power system, a series of switching operations must be performed. These include, for example, disconnecting the local distribution network from the grid operator, starting a network generator and connecting it to the local distribution network's supply lines, and / or restoring the grounding of the local distribution network that was lost due to the disconnection from the grid operator. Furthermore, the grid operator's status must be monitored even in island operation. This is necessary, for instance, to initiate synchronization of the AC voltage in the local distribution network with that in the grid operator when AC power returns, and to reconnect the local distribution network to the grid operator. These and potentially other requirements are typical for the operation of an emergency power system, but details may vary depending on the country where the system is deployed.Any country-specific requirements are listed in relevant guidelines, norms and standards and are usually implemented by means of a switching device that is suitable for the respective country of use.

[0004] Documents WO 2021 / 144 103 A1 and DE 10 2020 101 002 A1 each disclose a switching device for the selective supply of at least one load from an AC network, e.g. an EVN, or a bidirectional inverter, comprising an input with a network neutral conductor connection and a network phase conductor connection for connection to the AC network, a first output with an inverter neutral conductor connection and an inverter phase conductor connection for connection of the bidirectional inverter, and a second output with a load neutral conductor connection and a load phase conductor connection for connection of the load.The switching device further comprises a switching element with a first and a second normally closed contact and a normally open contact, which are connected in a circuit to the mains line connection, the inverter line connection and the load line connection and whose control is connected to a control input of the switching device.

[0005] The known switching device is particularly energy-efficient in operation, as activation of the switching element and the associated power loss only occur in the event of an AC network failure, which is relatively rare. However, detecting a successful AC network disconnection during the transition to islanding, as well as detecting a network reconnection during islanding, is more complex.

[0006] US Patent 10,008,878 B2 discloses a power control system for efficient operational control between distributed energy generation systems. The power control system comprises a power generation device that produces power while a current sensor detects a forward power flow. It further comprises another distributed energy source and a power control unit with an output unit, wherein the power control unit is capable of outputting power from the other distributed energy source while the power generation device and the other distributed energy source are disconnected from the grid. An output of the output unit supplies the current sensor with an auxiliary current, the auxiliary current flowing in the same direction as the forward power flow. Task

[0007] The application is based on the objective of providing a switching device that improves the transition from grid operation to island operation. It also aims to present an emergency power system and a method for operating the emergency power system that improves the transition from grid operation to island operation. Solution

[0008] The objective of providing a switching device of the type mentioned above is achieved by an article having the features of independent claim 1. The objective of providing an emergency power supply system is achieved by an article having the features of independent claim 10. The objective of providing a method for operating the emergency power supply system is achieved by an article having the features of independent claim 11. Embodiments of the switching device are described in claims 2 to 9. Embodiments of the method are described in claims 12 to 19. Description

[0009] A switching device is configured to supply a load either in grid operation or in island operation. The switching device features: - a network connection with a first phase conductor connection and a first neutral conductor connection for connecting an AC network, - an inverter connection with at least two connection terminals for connecting a bidirectional inverter, and - a load connection with a second phase conductor connection and a second neutral conductor connection for connecting the load, - a mains monitoring switch with an actuating coil connected to the mains connection and a monostable contact that can be actuated by the actuating coil, - an electromechanical switching unit with an actuator, a first switching contact, in particular a normally closed first switching contact, and a positively guided auxiliary contact, wherein the first switching contact is arranged in a connecting line between the first phase conductor connection and a connection terminal of the inverter connection associated with the first phase conductor connection, - a status terminal with an attached electrical circuit for signaling the state of the switching device.

[0010] The monostable contact and the positively guided auxiliary contact are arranged in the circuit and interconnected in such a way that, in a rest state of the monostable contact, the two switching states of the switching unit, namely first switching contact open and first switching contact closed, each generate a distinguishable impedance of the circuit at the status terminal.

[0011] The monostable contact and the positively guided auxiliary contact are arranged in the circuit and are in such a configuration within the switching device that only when the first switching contact is open does activation of the network monitoring switch cause a change in the impedance of the circuit.

[0012] The circuit allows the connection status of the AC network and the switching status of the first switching contact to be reliably determined and signaled at the status terminal.

[0013] A monostable contact refers to a switching component that has two states: a stable state, namely the resting state, and an unstable state.

[0014] The monostable contact remains in its stable state as long as no external force or signal is applied. This is the "normal" or resting state of the contact. When an external force or control signal is applied, the contact temporarily switches to its unstable state. As soon as the applied force or signal is removed, the contact automatically returns to its stable state. In the described switching device, the monostable contact serves to detect an alternating voltage present in the AC network. In particular, during island operation, it can detect whether an AC voltage failure in the AC network persists or whether the AC voltage has returned.

[0015] The rest state of the monostable contact therefore refers to the state of the contact that is assumed when the actuating coil is deactivated, i.e., when it is not energized.

[0016] The transfer switch switches the loads between grid operation and island operation. It is an essential component of emergency power systems that are both connected to the public power grid and capable of operating autonomously, i.e., in the event of a public power grid failure. Such systems are used, for example, in critical infrastructure, industrial plants, hospitals, and also in residential buildings.

[0017] In grid operation, loads are connected to the AC grid, e.g., EVN. In grid operation, energy can be drawn from the AC grid, and optionally, surplus energy generated, e.g., by photovoltaics (PV) or wind turbines, can be fed into the AC grid. Grid operation offers stability and a constant energy supply as long as the AC grid is available and stable.

[0018] In island mode, also known as self-sufficient operation, loads are supplied independently of the AC grid. The connected loads are powered by one or more local energy sources, such as generators, battery storage, or renewable energy sources. Island mode is activated, for example, in emergencies, during maintenance work on the public grid, or in the event of grid outages.

[0019] The transfer switch plays a crucial role by enabling switching between grid-connected and islanded operation. In critical situations, such as an AC grid outage, it or the inverter connected to the transfer switch detects the interruption and switches the system to islanded operation, ensuring the continued power supply to the connected loads. Once the public power grid is stable again, the transfer switch detects the return of AC voltage and switches the system back to grid operation, enabling the use of the AC grid.

[0020] The transfer switch can be part of an emergency power system and energy self-sufficiency systems. It ensures a power supply even in the event of a failure of a higher-level AC grid, e.g., a utility company, and helps to protect critical loads against power outages and fluctuations in the AC grid.

[0021] A positively guided auxiliary contact is an electrical contact used in the switching device to ensure safety and monitoring. The positive guidance ensures that the positively guided auxiliary contact is mechanically linked to the open and closed states of another contact in the switching device. In the switching device, this other contact can be, for example, the first switching contact. The positively guided auxiliary contact offers a high level of safety because it allows for the detection of fault conditions such as stuck contacts. In particular, the switching state of the first switching contact of the switching unit, and the disconnection of the mains connection from the inverter connection of the switching device, can be reliably detected.

[0022] The feature that a first contact is "forcedly guided" to a second contact is to be understood, within the meaning of the present application, as meaning that the switching operations of the two contacts are mechanically coupled and cannot occur independently of each other. This applies regardless of whether the forcefully guided contacts are two auxiliary contacts, two switching contacts, or one auxiliary contact and one switching contact. In the case of forcefully guided contacts in opposite directions, the forceful guidance can be designed in such a way that a simultaneous closed state of both forcefully guided contacts is mechanically prevented.

[0023] In a first embodiment of the positively guided auxiliary contact, this means, for example, that if the other contact is closed, it is mechanically impossible for the positively guided auxiliary contact to be closed at the same time. Therefore, if the other contact is closed, the auxiliary contact must be open, and vice versa.

[0024] In a second embodiment of the positively guided auxiliary contact, this means, for example, that when the other contact is closed, it is mechanically impossible for the positively guided auxiliary contact to be open simultaneously. Therefore, if the other contact is closed, the auxiliary contact must be closed, and vice versa. This enables reliable monitoring and thus control of the switching state of the other contact.

[0025] In island mode, the inverter operates in voltage regulation mode. In grid-connected mode, the inverter operates in current regulation mode. Grid-connected mode can also be referred to as grid-parallel operation.

[0026] The switching device therefore enables a safe transition from grid operation to island operation. Fault conditions can be avoided. In particular, by detecting the impedance change at the status terminal, it can be prevented that an inverter in the local distribution network operates in voltage-regulating mode to establish an island grid while the local distribution network is still connected to the faulty upstream AC grid. Moreover, this can be implemented cost-effectively with the described switching device.

[0027] Each connection on the switching device can also be called a terminal or terminal block. Electrical conductors can be connected to the switching device at these terminals. The connections enable the safe and organized connection of cables or wires to the switching device for the transmission of electrical current and / or signals.

