Battery storage system

Abstract

The invention discloses a battery storage system (1) for connection to an energy supply network (4), which system comprises a transformer (9) having a primary winding (15) and a number of secondary windings (18_1... 18_m). The battery storage system (1) also comprises a number of power converter units (22_1... 22_m), wherein each secondary winding (18_1... 18_m) is electrically connected to an AC terminal (25_1... 25_m) of one of the power converter units (22_1... 22_m). Each DC terminal (28_1... 28_m) of the power converter units (22_1... 22_m) is electrically connected to a battery storage unit (31_1... 31_m).

Description

[0001] Description

[0002] Battery storage system

[0003] The invention relates to a battery storage system for connection to an energy supply network and a method for operating a battery storage system.

[0004] In electrical power generation, rotating machines are currently being replaced by renewable energy generation facilities (such as solar energy), with these facilities being connected to an electrical power grid via power electronic circuits. This presents various challenges, such as more volatile feed-in power and lower instantaneous reserves in the power grid.

[0005] One way to meet these challenges is the use of electrical battery storage units (e.g., based on lithium-ion batteries) connected to the power grid via power converters. In the event of excess energy generation, the battery storage units can be charged; in the event of insufficient generation, energy can be drawn from the battery storage units. Furthermore, the battery storage units can be used to minimize frequency deviations in the event of grid faults associated with these frequency deviations.

[0006] The invention is based on the object of specifying a battery storage system and a method for operating a battery storage system which can be implemented cost-effectively.

[0007] This object is achieved according to the invention by a battery storage system and by a method according to the independent patent claims. Advantageous embodiments of the battery storage system and the method are specified in the dependent patent claims.

[0008] A battery storage system for connection to an energy supply network with

[0009] - a transformer with a primary winding and a number of secondary windings,

[0010] - a number of converter units, each secondary winding being electrically connected to an AC terminal of one of the converter units, and

[0011] - One DC connection of each converter unit is electrically connected to a battery storage unit. This battery storage system can be implemented cost-effectively because only a single transformer is required for the (particularly large) number of converter units and the associated battery storage unit. This transformer has a number of secondary windings, so that the converter units can each be connected to a secondary winding.

[0012] It is therefore a modular battery storage system. This allows the battery storage system to be easily adapted to a different number of battery storage units, especially when expanding an existing battery storage system with additional battery storage units. The battery storage system is therefore highly scalable.

[0013] The battery storage system can be designed so that

[0014] - the secondary windings are galvanically isolated from each other. This enables a simple modular design, even for different numbers of battery storage units.

[0015] The battery storage system can be designed so that

[0016] - Each secondary winding is assigned a (particularly separate) converter unit. The number of converter units is therefore at least as large as the number of secondary windings. This also enables a modular design of the battery storage system.

[0017] The battery storage system can be designed so that

[0018] - the transformer has at least 4, in particular at least 10, secondary windings.

[0019] The transformer is, in particular, a multi-secondary winding transformer. This makes it possible to connect a larger number of battery storage units to a power grid using a single transformer.

[0020] The battery storage system can be designed so that

[0021] - the secondary windings each have a secondary voltage of essentially the same amplitude. The secondary windings can therefore be designed so that they each provide a secondary voltage of essentially the same amplitude. This simplifies the practical implementation of the battery storage system.

[0022] The battery storage system can be designed so that

[0023] - each of the secondary windings has a different phase shift compared to the primary winding. In other words, all secondary windings have a different phase position. The phase shifts or phase positions of all secondary windings therefore differ from one another. This advantageously results in only comparatively low grid perturbations during operation of the battery storage system; in particular, comparatively few harmonics are generated. This means that little or no compensation measures (e.g., filters to filter out harmonics) are necessary.

[0024] The battery storage system can be designed so that

[0025] - the converter units each comprise controlled power semiconductor components, in particular IGBTs, MOSFETs, or thyristors. The converter units can be designed as self-commutated converter units, in which case they comprise IGBTs or MOSFETs, in particular. However, the converter units can also be designed as line-commutated converter units, in which case they comprise thyristors, in particular. This allows the converter units to be adapted to different requirements.

[0026] The battery storage system can be designed so that

[0027] - the power semiconductor components are based on silicon carbide (SiC) or gallium nitride (GaN). This allows for the realization of power converter units with low electrical losses.

