EP4091229A1

EP4091229A1 - Changeover device, retrofit kit and method for supplying electrical power to a load

Info

Publication number: EP4091229A1
Application number: EP20833769.1A
Authority: EP
Inventors: Claus Allert
Original assignee: SMA Solar Technology AG
Current assignee: SMA Solar Technology AG
Priority date: 2020-01-16
Filing date: 2020-12-15
Publication date: 2022-11-23
Also published as: JP2023510004A; DE102020101002B4; CN115280630A; US20220352747A1; WO2021144103A1; DE102020101002A1

Abstract

A changeover device (1) for selectively supplying power to at least one load (3) from a grid (4) or a bidirectional inverter (2) comprises an input with a grid neutral conductor connection (5) and a grid outer conductor connection (6) for connection to the grid (4), a first output with an inverter neutral conductor connection (7) and an inverter outer conductor connection (8) for connection of the bidirectional inverter (2), a second output with a load neutral conductor connection (9) and a load outer conductor connection (10) for connection of the load (3), and a switching element (11), the control system of which is connected to a control input (18) of the changeover device (1). The switching element (11) comprises a first and a second normally closed contact and a normally open contact, which are connected in an interconnection to the grid outer conductor connection (6), the inverter outer conductor connection (8) and the load outer conductor connection (10). An associated method is also disclosed.

Description

Switching device, retrofit kit and method for the electrical supply of a load

The invention relates to a switching device for the optional supply of a load from a superordinate distribution network or from a local energy supply system. The local energy supply system includes an inverter with a voltage-setting function, which is able to set up a local island network.

The invention also relates to a retrofit kit with a switching device for a local energy supply system and a method for switching an energy supply to a load.

In particular, the invention relates to so-called emergency power, backup power or backup systems, which protect grid-connected energy supply systems in the event of a power failure, i.e. to be able to continue to supply at least some of the connected loads, for example according to predetermined priorities, in the event of a power failure. To do this, a series of switching operations must be carried out, for example disconnection from the network, starting a network generator and connecting it to the supply lines. In addition, the state of the network must be monitored, for example to initiate synchronization of the local producers when the network returns and to be able to reconnect the system to the network. These and many other requirements must be met, and their fulfillment is regulated in various directives, norms and standards in different countries.

In addition, the invention relates to smaller backup power plants with which only a few loads are to be supplied. Such backup power systems are used in particular in networks that have a high level of stability, which means that they ensure that the loads are supplied without interference for more than 90% of the time. Conversely, this means that such reserve power systems are kept permanently ready for operation, but are only used very rarely. The backup power system, usually the inverter it contains, usually includes a controller that monitors both the status of the grid monitored and the switches for switching from grid operation to backup power operation controlled.

The document DE 102012011708 A1 discloses an inverter device with at least one inverter unit, which can be connected to a regenerative energy source and to an accumulator device and, via a connection device, to a line harness between a public energy network and consumers. The inverter unit is assigned a control unit which interacts with a power meter to measure the voltage applied to the public energy network. A safety circuit is assigned to the inverter unit, comprising a first switch device between the connection device and the public energy network, and a second switch device between the inverter unit and the connection device. If the public power grid fails, the control unit switches the first and the second switch device to a disconnecting state and then connects the inverter unit, which is switched to a voltage-controlled mode, to the consumers via the second switch device for their emergency power supply.

Switches that are open in the idle state (so-called normally-open switches) or switches that are closed in the idle state (so-called normally-closed switches) can be used for switching.

For safety reasons, open switches are usually used in the idle state, often integrated into the inverter as shown in FIG. 1. However, this solution has the disadvantage that this switch has to be kept actively closed 98% or more of the times in stable networks, which causes a considerable energy requirement. In addition, the switch in this configuration must be designed for the full current carrying capacity of all connected loads, whereby the switch must still function reliably in the event of a short circuit.

