STORAGE DEVICE AND METHOD FOR TRANSMITTING A DIRECT CURRENT

Description

[0001] The invention relates firstly to a storage device with two-pole storage elements for electrical charges, with converter groups of series-connected full bridges, wherein exactly one of the full bridges of each of the converter groups is connected to poles of each of the storage elements, and with a control unit for determining storage states and optimising charging and discharging processes of the storage elements via the full bridges on the basis of the respective storage state, and with a two-pole connection on each of the converter groups.The invention further relates to a method for transmitting a current between an aggregate and a storage device with two-pole storage elements, with at least two converter groups of full bridges each connected in series, wherein exactly one of the full bridges of each of the converter groups is connected to each of the storage elements, and with a control unit which determines the storage states of the storage elements and optimises their charging and discharging processes via the full bridges on the basis of the respective storage state, and with a two-pole connection on each of the converter groups.

[0002] Such a storage device is known from DE 10 2014 213167 A1. CN 208112522 U proposes supplying one or more consumers directly with alternating or three-phase current from the terminals of a storage device with three converter groups connected in parallel to storage elements.

[0003] In the background of the invention, DE 10 2011 089 312 A1, DE 10 2012 223 484 A1, DE 10 2014 215 070 A1, and CN 108183622 A disclose storage devices with multiple full-bridge converter groups, each connected to its own storage elements. Storage devices with only one full-bridge converter group each are known from DE 10 2012 209 179 A1, US 2013 / 0127251 A1, and DE 10 2017 124 126 A1.

[0004] In the further background of the invention, interchangeable memory modules each comprising a battery and an integrated control unit, for example for mobile computers, cameras or drones, are known, wherein the control unit monitors the battery status of the battery. Task

[0005] The invention is based on the object of simplifying direct current transmission. Solution

[0006] Based on the known storage device, the invention proposes that the control unit comprise control modules networked with one another via a data bus, further characterized by storage modules, wherein the full bridges are part of the storage modules, with a bus connection for connection to the data bus, with exactly one of the storage elements each, and with one of the control modules, which determines its storage state and optimizes its charging and discharging processes, and which has an interface with four control lines to one of the full bridges for each converter group, wherein the storage device is configured to apply a DC voltage to the connections of at least two of the converter groups. The converter groups used in the known storage device can, in principle, implement any desired current and voltage profile.The storage device according to the invention is thus suitable for receiving and delivering direct current directly at the two-pole connection of the converter group. The storage element can contain different cells, in particular battery cells or capacitors, or a combination of both.

[0007] The storage state describes the condition of all cells (in the case of battery cells: "battery health") of a storage element and includes the state of charge (SoC), predicted values for possible output or input energy quantities, and limit values for charging and discharging power and current that do not physically damage the cells and minimize wear. In addition to the currently measured voltage between the terminals and the temperature of each cell, the history of these values stored in the control unit is also used to determine the respective storage state.

[0008] Analogous to the storage state of the storage elements, the control unit can also determine the respective full-bridge state of each full-bridge from its temperature and incorporate it into the optimization. Alternatively, the full bridges of a storage device according to the invention can be oversized in such a way that overload cannot occur, making monitoring and consideration of the full-bridge state unnecessary.

[0009] In each full bridge (also known as an H-bridge, here a four-quadrant controller), four power switching elements, preferably four transistors, are connected in an H-shape according to a well-known scheme. A binary control voltage is applied to four control lines of the full bridge, each of which defines the switching state of exactly one of the power switching elements. On the input side of the full bridge, the power switching elements are connected to the terminals of the storage element in such a way that, depending on the switching states of the power switching elements, the terminals on the output side can be switched either as anode or cathode, short-circuited, or de-energized.