[0028] The battery storage system can be designed so that

[0029] - a disconnector and / or an earthing switch is arranged between at least one, in particular all, of the secondary windings and the respective AC connection of the converter unit. In particular, a disconnector-earthing switch combination device can be arranged. This simplifies, for example, maintenance of a battery storage unit that is out of service.

[0030] The battery storage system can be designed so that

[0031] - several converter units are connected in parallel and the parallel converter units are connected to the battery storage unit, or

[0032] - several power converter units are electrically connected in series and the power converter units electrically connected in series are connected to the battery storage unit.

[0033] In the case of parallel connection, larger currents can be provided (particularly with uniform / similar converter units). The AC connections of the converter units can each be connected to its own secondary winding. Alternatively, the AC connections of several converter units can be connected to a common secondary winding. In the latter case, decoupling elements such as choke coils can be provided to dampen compensating processes between the converter units.

[0034] In the case of series connection of the converter units, larger DC voltages can be provided for the respective battery storage unit (especially in the case of uniform / similar converter units).

[0035] The battery storage system can be designed so that

[0036] - at least one battery storage unit, in particular several or all battery storage units, is connected to a (in particular separate) unit for generating renewable electrical energy. This makes it possible to charge the battery storage unit directly by means of the unit for generating renewable electrical energy.

[0037] The battery storage system can be designed so that

[0038] - the unit for generating renewable electrical energy is a solar module unit.

[0039] The battery storage system can be designed so that

[0040] - the solar module unit comprises a plurality of solar modules electrically connected in series. The solar module unit can therefore comprise a series circuit of solar modules. The solar module unit can also comprise a plurality of series circuits of solar modules, wherein these series circuits are arranged in a parallel circuit; these series circuits thus form a parallel circuit.

[0041] The battery storage system can be designed so that

[0042] - a DC-DC converter, in particular a boost converter or a buck converter, is connected between the battery storage unit and the solar module unit. This allows the voltage of the battery storage unit and the voltage of the solar module unit to be matched even better.

[0043] A

[0044] Method for operating a battery storage system connected to an energy supply network with

[0045] - a transformer with a primary winding and a number of secondary windings,

[0046] - a number of converter units, each secondary winding being electrically connected to an AC terminal of one of the converter units, and wherein

[0047] - a DC connection of each of the converter units is electrically connected to a battery storage unit, wherein in the method

[0048] - electrical energy from the power grid via the transformer and one of the converter units to the respective

[0049] Battery storage unit is transferred or

[0050] - electrical energy from one of the battery storage units is transferred to the power grid via the respective power converter unit and the transformer.

[0051] The procedure can be carried out in such a way that

[0052] - the battery storage unit is charged with electrical energy from the power grid, or

[0053] - the battery storage unit is discharged and the electrical energy provided thereby is used to support the

[0054] energy supply network to the energy supply network.

[0055] The procedure can also be carried out in such a way that

[0056] - Electrical energy is provided by a solar module unit, and the battery storage unit is charged with this electrical energy. The battery storage system and the method have the same or similar properties and / or advantages.

[0057] In the following, the invention is explained in more detail using exemplary embodiments. The same reference numerals refer to the same or similarly acting elements.

[0058] Figure 1 shows an example of a

[0059] Battery storage system, in

[0060] Figure 2 shows an example of a

[0061] Battery storage system with solar module units, in

[0062] Figure 3 shows an example of a

[0063] Battery storage system in which the DC connections of two converter units are connected in series, in

[0064] Figure 4 shows an example of a

[0065] Battery storage system in which the DC connections of two converter units are connected in parallel, and in

[0066] Figure 5 shows an example of a

[0067] Battery storage system in which the AC connections of two converter units and the DC connections of the two converter units are each connected in parallel.

[0068] Figure 1 shows an example of a

[0069] Battery storage system 1 is shown. This battery storage system 1 has a device 3 for connecting (grid connection) battery storage units 31 to a power grid 4. The power grid 4 can be an alternating current power grid, in particular a medium-voltage alternating current power grid or a high-voltage alternating current power grid.

[0070] The device 3 for grid connection comprises a transformer 9 with a transformer core 12, a primary winding 15, and m secondary windings 18_1 to 18_m. The m secondary windings 18_1 to 18_m are electrically insulated from one another. The m secondary windings 18_1 to 18_m are galvanically isolated from one another.

