Method for operating an electrical energy storage device for providing control power, as well as control device for the energy storage device and energy storage system for providing control power.

Abstract

Method for operating an electrical energy storage device (15) for providing control power in an electrical transmission network (10), wherein, according to a predetermined prequalification specification (28), a lower operating limit (31) and an upper operating limit (30) are provided for a state of charge (L) of the energy storage device (15), each of which guarantees that the energy storage device (15) is still able to provide a predetermined minimum power profile for at least a predetermined minimum duration when the respective limit is reached, characterized in that a charging limit (35) is provided in an operating range (34) limited by the lower operating limit (31) and the upper operating limit (30) for a predetermined additional load management application (13) that is independent of the control power provision, wherein the charging limit (35) on the one hand and one of the two operating limits (30,31) on the other hand, a buffer area (36) is defined which corresponds to an amount of energy guaranteed for the load management application (13), and thus a residual area (37) of the operating area (34) reduced by the buffer area (36) results and is controlled by a charge state control (18) of the energy storage (15): , - when the load management application (13) is inactive, if there is no power demand (39) from the load management application (13), the state of charge (L) is maintained in the residual range (37) by recharging and / or discharging the energy storage (15), and - when the load management application (13) is active, when the power request (39) of the load management application (13) is present, the charge state (L) is also directed into the buffer area (36).

Description

[0001] The invention relates to a method for operating an electrical energy storage device, for example, a battery storage device. The energy storage device provides control power in an electrical transmission network or power grid. The invention also includes a control device for controlling the state of charge of the energy storage device and an energy storage system.

[0002] For an electrical transmission grid or power grid, primary control power (PCP) is provided to stabilize the grid frequency. This control power is fed in when the grid frequency drops and withdrawn when it increases excessively. An electrical energy storage system, which can be designed as a battery storage system, for example, can be used to provide this control power. Decentralized approaches are also envisaged. However, it must be ensured that the respective energy storage system (energy storage system plus the associated control system) can be relied upon to provide the control power. For an energy storage system to be approved for control power provision, it must therefore meet a prequalification specification. This specification regulates the requirements for the provision of control power using an electricity storage system.In particular, an energy storage device may not be charged or discharged arbitrarily, since for a predefined extreme case, when the grid frequency rises above a predetermined maximum or falls below a predetermined minimum, the energy storage device must be able to provide a predetermined minimum power profile according to its prequalification specification for at least a predetermined minimum period of time. This is only possible if the state of charge of the energy storage device is maintained between a lower operating limit and an upper operating limit specified by the prequalification specification. The lower operating limit may only be undercut in the aforementioned extreme case, and the upper operating limit may only be exceeded in the aforementioned extreme case.

[0003] It is known from US 2017 / 0 104 345 A1 that, in addition to providing control power, an energy storage system can also be used to supply a campus, i.e., a local electrical network, a property network, or a local balancing group. The balancing group is the part of the electrical network that, together with the energy storage system, is connected via the same electricity meter or connection point to the transmission grid for which the energy storage system also provides control power. Two systems do not have to be connected via the same connection point, but can still be in the same balancing group. A balancing group can also describe an energy quantity account, for example, of an energy supplier. In this case, different electricity meters are summarized in a single account.The state-of-the-art method requires a complex balancing of the control power and the power provided to the campus, as well as the energy supply for recharging the energy storage system, in order to achieve a target charge level. Due to the complexity of this method, an error could occur during the operation of the energy storage system, resulting in incorrect control power provision.

[0004] DE 10 2012 113 050 A1 discloses a method comprising an energy storage device that can absorb and release electrical energy, in particular energy from an alternating current grid. The energy storage device comprises at least two electrochemical elements that differ in their efficiency. If the alternating current grid requires regulating power for a short period of time, energy is provided from the electrochemical element with the higher efficiency. If, however, the alternating current grid requires regulating power for a longer period of time, this is provided from the electrochemical element with the lower efficiency, since this element cannot absorb or release energy as quickly and can provide regulating power for a longer period of time. The result is an excessive load on the electrochemical element with the higher efficiency.

[0005] US 2010 / 0 090 532 A1 discloses a method for responding to changes in the operating frequency of an electricity grid using energy storage devices that are energetically coupled to the electricity grid. This method involves determining whether the operating frequency of the electricity grid corresponds to a nominal operating frequency within a specified range.