These requirements make the known configuration shown in FIG. 1 complex and expensive. This is all the more difficult in the case of small systems, where, for example, only one consumer should be protected in the event of a network fault, which also occurs extremely rarely. There is therefore a need for switching devices for backup power systems, in particular in stable networks, which can be made small and inexpensive and also incur little costs in stand-by mode. It is therefore the object of the present invention to provide a switchover device that is compact and inexpensive, inexpensive to maintain and that can also be added to existing installations at a later date.

A switching device according to the invention has the features of independent claim 1. Preferred embodiments of the switching device are described in the dependent claims 2 to 12. A retrofit kit according to the invention is described in claim 13. A method according to the invention is described in claim 14. Claim 15 aims at a preferred embodiment of the method.

A switching device according to the invention is used to optionally supply at least one load from a network or from a bidirectional inverter. For example, a battery or a fuel cell can be connected to the bidirectional inverter and it can be equipped with a voltage-setting function, i.e. it can be capable of expanding a local island network.

The switching device according to the invention comprises an input with a network neutral conductor connection and a network outer conductor connection for connection to the network, a first output with an inverter neutral conductor connection and an inverter outer conductor connection for connecting an inverter output of the bidirectional inverter, and a second output with a load neutral conductor connection and a load outer conductor connection for connecting the load. Furthermore, the switching device according to the invention comprises a switching element, the control of which is connected to a control input of the switching device. The switching element comprises a first and a second normally-closed contact and a normally-open contact, the first normally-closed contact having a first line-side connection and a first inverter-side connection and the second normally-closed contact having a second line-side connection and a first has connection on the load side and the normal The open contact has a second connection on the inverter side and a second connection on the load side. The network external conductor connection is connected to the first network-side connection and the second network-side connection, the inverter external conductor connection is connected to the first inverter-side connection. Furthermore, the load external conductor connection is connected to the first load-side connection and the second load-side connection.

The switching device can - but does not necessarily have to - additionally include a secure power supply (PLC) connection with a PLC neutral conductor connection and a PLC external conductor connection for connection to a secure power supply (PLC) output of the inverter. The PLC connection of the switchover device is therefore typically present when an inverter is to be connected to the switchover device, which in turn provides a PLC output. If the switchover device includes the additional PLC connection, the second connection on the inverter side can be connected to the PLC external conductor connection. In this case, it is not provided that the second connection on the inverter side is connected to the inverter external conductor connection within the switchover device.

Via the optionally available PLC connection of the switching device, the switching device according to the invention can be operated both on inverters which in turn have a PLC output and on inverters that do not have such a PLC output. In the first case, the switching device has the optional PLC connection, while in the latter case it is typically not available. The switching device according to the invention can thus be used regardless of whether the inverter itself has a PLC output or not. This takes into account the fact that both inverters that have a PLC output and inverters that do not have a PLC output are currently available.

If an inverter with a PLC output is connected to the grid via its inverter output, its PLC output is voltage-free. On the other hand, when the inverter with its inverter output is disconnected from the grid, one is located by a DC / AC converter AC voltage provided by the inverter to its PLC output. Conventionally, for example, smaller local loads are connected to the PLC output of the inverter. The local loads can continue to be supplied via the PLC output of the inverter even in the event of a power failure, for example from a battery connected to the inverter on the DC side or from a fuel cell. In the present case, the PLC output of the inverter is not connected directly to the load, but to the load with the switching device interposed.

In an alternative embodiment in which the switchover device does not include the additional PLC connection, the second inverter-side connection of the switchover device can be connected to the inverter outer conductor connection of the switchover device.

If the changeover device does not have an additional PLC connection and all-pole disconnection in the event of a mains failure is not specified in the standard, the neutral conductor connection can be connected directly to the load neutral conductor connection and the inverter neutral conductor connection. If, on the other hand, the switching device has the additional PLC connection, then the network neutral conductor connection is advantageously connected directly to the inverter neutral conductor connection, the load neutral conductor connection, and the PLC neutral conductor connection, if all-pole disconnection in the event of a network fault is not specified in the standard Switching device connected. In these cases, the switching device according to the invention manages with only three contacts, which are available integrated in common inexpensive relays or contactors.