[0010] In the storage device according to the invention, the control unit has interconnected control modules, each of which measures the storage state of precisely one of the storage elements and optimizes its charging and discharging processes. Each control module digitizes and stores only analog measured values, such as the voltage and temperature of the storage cells as well as the temperatures of the full bridges of the associated storage element, and uses these to determine the secondary parameters, such as the storage state and full bridge state, for this storage element. In such a modularized storage device, only those parameters required for dynamic power regulation and energy flow control, or explicitly requested data sets, such as diagnostic data, are then transmitted to a higher-level central controller, which distributes the current demand to the full bridges based on the parameters and data sets.The amount of data to be processed by the central controller is thus significantly reduced compared to the current state of the art. Alternatively, the control modules can independently determine and coordinate the current power and energy requirements without a higher-level central controller. Furthermore, the modularization of the control unit simplifies the replacement of a single, for example, defective memory element along with the associated control module.

[0011] Other In the memory device according to the invention, the control modules are connected to each other and, if necessary, to a central controller via a data bus. Bus technology for data transmission is generally known.

[0012] The memory device according to the invention is produced from memory modules, wherein each memory module has exactly one of the memory elements, one of the control modules for determining its memory state and optimizing its charging and discharging processes and a bus connection for connection to the data bus, wherein the control module has an interface with four control lines to one of the full bridges. Other In such a storage module for a storage device with multiple converter groups, the control module has such an interface for each converter group. The control module then optimizes the charging and discharging processes of the storage element via all full bridges attached to the storage element. If the control module saves the storage state of the storage element, such a storage module can be removed and replaced in a storage device according to the invention.

[0013] If the converter group is a permanently connected assembly of the storage device, such a storage module can be separated from the associated full bridges during operation of the storage device according to the invention under load. In the storage device according to the invention, the full bridges are part of the storage module - the storage capacity of a storage device according to the invention can be easily adapted to the respective requirements by varying the number of storage modules. When such a storage module is removed from a storage device according to the invention or to add another storage module, the full bridges of the adjacent storage modules are electrically separated. To maintain the function of the converter groups, the separation point can be bridged with a bypass.

[0014] Preferably, a storage device according to the invention comprises a switching device by means of which the terminals of the converter groups can be connected. Such a storage device according to the invention has increased storage capacity and higher performance when absorbing and discharging energy.

[0015] Such a storage device according to the invention preferably has an AC connection to which several, in particular two, of the converter groups can be connected by means of the switching device as an alternative to the connections. Such a storage device according to the invention can receive or provide direct or alternating current for different energy sources or consumers as required.

[0016] Preferably, such a storage device according to the invention further comprises a three-phase connection to which several, in particular three, of the converter groups can be connected by means of the switching device, alternatively to the connections in a star connection (e.g., for household electricity) or in a delta connection (e.g., for starting a three-phase machine). Such a storage device according to the invention can receive or provide direct or three-phase current for different energy sources or consumers, as required.

[0017] A storage device according to the invention preferably has an auxiliary energy storage device, which in particular supplies the central control unit with energy. In such a storage device according to the invention, the auxiliary energy storage device can be, for example, a storage element or a high-performance capacitor.

[0018] A storage device according to the invention preferably has isolating elements by means of which each of the full bridges can be separated from the associated storage element, preferably in a single-pole manner, wherein each of the storage elements is permanently connected to at most one of the full bridges. If different full bridges on the same storage element are controlled by the converter groups, potential differences between the converter groups can lead to ring currents. These ring currents are prevented by isolating individual full bridges using the isolating elements.

[0019] In principle, it is sufficient for the function if all but one of the full bridges can be separated. This full bridge can be permanently connected to the respective storage element, i.e., without a separating element. In particular, these permanently connected full bridges can be assigned to a common converter group. To standardize and thus simplify the design, all full bridges can alternatively be equipped with corresponding separating elements. These separating elements in the respective storage module are controlled by the control module. Each of the separating elements is connected to the control module via a control line.

[0020] A storage device according to the invention is preferably used in a motor vehicle with at least one electrically operated motor, in an electrical domestic energy storage device with at least one, in particular three-phase, low-voltage connection or in a charging station with at least one at least single-phase charging connection for an electrically operated motor vehicle.