[0071] In general, the transformer has m secondary windings. For example, the transformer can have at least 4 secondary windings, preferably at least 10 secondary windings. However, the transformer 9 can also have significantly more secondary windings, for example at least 20, at least 50, or at least 100 secondary windings. The transformer is a multi-secondary winding transformer.

[0072] The m secondary windings 18_1 to 18_m each essentially have a secondary voltage with the same amplitude. Each of the secondary windings 18_1 to 18_m exhibits a different phase shift relative to the primary winding. This results in only a few harmonics and minimal system perturbations. As a result, little or no compensation measures (e.g., filters) are necessary, resulting in a cost advantage.

[0073] Each secondary winding 18 of the transformer is assigned a (separate) power converter unit 22. Each power converter unit 22 has an AC connection 25 and a DC connection 28. For example, the first secondary winding 18_1 is electrically connected to an AC connection 25_1 of a first power converter unit 22_1; the first secondary winding 18_1 is therefore assigned to the first power converter unit 22_1. The second secondary winding 18_2 is electrically connected to an AC connection 25_2 of a second power converter unit 22_2, etc. The number of power converter units 22 is therefore at least as large as the number of secondary windings 18.

[0074] A disconnect switch and / or a grounding switch 24_1 (particularly in the form of a disconnector-grounding switch combination device 24_1) is connected between the first secondary winding 18_1 and the AC connection 25_1 of the first power converter unit 22_1. This disconnect switch and / or grounding switch 24_1 is optional and can also be omitted. The disconnect switch and / or grounding switch 24_1 makes it possible, if necessary (for example during maintenance or repair), to de-energize or ground the first power converter unit 22_1 and / or to disconnect the first battery storage unit 31_1 from the power supply network 4.

[0075] The DC connection 28_1 of the first converter unit 22_1 can optionally be provided with a capacitor (not shown) for smoothing the DC voltage.

[0076] The DC terminal 28_1 of the first power converter unit 22_1 is electrically connected to the first battery storage unit 31_1. The first power converter unit 22_1 supplies the first battery storage unit 31_1 with DC power or converts the DC power provided by the first battery storage unit 31_1 into AC power.

[0077] The first power converter unit 22_1 comprises controlled power semiconductor components (e.g., IGBTs, MOSFETs, or thyristors). The first power converter unit 22_1 can form a self-commutated power converter, in which case it particularly comprises IGBTs or MOSFETs.

[0078] However, the first converter unit 221 can also form a line-commutated converter (in which case it comprises, in particular, thyristors). Power semiconductor components based on silicon carbide (SiC) or gallium nitride (GaN) can be used as power semiconductor components. However, other power semiconductor components can also be used as power semiconductor components, for example, power semiconductor components based on silicon (Si).

[0079] The battery storage unit 31_1 can be implemented on the basis of accumulators (batteries), such as lithium-ion batteries. Such a battery storage unit 31_1 can, in particular, comprise a series connection of batteries. In the battery storage unit 31_1, several such series connections can also be connected in parallel.

[0080] The operation of battery storage system 1 is explained below using the example of the first battery storage unit 31_1. The other battery storage units 31_2 to 31_m are operated in a similar manner.

[0081] The primary winding 15 of the transformer 9 is connected to the energy supply network 4. During the charging process of the first battery storage unit 31_1, the transformer 9 transforms the alternating voltage of the energy supply network 4 down to a low voltage (for example to a voltage less than or equal to 1.5 kV or in particular less than or equal to 1 kV); an alternating current with this lower voltage is output at the first secondary winding 18_1. The isolating switch 24_1 is closed; the earthing switch is open. The alternating current is fed to the alternating current terminal 25_1 of the first power converter unit 22_1. The first power converter unit 22_1 converts the alternating current provided by the first secondary winding 18_1 into direct current and outputs the direct current at its direct current terminal 28_1. The direct current is optionally smoothed by a smoothing capacitor.The direct current now flows to the first battery storage unit 31_1 and supplies this first battery storage unit 31_1 with electrical energy. The first battery storage unit 31_1 is charged with this electrical energy.

[0082] During the discharging process, the first battery storage unit 31_1 is discharged. The electrical energy thus provided is transferred to the first power converter unit 22_1 by means of a direct current. The first power converter unit 22_1 converts the direct current provided by the first battery storage unit 31_1 into alternating current at low-voltage potential. The isolating switch 24_1 is closed; the grounding switch is open. The alternating current now flows to the first secondary winding 18_1 of the transformer 9.