If the switching device includes the additional PLC connection, the control input of the switching device can be designed identically to the PLC outer conductor connection of the switching device. The control of the switching device can be connected with its first connection to the PLC external conductor connection and with its other connection to the PLC neutral conductor connection of the switching device. In such a variant, a control signal applied to the control input - and thus also to the PLC external conductor connection - can simultaneously be a voltage supply for controlling the switching operation of the Provide switching device. This is described in detail in connection with FIG. 3.

The switching device according to the invention with the two normally-closed contacts and the one normally-open contact does not require any energy supply in the event that the supply can be from the higher-level distribution network. In the de-energized (not switched) basic state of the switching element, the supply of the consumers from the grid is guaranteed via the second normally-closed contact, and the inverter is connected to the grid via the first normally-closed contact. Only when the higher-level network fails and the consumers connected to the switchover device are to be supplied by the inverter also connected to the switchover device, the switching element is energized so that the normally-closed contacts are opened and the normally-open contact is closed. These switching operations create a local network that is separated from the higher-level network and in which the inverter can supply the connected loads. This means that the switching device, or its switching element, only consumes energy in the rare event of a network fault or a network failure. Thus, the switching device according to the invention is overall more energy-efficient and more cost-effective than previously known switching devices.

An additional advantage results from the use of normally closed contacts for separation from the higher-level network. In the solution known in the prior art, as sketched in FIG. 1, the normally open disconnector can no longer be activated in the event of a fault on the inverter and is thus opened. As a result, the loads are not supplied even if the distribution network is functioning correctly. By using the switching device according to the invention, in the event of a fault on the inverter in the event of a power failure, there can be no disconnection and, of course, no emergency power supply by the inverter either. If the network is stable, however, the loads can continue to be supplied, since the normally closed contacts do not need any control in order to remain closed. In a method according to the invention for switching an energy supply to a load by means of a switching device according to the invention, the connected bidirectional inverter determines a network status and, in the event of a critical network status, provides a control signal for the control input so that the switching element is actuated and the normally closed contacts are opened and the normally open contact is closed. The connected bidirectional inverter then starts up and provides a voltage at its inverter outer conductor connection or - if the inverter itself has a PLC output - at its PLC output, which via the now closed normally open contact to the load outer conductor connection and is output to the connected loads.

A critical network state should be understood here as all states that do not allow the connected loads to function correctly.

The switching element can be designed as a relay, for example, but it can also be a contactor with or without feedback contacts. The switching contacts can be integrated in a switching element or distributed over several individually controllable switching elements.

The control input of the switching device according to the invention can be connected to the bidirectional inverter, so that the control of the switching element can be triggered directly by the inverter. This is particularly advantageous if the connected inverter also takes over the grid status monitoring. In principle, the network status monitoring can also be taken over by another external controller, which then controls the switching element in the event of a critical network status and instructs the connected inverter to start up and create a local island network.

In a variant of the method in which the switching device has an additional PLC connection, a voltage supply for the control of the switching element can be provided via the control signal.

Due to the compact design of the switching device, it can be designed for installation in a distribution box of a house installation or for installation in an inverter housing. In a further embodiment, the switching device also has energy supply connections for connecting a further energy source. The further energy source can preferably be a renewable, local energy source, such as a photovoltaic system installed on site. As an alternative or in addition, other local energy sources can be integrated into the local installation via the switching device according to the invention and, particularly advantageously, additionally feed into the local island network in the event of a network fault.

In an advantageous embodiment, the switchover device is part of a retrofit kit with which a system for supplying a load in the event of a critical network condition can be upgraded. The system has supply lines to the load to be supplied. By interposing the switching device in the feed lines to the load and connecting a bidirectional inverter with a voltage-setting function to the switching device, an emergency power supply for a load can be subsequently installed in a simple, compact and inexpensive manner. A further advantage of the switching device according to the invention proves here that by being designed as a compact unit separate from the inverter, the dimensioning of the current carrying capacity of the switches included can be selected to match the system or the loads to be supplied and can even be changed subsequently without great effort .

