Energy supply which is gentle on batteries

Abstract

The invention relates to an apparatus (1) for providing electrical energy, comprising a current generator (2), a first battery (3), a second battery (4) and a controller (5), wherein the controller (5) is configured such that a first current converter (6) of the first battery (3) is controlled such that the first battery (3) is repeatedly only discharged and then only switched to charging, and a second current converter (7) of the second battery (4) is controlled such that the second battery (4) is repeatedly only charged and then only switched to discharging if either the first battery (3) has reached a lower limit value (8) for its charging state or the second battery (4) has reached an upper limit value (9) for its charging state. The invention also relates to a method for operating an apparatus (1) for providing electrical energy.

Description

Description JUEL Battery-saving energy supply TECHNICAL FIELD

[0001] The invention relates to a device for providing electrical energy, comprising a power generator, a first battery, and a second battery. The invention further relates to a method for operating a device for providing electrical energy. BACKGROUND D

[0002] It is known from the state of the art that the use of batteries is almost unavoidable when supplying energy to systems using fuel cells or generators powered by gas engines. Since both fuel cells and gas engines are very difficult to compensate for load changes, the batteries must absorb these load changes. To do this, they supply the appropriate energy during load peaks and absorb the excess energy from the generator or fuel cell when load decreases until the generators have compensated for the load changes. These load changes lead to constant charging and discharging of the battery, which reduces the service life of the battery(ies). This also includes the parallel operation of multiple batteries / energy storage systems.

[0003] Since diesel generators are very good at balancing load changes, additional measures were not necessary until now. Only with the introduction of gas engines as prime movers for generators or fuel cells did additional measures become necessary to balance load changes. Batteries were generally used for this purpose, all of which were always operated in the same mode. As a result, these batteries had to switch very quickly from discharging during load peaks to charging during load reductions, resulting in a constant cycle of charging and discharging, which had a negative impact on the lifespan of the batteries. SUMMARY OF THE INVENTION

[0004] The object of the invention is to provide a device for providing electrical energy that is improved with regard to the service life of the batteries used. A further object of the invention is to provide a correspondingly improved method for operating a device for providing electrical energy.

[0005] The invention solves the problem directed to a device for providing electrical energy by providing that in such a device for providing electrical energy comprising a power generator, a first battery, a second battery and a controller, the controller is configured such that a first power converter of the first battery is controlled such that the first battery is repeatedly only discharged and only then switches to charging and a second power converter of the second battery is controlled such that the second battery is repeatedly only charged and only then switches to discharging when either the first battery has reached a lower limit for its state of charge or the second battery has reached an upper limit for its state of charge.

[0006] According to the invention, a battery converter is controlled so that the associated battery only absorbs peak loads, thus only discharging the battery. The converter of a second battery is switched so that it only absorbs the excess energy that arises when the load in the grid is reduced, so that the second battery is only charged.

[0007] If the batteries reach a certain, pre-defined upper or lower limit, the batteries are switched and the battery that was previously discharged, for example, is switched to charging and the battery that was previously charged, for example, is switched to discharging.

[0008] This measure greatly reduces the number of charging and discharging cycles of the batteries and extends their service life accordingly.

[0009] It is advisable for the first and second converters to be bidirectional converters. The batteries connected to these converters allow excess energy to be stored when not needed and fed back into the grid when needed. This is particularly advantageous in systems with storage systems where energy generation and consumption are variable.

[0010] In an advantageous embodiment of the invention, the power generator, first battery, and second battery are connected to one another via a bus, with the first power converter being arranged between the bus and the first battery, and the second power converter being arranged between the bus and the second battery. A common bus enables a simpler and more efficient system architecture in which all components are centrally connected to one another via the bus. This facilitates installation and maintenance of the system and reduces the number of required connections. Furthermore, the use of a common bus enables efficient distribution and control of energy between the various components. By arranging the power converters between the bus and the batteries, the energy flows can be effectively regulated and monitored. This leads to improved energy management and greater efficiency of the overall system.Furthermore, if all components are connected via the bus, they can be easily added, removed, or replaced without having to reconfigure the entire system. This increases the flexibility and scalability of the system and allows it to respond to the changing requirements and needs of the application. Finally, the use of multiple batteries connected via a common bus can increase redundancy and safety. If one battery fails or requires maintenance, the system can continue to function by drawing power from another battery or the power generator. Power converters can control the energy flow accordingly to maintain the stability of the system.