[0006] If it is determined that the operating frequency is outside this range, the operating frequency is regulated by transferring energy between the energy storage devices and the electricity grid.

[0007] If the operating frequency is within this range, it is determined whether the state of charge of the energy storage devices is within specified limits, and energy is transferred between the energy storage devices and the electricity grid to bring the state of charge within the specified limits. If the operating frequency is within the range and the state of charge of the energy storage devices is outside the specified limits, energy is transferred between the energy storage devices and the electricity grid to bring the state of charge within the specified limits. US 2010 / 0 090 532 A1 discloses a state of charge-dependent support of the operating frequency of an electricity grid.

[0008] The invention is based on the object of making an electrical energy storage device error-robust and available both for the provision of control power and for additional use.

[0009] The object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are disclosed by the dependent claims, the following description, and the figures.

[0010] The invention provides a method for operating an electrical energy storage device. The energy storage device can be, for example, a battery storage device, i.e., an arrangement comprising one or more electrical batteries or accumulators. The energy storage device can additionally or alternatively comprise, for example, a pumped-storage power plant. The energy storage device provides control power in an electrical transmission grid or power grid. The control power is, in particular, primary control power (PCP).The method assumes that the energy storage device is qualified for the provision of control power. This means that, according to a predetermined prequalification specification, a lower operating limit and an upper operating limit are provided for a state of charge of the energy storage device. These limits guarantee that, when these limits are reached, the energy storage device is still capable of providing a predetermined minimum power profile for a predetermined minimum period of time. When the lower operating limit is reached, it is thus ensured that the energy storage device can be further discharged, i.e., can provide control power, in accordance with the minimum power profile and for the minimum period of time. The minimum power profile can, for example, be a power specification for the energy storage device.When the upper operating limit is reached, the energy storage system is still able to continue to absorb control power for the minimum period of time and in accordance with the minimum power profile, in accordance with the prequalification specification.

[0011] In order to utilize this energy storage device for another application without jeopardizing the ability to provide control power, the following is provided. The invention assumes that the lower operating limit is smaller than the upper operating limit, so that a range arises between the lower operating limit and the upper operating limit, referred to here as the operating range, within which the state of charge can be varied without reaching the operating limits. This operating range is used for a predetermined, additional load management application that is independent of the control power provision.A load management application means that the energy storage device is used to provide additional electrical power for a power supply, for example, of a building or factory or a charging station and / or to absorb electrical power from a power source that uses renewable energy (for example photovoltaics or wind power). The energy storage device therefore supplies the load management application with electrical energy and / or stores electrical energy for the load management application. The resulting energy flow corresponds to the electrical power. Since the invention can be used both for outputting and absorbing electrical power, the term "charging" is used below for both recharging and discharging the energy storage device.

[0012] The method provides for a charging limit to be set in the operating range, i.e., between the lower operating limit and the upper operating limit. The operating range is thus divided into two parts by the charging limit. Accordingly, a buffer range is defined by the charging limit on the one hand and one of the two operating limits on the other. If the charging limit is a charging limit, the buffer range is limited or defined by the charging limit and the lower operating limit. If the charging limit is a discharging limit, the buffer range is limited or defined by the charging limit and the upper operating limit. The buffer range corresponds to an amount of energy guaranteed for the load management application in question.From the charging limit to the corresponding operating limit, an amount of energy is converted (released or absorbed) into the energy storage system when passing through the buffer range, which is assigned or guaranteed to the load management application. The said operating range between the lower and upper operating limits is thus, on the one hand, divided into the buffer range, and, on the other hand, this results in a remaining operating range reduced by the buffer range.

[0013] The state of charge of the energy storage device is influenced by the simultaneous provision of control power and controlled by a state of charge controller. For this purpose, the energy flow or the power in and / or out of the energy storage device can be controlled, for example, using power electronics, in particular a DC-DC converter or a switching converter or power converter. When the load management application is inactive, i.e. when there is no power demand from the load management application, the state of charge controller maintains the state of charge in the aforementioned residual range by recharging and / or discharging the energy storage device. The state of charge can therefore still vary when the load management application is inactive because the provision of control power is still ongoing. This is because primary control power is continuously controlled, i.e. the energy storage device (the battery) receives a control signal (power control signal) every second, for example, which it must run down.The aforementioned recharging and discharging, of course, do not occur simultaneously; rather, both processes can occur sequentially, depending on which limit of the remaining range the state of charge is approaching or which limit has been reached. When a load management application is active, if a power demand from the load management application is present, the state of charge is also directed into the buffer range by the state of charge control. In other words, the buffer range is also utilized.