[0028] A connection can, for example, have screw terminals, spring terminals, push-in terminals and / or connectors. Solder contacts are also possible.

[0029] In one embodiment of the switching device, the monostable contact of the network monitoring switch is configured as a normally closed contact, and the positively guided auxiliary contact of the switching unit is configured as a normally open contact. The positively guided auxiliary contact is arranged in series with the monostable contact in the circuit.

[0030] In one embodiment of the switching device, the monostable contact of the network monitoring switch is configured as a normally open contact, and the positively guided auxiliary contact of the switching unit is configured as a normally closed contact. In this case, the auxiliary contact is arranged in parallel to the monostable contact in the circuit.

[0031] In one embodiment of the switching device, the switching unit has, in addition to the first switching contact and the positively guided auxiliary contact, a further switching contact or several further switching contacts which are positively guided to each other.

[0032] In one embodiment of the switching device, the actuating coil for actuating the monostable contact is arranged parallel to the mains connection.

[0033] In an alternative embodiment of the switching device, the additional switching contact, or one of the additional switching contacts of the switching unit, is designed as a normally open contact. The actuating coil and the additional switching contact are connected in series, parallel to the mains connection.

[0034] This alternative design is particularly low-loss, since the actuating coil is only energized during island operation and only when the AC mains power returns. Otherwise, it generates no power loss.

[0035] In one embodiment of the switching device, the additional switching contact, or one of the several additional switching contacts, is arranged in a connecting line between the first neutral conductor terminal and a terminal associated with the first neutral conductor terminal. The additional switching contact, or one of the several additional switching contacts, can optionally be configured as a normally closed contact. In this embodiment, all-pole isolation of the AC network from the local distribution network can be achieved. All-pole isolation means that the neutral conductor and phase conductor are separated. This is advantageous because it allows compliance with regulations in various countries that require all-pole isolation. In other countries where all-pole isolation is not necessary or even prohibited, other embodiments of the switching device can be used if required.

[0036] In one embodiment of the switching device, the second phase conductor connection is directly connected to a terminal associated with the inverter connection. The second neutral conductor connection is directly connected to a terminal different from the inverter connection and / or directly to the first neutral conductor connection. "Directly connected" in this context means that the connection is made without any intermediate switching elements, i.e., it cannot be broken by a circuit. In this context, a fuse is not to be interpreted as a switching element. This means that the status of a "direct connection" is not changed by the additional insertion of a fuse, but remains a "direct connection" even if a fuse is added.

[0037] In one embodiment, the switching device is designed for split-phase operation. Here, the grid connection has two first phase conductor connections and one first neutral conductor connection. One of the first phase conductor connections is connected to a first phase conductor of the split-phase network, and the other is connected to a second phase conductor of the split-phase network. Furthermore, the inverter connection has at least two connection terminals, optionally three. Each of the two first phase conductor connections is connected to a different connection terminal via a separate switching contact of the switching unit, in particular via a separate normally closed switching contact.The switching unit includes the additional switching contact, which may in particular be designed as a normally open switching contact, which is arranged between the first neutral conductor connection and one of the connection terminals, and is designed to connect the corresponding connection terminal to the first neutral conductor connection in island operation.

[0038] In this embodiment, one of the connection terminals associated with the inverter connection can be connected to one of the two first phase conductor connections in grid-parallel operation and to the first neutral conductor connection via the additional switching contact in island operation. In this embodiment, only those loads are supplied with electrical energy in island operation that are connected between the first phase conductor connection (connected to the first phase conductor of the split-phase network) and the neutral conductor connection in grid-parallel operation, but not those loads that are connected between the phase conductor connection (connected to the second phase conductor of the split-phase network) and the neutral conductor connection in grid-parallel operation.

[0039] The fact that in this embodiment only certain loads, namely the loads connected to the corresponding first phase conductor connection, are supplied in island operation, can be taken into account during the initial division of the local distribution network and the distribution of the loads to the respective phase conductors of the split-phase network.

[0040] The advantage of this embodiment is that, in island mode, the addition of a so-called autotransformer, also known as a power factor converter, is unnecessary. This would otherwise be required within the switching device to establish the potential reference between the phase conductors and the neutral conductor. However, the autotransformer would increase the cost of the switching device. Therefore, the described embodiment allows for a more cost-effective design of the switching box. Conversely, the design of the local distribution network can take into account that, in island mode, only certain loads, and not all loads in the local distribution network, are supplied with electrical energy.

[0041] An emergency power system comprises a bidirectional inverter connectable to a battery and the described transfer switch. The inverter has a measuring unit for detecting the circuit impedance. This measuring unit is connected to the status terminal of the transfer switch via a measuring terminal. The inverter also has a power terminal, which is connected to the inverter terminal of the transfer switch and is designed to allow power exchange between the inverter's power terminal and the transfer switch's inverter terminal in island mode under certain conditions, and to suppress such exchange under other conditions. This power exchange is enabled or suppressed depending on the detected circuit impedance.

[0042] The connection for enabling or suppressing power exchange is established, for example, via a relay in the inverter, which opens when the grid connection fails. Only when it is ensured that the open first switching contact of the switching unit reliably disconnects the grid connection and the connected AC network, and that no AC voltage is present in the AC network (i.e., the AC network is deactivated), which is confirmed by the switching state of the monostable contact of the grid monitoring switch, is the relay closed again to supply the loads in island mode. Only then is a voltage applied via the inverter's power connection—and thus at the inverter connection of the switching device—to electrically supply the loads connected to the switching device's load connection.

[0043] The emergency power system enables a safe transition from grid operation to island operation. In particular, it prevents a situation where voltage is already applied to the inverter connection even though the faulty AC network connected to the grid has not yet been safely disconnected.

[0044] One method for operating the described emergency power system includes: - Operation of the emergency power system in a grid-connected mode with the switching unit actuator deactivated, whereby the following steps are performed in the event of a detected AC grid failure: - Suppressing a power exchange between a power terminal of the inverter and the inverter terminal of the switching device and activating the actuator to open the first switching contact, - Measuring the impedance of the circuit, - Operating the emergency power system in island mode by enabling power exchange between the inverter's power connection and the switching device's inverter connection when the circuit impedance at the status terminal indicates that either of the two events is true: i) the first switching contact is in its open state, and ii) the network monitoring switch is not actuated by an alternating voltage of an AC network connected to the mains connection, which is why the monostable contact is in its rest state.

[0045] Event ii) can occur, for example, if an alternating voltage in the AC network is outside specified tolerance criteria and, in particular, is not present.

[0046] The procedure for operating the emergency power system enables a safe transition from grid operation to island operation.

[0047] The loss of AC grid power can be detected by the inverter at its power connection via an integrated failure detection unit. Such an internal unit could, for example, be an anti-islanding detection unit. The inverter's failure detection unit can also detect not only AC grid failures but also non-compliant AC grid voltages.

[0048] In one embodiment of the method, the emergency power system signals a fault condition depending on the circuit impedance. For example, the emergency power system signals the fault condition when the circuit impedance indicates that the mains monitoring switch is not actuated by an alternating voltage from an AC network connected to the mains supply, meaning the monostable contact is in its resting state, and the first switching contact—especially despite an activated actuator—is closed. In the case of the first switching contact being closed, it could be stuck and would need to be replaced. Therefore, signaling this fault condition of the emergency power system and providing corresponding information to a user of the emergency power system is advisable.

[0049] In one embodiment of the method, during island operation of the emergency power system, the return of a properly operating AC network is signaled by a change in the impedance of the circuit at the status terminal. Specifically, during island operation, when the AC network returns, the actuating coil of the network monitoring switch is energized, triggering a corresponding switching operation of the monostable contact.

[0050] In grid-parallel operation, the proper operation of the AC grid can be ensured by monitoring the AC grid voltage at the inverter's power terminal using an internal measuring unit. If the grid voltage fluctuates outside a tolerance range and / or leaves a tolerance range, the inverter can detect improper operation of the AC grid.

[0051] In one embodiment of the method, the emergency power system, in response to the signal indicating the return of the properly operating AC network, performs the following steps: - Suppressing the power exchange between the inverter connection of the switching device and the inverter, - Deactivation of the actuator to close the first switching contact, - optionally synchronizing a voltage at the inverter's power terminal with a voltage present in the AC grid, and - Operating the emergency power system in the grid operation by enabling the exchange of power between the inverter connection of the switching device and the inverter.

[0052] The step of synchronizing the voltage at the inverter's power terminal with the voltage present in the AC grid is optional; it can be performed but is not mandatory. The inverter can operate in grid-connected mode and in island mode in voltage-regulating mode. In one embodiment of the method, the switch between current-regulating and voltage-regulating operation occurs with suppressed power exchange between the inverter and the inverter terminal of the switching device.