[0311] In a further advantageous embodiment of the invention, the upper limit is below a technical maximum value and the lower limit is above a technical minimum value. Thus, the full capacity of the batteries is not fully utilized, which also contributes to extending the service life of the batteries. The limits are not fixed and can also be adjusted dynamically.

[0012] It is advantageous if the controller is configured to reduce the power output of the power generator when the state of charge of the first battery reaches the upper limit while the state of charge of the second battery is still far from the lower limit. It is also advantageous if the controller is configured to increase the power output of the power generator when the state of charge of the first battery reaches the lower limit while the state of charge of the second battery is still far from the upper limit. Furthermore, it is advantageous if the controller is configured to use the distance of the state of charge of the second battery from the upper limit that has not been reached or from the lower limit that has not been reached to determine the size of a power change of the power generator.

[0013] This approach can be applied to two batteries installed in a system, as well as to multiple batteries installed in a system. If one of the batteries reaches the upper limit while the other battery is still far from the lower limit, this means that more energy has been fed from the grid into the batteries due to load reductions. To compensate for this, the generator's output is reduced slightly.

[0014] If one of the batteries reaches the lower limit while the other battery is still far from the upper limit, this means that more load peaks had to be covered from the battery than load reductions had to be added. To compensate for this, the power generator's output is increased slightly.

[0315] The power output of the generator can be changed using fixed values, but this can sometimes lead to the generator oscillating.

[0016] It is better to determine an amount by which the generator's output must be increased or decreased, which can be achieved through an appropriate control process. This can occur when a limit is reached or dynamically. The greatest of the two distances between the actual state and the respective limit is determined, and the generator's output is thus varied depending on the generator's characteristics and the respective charge levels. The generator's load can be controlled to a fixed setpoint or to a value that smooths out load changes in the grid and dynamically adjusts the setpoint to consumption. In addition, an additional setpoint can be calculated that takes the battery discharge or charge power into account.

[0017] If one battery reaches its upper limit before the other battery reaches its lower limit, the difference between the actual state of charge of the battery being discharged and the lower limit is determined. Multiplied by a factor depending on the generator's characteristics, this determines the amount by which the generator's output must be reduced.

[0018] If one of the batteries reaches its lower limit before the other battery reaches its upper limit, the difference between the actual state of charge of the battery being charged and the upper limit is determined. Multiplied by a factor that depends on the characteristics of the generator, this determines the amount by which the generator's output should be increased.

[0019] This control process allows the generator's output to change more quickly at large distances, and the adjustment becomes increasingly smaller and more precise as the distances from the limit values ​​decrease. Oscillation of the generator is thus eliminated. [C0201 Through this equalisation process, the batteries ideally reach their respective limit values ​​almost simultaneously.

[0021] This will result in a steady state for the generator over the course of operation, in which the energy from peak loads and the energy from load reductions in the grid are roughly balanced, and the energy from the batteries hardly needs to be balanced. This means that the generator can operate with almost constant energy production and only very minimal changes in energy production are required, which in turn leads to a longer service life of the generator.

[0022] Another possibility would be to make this balancing process more variable using a control unit, thus better adapting and optimizing it to the specific situation. This could further increase the service life of the individual components.

[0023] Finally, it is practical if the power generator is a gas generator or a fuel cell. Fuel cells and gas generators generally have lower emissions than conventional combustion engines. Hydrogen fuel cells, in particular, produce water as their primary emission, making them a clean energy source. Gas generators that use natural gas also have lower CO2 and pollutant emissions than generators based on gasoline or diesel.

[0024] The object directed to a method is achieved by a method for operating a device for providing electrical energy, the device comprising a power generator, a first battery, a second battery and a controller, wherein a first power converter of the first battery is is controlled so that the first battery is always only discharged and then switches to charging and a second power converter of the second battery is controlled so that the second battery is always only charged and then switches to discharging when either the first battery has reached a lower limit for its state of charge or the second battery has reached an upper limit for its state of charge.

[0025] It is advantageous to reduce the power of the generator when the state of charge of the first battery reaches the upper limit while the state of charge of the second battery is still far from the lower limit. Furthermore, it is advantageous if the power of the generator is increased when the state of charge of the first battery reaches the lower limit while the state of charge of the second battery is still far from the upper limit.

[0027] It is useful to use the distance between the state of charge of the second battery and the upper limit value that has not been reached or the lower limit value that has not been reached to determine the magnitude of a change in the power output of the power generator.