[0014] Overall, the method embeds a load management application in the available operating range between our operating limit and the upper operating limit. The invention therefore offers the advantage that this additional load management application can be added by simply monitoring an additional charging limit, eliminating the need for complex and thus error-prone monitoring of the energy storage device's state of charge. The same mechanism for recharging, discharging, and monitoring can be used in the state of charge control as is already implemented in the state of charge control in connection with the lower and upper operating limits. Only an additional charging limit is defined. The charging limit and one of the two operating limits define a buffer range, i.e., they delimit it.If the load management application requires energy supply when a power request is made, the buffer range is defined by the lower operating limit. If the load management application requires energy consumption when a power request is made, the buffer range is limited by the upper operating limit. Energy consumption can be relevant, for example, in connection with the generation of electrical power from a renewable energy source, such as wind and / or photovoltaics. In this case, it is necessary to absorb and temporarily store the generated electrical energy.

[0015] The invention also allows for more than one recharging limit to be provided for multiple load management applications. The recharging limits then accumulate depending on which of the load management applications is active.

[0016] The invention also includes embodiments which provide additional advantages.

[0017] Despite the load management application, it must of course be ensured that the prequalification specification is guaranteed to be met or adhered to, i.e., that the predetermined minimum power profile can still be provided for the predetermined minimum period of time when one of the operating limits is reached. One embodiment of this provides that the load management application is deactivated if the state of charge of the energy storage system is within the buffer range and the state of charge reaches the operating limit delimiting the buffer range. If the state of charge leaves the buffer range toward the operating limit and not toward the remaining range, the load management application is deactivated. This results in load shedding. The energy storage system is then advantageously available exclusively for the provision of control power.

[0018] The aforementioned load shedding is of course only intended in an emergency, when the energy storage system is no longer able to provide both the control power and supply the load management application. The state of charge control can of course counteract this load shedding by recharging or discharging. For this purpose, one embodiment provides that the state of charge is guided back to the residual range if it is in the buffer range. For this purpose, in the event that the state of charge is in the buffer range and the state of charge reaches the operating limit delimiting the buffer range, i.e. the lower or upper operating limit, and / or the load management application is inactive, the state of charge is then guided to the residual range by recharging the energy storage system in the case of the lower operating limit and / or by discharging the energy storage system in the case of the upper operating limit.Of course, this is only intended if the extreme case described above does not apply, i.e., the provision of control power requires the energy storage system to exceed the operating limit and provide the minimum power profile. This design has the advantage that the energy storage system is returned to the residual range and is thus available again for load management applications.

[0019] Some embodiments relate to the question of how the energy storage device can be charged or discharged. According to one of these embodiments, recharging and / or discharging takes place by controlling at least one power source other than the energy storage device (for example, a power plant) and / or at least one power consumer within a predetermined charging period during which the charging process is to take place, in order to thereby exchange a predetermined charging power (for charging or discharging the energy storage device) with the transmission grid or, within the balancing group, directly with the energy storage device. The power source is to supply charging power in order to be able to charge the energy storage device. The power consumer is to receive charging power in order to be able to discharge the energy storage device. This process can therefore be power-neutral with regard to the transmission grid.During the charging period, the energy storage system's state of charge control sets a target power flow from the energy storage system offset by the specified charging power. The offset corresponds to the amount of charging power. In other words, the energy storage system's operating point is offset or shifted. This coordinates the energy storage system with at least one power source and / or at least one power consumer. The operating point is offset in such a way that the charging power supplied by a power source can flow into the energy storage system, and the charging power consumed by a power consumer can flow out of the energy storage system. However, not all of the charging power needs to arrive, as part of it can be used up as control power in the transmission grid during this time. This is then recorded as control power provided by the energy storage system.