[0083] The transformer 9 transforms the low voltage of the alternating current to the alternating voltage of the power supply network 4. Alternating current with this higher alternating voltage is transmitted to the power supply network 4. This alternating current can be used to support the power supply network 4, for example, to counteract an undesirable frequency reduction in the power supply network.

[0084] The battery storage system 1 according to Figure 1 can be designed as a three-phase system, i.e. the first secondary winding 18_1, the first isolating switch / earthing switch 24_1, the first power converter unit 22_1, the first battery storage unit 31_1, etc. can be designed as a three-phase system. In this case, for example, three secondary windings 18_1 are present, which can be connected in a star connection, for example. In this case, a so-called active front-end power converter, which has a three-phase AC voltage connection, can also be used as the power converter. Alternatively, power converters based on full-bridge modules and / or half-bridge modules (in particular modular multilevel power converters) can also be used.

[0085] The second secondary winding 18_1 to the m-th secondary winding 18_m as well as the isolating switches / earthing switches 24, converter units 22, battery storage units 31, etc. connected to these secondary windings 18 are constructed in the same way and / or function in the same way.

[0086] Figure 2 shows an exemplary embodiment of a battery storage system 1 in which the first battery storage unit 31_1 is connected to a first unit for generating renewable electrical energy 205_l via a first DC-DC converter 202_l. As a result, the first battery storage unit 31_1 can be charged (exclusively or additionally) by means of the first unit for generating renewable electrical energy 205_l. In the exemplary embodiment, the first unit 205_l for generating renewable electrical energy is a first solar module unit 205_l. In other exemplary embodiments, however, a different unit for generating renewable electrical energy can also be used, for example a fuel cell operated with regeneratively generated fuel.

[0087] The first solar module unit 205_l has a plurality of solar modules 207_l to 207_n arranged in series. In addition to the series connection of the solar modules 207_l to 207_n, the solar module unit 205_l can optionally have further solar modules. The further solar modules can, for example, form one or more further series connections of solar modules, wherein the one or more further series connections can each be connected in parallel to the series connection of the solar modules 207_l to 207_n. The first DC-DC converter 202_l is connected between the first battery storage unit 31_l and the first solar module unit 205_l. The first DC-DC converter 202_l is optional and can also be omitted.

[0088] The first DC-DC converter 202_l can be configured, in particular, as a boost converter 202_l or a buck converter 202_l. The DC-DC converter 202_l makes it possible to adapt the DC voltage applied to the first solar module unit 205_l (i.e., the DC voltage provided by the first solar module unit 205_l) to the voltage of the first battery storage unit. This can be achieved by increasing or decreasing the DC voltage applied to the first solar module unit 205_l by means of the DC-DC converter 202_l.

[0089] Figure 3 shows an exemplary embodiment of a battery storage system 1 in which the first direct current connection 28_1 of the first power converter unit 22_1 and the second direct current connection 28_2 of the second power converter unit 22_2 are electrically connected in series and thus form a series circuit. This series connection of the two direct current connections 28_1 and 28_2 is connected to the first battery storage unit 31_1. Due to the series connection, the direct voltages of the first power converter unit 22_1 and the second power converter unit 22_2 are added together, so that a higher direct voltage is applied to the first battery storage unit 31_1. As a result, the first battery storage unit 31_1 can be charged to a higher direct voltage compared to the exemplary embodiment according to Figure 2. This makes it possible to adapt uniform power converter units to different DC voltages of the battery storage unit if necessary.The optional disconnectors, grounding switches, step-up converters, and / or step-down converters have been omitted in this and the following figures of the exemplary embodiments for the sake of clarity, but they can also be used in these exemplary embodiments. In other exemplary embodiments, the DC connections of more than two converter units can also be electrically connected in series.

[0090] Figures 4 and 5 each show an exemplary embodiment of a battery storage system 1 in which the first direct current connection 28_1 of the first power converter unit 22_1 and the second direct current connection 28_2 of the second power converter unit 22_2 are electrically connected in parallel and the parallel-connected direct current connections 28_1 and 28_2 are connected to the first battery storage unit 31_1. By connecting the direct current connections of the power converter units in parallel, the output direct currents of the first power converter unit 22_1 and the second power converter unit 22_2 are added together, so that the first battery storage unit 31_1 is supplied with a larger direct current. As a result, the first battery storage unit 31_1 can be charged and / or discharged with a larger direct current compared to the exemplary embodiment according to Figure 2.