[0053] In one embodiment of the method, power exchange is suppressed by deactivating an AC / DC converter of the bidirectional inverter and / or opening a relay of the inverter associated with the power output. The AC / DC converter can, in particular, comprise a bridge circuit with clocked semiconductor switches. To deactivate the AC / DC converter, the clocking of the semiconductor switches can be stopped.

[0054] In one embodiment of the method, the inverter has a control output that is activated when the AC grid malfunctions. The activation of the control output can be achieved, for example, via an internal inverter relay. This results in a voltage, particularly an AC voltage, being supplied to the control output when it is activated, a voltage that is not present when the control output is deactivated. The control output is connected to the actuator of the first switching unit and activates the actuator when the AC grid malfunctions. In this embodiment, the inverter can then automatically activate the actuator of the switching unit of the transfer switch via the control output when the AC grid malfunctions, particularly in the event of an AC grid failure, thus initiating islanding operation without requiring any user intervention.Alternatively or additionally, it is also possible for the actuator to be manually controlled by a user of the emergency power system.

[0055] In one embodiment of the method, the emergency power system is designed for split-phase operation and includes a switching device designed for split-phase operation. In split-phase operation, the inverter provides a first AC voltage with a first amplitude at the connection terminals of the inverter terminals during grid operation, and a second AC voltage with a second amplitude at the connection terminals of the inverter terminals during island operation, the second amplitude being half the first amplitude.

[0056] In one embodiment of the method, the control output is connected to the inverter's AC / DC converter. This allows the AC voltage supplied by the inverter to be monitored during island operation of the emergency power system. In particular, the AC / DC converter can be deactivated if the AC voltage supplied during island operation falls outside predefined tolerance criteria. By deactivating the AC / DC converter in a timely manner, it is possible to prevent the switching contact from being unintentionally closed due to an AC voltage supplied during island operation that is outside the predefined tolerances.

[0057] In island mode, excessive power consumption by the loads connected to the switching device can lead to an overload exceeding the inverter's nominal power. In this case, the AC voltage supplied by the inverter to the island grid can drop, at least temporarily. If the switching unit's actuator is also connected to the AC / DC converter and thus reacts to the voltage drop, this can cause the first switching contact to close. In this case, the AC voltage supplied in island mode would spread, at least temporarily, to the AC grid and could cause further damage. This can be avoided by the described design. Deactivation of the AC / DC converter can occur very quickly, especially faster than opening an optional internal inverter relay.In this way, an unintentional spread of AC voltage to the AC network – which may still be undergoing maintenance – can be quickly and reliably prevented. A voltage threshold assigned to the switching unit, below which the first switching contact closes, can be determined in laboratory tests on the respective type of switching unit. The voltage threshold determined in this way can then be used in the procedure for deactivating the DC / AC converter. Alternatively, instead of laboratory tests, the voltage threshold can also be programmed into the inverter, for example, during the initial installation of the emergency power system. This is explained in more detail in conjunction with the [document / section / etc.]. Fig. 4 explained. Brief description of the characters

[0058] The following section provides further explanation and description of exemplary implementations of this application with reference to the figures. They show Fig.1 schematically a first embodiment of an emergency power system, Fig. 2 schematically a second embodiment of the emergency power system, Fig. 3 schematically a third embodiment of the emergency power system, Fig. 4 schematically a fourth embodiment of the emergency power system.

[0059] The same reference symbols are used in the figures for identical or similar elements. Representations in the figures may not be to scale. Character description

[0060] In Fig. Figure 1 shows a first embodiment of an emergency power system 100 with a first embodiment of the switching device 10. The emergency power system 100 comprises a bidirectional inverter 30 and the switching device 10.

[0061] The switching device 10 is designed to supply a load 50 with electrical energy, whereby the load 50 can be supplied either in grid operation or in island operation. The switching device 10 is designed to switch the supply of the load 50 between supply via an AC network 60 in grid operation and supply via the inverter 30 from a battery 40 in island operation.

[0062] The AC network 60 is designed as an example of a three-phase alternating current network, which has three phases L1, L2, L3 and a neutral conductor N. The AC network 60 also has a connection to earth potential PE.

[0063] The switching device 10 has a network connection 14 with a first phase conductor connection 14p and a first neutral conductor connection 14n. The network connection 14 is intended for connecting to the AC network 60. The first phase conductor connection 14p is connected to the first phase conductor L1 of the AC network 60. The first neutral conductor connection 14n is connected to the neutral conductor N of the AC network 60. The network connection 14 is configured for transferring electrical power, e.g., for supplying the load 50 from the AC network 60.

[0064] The switching device 10 further comprises an inverter connection 18 with two connection terminals 18p, 18n. The inverter connection 18 is intended for connecting the bidirectional inverter 30. The inverter connection 18 is configured for transferring electrical power, e.g., for supplying the load 50 from the battery 40 via the inverter 30. The switching device 10 is connected to a power terminal 38 of the inverter 30 via the inverter connection 18.

[0065] The switching device 10 further comprises a load terminal 15 with a second phase conductor terminal 15p and a second neutral conductor terminal 15n. The load terminal 15 is provided for connecting the load 50. The load terminal 15 is configured for transferring electrical power to supply the loads 50 via the switching device 10. Although only one load 50 is shown as an example, the load 50 can also comprise several loads 50 to be supplied, which are connected in parallel to each other to the load terminal 15.

[0066] The first and second phase conductor connections 14p, 15p, as well as the first and second neutral conductor connections 14n, 15n, and the further connections 16, 18, as well as the actuator connection 17, are set up to establish an electrical connection.

[0067] The switching device 10 further comprises a status terminal 16 for signaling a state of the switching device 10 and a circuit 13. Within the switching device 10, the circuit 13 is connected to the status terminal 16. A change in the impedance of the circuit 13 is detectable at the status terminal 16. The status terminal 16 is connected to a measuring terminal 36 of the inverter 30. The inverter 30 has a measuring unit 35 via which a change in the impedance of the circuit 13 can be determined at the status terminal 16.

[0068] The switching device 10 further comprises a mains monitoring switch 11 with an actuating coil 11.1 connected to the mains connection 14 and a monostable contact 11.2 that can be actuated by the actuating coil 11.1. In the illustrated first embodiment of the switching device 10, the monostable contact 11.2 is closed in the rest state. The rest state refers to the state of the monostable contact 11.2 that is assumed when the actuating coil 11.1 is deactivated, i.e., not energized.

[0069] The switching device 10 further comprises an electromechanical switching unit 12 with an actuator 12.1, a normally closed first switching contact 12.2, a positively guided normally open second switching contact 12.5, and a positively guided auxiliary contact 12.6. The actuator 12.1 actuates the first switching contact 12.2. The actuator 12.1 can be actuated by the inverter 30 via a control output 37 of the inverter. Thus, the inverter 30 can effect a grid disconnection by opening the first switching contact 12.2 via the control output 37.

[0070] Both positively guided contacts 12.5 and 12.6 are positively guided to the first switching contact 12.2 in an inverse or opposite manner. When the first switching contact 12.2 is open, the positively guided contacts 12.5 and 12.6 are closed, and vice versa. Therefore, when the first switching contact 12.2 is normally closed, the positively guided contacts 12.5 and 12.6 are positively open when the normally closed first switching contact 12.2 is closed.

[0071] The first switching contact 12.2 is arranged in a connecting line between the first phase conductor connection 14p and a connection terminal 18p of the inverter connection 18 assigned to the first phase conductor connection 14p.

[0072] The monostable contact 11.2 and the positively driven auxiliary contact 12.6 are arranged in the circuit 13 and connected in series. The monostable contact 11.2 is closed in the resting state. The two switching states of the switching unit 12 lead, via the positively driven auxiliary contact 12.6 connected to the first switching contact 12.2, to a change in the impedance of the circuit 13, which can be detected by the inverter 30 via the status terminal 16.

[0073] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. The auxiliary contact 12.6, which is inversely or oppositely guided to the first switching contact 12.2, is then open and the circuit 13 is interrupted. This can be detected via the status terminal 16.

[0074] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed, and the circuit 13 is closed and therefore low-impedance. This can be detected via the status terminal 16.

[0075] The actuating coil 11.1 is connected in series with the further positively guided switching contact 12.5. The series connection of the actuating coil 11.1 and the further positively guided switching contact 12.5 is connected in parallel to the mains connection 14. This is particularly low-loss, since the actuating coil 11.1 is only energized in island mode and there only when the AC mains 60 is restored. Otherwise, it generates no power loss.