[0021] Based on the known method, the invention proposes that the control unit have control modules networked with one another via a data bus, further characterized by memory modules, wherein the full bridges are part of the memory modules, each with exactly one of the memory elements (13), and with one of the control modules, which determines its memory state and optimizes its charging and discharging processes, and which is connected to one of the full bridges per converter group via four control lines, wherein the current at the terminals of at least two of the converter groups is transmitted as direct current. The method according to the invention can be carried out using a memory device according to the invention and is equally characterized by the advantages mentioned above.

[0022] In a method according to the invention, the power unit is preferably a photovoltaic system from which the storage device and a motor vehicle are simultaneously charged. In the method according to the invention, the energy generated by the photovoltaic system is then transferred to the motor vehicle essentially without loss without intermediate storage. Example

[0023] The invention is explained below using exemplary embodiments. Fig. 1 shows a house according to the invention, a motor vehicle according to the invention and a charging station according to the invention, Fig. 2a schematically shows the charging of a first storage device according to the invention in the house with three-phase current from a public low-voltage network, Fig. 2b shows a storage module of the storage device and Fig. 2c shows the withdrawal of three-phase or alternating current from the first storage device, Fig. 3a shows the transmission of direct current from a solar system to the first storage device, Fig. 3b... with simultaneous charging of the motor vehicle, Fig. 4 shows a second storage device according to the invention in the motor vehicle, and Fig. 5 shows a third storage device according to the invention in the charging station.

[0024] Figure 1shows a house 1 according to the invention with a first storage device 2 according to the invention, a motor vehicle 3 according to the invention with a second storage device 4 according to the invention and a charging station 5 according to the invention with a third storage device 6 according to the invention.

[0025] House 1 has a photovoltaic system 7 (20 kWp, Usmpp: 700 V, Impp: 3x8 A) and is connected to the public low-voltage network 8 (400 VAC, 40 A, three-phase, 50 Hz ) connected. The Figure 2aThe schematically illustrated first storage device 2 comprises a storage group 9 with 34 storage modules 10, six converter groups 11 (for simplicity, only three of the converter groups 11 are shown) on the storage group 9, an auxiliary energy storage unit (LiFePO 4 ) (not shown), and a central control unit (also not shown). For charging from the low-voltage network 8, the three phases 12 of the low-voltage network 8 are connected to the converter groups 11 in a delta circuit.

[0026] Each of the Figure 2bThe storage module 10 shown in detail has a storage element 13 (25.6 V) made up of eight battery cells 14 (Li-Ion) connected in series, each with 3.2 V, six full bridges 16 connected in parallel to the poles 15 of the storage element 13 (for the sake of simplicity, only two of the full bridges 16 are shown) and a control module 17, as well as a temperature sensor 18 on each battery cell 14 and on the full bridges 16 and a voltage sensor 19 on each battery cell 14. The control module 17 is connected to the temperature sensors 18 and the voltage sensors 19 by data lines 20 and to the full bridges 16 by control lines 21 and to the central control via a data bus 22. The interface of the control module 17 to the full bridges 16 (not shown) is hard-wired via the data lines 20 and the control lines 21; the full bridges 16 are integrated into the respective converter group 11 and the control module 17 to the data bus 22 via plug connections (not shown).

[0027] A microcontroller (not shown) in the control module 17 processes all measured values of temperatures and voltages of the battery cells 14 and full bridges 16 in the memory module 10, calculating secondary values such as power and energy quantities using global measured values, such as the converter group current. Individual values and results are stored in a data memory (not shown) in the control module 17 and used to determine the energy quantity SoC (state of charge) stored in the memory element 13. The control module 17 provides the SoC and the current temperatures on the data bus 22, receives control commands from the central controller via the data bus 22, checks and evaluates them, e.g., with regard to the admissibility of the switching state, and controls the full bridges 16 accordingly.