The invention is described below on the basis of exemplary embodiments with reference to drawings, from which, when viewed together with the features of the claims, further features, properties and advantages of the invention emerge.

Show it:

1 shows a schematic representation of a local energy supply system according to the prior art and

2 shows an exemplary embodiment of a first embodiment of a switching device according to the invention with connected components. 3 shows an exemplary configuration of a second embodiment of a switching device according to the invention with connected components.

4 shows an exemplary configuration of a third embodiment of a switching device according to the invention with connected components.

FIG. 1 shows a local energy supply system with an inverter 29 and a battery 26 connected to it, as is known in the prior art. An outer conductor of a higher-level network 4 is connected to a network external conductor connection 6. A switch 27, which is used to separate the outer conductor, is integrated in the inverter 29. In the event of a network fault, the switch 27 is opened and the loads 3, a local energy source 24/25 and the inverter 29 with the connected battery 26 are disconnected from the network 4. The inverter 29 can set up a local network and supply the loads 3. The local energy source consisting of a generator 25 with an inverter 24 can switch on and feed energy into the local network 28.

The switch 27 is designed as a normally open switch, which means that energy must be used to keep this switch 27 closed at all times when the network 4 is available without interference. Even in cases in which the network 4 is available without interference, but the inverter 29 would not be functional, the switch 27 is opened and thus the loads 3 are not supplied. This is disadvantageous, particularly in very stable networks 4.

In addition, the entire current flows from the network into the battery 26 and vice versa, from the photovoltaic generator 25 to the network 4 and from the network 4 to the loads 3 via the switch 27, which must therefore be designed for the maximum possible current. This can mean that very powerful and therefore expensive switches have to be used here.

FIG. 2 shows a first embodiment of a switching device 1 according to the invention. The energy supply network 4 is designed as a three-phase network with an external conductor L1, L2, L3 and a neutral conductor N. Only that is exemplary External conductor L1 and the neutral conductor N are connected to the input of the switching device 1 at a network external conductor connection 6 and a network neutral conductor connection 5. Further loads 21 can be connected to the outer conductors L2, L3, which, however, are at least not supplied via the switching device 1 in the event of a power failure.

At a first output of the switching device 1, a bidirectional inverter 2 is connected to an inverter neutral conductor connection 7 and an inverter external conductor connection 8. A battery 26 is connected to the bidirectional inverter 2. The battery 26 can be charged from the network 4 and / or from a local energy source, here a photovoltaic generator 25.

At a second output of the switching device 1, a load 3 is connected to a load neutral conductor connection 9 and a load external conductor connection 10. The load 3 can comprise several partial loads, e.g. individual consumers, and should continue to be supplied in the event of a power failure or a power failure.

In the example, a further energy source, which comprises a PV inverter 24 and a photovoltaic generator 25, is connected to a PV outer conductor connection 22 and a PV neutral conductor connection 23.

The switching device 1 has a switching element 11 with two normally-closed contacts 11a, 11b and one normally-open contact 11c. The first normally closed contact 11a has a first grid-side connection 12 and a first inverter-side connection 14, the second normally-closed contact 11b has a second grid-side connection 13 and a first load-side connection 15 and the normally open contact 11c has a second inverter-side connection 16 and a second load-side connection 17. The external conductor connection 6 is connected to the first network-side connection 12 and the second network-side connection 13, the inverter external conductor connection 8 is connected to the first inverter-side connection 14 and the second inverter-side connection 16 and the load external conductor connection 10 is connected to the first load-side connection 15 and the second load-side terminal 17 connected. The neutral conductor connection 5 is directly connected to the load neutral conductor connection 9, the inverter neutral conductor connection 7 and the PV neutral conductor connection 23, which in many countries that do not require all-pole disconnection from the grid 4 by standards represents possible and particularly inexpensive embodiment. As a result, the switching element 11 only needs three contacts.