[0076] The unstable state of the monostable contact 11.2 can be achieved by energizing the actuating coil 11.1, which then actuates the monostable contact 11.2. This requires, firstly, that sufficient electrical power is supplied by the AC mains 60 via the mains connection 14. Secondly, it requires that the other positively guided switching contact 12.5 is closed. This is the case when the first switching contact 12.2 is open – due to the opposing positive guidance.

[0077] When the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed. The further switching contact 12.5, which is positively driven in the opposite direction to the first switching contact 12.2, is then also closed. This is the case during island operation of the transfer switch 10, in which the load 50 is disconnected from the AC network 60 by the open first switching contact 12.2 and is supplied via the inverter 30 from the battery 40. Island operation occurs, for example, in the event of a failure of the AC network 60. However, even in island operation, it is important to detect the return of the AC network 60, i.e., the return of the AC voltage in the AC network 60, which is done within the transfer switch 10 by means of the network monitoring switch 11.Specifically, when the AC network 60 returns, i.e., when the AC network 60 is operating correctly again and supplying enough energy to the actuating coil 11.1, current flows through the actuating coil 11.1. The monostable contact 11.2 then leaves its resting state and opens. The previously closed circuit 13 is interrupted, which can be detected via the status terminal 16.

[0078] If the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, and the further switching contact 12.5, which is positively driven in the opposite direction to the first switching contact 12.2, are then each open.

[0079] The possible states are listed in the table below: network monostable contact 11.2 Network disconnection takes place Switching contact 12.5, 12.6 Circuit 13 Network OK open Yes closed open Network OK closed no open open NOK network closed Yes closed closed NOK network closed no open open

[0080] In the Fig.In the first embodiment of the switching device 10 shown in Figure 1, a closed circuit 13 corresponds to an AND connection of the events: i) a failure of the AC network 60 and ii) a separation of the AC network 60 by the open first switching contact 12.2.

[0081] In the Fig. In the first embodiment of the switching device 10 shown in Figure 1, the monostable contact 11.2 and the positively guided auxiliary contact 12.6 are arranged in the circuit 13 and in such a configuration of the switching device 10 that only when the first switching contact 12.2 is open does activation of the mains monitoring switch 11 cause a change in the switching state of the circuit 13.

[0082] The inverter 30 can be connected to the battery 40. The inverter is configured to convert direct current (DC) or DC voltage from the battery 40 into alternating current (AC) or AC voltage, and conversely, to convert AC current or AC voltage into DC current or DC voltage for charging the battery. For power conversion, the inverter 30 has a DC / DC converter and an AC / DC converter 32. The DC / DC converter 32 and the AC / DC converter 32 can each have bridge circuits with switchable semiconductor switches for power conversion.

[0083] Typically, in island mode, the inverter 30 operates in voltage-regulating mode and supplies the loads 50 with electrical energy from the battery 40. Typically, in grid-connected mode, the inverter 30 operates in current-regulating mode and can, for example, charge the battery 40 with electrical energy from the AC grid 60.

[0084] The inverter 30 has the measuring unit 35, which is connected via the measuring terminal 36 to the status terminal 16 of the switching device 10. The measuring unit 35 serves to detect the impedance of the circuit 13.

[0085] The inverter also has relays 33 and 34. Relay 33 allows the AC / DC converter 32 to be connected to and disconnected from the power output 38 of the inverter 30. Relay 34 allows the AC / DC converter 32 to be connected to and disconnected from the control output 37 of the inverter 30.

[0086] The power terminal 38 of the inverter 30 is connected to the inverter terminal 18 of the switching device 10. The power terminal 38 is designed to enable or suppress power exchange between the power terminal 38 of the inverter 30 and the inverter terminal 18 of the switching device 10 in island operation, depending on the impedance of the circuit 13 detected via the measuring terminal 36.

[0087] This is achieved by the inverter's internal relay 33, which is initially opened by the inverter 30 in the event of a failure of the AC network 60 and only closed again to initiate island operation once a safe disconnection from the AC network 60 has been established by the open first switching contact 12.2, and an AC voltage is not present or insufficient in the AC network 60. The absence or insufficient presence of the network results in a closed switching state of the monostable contact 11.2 of the network monitoring switch 11.

[0088] The described emergency power system 100 can be operated using the following method. This method can, for example, run on a computer unit with a processor, memory, and input and output interfaces. The computer unit can, for example, include a controller for the inverter 30 and may optionally be installed within the inverter 30. Alternatively, the computer unit can be installed outside the inverter 30 within the emergency power system 100 or even outside the emergency power system 100 altogether.

[0089] The emergency power system 100 is operated in grid mode with actuator 12.1 deactivated. In grid mode, battery 40 can be charged with electrical power from the AC grid 60 to ensure sufficient energy is available for potentially necessary island operation.

[0090] The failure of the AC network 60 can be detected, for example, directly by the inverter 30 at its power connection 38 by an associated inverter-internal failure measuring unit, which may include, for example, a corresponding anti-islanding detection (AID) unit.

[0091] In the event of a detected failure of the AC network 60, the following steps are performed: - Suppressing the power exchange between the inverter 30 and the inverter terminal 18 of the switching device 10 by stopping the clocking of the AC / DC converter and / or by opening the relay 33 and activating the actuator 12.1 to open the first switching contact 12.2 and disconnect the AC network 60 from the inverter 30, - Measuring the impedance of circuit 13 using measuring unit 35, - If the measurement of the impedance of circuit 13 shows that circuit 13 is closed: Operation of the emergency power system 100 in island mode by enabling a power exchange between the power connection 38 of the inverter 30 and the inverter connection 18 of the switching device 10.

[0092] In the Fig. In the first embodiment shown in Figure 1, the closed circuit 13 means that the first switching contact 12.2 is in its open state and the network monitoring switch 11 is not actuated by an alternating voltage from an AC network 60 connected to the network terminal 14; that is, the monostable contact 11.2 is in its resting state. This can occur, for example, if an alternating voltage in the AC network 60 is outside specified tolerance criteria and, in particular, is not present.

[0093] The power exchange between the power terminal 38 of the inverter 30 and the inverter terminal 18 of the switching device 10 is suppressed if a fault condition exists. The fault condition exists if the circuit 13 is not closed.

[0094] In such a case, the switching contact 12.2 could be stuck and would need to be replaced. Therefore, it is advisable to detect this faulty condition of the emergency power system 100 and, optionally, to issue the corresponding information to a user of the emergency power system 100.

[0095] In island mode, the emergency power system 100 signals the return of a properly operating AC network 60 by opening the previously closed circuit 13 at the status terminal 16. When the AC network 60 is operating correctly, specifically when the AC network voltage is back within specified tolerance criteria, the actuating coil 11.1 is activated and energized, thus opening the monostable contact 11.2, as long as the AC network 60 is still disconnected with the first switching contact 12.2 open and the second positively driven switching contact 12.5 closed. Circuit 13 is then interrupted. Therefore, current only flows through the actuating coil 11.1 when the AC network 60 returns to island mode, i.e., with the first switching contact 12.2 open and the second positively driven switching contact 12.5 closed. This enables low-loss operation.

[0096] The emergency power system 100 can then, in response to the signaling of the return of the properly operating AC network 60, perform the following steps: - Suppression of the power exchange between the inverter terminal 18 of the switching device 10 and the inverter 30 by stopping the clocking of the AC / DC converter and / or by opening the relay 33, - Deactivation of actuator 12.1 to close the first switching contact 12.2 and connect the inverter 30 to the AC network 60, - optionally synchronizing a voltage at the power terminal 38 of the inverter 30, whereby the voltage is synchronized with the voltage of the AC network 60, and - Operating the emergency power system 100 in grid operation by enabling the exchange of power between the inverter connection 18 of the switching device 10 and the inverter 30.

[0097] In grid-connected operation, the inverter 30 outputs a voltage synchronized with the AC grid 60 and operates in power-supply mode. In grid-connected operation, charging the battery 40 is possible, for example. Generally, in grid-parallel operation, power can flow via the bidirectional inverter 30 either from the AC grid 60 to the battery 40, or vice versa, from the battery 40 to the AC grid 60.

[0098] The inverter 30 is operated in island mode in voltage-regulating mode. A switch between current-regulating mode and voltage-regulating mode occurs with suppressed power exchange between the inverter 30 and the inverter connection 18 of the switching device 10.