[0028] For supplying both three-phase consumers with 400 VAC as well as single-phase consumers with 230 VACin House 1 as in Figure 2c shown three phases 23 and the neutral conductor 24 of the house network (400 VAC, 50 Hz, three-phase) connected in star connection to the converter groups 11. The consumers and the house network are not shown.

[0029] To avoid ring currents due to potential differences between converter groups 11 simultaneously connected to a storage element 13, full bridges 16 are individually separated from the respective storage element 13 with a separating element (not shown) when this storage element 13 is not used in the respective converter group 11. To maintain the current flow in the converter group 11, the full bridge 16 bridges the separated storage element 13.

[0030] To charge the battery cells 14 of the storage elements 13 in Figure 3a From the photovoltaic system 7, three strings 25 (Umpp: 28 V, Uoc: 35 V) are produced, each consisting of 25 photovoltaic modules 26 (Pmpp: 260W ) of the photovoltaic system 7 are connected in parallel to one of the converter groups 11. For simplicity, only one connection is shown. This allows each of the strings 25 to be independently adjusted to the optimal operating point using the MPPT method. At the optimal operating point, each of the strings 25 delivers at Usmpp = 700 VDC a peak performance of 6.5 kW.

[0031] Depending on the solar radiation, the temperature of the photovoltaic modules, and the state of charge (SoC) of the storage elements 13, the optimal operating point is constantly shifting. Since the solar radiation and the temperature of the photovoltaic modules are unknown disturbances to the MPPT controller of a converter group 11, the operating point must be continuously searched for iteratively. To do this, several load points above and below the current load point must be approached by modulating the output voltage Vsout of the converter groups 11, and the associated total power must be calculated by the central controller. The output voltage assigned to the highest power is then used as the new optimal operating point. The switching sequence of the storage modules 10 and the control of Vsout is optimized for a continuous current load on the storage modules 10 and balancing the energy flows.

[0032] Figure 3bshows how, while the storage device 2 is being charged from the photovoltaic system 7, the motor vehicle 3 is simultaneously charged: For this purpose, all converter groups 11 are connected to the same storage elements 13. The strongly fluctuating voltage of the photovoltaic system 7 from 0 to 875 V is regulated in the respective MPPT power optimum by three of the inverter groups 11 and the energy at 700 VDC and 3x8 A per inverter group 11 are stored in the storage elements 13 for fractions of a second. For this purpose, up to 28 of the storage elements 13 are switched on. At the same time, three other inverter groups 11 extract this energy in the form of 400 VDC and 41 A. To do this, it switches on sixteen of the storage elements 13.

[0033] The Figure 4The second storage device 4 according to the invention in the motor vehicle 3, shown in detail, again has three storage groups 27, each with a connected converter group 28 and a control module (not shown), as well as a switching device 29 for switching the converter groups 28 between a three-phase connection 30 for the motor 31 (690 VAC, three-pole, 0-100 Hz, 100 kW ) of the motor vehicle 3, a further AC connection 32 for single- or three-phase charging and a DC connection 33.

[0034] The full bridges of converter groups 28 are permanently connected as an assembly; the memory modules of memory groups 27 each consist of only one memory element and a control module with interfaces to the respective full bridges. The full bridges, the memory modules, and their details are not shown in detail.

[0035] When motor vehicle 3 is in operation, only motor 31 is switched on. Thus, each inverter group 28 supplies exactly one motor winding. The phase voltage of motor 31 is 690 V, to significantly reduce the currents to below 100 A to minimize. The three-phase alternating voltage is synthesized in voltage and frequency in both energy flow directions.

[0036] In DC charging mode via the DC connection 33, the motor vehicle 3 allows an input voltage of 30 V until 870 V at 0 to 500 A charging current and distributes the energy to the individual storage elements 13 internally. This results in a maximum charging power of approx. 350 kW.