A control 19 of the switching element 11 is connected to a control input 18 of the switching device 1. A control signal can be applied to the control input so that the switching element 11 picks up, i.e. the normally-closed contacts are opened and the normally-open contact is closed. A controller (not shown), which can be located in the connected inverter 2, uses sensors (not shown in FIG. 2) attached to the external conductor connection 6, for example, to determine a network status and, in the event of a critical network status, provides the control signal for the control input 18. As a result, the normally closed contacts 11a, 11b are opened and the connection of the outer conductor connection 6 to the outer conductor connections 8, 9 and 22 is interrupted. At the same time or with a slight delay thereafter, the normally open contact 11c closes, so that the inverter external conductor connection 8 is connected to the load external conductor connection 10. The inverter 2 starts up in voltage-setting mode and provides a local network 28 that is suitable for supplying the load 3. The PV inverter 24 is also connected to the second load-side connection 17 via its outer conductor connection 22, now detects the recurring network (provided by the inverter 2), synchronizes with it and can then feed into the local network 28. With this additional energy, connected loads 3 can be supplied and also fed into the battery 26.

The switching device 1 can advantageously also contain energy meters (not shown) that detect the respective energy flows at the outer conductor connections 6, 8, 9 and 22 and forward them to a controller (not shown) that processes and / or also forwards this data.

The switching device 1 can be used particularly advantageously in supply lines L1 and N of an existing installation to a load 3 by separating the supply lines and connecting them to the outer conductor connections 5, 6 and 9, 10 of the switching device 1. This makes it possible to expand an existing installation with a backup or emergency power function. Since the switching device 1 can be made small and compact, it can be integrated into a house distribution box, for example. New lines may only have to be laid to connect inverter 2. Retrofitting with a local energy source, which includes, for example, a PV inverter 24 and a photovoltaic generator 25, is also easily possible.

In Fig. 3, a second embodiment of the switching device 1 according to the invention is shown with components connected to it. The second embodiment is similar in many respects to the first embodiment of the switching device 1 already shown in FIG. 2. For the similar aspects, reference is therefore made to the description of the figures in FIG. The following mainly shows the differences between the second embodiment and the first embodiment of the switching device 1.

Also known as battery inverters are bidirectionally operating inverters 2 with a so-called secure power supply (SPS) function. In FIG. 3, the inverter 2 connected to the battery 26 is designed as such an inverter with a PLC function. In accordance with the inverter 2 from FIG. 2, the inverter 2 having a PLC function in FIG. 3 comprises a battery connection 34 for connecting the battery 26 and a network connection 35 for connecting an energy supply network 4. Similar to the first embodiment in FIG In the second embodiment, the network connection 35 of the inverter 32 is electrically connected to the power supply network 4 via the switching device 1, in particular via the first inverter-side connection 7, 8 and the input 5, 6 of the switching device 1 32, however, also a so-called PLC output 36 for supplying one or more local loads in the event of a failure of the energy supply network.

The inverter 32, which has a PLC function, usually comprises two operating modes in its operation. In a first operating mode (network operation), which is assumed when the energy supply network 4 is operating properly, power can be exchanged between the battery connection 34 and the network connection 35. In contrast, the PLC output 36 is galvanically isolated from both the mains connection 35 and from the battery connection 34. In a second operating mode (back-up operation), on the other hand, there is an exchange of power between the battery connection 34 and the PLC output 36 made possible, while the network connection 35 is galvanically isolated from both the battery connection 34 and from the PLC output 36. The inverter 32, which has a PLC function, is now able to disconnect its mains connection 35 from the mains 4 in the event of a mains failure and to provide an alternating voltage supplied by the battery at its PLC output 36.