[0099] The control output 37 of the inverter 30 is activated when the AC network 60 malfunctions. Control output 37 is connected to the actuator 12.1 of the switching unit 12 and activates the actuator when the AC network 60 malfunctions. This opens the first switching contact 12.2 and disconnects the connection to the AC network 60. Therefore, in the event of a failure of the AC network 60, the inverter can activate the actuator 12.1 of the switching unit 12 of the transfer switch 10 via control output 37, thus initiating island operation without requiring user intervention. Alternatively, the actuator 12.1 can also be manually controlled by a user of the emergency power system 100. However, this requires user intervention.

[0100] In Fig.Figure 2 shows a second embodiment of the emergency power system 100. The second embodiment of the emergency power system includes a second embodiment of the switching device 10.

[0101] The switching device 10 comprises the mains monitoring switch 11 with the actuating coil 11.1 connected to the mains connection 14 and the monostable contact 11.2 that can be actuated by the actuating coil 11.1. The actuating coil 11.1 is arranged in parallel to the mains connection 14. In the second embodiment of the switching device 10 shown, the monostable contact 11.2 is closed in the rest state. The rest state refers to the state of the monostable contact 11.2 that is assumed when the actuating coil 11.1 is deactivated, i.e., not energized.

[0102] The switching device 10 further comprises the electromechanical switching unit 12 with the actuator 12.1, the normally closed first switching contact 12.2, a further normally closed positively guided switching contact 12.3 and the positively guided auxiliary contact 12.6. The first switching contact 12.2 is arranged in the connecting line between the first phase conductor connection 14p and a connection terminal 18p of the inverter connection 18 associated with the first phase conductor connection 14p.

[0103] Actuator 12.1 controls the first switching contact 12.2. Actuator 12.1 can be controlled by inverter 30 via its control output 37. Thus, inverter 30 can disconnect the power supply by opening the first switching contact 12.2 via control output 37.

[0104] The monostable contact 11.2 and the positively driven auxiliary contact 12.6 are arranged in the circuit 13 and connected in series. The monostable contact 11.2 is closed in the resting state. When the monostable contact 11.2 is in the resting state, the two switching states of the switching unit 12, via the positively driven auxiliary contact 12.6 connected to the first switching contact 12.2, cause a change in the impedance of the circuit 13, which can be detected by the inverter 30 via the status terminal 16.

[0105] The positively guided auxiliary contact 12.6 is positively guided with the first switching contact 12.2, specifically in an opposing manner. When the first switching contact 12.2 is open, the positively guided auxiliary contact 12.6 is closed, and vice versa. With the first switching contact 12.2 normally closed, the positively guided auxiliary contact 12.6 is therefore positively guided open when the normally closed first switching contact 12.2 is closed.

[0106] A further positively guided switching contact 12.3 is arranged in a connecting line between the first neutral conductor terminal 14n and the terminal 18n associated with the first neutral conductor terminal 14n. The further positively guided switching contact 12.3 is configured as a normally closed contact. It is positively guided in the same direction as the first switching contact 12.2. When the first switching contact 12.2 is open, the further positively guided switching contact 12.3 is also open, and vice versa. Therefore, when the first switching contact 12.2 is normally closed, the further positively guided switching contact 12.3 is positively closed.

[0107] A second, additional forcibly guided switching contact 12.4 is arranged between the connecting line in which the additional forcibly guided switching contact 12.3 is located and earth potential PE. The second additional forcibly guided switching contact 12.4 is designed as a normally open contact and is forcibly guided to the first switching contact 12.2 in the opposite direction. When the first switching contact 12.2 is open, the second additional forcibly guided switching contact 12.4 is closed, and vice versa. Thus, when the first switching contact 12.2 is normally closed, the second additional forcibly guided auxiliary contact 12.4 is forcibly open when the normally closed first switching contact 12.2 is closed. In island mode, a suitable earth reference for the island network can be achieved via the second additional forcibly guided switching contact 12.4, for example, because the effect of the earth reference present in the AC network 60 is prevented by an all-pole disconnection of the AC network 60.

[0108] The monostable contact 11.2 and the positively driven auxiliary contact 12.6 are arranged in the circuit 13 and connected in series. The monostable contact 11.2 is closed in the resting state. The two switching states of the switching unit 12 lead, via the positively driven auxiliary contact 12.6 connected to the first switching contact 12.2, to a change in the impedance of the circuit 13, which can be detected by the inverter 30 via the status terminal 16.

[0109] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then open and the circuit 13 is interrupted. This can be detected via the status terminal 16.

[0110] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed, and the circuit 13 is closed. This can be detected via the status terminal 16.

[0111] The unstable state of the monostable contact 11.2 can be achieved by energizing the actuating coil 11.1 of the monostable contact 11.2. This requires that sufficient electrical power is supplied by the AC network 60 via the network connection 14, i.e., that the AC network is operating correctly and therefore available. The circuit 13 is thus interrupted due to the open monostable contact 11.2 when the AC network 60 is properly available.

[0112] When the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed. The further switching contact 12.3, which is positively driven in the same direction as the first switching contact 12.2, is then open. The second further switching contact 12.4, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed.

[0113] The actuating coil 11.1 is activated if the AC network 60 is operating correctly or at least supplies sufficient energy to the actuating coil 11.1. When current flows through the actuating coil 11.1, the monostable contact 11.2 leaves its resting state and opens. The circuit 13 is interrupted, which can be detected via the status terminal 16. In this way, the return of power to the AC network 60 can be detected in the islanded operation of the emergency power system 100.

[0114] If the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. The second switching contact 12.3, which is positively driven in the same direction as the first switching contact 12.2, is then also closed. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, and the second additional switching contact 12.4, which is positively driven in the opposite direction to the first switching contact 12.2, are then each open.

[0115] In the Fig. In the embodiment shown in Figure 2, an all-pole isolation of the AC network 60 from the local distribution network can be achieved. This all-pole isolation involves disconnecting the neutral conductor via the additional positively driven switching contact 12.3 and the phase conductor via the first switching contact 12.2.

[0116] The possible states are listed in the table below: network monostable contact 11.2 Network disconnection takes place Switching contact 12.6 Circuit 13 Network OK open Yes closed open Network OK open no open open NOK network closed Yes closed closed NOK network closed no open open

[0117] In the Fig.In the second embodiment of the switching device 10 shown in Figure 2, a closed circuit 13 corresponds to an AND connection of the events: i) a failure of the AC network 60 and ii) a separation of the AC network 60 by the open first switching contact 12.2.

[0118] In the Fig. In the second embodiment of the switching device 10 shown in Figure 2, the monostable contact 11.2 and the positively guided auxiliary contact 12.6 are arranged in the circuit 13 and in such a configuration of the switching device 10 that only when the first switching contact 12.2 is open does activation of the mains monitoring switch 11 cause a change in the switching state of the circuit 13.

[0119] The described emergency power system 100 can be operated using the following method. This method can, for example, run on a computer unit with a processor, memory, and input and output interfaces. The computer unit can, for example, include a controller for the inverter 30 and may optionally be installed within the inverter 30. Alternatively, the computer unit can be installed outside the inverter 30 within the emergency power system 100 or even outside the emergency power system 100 altogether.

[0120] The emergency power system 100 is operated in grid mode with actuator 12.1 deactivated. In the event of a detected failure of the AC grid 60, for example due to inverter 30, the following steps are executed: - Suppressing the power exchange between the inverter 30 and the inverter terminal 18 of the switching device 10 by stopping the clocking of the AC / DC converter 32 and / or by opening the relay 33 and activating the actuator 12.1 to open the first switching contact 12.2 and disconnect the AC network 60 from the inverter 30, - Measuring the impedance of circuit 13 using measuring unit 35, - If the measurement of the impedance of circuit 13 shows that circuit 13 is closed: Operation of the emergency power system 100 in island mode by enabling a power exchange between the power connection 38 of the inverter 30 and the inverter connection 18 of the switching device 10.

[0121] In the Fig.In the second embodiment shown in Figure 2, the closed circuit 13 means that the first switching contact 12.2 is in its open state and the network monitoring switch 11 is not actuated by an alternating voltage from an AC network 60 connected to the network terminal 14, whose monostable contact 11.2 is therefore in its resting state. This can occur, for example, if an alternating voltage in the AC network 60 is outside specified tolerance criteria and, in particular, is not present.

[0122] Power exchange between the power terminal 38 of the inverter 30 and the inverter terminal 18 of the switching device 10 is only carried out to initiate island operation once a fault-free state exists. A fault-free state exists when the circuit 13 is closed. Conversely, power exchange between the power terminal 38 of the inverter 30 and the inverter terminal 18 of the switching device 10 is suppressed to initiate island operation if a fault is present. A fault exists when the circuit 13 is open.