[0020] The control of the at least one power source and / or the at least one power consumer can be achieved by providing a flexible power source and / or a flexible consumer, which can therefore be controlled as needed for a charging process of the energy storage device and is arranged in the same balancing group, i.e. is connected to the transmission grid via the same connection point as the energy storage device. The charging process therefore takes place within the balancing group and is not recorded in the transmission grid. Additionally or alternatively, it can be provided that the control of the at least one power source and / or the at least one power consumer takes place by means of a schedule transaction on an energy exchange, whereby the state of charge control signals a bid on the energy exchange according to the predetermined charging power. A schedule transaction is therefore triggered automatically.This requires the at least one power source and / or the at least one power consumer to exchange charging power during the charging period, i.e., during a predetermined time interval. This ensures that, during the charging period, if the target power flow in the energy storage device is offset by the power amount, the at least one power source and / or the at least one power consumer exchanges a corresponding amount of charging power with the transmission grid at another location in the transmission grid, i.e., at at least one other connection point.In total, there are three options for the charge management or charge state control of the energy storage system, namely the aforementioned exchange transaction and / or the aforementioned control of a flexible power source and / or power consumer in the same balancing group and finally the payment of balancing energy, i.e. there is no balancing of the schedule transaction.

[0021] However, during the charging process of the energy storage system, i.e., during recharging or discharging, the provision of control power for the transmission grid or power grid can still be carried out. For this purpose, the charging process of the energy storage system, i.e., the power exchange or transfer, or the power flow of the energy storage system, is modulated or adjusted according to a request signal for the provision of control power. For example, if a charging power of 10 kilowatts is set and 3 kilowatts of control power are temporarily requested during the charging process, the power flow of the charging process is reduced to the remaining 7 kilowatts.One embodiment provides that during the aforementioned charging period, the charge state controller generates a differential signal that signals a difference between a charging power profile signal (in the example, 10 kilowatts) and the control power requirement signal (i.e., the required control power, in the example, 3 kilowatts). The differential signal thus describes which portion of the required control power is already provided by the charging power of the at least one controlled power source and / or the at least one controlled power consumer (in the example, 3 kilowatts). However, the energy storage device is responsible for this control power. Therefore, the amount of charging power remaining for the actual charging process (in the example, 7 kilowatts) is determined. This is expressed by the differential signal.Accordingly, the power exchange between the transmission grid and the energy storage system for recharging and / or discharging is modulated depending on the difference signal. If there is a lack of control power because the demand signal is rising, the power exchange is throttled so that more of the charging power in the transmission grid is available as control power. If, however, less or no control power is required according to the demand signal, the power exchange at the energy storage system is increased accordingly so that the energy storage system uses more of the charging power for recharging and / or discharging. In other words, the dynamic control power continues to be provided by the energy storage system.For example, the charging power can be provided by the at least one power source and / or the at least one power consumer with a temporally constant curve, while the demand signal signals a control power that varies over time. This temporal variation can then be compensated, balanced, or fulfilled by modulating the power exchange at the energy storage device.

[0022] Even during load management, i.e., when a load management request is active, control power continues to be provided. One embodiment provides that, when the load management application is active, the energy storage system's state of charge control generates a power control signal that controls the energy storage system's power exchange with the transmission grid and the load management application, depending both on the load management application's power request and on the control power requirement (signaled by the aforementioned request signal). The power control signal can be used, for example, to control the energy storage system's power electronics, which can regulate the energy storage system's power flow.Advantageously, the signals are superimposed so that the energy storage system's power exchange meets both the power requirement of the load management application and the control power requirement. This allows control power to be provided by the load management application itself if the control power requirement and the power requirement of the load management application at least partially balance each other. For example, if power consumption is necessary for the provision of control power and the load management application consists of supplying an electrical consumer, the embodiment coordinates the load management application with the transmission grid in such a way that the control power to be absorbed is consumed by the load management application.The power exchange between the energy storage system and the load management application can thus also be carried out entirely or partially on a balancing basis with the load management application, by transferring the power to the balance sheet. This allows for a balancing exchange of electricity quantities from different meters.

[0023] For the provision of control power, it has proven advantageous if the minimum duration specified in the prequalification specification lies in a range of 10 minutes to 60 minutes. The preferred minimum duration is 30 minutes. When the lower operating limit is reached, it is guaranteed that the minimum duration will still elapse until the energy storage system is fully discharged at the maximum control power demand, as specified for the energy storage system in the prequalification specification. The same applies to a full charge of the energy storage system when the upper operating limit is reached. If the minimum duration is at least 30 minutes, the energy storage system is advantageously qualified for the German electrical energy market.

[0024] The invention also encompasses a control device by means of which the state of charge control in an energy storage device can be implemented while the latter is operated on an electrical transmission network. For this purpose, the control device has a computing device configured to carry out an embodiment of the method according to the invention. For this purpose, the computing device can be implemented, for example, on the basis of at least one microprocessor and / or at least one microcontroller. The control device can be configured, for example, as a control computer for power electronics of the energy storage device. The method steps can be implemented, for example, as program code for the computing device, which can be stored in a data memory of the computing device.