[0037] In DC grid storage mode via the DC connection 33 according to CSS Integration Level 3 - V2H or higher, a freely selectable voltage and power can be drawn from or stored in the motor vehicle 3. In this operating mode, the connection to the first storage device 2 according to the invention is established.

[0038] The DC connection 33 enables direct coupling of two motor vehicles 3 for direct DC-based energy exchange. Each motor vehicle 3 selects the storage elements itself based on the negotiated charging voltage and current.

[0039] For charging at a standard household socket via the AC connection 32, all converter groups 28 are supplied with a voltage of 230 VAC The input voltage can be between 30 and 870 V at 0-100 Hz lay.

[0040] For charging at a standard three-phase socket or directly with a Type 2 plug compatible with the CCS standard via the AC connection 32, each of the three inverter groups 28 is connected in star with 230 V of the external network. At 400 VAC The maximum charging power is currently limited to 43 kW at 63 A and 400 VAC limited.

[0041] An adapter (not shown) allows the island operation of single- or three-phase consumers via the AC connection 32 directly from the motor vehicle 3. The adapter is connected to the motor vehicle 3 via a CCS plug and associated cable.

[0042] An adapter (not shown) allows the direct connection of a photovoltaic system 7 to the motor vehicle 3 via the DC connection 33, without a detour via the first storage device 2 according to the invention or external power converters.

[0043] The Figure 5 The storage device 6, shown schematically in detail, has three storage groups 34, each with two converter groups 35 and three charging connections 36, and is in turn connected to the public low-voltage grid 8. The grid connection power is between 43 kW and 150 kW, depending on the capacity of the power grid. The input voltage of the charging station 5 can be between 90 and 690 VAC at 15 to 60 Hz The possible charging power for vehicle 3 is up to 350 regardless of the grid connection parameters. kW, at a charging voltage of up to 800 VDC. This allows the charging station 5 to provide a significantly higher charging capacity for the motor vehicle 3 of up to 350 kW, than the low-voltage network 8 with a minimum of 43 kW provides.

[0044] The three phases 37 of the low-voltage network 8 are connected to three of the converter groups 35. The energy is stored proportionally in the storage groups 34. Three further converter groups 35 simultaneously extract the energy from the storage groups 34 and generate a continuously variable DC voltage which, at the full rated current of 500 A from 30 to 870 V can be regulated.

[0045] To ensure optimal utilization of the installed power of the entire system in typical applications and to reduce power losses, the DC output current of 500 A to the storage groups 34 with 170 each A distributed via switching elements 38. Each storage group 34 supplies an independent CCS charging connection 36, so that a maximum of three motor vehicles 3 can be charged simultaneously with up to 68 / 135 kW at 400 / 800 VDC can be loaded.

[0046] If only one CCS connection is occupied, the power of the two other storage groups 34 can be connected in parallel via the switching elements 38, depending on the power requirement of the motor vehicle 3, and thus a single motor vehicle 3 can be supplied with up to 200 / 350 kW When two vehicles 3 are connected, one can be charged with up to 135 / 270 kW and the other with up to 68 / 135 kW The parallel connection of the storage groups 34 is carried out dynamically via the switching elements 38 during the charging process, without the user having to interrupt the charging process.

[0047] A further storage device (not shown) essentially corresponds to the third storage device 6. However, instead of battery cells, capacitors are used as storage elements. In this storage device, the maximum charging power corresponds to the grid connection power (here: 350 kW). Compared to the third storage device 6, these storage devices are characterized by a reduced overall weight and significantly smaller housing dimensions, while at the same time significantly reducing acquisition and operating costs. There is no longer any possibility of storing more energy (e.g., 100 kWh ) to a motor vehicle 3 than a weak low-voltage network with a connected load of e.g. 43 kW can deliver.