[0123] In such a case, the switching contact 12.2 could be stuck and would need to be replaced. Therefore, it is advisable to detect this faulty condition of the emergency power system 100 and, optionally, to issue the corresponding information to a user of the emergency power system 100.

[0124] In island mode, the emergency power system 100 signals the return of a properly operating AC network 60 by opening circuit 13 at status terminal 16. When the AC network 60 is operating properly, specifically when the voltage returns from island mode and is again within specified tolerance criteria, the actuating coil 11.1 is energized and activated, thus opening the monostable contact 11.2. Circuit 13 is then interrupted.

[0125] The emergency power system 100 can then, in response to the signaling of the return of the properly operating AC network 60, perform the following steps: - Suppression of the power exchange between the inverter terminal 18 of the switching device 10 and the inverter 30 by stopping the clocking of the AC / DC converter and / or by opening the relay 33, - Deactivation of actuator 12.1 to close the first switching contact 12.2 and connect the inverter 30 to the AC network 60, - optionally synchronizing a voltage at the power terminal 38 of the inverter 30, whereby the voltage is synchronized with the voltage of the AC network 60, and - Operating the emergency power system 100 in grid operation by enabling the exchange of power between the inverter connection 18 of the switching device 10 and the inverter 30.

[0126] In Fig. Figure 3 shows a third embodiment of an emergency power system 100. The third embodiment of the emergency power system includes a third embodiment of the switching device 10.

[0127] The switching device 10 comprises the mains monitoring switch 11 with the actuating coil 11.1 connected to the mains connection 14 and a monostable contact 11.2 that can be actuated by the actuating coil 11.1. In the illustrated third embodiment of the switching device 10, the monostable contact 11.2 is open in the rest state. The rest state refers to the state of the monostable contact 11.2 that is assumed when the actuating coil 11.1 is deactivated, i.e., not energized.

[0128] The switching device 10 further comprises the electromechanical switching unit 12 with the actuator 12.1, the normally closed first switching contact 12.2, a further normally closed positively guided switching contact 12.3 and the positively guided auxiliary contact 12.6. The first switching contact 12.2 is arranged in the connecting line between the first phase conductor connection 14p and a connection terminal 18p of the inverter connection 18 associated with the first phase conductor connection 14p.

[0129] Actuator 12.1 controls the first switching contact 12.2. The actuator can be controlled by inverter 30 via its control output 37. Thus, inverter 30 can disconnect the power supply by opening the first switching contact 12.2 via control output 37.

[0130] The monostable contact 11.2 and the positively driven auxiliary contact 12.6 are arranged in the circuit 13 and connected in parallel. The monostable contact 11.2 is open in the resting state. With the monostable contact 11.2 in the resting state, the two switching states of the switching unit 12 result in an impedance change of the circuit 13 via the positively driven auxiliary contact 12.6, which is positively driven by the first switching contact 12.2. This change can be detected by the inverter 30 via the status terminal 16.

[0131] The compulsory assistance contact 12.6 is in Fig.3 is designed as a normally closed contact and is positively guided with the first switching contact 12.2 in a synchronous manner. When the first switching contact 12.2 is open, the positively guided auxiliary contact 12.6 is open, and vice versa. With the normally closed first switching contact 12.2, the positively guided auxiliary contact 12.6 is therefore positively closed when the normally closed first switching contact 12.2 is closed.

[0132] The additional positively guided switching contact 12.3 is located in the connecting line between the first neutral conductor terminal 14n and the terminal 18n associated with the first neutral conductor terminal 14n. The additional positively guided switching contact 12.3 is configured as a normally closed contact. The additional positively guided switching contact 12.3 is positively guided with the first switching contact 12.2 in a synchronous manner. When the first switching contact 12.2 is open, the additional positively guided switching contact 12.3 is open, and vice versa. Therefore, when the normally closed first switching contact 12.2 is closed, the additional positively guided switching contact 12.3 is positively closed.

[0133] A second forcibly guided switching contact 12.4 is arranged between the connecting line in which the second forcibly guided switching contact 12.3 is located and earth potential PE. The second forcibly guided switching contact 12.4 is designed as a normally open contact. The second forcibly guided switching contact 12.4 is forcibly guided with the first switching contact 12.2 in an inverse relationship. When the first switching contact 12.2 is open, the second forcibly guided switching contact 12.4 is closed, and vice versa. Thus, when the first switching contact 12.2 is normally closed, the second forcibly guided switching contact 12.4 is forcibly open when the first switching contact 12.2 is closed. The second forcibly guided switching contact 12.4...4. In island operation, a suitable earth reference of the island network can be achieved, for example because an earth reference present on the AC network 60 is no longer effective due to the all-pole separation of the AC network 60 in island operation.

[0134] The monostable contact 11.2 and the positively driven auxiliary contact 12.6 are arranged in the circuit 13 and connected in parallel. The monostable contact 11.2 is open in its resting state. In the resting state of the monostable contact 11.2, the two switching states of the switching unit 12 cause a change in the impedance of the circuit 13 via the positively driven auxiliary contact 12.6, which is positively driven by the first switching contact 12.2. This change can be detected by the inverter 30 via the status terminal 16.

[0135] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. The auxiliary contact 12.6, which is synchronously driven with the first switching contact 12.2, is then also closed, and the circuit 13 is closed. This can be detected via the status terminal 16.

[0136] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60. The auxiliary contact 12.6, which is synchronously driven with the first switching contact 12.2, is then open, and the circuit 13 is open. This can be detected via the status terminal 16.

[0137] The unstable closed state of the monostable contact 11.2 can be achieved by energizing the actuating coil 11.1 of the monostable contact 11.2. This requires that sufficient electrical power is supplied by the AC network 60 via the network connection 14, i.e., that the AC network is operating correctly and is available. The circuit 13 is therefore closed when the AC network is properly available.

[0138] When the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60. The auxiliary contact 12.6, which is positively driven in the same direction as the first switching contact 12.2, is then open. The second auxiliary contact 12.3, which is positively driven in the same direction as the first switching contact 12.2, is then also open. The second auxiliary contact 12.4, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed.

[0139] The actuating coil 11.1 is activated if the AC network 60 is operating correctly or at least supplies sufficient energy to the actuating coil 11.1. When current flows through the actuating coil 11.1, the monostable contact 11.2 leaves its resting state and closes. The circuit 13 is closed, which can be detected via the status terminal. In this way, during an island operation of the emergency power system 100, the return of the AC network 60 can be detected by a change in impedance from an open to a closed circuit 13.

[0140] If the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. The auxiliary contact 12.6, which is positively driven in the same direction as the first switching contact 12.2, and the further switching contact 12.3 are then also closed. The second further switching contact 12.4, which is positively driven in the opposite direction to the first switching contact 12.2, is then open.

[0141] In this Fig. In the embodiment shown in Figure 3, an all-pole isolation of the AC network 60 from the local distribution network can be achieved. This all-pole isolation involves disconnecting the neutral conductor via the further positively driven switching unit 12.3 and the phase conductor via the first switching unit 12.2.

[0142] The possible states are listed in the table below: network monostable contact 11.2 Network disconnection takes place Switching contact 12.6 Circuit 13 Network OK closed Yes open closed Network OK closed no closed closed NOK network open Yes open Open NOK network open no closed closed

[0143] In Fig.Figure 4 shows a fourth embodiment of the emergency power system 100. This fourth embodiment of the emergency power system includes a fourth embodiment of the switching device 10. The fourth embodiment of the switching device 10 is designed for split-phase operation.

[0144] The grid connection 14 has two first phase conductor connections 14p, 14p2 and the first neutral conductor connection 14n. One of the first phase conductor connections 14p is connected to a first phase conductor L1, the other first phase conductor connection 14p2 is connected to a second phase conductor L2 of the AC network 60, which is designed as a split-phase network. The first neutral conductor connection 14n is connected to a neutral conductor N of the split-phase network. The inverter connection 18 has three connection terminals 18p, 18p2, 18n. Alternatively, however, it is also possible that the inverter connection 18 has only two connection terminals 18p and 18p2 (in Fig. 4 not shown).

[0145] The switching device 10 comprises the mains monitoring switch 11 with the actuating coil 11.1 connected to the mains connection 14 and the monostable contact 11.2 that can be actuated by the actuating coil 11.1. In the fourth embodiment of the switching device 10 shown, the monostable contact 11.2 is closed in the rest state. The rest state here refers to the state of the monostable contact 11.2 that is assumed when the actuating coil 11.1 is deactivated, i.e., not energized.

[0146] The switching device 10 further comprises the electromechanical switching unit 12 with the actuator 12.1, the normally closed first switching contact 12.2, a further normally closed positively guided switching contact 12.3, a second further normally open positively guided switching contact 12.5, a third further normally open positively guided switching contact 12.7 and the positively guided auxiliary contact 12.6.