To implement the PLC function, the inverter 32 can have a switching device 33 with four interconnected switching contacts 33.1 - 33.4, which connect a DC / AC converter of the inverter 32 either to the mains connection 35 of the inverter 32 or to the PLC connection 36 of the inverter 32 associate. The coupling of the switching contacts 33.1-33.4 to one another is symbolized in FIG. 3 by a dashed line. Specifically are the four switch contacts

33.1 - 33.4 of the switching device 33, a first switching contact 33.1 and a second switching contact 33.2 are set up to connect or disconnect the DC / AC converter of the inverter 32 to the mains connection 35, while a third switching contact 33.3 and a fourth switching contact 33.4 are set up DC / AC converter with the PLC output 36 of the inverter 2 to connect or disconnect. The first switch contact 33.1 and the second switch contact

33.2 open a coupling in the same direction with one another, i.e. close or open together. The third switching contact 33.3 and the fourth switching contact 33.4 are also coupled in the same direction with one another. In contrast, the first switching contact 33.1 and the third switching contact 33.3 can be inversely coupled to one another. If, for example, the first switching contact 33.1 closes, the third switching contact 33.3 can open at the same time due to the inverse coupling. The same inverse coupling can also be present between the second switching contact 33.2 and the fourth switching contact 33.4. Usually, only one pair of the two pairs of switching contacts 33.1-33.4 is closed during operation, while the other pair of switching contacts 33.1-33.4 is open. In addition, a state is also possible in which both pairs of switching contacts 33.1, 33.2 and 33.3, 33.4 are open.

In addition to the connections already shown in FIG. 2, the switching device 1 in the second embodiment now includes a PLC outer conductor connection 30 and a PLC neutral conductor connection 31. The PLC outer conductor connection 30 and the PLC neutral conductor connection 31 are each included their corresponding conductor connections of the PLC connection 36 of the inverter 32 are connected. The load neutral conductor connection 9 is connected to the PLC neutral conductor connection 31. The load outer conductor connection 10 is connected to the PLC outer conductor connection 30 via the normally open contact 11c of the switching element 11. The control 19 of the switching element 11 is connected with a first connection to the SPS external conductor connection 30 and with a second connection with the SPS neutral conductor connection 31.

Operation of the switching device 1 is now as follows. The network status monitoring can advantageously take place here by controlling the inverter 32 (not explicitly shown in FIG. 3). When the network 4 is operating properly, the first switching contact 33.1 and the second switching contact 33.2 of the switching device 33 are kept closed by the control of the inverter 32. The third switching contact 33.3 and the fourth switching contact 33.4, however, remain open. The PLC output 36 of the inverter 32 is thus voltage-free. Because of this, the control 19 of the switching element 11 is also voltage-free, which is why the normally closed contacts 11a, 11b of the switching element 11 are closed and the normally open contact 11c is open. The network connection 35 of the inverter 32 is thus connected to the network 4 via the closed first 33.1 and second contact 33.2 of the inverter 32 and via the normally closed contact 11a of the switching device 1. An exchange of power between the battery 26 and the network 4 as well as between the PV generator 25 and the network 4 can take place. The load 3 connected to the switching device 1 is supplied via the network 4.

A failure of the network 4 is recognized by the control of the inverter 32. This now opens the first switch contact 33.1 and the second switch contact 33.2 of the inverter 32 and closes the third switch contact 33.3 and fourth switch contact 33.4. The inverter 32 thus separates its network connection 35 from the first output of the switching device 1 with the inverter neutral conductor connection 7 and the inverter outer conductor connection 8 and thus from the network 4. At the PLC output 36 of the inverter 32, the DC / AC Converter set a voltage that is fed from the battery 26. The voltage present at the PLC output 36 of the inverter 32 is also present the PLC connection 30, 31 of the switching device 1, and thus to the control 19 of the switching element 11 of the switching device 1. In response to this, the control 19 closes the normally open contact 11c and opens the normally closed contacts 11a, 11b of the switching device 1. As a result, the load 3 connected to the load terminal 9, 10 of the switching device 1 is removed from the battery 26 via the inverter 32 and supplied from the PV generator 25 via the PV inverter 24.