[0091] The embodiments of Figures 4 and 5 differ only in the wiring of the AC connections 25 of the power converter units. In the embodiment of Figure 4, the AC connections 25 of the power converter units are each connected to their own secondary winding. The first AC connection 25_1 of the first power converter unit 22_1 is electrically connected to the first secondary winding 18_1; the first power converter unit 22_1 is therefore supplied with AC current exclusively from the first secondary winding 18_1. The second AC connection 25_2 of the second power converter unit 22_2 is electrically connected to the second secondary winding 18_2; the second power converter unit 22_2 is therefore supplied with AC current exclusively from the second secondary winding 18_2.In contrast, in the embodiment of Figure 5 the AC connections of the power converter units are connected to a common secondary winding. Thus, the first AC connection 25_1 of the first power converter unit 22_1 is electrically connected to the first secondary winding 18_1; the second AC connection 25_2 of the second power converter unit 22_2 is also electrically connected to the first secondary winding 18_1. The first power converter unit 22_1 and the second power converter unit 22_2 are therefore both (exclusively) supplied with AC current from the first secondary winding 18_1 or output AC current to the first secondary winding 18_1. Electrical decoupling elements 503 (here: choke coils) are arranged at the AC connections of the power converter units in order to limit the level of any compensating currents flowing between the power converter units 22_1 and 22_2.

[0092] In other embodiments, the AC connections and / or DC connections of more than two converter units can also be electrically connected in parallel.

[0093] A battery storage system and a method for operating a battery storage system that can be implemented cost-effectively have been described. The battery storage system and the method are versatile and can be easily adapted to different requirements regarding the number of battery storage units used and / or the direct currents and voltages used. The battery storage system and the method have a number of advantages, which are listed below.

[0094] Only a single transformer is required. Therefore, even systems with high electrical output can be realized with comparatively low material usage and therefore low costs. The number of circuit breakers used, if any, is also correspondingly low. The number of power semiconductors required is also comparatively low, since, at least in the case of single-phase secondary windings (secondary winding systems), a large number of three-phase converters is not required.

[0095] A multi-secondary-winding transformer with a plurality of isolated secondary windings is used. Each secondary winding exhibits a different phase shift relative to the primary winding. This allows for grid-friendly performance, resulting in comparatively fewer harmonics and thus requiring no or significantly fewer filters.

[0096] A number of similar power converter units enable a modular design of the battery storage system.

[0097] When using self-commutated converter units (which can also be operated with higher pulses), a desired efficiency factor (cosine of the phase shift angle phi between current and voltage) can be set with respect to the power grid, which in turn can eliminate the need for compensation devices required in other solutions. Resonant switching power electronics modules can also be advantageously used with converter units and / or DC-DC converters.

[0098] The battery storage system described can be used flexibly and has a finely staged and redundant structure. For example, even if individual battery storage units fail, continued operation is possible, possibly with slightly lower power and slightly worse grid feedback. Due to the large number of converter units, the individual converter units can each be operated at a comparatively low voltage. This means they can be manufactured cost-effectively. Power semiconductor components can also be used, in particular those based on silicon carbide (SiC) or gallium nitride (GaN), which have only low electrical losses. If the voltage per converter unit is not significantly higher than 600V, for example, then power semiconductor components based on gallium nitride can advantageously be used.

[0099] The flexibility of the application possibilities of the battery storage system can be further increased if a series connection or a parallel connection of the power converter units is used, more precisely a series connection or a parallel connection of the AC connections and / or the DC connections of the power converter units.

[0100] At (low) voltages that are favorable for battery storage units (particularly with regard to fault management, maintenance, voltage balancing, etc.), an integrated system with higher power can be realized for direct connection to the power grid.

[0101] Reference symbol:

[0102] 1 battery storage system

[0103] 3 Device for connecting the battery storage units to the grid

[0104] 4 Energy supply network

[0105] 9 Transformer

[0106] 12 Transformer core

[0107] 15 Primary winding

[0108] 18 Secondary winding

[0109] 22 Converter unit 24 Disconnector, earthing switch, isolator-earther

[0110] Combining device

[0111] 25 AC connection

[0112] 28 DC connection 31 Battery storage unit

[0113] 202 DC-DC converter, boost converter, step-down converter

[0114] 205 Unit for the generation of renewable electrical energy

[0115] Energy, solar module unit

[0116] 207 Solar module 503 Decoupling element, choke coil

Claims

Patent claims 1. Battery storage system (1) for connection to an energy supply network (4) with - a transformer (9) with a primary winding (15) and a number of secondary windings (18 1 ... 18_m), - a number of converter units (22 1 ... 22_m), each secondary winding (18 1 ... 18_m) being electrically connected to an AC terminal (25_1 ... 25_m) of one of the converter units (22_1 ... 22_m), and - one DC connection (28 1 ... 28_m) of each of the converter units (22_1 ... 22_m) is electrically connected to a battery storage unit (31 > 1 ... 31_m).