[0028] Finally, it is advantageous if the magnitude of a power generator's output change is determined periodically or continuously depending on the distances between the charge levels of the first and second batteries and their respective lower and upper limits. The generator's load can be controlled to a fixed setpoint or to a value that smooths out load changes in the grid and dynamically adjusts the setpoint to consumption. In addition, an additional setpoint can be calculated that takes the discharge or charging power of the batteries into account. The invention presented here reduces the number of charging and discharging cycles of the batteries through clever control and thus extends their service life without impairing the system dynamics.

[0030] In addition, appropriate control of energy generation can extend the operating life of the power generator.

[0031] With previous methods, the battery converter always had to switch between charging and discharging very quickly, or if the battery was directly connected to the grid, the battery was constantly discharging and charging, which had a negative impact on its service life.

[0032] Since the generator also had to monitor the battery's charge level, controlling the generator was comparatively complex. If the battery was too low, the generator had to quickly recharge it so that further load peaks could be absorbed. If the battery was too full, the generator had to quickly reduce its output to prevent the battery from being overcharged when the grid load decreased.

[0033] Because two batteries with different charge levels are installed in the network, when one of the battery limits is reached - battery too full or too empty - only the batteries need to be switched and the power generator only needs to change its energy production slowly, if at all.

[0034] This process significantly extends the lifespan of the batteries and the power generator. SHORT DESCRIPTION OF THE SIGNS

[0035] FIG 1 Device for providing electrical energy according to the invention with an AC bus in a first state,

[0036] FIG 2 Device for providing electrical energy according to the invention with an AC bus in a second state,

[0037] FIG 3 Device for providing electrical energy according to the invention with a DC bus in a first state and

[0038] FIG 4 Device for providing electrical energy according to the invention with a DC bus in a second state. DESCRIPTION OF THE EMBODIMENT

[0039] Figure 1 shows a device 1 for providing electrical energy according to the invention, the device 1 comprising a power generator 2, for example a gas generator 11, a first battery 3, a second battery 4 and a controller 5 which is connected to the power generator 2, the first battery 3 and the second battery 4 for signal transmission. The controller 5 is configured such that a first power converter 6 of the first battery 3 is controlled such that the first battery 3 is repeatedly only discharged and only then switches to charging, and a second power converter 7 of the second battery 4 is controlled such that the second battery 4 is repeatedly only charged and only then switches to discharging when either the first battery 3 has reached a lower limit value 8 for its state of charge or the second battery 4 has reached an upper limit value 9 for its state of charge.For this purpose, the controller 5 is also connected to the first power converter 6 and the second power converter 7 for signal transmission. The first power converter 6 and the second power converter 7 are bidirectional power converters and are connected such that, in a first state of the device 1, the first power converter 6 functions as an AC / DC rectifier and the second power converter 7 as a DC / AC inverter, and in a second state, the first power converter 6 functions as a DC / AC inverter and the second power converter 7 as an AC / DC rectifier.

[0040] Figure 1 shows that the power generator 2, the first battery 3 and the second battery 4 are connected to one another via a bus 10, wherein the first power converter 6 is arranged between the bus 10 and the first battery 3 and wherein the second power converter 7 is arranged between the bus 10 and the second battery 4.

[0041] The charge levels of the first battery 3 and the second battery 4 are each indicated by an arrow to the left of the batteries 3, 4. The length of the arrow represents the level of the charge level and the direction of the arrow indicates whether the respective battery 3, 4 should currently be charged or discharged when Deviations from an average load occur that cannot be compensated by generator 2. The upper limit 9 for the state of charge of batteries 3 and 4 is below a technical maximum value, and the lower limit 8 is above a technical minimum value. The embodiment in Figure 1 shows only two batteries 3, 4. However, the invention is not limited to this. If more batteries 3, 4 are used, they are divided into two or more branches.

[0043] Figure 1 also shows loads connected to the bus 10, such as a motor 14 connected to the bus 10 via an inverter 13, which drives a propeller 15, or a transformer 16 for further loads.

[0044] In the embodiment of Figure 1, the energy flow direction 17 is from top to bottom in almost all branches, except for the branch with the first power converter 6 or the first battery 3, which has a maximum state of charge and is discharged when necessary. Figure 2 shows the same device 1 as Figure 1, but in a state in which the first battery 3 and the second battery 4 have swapped roles. Now the first power converter 6 is controlled so that it only absorbs the excess energy, and the first battery 3 is charged in the process. The second power converter 7, on the other hand, is controlled so that it only absorbs the load peaks, and the second battery 4 is discharged in the process. In the embodiment of Figures 1 and 2, the bus 10 is an AC bus. According to the invention, however, the bus 10 can also be a DC bus. For example, the power generator 2 could be a gas generator 11, which is directly followed by an AC / DC converter, so that the connection to the bus 10 is a DC connection.