The second embodiment of the switching device 1 can be used particularly advantageously in connection with an inverter 32 which comprises a PLC function and a corresponding PLC output 36. In this case, the inverter 32 disconnects itself from the network 4 in the event of a power failure and, due to its PLC function, also provides a voltage at its PLC output 36. The voltage of the PLC connection 36 of the inverter is transmitted to the switching device 1 at its PLC connection 30, 31 and thus serves as a control signal for the control 19 of the switching element 11. The control signal signals the control 19 of the failure of the network 4, and also serves as a supply voltage for the control 19 of the switching element 33. Therefore, the PLC external conductor connection 31 forms at the same time also the control input 18 of the switching device 1. A separate control input of the switching device 1 can be omitted here.

The description of FIG. 3 was carried out by way of example for the case that the switching device 33 of the inverter 32 has an all-pole separation between the DC / AC converter and the inverter output 35, as well as between the DC / AC converter and the PLC output 36 of the inverter. For this reason, the switching device 33 comprises the four switching contacts 33.1-33.4. If all-pole disconnection is not required, however, the first switching contact 33.1 and the fourth switching contact 33.4 of the inverter 32 can be omitted and replaced by an inseparable (i.e. non-switchable) connection. In order to symbolize this, the first switching contact 33.1 and the fourth switching contact 33.4 are each shown in FIG. 3 with dashed lines.

FIG. 4 shows a third embodiment of the switching device 1, which is similar in the second embodiment in FIG. 3. Here, too, reference is made to the similar points in the description of FIG. 3. The third embodiment according to FIG. 4 differs from the second embodiment shown in Figure 3 in that the PLC output 36 is connected directly, in particular without the interposition of the third 33.3 and fourth switching contact 33.4, to a bridge output of the DC / AC converter assigned to the inverter 32.

To output the control signal to the switching device 1, the inverter 32 according to FIG. 4 has an additional connection 37 with a neutral conductor connection 37.1 and an outer conductor connection 37.2. The additional external conductor connection 37.2 is connected to the bridge output of the inverter 32 with an additional switching contact 38.1 interposed. Furthermore, the additional connection 37 is connected to the two-pole control input 18 of the switchover device 1.

When the switching device is in operation, when a failure of the network 4 is detected, the connection of the inverter 32 to the network 4 is first disconnected by opening the first switching contact 33.1 and the second switching contact 33.2. In addition, a control signal for the switching device 1 is output at the additional connection 37 of the inverter 32 by closing the additional switching contact 38.1. The control signal is also applied to the control input 18 of the switchover device 1 connected to the additional connection 37 of the inverter 32. The control signal signals to the switching device 1 the failure of the network 4 and at the same time provides a supply voltage for the control 19, which then switches the switching device 11. In particular, the normally closed contacts 11a and 11b of the switching mechanism 11 are opened. This results in a separation of the network external conductor connection 8 from the inverter external conductor connection 8 of the switching device 1 and, on the other hand, a separation of the power supply connection 22 from the network external conductor connection 8. Coupled with the normally closed contacts 11a, 11b, the normally open contact 11c is closed. In this case, the load outer conductor connection 10 is connected to the PLC outer conductor connection 30 of the switching device 1, whereby the connection between the PLC output 36 of the inverter 32 and the load 3 is established. Similar to FIG. 3, the first switching contact 33.1 is also shown in dashed lines in FIG. 4 in order to symbolize that it is only required when all-pole disconnection is required and that it can otherwise be replaced by an inseparable connection.