2. Battery storage system (1) according to claim 1, characterized in that - the secondary windings (18 1 ... 18_m) are galvanically isolated from each other.

3. Battery storage system (1) according to claim 1 or 2, characterized in that - each secondary winding (18_1 ... 18_m) is assigned a converter unit (22_1 ... 22_m).

4. Battery storage system (1) according to one of the preceding claims, characterized in that - the transformer has at least 4, in particular at least 10, secondary windings ( 18 > 1 ... 18_m).

5. Battery storage system (1) according to one of the preceding claims, characterized in that - the secondary windings (18 1 ... 18_m) each have a secondary voltage of essentially the same amplitude.

6. Battery storage system (1) according to one of the preceding claims, characterized in that - each of the secondary windings (18 1 ... 18_m) has a different phase shift compared to the primary winding (15).

7. Battery storage system (1) according to one of the preceding claims, characterized in that - the converter units (22_1 ... 22_m) each comprise controlled power semiconductor components, in particular IGBTs, MOSFETs or thyristors.

8. Battery storage system (1) according to claim 7, characterized in that - the power semiconductor components are power semiconductor components based on silicon carbide or gallium nitride.

9. Battery storage system (1) according to one of the preceding claims, characterized in that - a disconnector and / or an earthing switch (24_1 ... 24_m) is arranged between at least one, in particular all, of the secondary windings (18_1 ... 18_m) and the respective AC connection (25_1 ... 25_m) of the converter unit (22_1 ... 22_m).

10. Battery storage system (1) according to one of the preceding claims, characterized in that - several converter units (22_1, 22_2) are connected in parallel and the parallel-connected converter units (22_1, 22_2) are connected to the battery storage unit (31_1), or - several converter units (22_1, 22_2) are electrically connected in series and which are electrically connected in series switched converter units (22_1, 22_2) are connected to the battery storage unit (31_1).

11. Battery storage system (1) according to one of the preceding claims, characterized in that - at least one battery storage unit (31_1), in particular several or all battery storage units, is connected to a unit for generating regenerative electrical energy (205_l).

12. Battery storage system (1) according to claim 11, characterized in that - the unit for generating renewable electrical energy (205_l) is a solar module unit.

13. Battery storage system (1) according to claim 12, characterized in that - the solar module unit comprises a plurality of solar modules electrically connected in series.

14. Battery storage system (1) according to claim 12 or 13, characterized in that - a DC-DC converter, in particular a boost converter or a buck converter (34_1 ... 34_m), is connected between the battery storage unit and the solar module unit.

15. Procedure for operating a Battery storage system (1) connected to the energy supply network (4) with - a transformer (9) with a primary winding (15) and a number of secondary windings (18 1 ... 18_m), - a number of converter units (22 1 ... 22_m), each secondary winding (18 1 ... 18_m) being electrically connected to an AC terminal (25_1 ... 25_m) of one of the converter units (22_1 ... 22_m), and wherein - a DC connection (28 1 ... 28_m) of the converter units (22_1 ... 22_m) is electrically connected to a battery storage unit (31 > 1 ... 31_m), wherein in the method - electrical energy originating from the power supply network (4) is transmitted via the transformer (9) and one of the power converter units (22_1) to the respective battery storage unit (31_1) or - electrical energy is transmitted from one of the battery storage units (31_1) via the respective power converter unit (22_1) and the transformer (9) to the power supply network (4).

16. Method according to claim 15, characterized in that - the battery storage unit ( 31_1 ) is charged with the electrical energy coming from the power supply network (4), or - the battery storage unit (31_1) is discharged and the electrical energy thus provided is transmitted to the energy supply network to support the energy supply network (4).

17. Method according to claim 15 or 16, characterized in that - electrical energy is provided by a unit for generating regenerative electrical energy (205_l), in particular by a solar module unit, and the battery storage unit (31_1) is charged with this electrical energy.

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