[0047] Alternatively, a DC power generator such as a fuel cell 12 can be used directly, as shown in Figures 3 and 4. The first and second power converters 6, 7 are then DC / DC- DC-DC converter. In the embodiment of Figures 3 and 4, a first inverter 18 is arranged between motor 14 and bus 10. Similarly, a second inverter 19 is arranged between transformer 16 and bus 10. REFERENCE NUMBER LIST 1 device for providing electrical energy 2 power generators 3 first battery 4 second battery 5 Control 6 first power converter 7 second power converter 8 lower limit 9 upper limit 10 buses 11 Gas generator 12 fuel cells 13 inverters 14 Engine 15 propellers 16 Transformer 17 Energy flow direction 18 first inverter 19 second inverter

Claims

Claims What is claimed: 1 . Device (1 ) for providing electrical energy, comprising a power generator (2), a first battery (3), a second battery (4) and a controller (5), characterized in that the controller (5) is configured such that a first power converter (6) of the first battery (3) is controlled such that the first battery (3) is repeatedly only discharged and only then switches to charging, and a second power converter (7) of the second battery (4) is controlled such that the second battery (4) is repeatedly only charged and only then switches to discharging when either the first battery (3) has reached a lower limit value (8) for its state of charge or the second battery (4) has reached an upper limit value (9) for its state of charge.

2. Device (1) according to claim 1, wherein the first power converter (6) and the second power converter (7) are bidirectional power converters.

3. Device (1) according to one of claims 1 or 2, wherein the power generator (2), first battery (3) and second battery (4) are connected to one another via a bus (10), wherein the first power converter (6) is arranged between the bus (10) and the first battery (3) and wherein the second power converter (7) is arranged between the bus (10) and the second battery (4).

4. Device (1) according to one of the preceding claims, wherein the upper limit value (9) is below a technical maximum value and the lower limit value (8) is above a technical minimum value.

5. Device (1) according to one of the preceding claims, wherein the controller (5) is configured to reduce the power of the power generator (2) when the state of charge of the first battery (3) reaches the upper limit value (9) while the state of charge of the second battery (4) is still away from the lower limit value (8).

6. Device (1) according to one of the preceding claims, wherein the controller (5) is configured to increase the power of the power generator (2) when the state of charge of the first battery (3) reaches the lower limit value (8) while the state of charge of the second battery (4) is still away from the upper limit value (9).

7. Device (1) according to one of claims 5 or 6, wherein the controller (5) is configured such that the distance of the state of charge of the second battery (4) from the unreached upper limit value (9) or from the unreached lower limit value (8) is used to determine the size of a power change of the power generator (2).

8. Device according to one of the preceding claims, wherein the power generator (2) is a gas generator (11) or a fuel cell (12).

9. Method for operating a device (1) for providing electrical energy, the device (1) comprising a power generator (2), a first battery (3), a second battery (4) and a controller (5), characterized in that a first power converter (6) of the first battery (3) is controlled such that the first battery (3) is repeatedly only discharged and then switches to charging and a second power converter (7) of the second battery (4) is controlled such that the second battery (4) is repeatedly only charged and then switches to discharging when either the first battery (3) has reached a lower limit value (8) for its state of charge or the second battery (4) has reached an upper limit value (9) for its state of charge.

10. The method according to claim 9, wherein a power of the power generator (2) is reduced when the state of charge of the first battery (3) reaches the upper limit value (9) while the state of charge of the second battery (4) is still away from the lower limit value (8).

11. Method according to one of claims 9 or 10, wherein the power of the power generator (2) is increased when the state of charge of the first battery (3) reaches the lower limit (8), while the charge level of the second battery (4) is still far from the upper limit (9).

12. Method according to one of claims 9 to 11, wherein the distance of the state of charge of the second battery (4) from the upper limit value (9) not reached or from the lower limit value (8) not reached is used to To determine the size of a change in the power output of the power generator (2).

13. The method according to claim 9, wherein the magnitude of a power change of the power generator (2) is determined periodically or continuously as a function of the distances between the charge states of the first and the second battery (3, 4) and their respective lower and upper limit values (8, 9).

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