List of reference symbols

1 switching device

2, 29, 32 inverters

3 load

4 network

5 -10, 12- 18, 22, 23 Connection 11 switching element

11a, 11b, 11c contacts 19 control 21 loads

24 inverters

25 photovoltaic generator

26 battery

27 switches

28 local network

30 Secure-Power-Supply (SPS) external conductor connection

31 Secure-Power-Supply (PLC) neutral conductor connection 33 Switching element

33.1 - 33.4 switch contact

35 Inverter output

36 Secure Power Supply (PLC) output

37 Connection

37.1 Neutral conductor connection

37.2 External conductor connection 38.1 Switching contact

Claims

Expectations

1. Switching device (1) for optionally supplying at least one load (3) from a network (4) or a bidirectional inverter (2), comprising

• an input with a network neutral conductor connection (5) and a network external conductor connection (6) for connection to the network (4)

• a first output with an inverter neutral conductor connection (7) and an inverter external conductor connection (8) for connecting an inverter output (35) of the bidirectional inverter (2, 32)

• a second output with a load neutral conductor connection (9) and a load outer conductor connection (10) for connecting the load (3)

• a switching element (11) whose control is connected to a control input (18) of the switching device (1), the switching element (11) comprising a first and a second normally closed contact and a normally open contact, the first normally closed Contact has a first grid-side connection (12) and a first inverter-side connection (14), the second normally closed contact has a second grid-side connection (13) and a first load-side connection (15), and the normally open contact has a second inverter-side connection ( 16) and a second load-side connection (17), wherein

• the mains external conductor connection (6) is connected to the first mains-side connection (12) and the second mains-side connection (13),

• the inverter outer conductor connection (8) is connected to the first inverter-side connection (14), and

• the load outer conductor connection (10) is connected to the first load-side connection (15) and the second load-side connection (17).

2. Switching device (1) according to claim 1, wherein the switching device (1) additionally has a secure power supply (PLC) connection with a PLC Neutral conductor connection (31) and a PLC outer conductor connection (30) for connection to a secure power supply (SPS) output (36) of the inverter (32), the second inverter-side connection (16) with the PLC outer conductor connection (30 ) connected is.

3. Switching device (1) according to claim 1, wherein the second inverter-side connection (16) is connected to the inverter outer conductor connection (8).

4. Switching device (1) according to claim 3, wherein the mains neutral conductor connection (5) is connected directly to the load neutral conductor connection (9) and the inverter neutral conductor connection (7).

5. Switching device according to claim 2, wherein the network neutral conductor connection (5) is directly connected to the inverter neutral conductor connection (7), the load neutral conductor connection (9), and to the PLC neutral conductor connection (31) of the switching device (1).

6. Switching device according to claim 2 or 5, wherein the control input (18) is identical to the PLC outer conductor connection (30).

7. Switching device (1) according to one of the preceding claims, wherein the switching element (11) is designed as a relay.

8. Switching device (1) according to one of the preceding claims, wherein the first and second normally-closed contact and the normally-open contact are integrated in a switching element (11).

9. Switching device (1) according to one of the preceding claims, wherein the control input (18) is connected to the bidirectional inverter (2).

10. Switching device (1) according to one of the preceding claims, wherein the switching device (1) is set up for installation in a distribution box of a house installation.

11. Switching device (1) according to one of the preceding claims, wherein the switching device (1) is integrated in the connected bidirectional inverter (2).

12. Switching device (1) according to one of the preceding claims, further comprising energy supply connections (22, 23) for connecting a further energy source (25), in particular a renewable local energy source.

13. Retrofit kit with a switching device (1) according to one of the preceding claims for a system with feed lines to a load (3), whereby by interposing the switching device (1) in the feed lines to the load (3) and connecting a bidirectional inverter (2 ) the system for supplying the load (3) from the inverter (2) is upgraded in the event of a critical grid condition.

14. A method for switching a power supply of a load (3) with a switching device (1) according to one of claims 1 to 12, wherein the connected bidirectional inverter (2, 32) determines a network status and, in the event of a critical network status, a control signal at the control input ( 18) provides so that the switching element (11) attracts and thereby the normally-closed contacts are opened and the normally-open contact is closed.

15. The method for switching a power supply to a load (3) according to claim 14, wherein a voltage supply for controlling the switching element (11) is provided via the control signal.