[0048] In the figures are 1House 2Storage device 3Motor vehicle 4Storage device 5Charging station 6Storage device 7Photovoltaic system 8Low-voltage grid 9Storage group 10Storage module 11Converter group 12Phase 13Storage element 14Battery cell 15Pole 16Full bridge 17Control module 18Temperature sensor 19Voltage sensor 20Data line 21Control line 22Data bus 23Phase 24Neutral conductor 25String 26Photovoltaic module 27Storage group 28Converter group 29Switching device 30Three-phase connection 31Motor 32AC connection 33DC connection 34Storage group 35Converter group 36Charging connection 37Phase 38Switching element

Claims

1. A storage device (2, 4) with two pole storage elements (13) for electrical charges, with inverter groups (11, 28, 35) including full bridges (16) connected in series, wherein exactly one of the full bridges (16) of each of the inverter groups (11, 28, 35) is connected with poles (15) of each of the storage elements (13), with a control unit configured to determine storage conditions and optimize charge and discharge processes of the storage elements (13) through the full bridges (16) based on a respective storage condition, and with a respective two-pole connection at each of the inverter groups (11, 28, 35), characterized in that the control unit includes control modules (17) connected with one another by a data bus (22), further characterized by storage modules (10), wherein the full bridges (16) form part of the storage modules (10), each of the storage modules with a bus connection configured to connect with the data bus (22), further with exactly one of the storage elements (13), and further with one of the control modules (17) that determines its storage condition and optimizes its charging and discharging processes and that includes an interface with four control conductors to one of the full bridges (16) for each of the inverter groups (11, 28, 35), wherein the storage device (2, 4) is configured to apply a DC voltage at the connections of at least two of the inverter groups (11, 28, 35).

2. The storage device (2, 4) according to the preceding claim, characterized by a switching device (29) by which the connections of the inverter groups (11, 28, 35) are connectable.

3. The storage device (2, 4) according to the preceding claim, characterized by an AC connection (32) connectable with two of the inverter groups (11, 28, 35) by the switching device (29) alternatively to the connections.

4. The storage device (2, 4) according to one of the claims 2 and 3, characterized by a three-phase connection (30) connectable with three of the inverter groups (11, 28, 35) by the switching device (29) as an alternative to the connection in a star circuit or a delta circuit.

5. The storage device (2, 4) according to one of the preceding claims, characterized by an auxiliary energy storage device.

6. The storage device (2, 4) according to one of the preceding claims, characterized by separation elements configured to separate one respective full bridge (16) from the associated storage element (13), advantageously by one pole separation, wherein each of the storage elements (13) is hard wired with one of the full bridges at the most.

7. A motor vehicle (3) including at least one electrically operated motor (31); an electrical domestic energy storage including at least one three phase low voltage connection or charging station (5) including an at least one at least one phase charging connection (36) for an electrically operatable motor vehicle (3) characterized by a storage device (2, 4) according to one of the claims 3 or 4.

8. A method for transmitting power between a power unit and a storage device (2, 4), the storage device comprising: two pole storage elements (13), inverter groups (11, 28, 35) including full bridges (16) respectively connected in series, wherein exactly one of the full bridges (16) of each of the inverter groups (11, 28, 35) is connected with poles (15) of each of the storage elements (13), a control unit that determines storage conditions and optimizes charging and discharging processes of the storage elements (13) through the full bridges (16) based on a respective storage condition, and a respective two-pole connection at each of the inverter groups (11, 28, 35), characterized in that the control unit includes control modules (17) connected by a data bus (22), further characterized by storage modules (10), wherein the full bridges (16) are included in the storage modules (10), the storage modules (10) respectively including exactly one of the storage elements (13) and one of the control modules (17) that determines a storage condition of the exactly one of the storage elements (13) and that optimizes the charging and discharging processes of the exactly one of the storage elements (13) and that is connected by four control conductors with one of the full bridges (16) for each of the inverter groups (11, 28, 35), wherein power is transmitted as direct current at connections of at least two of the inverter groups (11, 28, 35).

9. The method according to the preceding claim, characterized in that the power unit is a photovoltaic plant (7) that simultaneously charges the storage device (2) and a motor vehicle (3).