[0147] The first switching contact 12.2 is located in the connecting line between the first phase conductor connection 14p and a connection terminal 18p of the inverter connection 18 assigned to the first phase conductor connection 14p.

[0148] The additional positively driven switching contact 12.3 is located in the connecting line between the additional first phase conductor connection 14p2 and a connection terminal 18p2 of the inverter connection 18, which is associated with the additional first phase conductor connection 14p2. The additional positively driven switching contact 12.3 is designed as a normally closed contact. The additional positively driven switching contact 12.3 is positively driven in the same direction as the first switching contact 12.2. When the first switching contact 12.2 is open, the additional positively driven auxiliary contact 12.3 is open, and vice versa. Therefore, when the normally closed first switching contact 12.2 is closed, the additional positively driven auxiliary contact 12.3 is positively closed.

[0149] The electromechanical switching unit 12 includes the further normally open switching contact 12.7, which is arranged between the first neutral conductor connection 14n and one of the connection terminals 18p2, and is designed to connect the corresponding connection terminal 18p2 to the first neutral conductor connection 14n in island operation.

[0150] The monostable contact 11.2 and the positively driven auxiliary contact 12.6 are arranged in the circuit 13 and connected in series. The monostable contact 11.2 is closed in its resting state. In the resting state of the monostable contact 11.2, the two switching states of the switching unit 12 cause a change in the impedance of the circuit 13 via the positively driven auxiliary contact 12.6, which is positively driven by the first switching contact 12.2. This change can be detected by the inverter 30 via the status terminal 16.

[0151] The second positively guided switching contact 12.5 and the positively guided auxiliary contact 12.6 are each positively guided to the first switching contact 12.2, but in opposite directions. When the first switching contact 12.2 is open, the positively guided auxiliary contact 12.6 is closed, and vice versa. Thus, when the first switching contact 12.2 is normally closed, the positively guided auxiliary contact 12.6 is positively guided open when the normally closed first switching contact 12.2 is closed. The same applies to the second positively guided switching contact 12.5.

[0152] The third positively guided switching contact 12.7 is arranged between the connecting line in which the second positively guided switching contact 12.3 is located and the terminal 18n. The third positively guided switching contact 12.7 is configured as a normally open contact. The third positively guided switching contact 12.7 is positively guided to the first switching contact 12.2 in an inverse relationship. When the first switching contact 12.2 is open, the third positively guided switching contact 12.7 is closed, and vice versa. Thus, when the first switching contact 12.2 is normally closed, the third positively guided switching contact 12.7 is positively guided open when the first switching contact 12.2 is closed. The third positively guided switching contact 12.7 is also positively guided via the first switching contact 12.2.7. The connection terminal 18p2, which is connected to the second phase conductor L2 in the grid-parallel operation of the emergency power system 100, can be connected to the first neutral conductor connection 14n in the island operation of the emergency power system 100.

[0153] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is closed, the inverter 30 is connected to the AC network 60. This is the case, for example, during grid-parallel operation of the emergency power system 100. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then open and the circuit 13 is interrupted. This can be detected via the status terminal 16.

[0154] If, in the rest state of the monostable contact 11.2, the first switching contact 12.2 is open, the inverter 30 is disconnected from the AC network 60, at least with respect to the phase conductors L1 and L2 of the AC network 60. This is the case, for example, in island mode of the emergency power system 100. The auxiliary contact 12.6, which is positively driven in the opposite direction to the first switching contact 12.2, is then closed, and the circuit 13 is closed. This can be detected via the status terminal 16.

[0155] The unstable state of the monostable contact 11.2 can be achieved by energizing the actuating coil 11.1 of the monostable contact 11.2. For this to occur, sufficient electrical power must be supplied by the AC network 60 via the network connection 14, and in particular, there must be no failure of the AC network 60. Furthermore, the second positively guided switching contact 12.5 must be closed. This is the case when the first switching contact 12.2 is open – due to the opposing positive guidance.

[0156] The actuating coil 11.1 is connected in series with the second positively driven switching contact 12.5. The series connection of the actuating coil 11.1 and the second positively driven switching contact 12.5 is connected in parallel to the mains connection 14. This is particularly low-loss, as the actuating coil 11.1 only carries current during island operation and only when the AC mains 60 is restored. Otherwise, it generates no power loss.

[0157] In island mode, the third normally open switching contact 12.7 connects the first neutral conductor terminal 14n to the terminal 18p2 of the inverter terminal 18 that was connected to the second phase conductor L2 of the split-phase network in grid-parallel operation. This allows the loads 50, which are connected between the first phase conductor L1 and the neutral conductor N via the load terminal 15 of the switching device 10, to be supplied in island mode via the power terminal 38 of the inverter 30.

[0158] In grid-parallel operation, inverter 30 provides a first AC voltage with a first amplitude at connection terminals 18p and 18p2 of inverter connection 18. In island operation, it provides a second AC voltage with a second amplitude at connection terminals 18p and 18p2 of inverter connection 18, the second amplitude being half the amplitude of the first. Due to the third additional switching contact 12.7 being closed in island operation, this voltage is also present between connection terminals 18p and 18n. Since the second neutral conductor connection 15n is connected to connection terminal 18n, and the second phase conductor connection 15p is connected to connection terminal 18p, this AC voltage is also present at the loads 50 connected to load terminal 15 in island operation.

[0159] The control output 37 is connected to the AC / DC converter 32 of the inverter 30. During island operation of the emergency power system 100, the AC voltage supplied by the inverter 30 to the output of the AC / DC converter 32 is monitored. The AC / DC converter 32 can be deactivated if it is detected that the AC voltage supplied during island operation is outside predefined tolerance criteria. This prevents an AC voltage that would otherwise be output at the power output 38 from spreading into the AC network 60 in the event of an unintentional closing of the switching contact 12.2.

[0160] Specifically, in island mode, excessive electrical power consumption by load 50 in the local distribution network can lead to an overload exceeding the nominal power of inverter 30. In this case, the AC voltage can collapse or drop, at least temporarily. If actuator 12.1 is also connected to AC / DC converter 32 and the voltage drop affects it, this can cause the first switching contact 12.2 to close. In this case, the AC voltage supplied by inverter 30 in island mode would extend, at least temporarily, to the AC network 60 and could cause damage there. However, by quickly deactivating AC / DC converter 32, the supply of AC voltage to the power output 38 of inverter 30 can be suppressed before the first switching contact 12.2 closes unintentionally. Thus, when the first switching contact closes, 12.2. This prevents an AC voltage otherwise provided by the inverter 30 from spreading to the AC network 60.

[0161] Although deactivating the DC / AC converter 32 upon detection of a voltage dip is only possible in conjunction with the embodiment according to Fig. As explained in section 4, this also applies to the embodiments of the Fig. 1 to 3 are possible.

[0162] A voltage threshold, below which the AC / DC converter 32 is deactivated to suppress the spread of AC voltage to the AC network 60, can be programmed into the inverter 30, for example, during the initial installation of the emergency power system 100. Specifically, with the inverter's internal relay 33 open and the inverter's internal relay 34 closed, an AC voltage can be applied from the AC / DC converter 32. This AC voltage is then applied to the actuator 12.1, activating it and causing the switching contacts 12.2 and 12.3 to open, thereby disconnecting the phase conductors L1 and L2 of the AC network 60 from the inverter terminal 18. Consequently, no AC voltage from the AC network 60 is detectable at the power output 38 of the inverter 30. Now, the amplitude of the AC voltage provided by the AC / DC converter 32 is gradually reduced upon detection of the same.The moment the applied AC voltage is no longer sufficient to keep the actuator 12.1 in the activated state and thus the first switching contact 12.2 open, it falls back into its closed rest state. As a result, the inverter 30 can now detect the AC voltage supplied by the AC network 60 at its power output 38. The AC voltage provided by the AC / DC converter 32, at which the first switching contact 12.2 falls back, can then be used as the voltage threshold for the emergency power system 100. Although the learning process of the voltage threshold is only shown using the example of the emergency power system 100 according to... Fig. As explained in section 4, it can also be carried out with the other embodiments of the emergency power system 100. Reference symbol list 10 Switching device 11 network monitoring switches 11.1 Actuating coil 11.2 monostable contact 12 switching unit 12.1-12.5, 12.7 Switching contact 12.6 Help contact 13 Circuit 14 Network connection 14p, 14p2 First phase conductor connection 14n First neutral conductor connection 15 load connection 15p second phase conductor connection 15n second neutral conductor connection 16 Status connection 17 Actuator connection 18 Inverter connection 18p, 18p2 connection terminal 18n connection terminal 30 inverters 31 DC / DC converters 32 DC / AC converters 33 network relays 34 PLC relays 35 Unit of measurement (for impedance) 36 Measuring connection 37 Control output (of the inverter) 38 Power connection 40 battery 50 Last 60 AC network 100 emergency power system PE potential earth L1, L2, L3 Phase conductors N Neutral conductor

Claims

A switching device (10) for supplying a load (50) optionally in grid operation or in island operation, comprising: - a grid connection (14) with a first phase conductor connection (14p) and a first neutral conductor connection (14n) for connecting an AC grid (60), - an inverter connection (18) with at least two connection terminals (18p, 18p2, 18n) for connecting a bidirectional inverter (30), and - a load connection (15) with a second phase conductor connection (15p) and a second neutral conductor connection (15n) for connecting the load (50), - a grid monitoring switch (11) with an actuating coil (11.1) connected to the grid connection (14) and a monostable contact (11.2) actuated by the actuating coil (11.1), - an electromechanical switching unit (12) with an actuator (12.1), a first switching contact (12.2) and a forced-guided auxiliary contact (12.6), wherein the first switching contact (12.2) is arranged in a connecting line between the first phase conductor connection (14p) and a connection terminal (18p) of the inverter connection (18) associated with the first phase conductor connection (14p), - a status connection (16) with a circuit (13) connected thereto for signaling a state of the switching device (10), characterized in that the monostable contact (11.2) and the positively guided auxiliary contact (12.6) are arranged in the circuit (13) and are interconnected therein in such a way that in a rest state of the monostable contact (11.2) the two switching states of the switching unit (12): - first switching contact (12.2) open, - first switching contact (12.2) closed, each generate a distinguishable impedance of the circuit (13) at the status connection (16). Switching device (10) according to one of the preceding claims, characterized in that the first switching contact (12.2) is a normally closed first switching contact. Switching device (10) according to claim 1 or 2, characterized in that the monostable contact (11.2) of the network monitoring switch (11) is designed as a normally closed contact and the auxiliary contact (12.6) of the switching unit (12) is designed as a normally open contact, and wherein the auxiliary contact (12.6) is arranged in series with the monostable contact (11.2) in the circuit (13). Switching device (10) according to claim 1 or 2, characterized in that the monostable contact (11.2) of the network monitoring switch (11) is designed as a normally open contact and the auxiliary contact (12.6) of the switching unit (12) is designed as a normally closed contact, and wherein the auxiliary contact (12.6) is arranged in the circuit (13) in parallel to the monostable contact (11.2). Switching device (10) according to one of the preceding claims, characterized in that the switching unit (12) has, in addition to the first switching contact (12.2) and the auxiliary contact (12.6), a further switching contact (12.3) or several further switching contacts (12.3-12.5, 12.7) which are positively guided to one another. Switching device (10) according to one of the preceding claims, characterized in that the actuating coil (11.1) is arranged parallel to the mains connection (14). Switching device (10) according to claim 5, characterized in that the further switching contact (12.5) or one of the several further switching contacts of the switching unit (12) is designed as a normally open contact, and wherein a series connection of the actuating coil (11.1) and the further switching contact (12.5) is arranged in parallel to the mains connection (14). Switching device (10) according to one of claims 5 to 7, characterized in that the further switching contact or one of the several further switching contacts (12.3) is arranged in a connecting line between the first neutral conductor connection (14n) and a connection terminal (18n) associated with the first neutral conductor connection (14n) and is optionally designed as a normally closed contact. Switching device (10) according to one of the preceding claims, characterized in that the second phase conductor connection (15p) is directly connected to a connection terminal (18p), and wherein the second neutral conductor connection (15n) is directly connected to a different connection terminal (18n) and / or directly to the first neutral conductor connection (14n). Switching device (10) according to one of the preceding claims, characterized in that the switching device (10) is designed for split-phase operation, wherein the grid connection (14) has two first phase conductor connections (14p, 14p2), and the inverter connection (18) has at least two connection terminals (18p, 18p2), optionally also three connection terminals (18p, 18p2, 18n), wherein each of the two first phase conductor connections (14p, 14p2) is connected to a different connection terminal (18p, 18p2) via a separate switching contact (12.2, 12.3) of the switching unit (12), in particular via a separate normally closed switching contact (12.2, 12.3), and wherein the switching unit (12) connects the further switching contact (12.7), in particular the further normally open switching contact (12.7), which is arranged between the first neutral conductor connection (14n) and one of the connection terminals (18p2) and is designed to connect the corresponding connection terminal (18p2) to the first neutral conductor connection (14n) in island operation. Emergency power system (100) comprising a bidirectional inverter (30) connectable to a battery (40) and a switching device (10) according to one of the preceding claims, wherein the inverter (30) has a measuring unit (35) for detecting an impedance of the circuit (13) which is connected to the status terminal (16) of the switching device (10) via a measuring terminal (36), a power terminal (38) which is connected to the inverter terminal (18) of the switching device (10), and is designed to enable or suppress power exchange between the inverter (30) and the inverter terminal (18) of the switching device (10) in island operation depending on the detected impedance of the circuit (13). Method for operating an emergency power system (100) according to claim 11 comprising the steps: - Operating the emergency power system (100) in grid operation with the actuator (12.1) deactivated, wherein, in the event of a detected failure of the AC grid (60), the following steps are performed: - Suppressing power exchange between the inverter (30) and the inverter terminal (18) of the switching device (10) and activating the actuator (12.1) to open the first switching contact (12.2), - Measuring an impedance of the circuit (13), - Operating the emergency power system (100) in island operation by enabling power exchange between the power terminal (38) of the inverter (30) and the inverter terminal (18) of the switching device (10) when the impedance of the circuit (13) at the status terminal (16) signals that either of the following two events is true: i) the first switching contact (12.2) is in its open state, andii) the network monitoring switch (11) is not actuated by an alternating voltage of an AC network (60) connected to the network connection (14). Method according to claim 12, wherein the emergency power system (100) signals a fault condition when the impedance of the circuit (13) indicates that the network monitoring switch (11) is not actuated by an alternating voltage of an AC network (60) connected to the network connection (14) and the first switching contact (12.2) is in its closed state despite the actuator (12.1) being activated. Method according to claim 12 or 13, wherein in the island operation of the emergency power system (100) a return of a properly operating AC network (60) is signaled by a change in the impedance of the circuit (13) at the status terminal (16). A method according to any one of claims 12 to 14, wherein the emergency power system (100), in response to the signaling of the return of the properly operating AC network (60), performs the following steps: - suppressing the power exchange between the inverter terminal (18) of the switching device (10) and the inverter (30), - deactivating the actuator (12.1) to close the first switching contact (12.2), - optionally synchronizing a voltage at the power terminal (38) of the inverter (30) with a voltage present in the AC network (60), and - operating the emergency power system (100) in network operation by enabling the power exchange between the inverter terminal (18) of the switching device (10) and the inverter (30). Method according to one of claims 12 to 15, wherein the inverter (30) operates in a current-controlling manner in grid operation and in a voltage-controlling manner in island operation, and wherein optionally a change between the current-controlling operation and the voltage-controlling operation takes place with suppressed power exchange between the inverter (30) and the inverter connection (18) of the switching device (10). Method according to one of claims 12 to 16, wherein the power exchange is suppressed by deactivating an AC / DC converter (32) of the bidirectional inverter (30) and / or opening a relay (33) of the inverter (30) associated with the power connection (38). Method according to one of claims 12 to 17, wherein the inverter (30) has a control output (37) which is activated in the event of a malfunctioning AC network (60), wherein the control output (37) is connected to the actuator (12.1) of the switching unit (12) and activates it in the event of a malfunctioning AC network (60). Method according to one of claims 12 to 18, wherein the emergency power system (100) has a switching device (10) designed for split-phase operation, and wherein the inverter (30) provides a first AC voltage with a first amplitude at the connection terminals (18p, 18p2) of the inverter connection (18) in grid operation, and a second AC voltage with a second amplitude at the connection terminals (18p, 18p2) of the inverter connection (18) in island operation, wherein the second amplitude is half the first amplitude. Method according to one of claims 12 to 19, wherein the control output (37) is connected to the AC / DC converter (32) of the inverter (30), wherein in the island operation of the emergency power system (100) the AC voltage supplied by the inverter (30) is monitored, and wherein the AC / DC converter (32) is deactivated if the AC voltage supplied in the island operation is outside specified tolerance criteria, before an unintentional closing of the first switching contact (12.2) occurs.

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