[0025] Finally, the invention also includes the combination of an electrical energy storage device for operation on an electrical transmission grid and the control device according to the invention. Together, this results in the energy storage system according to the invention. The power electronics for adjusting the power flow into and / or out of the energy storage device can also be considered a component of the energy storage system. The power electronics fulfills the requirements of control power provision and load management.

[0026] The invention also includes combinations of the described embodiments.

[0027] Further features of the invention emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combination, but also in other combinations or on their own.

[0028] An exemplary embodiment of the invention is described below. It shows: Fig. 1 is a schematic representation of a transmission network to which an embodiment of the energy storage system according to the invention is connected; Fig. 2 a diagram explaining the prequalification specification; Fig. 3 a diagram illustrating an embodiment of the method according to the invention, which is carried out by a control device of an energy storage device of the energy storage system of Fig. 1 can be carried out; Fig. 4 a flow chart of the process; Fig. 5 diagrams illustrating a charging process of the energy storage device as it can be carried out according to the method.

[0029] In the figures, functionally identical elements are provided with the same reference numerals.

[0030] Fig. Figure 1 shows a transmission grid 10, which may, for example, be a public power grid at the medium-voltage or high-voltage level. The transmission grid 10 may be supplied or operated with electrical power by at least one power source Q, for example, a power plant.

[0031] A participant or balancing group 12 can be connected to a grid connection or connection point 11 of the transmission grid 10. A balancing group 12 can be an electrical network that combines all consumers and / or producers that are connected to the transmission grid 10 exclusively via the connection point 11. An electricity meter can be installed at the connection point 11, which measures or records the amount of energy exchanged with the transmission grid 10 by the balancing group 12.

[0032] A load management application 13 can be provided in the balancing group 12, which can be, for example, one or more office buildings and / or a production site (e.g., a production plant) and / or at least one electric charging station for electric vehicles and / or at least one household. In addition, an energy storage system 14 can be provided in the balancing group 12. The energy storage system 14 can have an electrical energy storage device 15, which can be connected to the connection point 11 and the load management application 13 via power electronics 16. The energy storage device 15 can, for example, be a battery storage device. The power electronics 16 can adjust or control an energy flow or power flow into and / or out of the energy storage device 15.For this purpose, the power electronics 16 can be controlled by a control device 17, which can have a charge state controller 18 for the energy storage device 15. The charge state controller 18 can set a charge state L of the energy storage device 15. For this purpose, the charge state controller 18 can receive a charge state signal 20 describing the current charge state L and / or a power request signal 21 and / or a request signal 22 for a control power requirement of the transmission grid 10. The power request signal 21 describes a power request of the load management application 13, i.e., its requested power (supply power or surplus power to be consumed).The state of charge control 18 can generate a power control signal 23 as a function of the power request signal 21 for the power request of the load management application 13 and as a function of the request signal 22 for the control power requirement, by which the power electronics 16 can be controlled, i.e. the power flow of the energy storage device 15 is controlled by the power control signal 23.

[0033] Overall, the following power flows can thus arise in the balancing group 12: For the load management application 13, a direct power flow 24 can occur from the transmission grid 10 via the connection point 11. The energy storage system 15 can exchange control power with the transmission grid 10 via the connection point 11, resulting in a control power provision 25 for the transmission grid 10 by the energy storage system 14. For recharging and / or discharging the energy storage system 15, an internal power flow 26 can occur between the energy storage system 15 and the load management application 13, and an external power flow 27 can occur between the energy storage system 15 and the transmission grid 10.

[0034] Fig. 1 finally shows an energy exchange B, which will be explained in more detail later.

[0035] Overall, it can be provided that by means of the energy storage device 15, on the basis of the energy storage device 15, both primary control power is provided for the transmission network 10 and a power requirement of the load management application 13 is at least partially satisfied or fulfilled.

[0036] Fig. Figure 2 explains how this is made possible by the energy storage system 15. In order for the energy storage system 15 to be permitted to provide control power in the transmission grid 10, it must meet a prequalification specification 28. Fig. Figure 2 illustrates the prequalification specification 28 graphically.

[0037] The usage restriction for energy storage unit 15 states that the full or highest possible primary control power must be able to be provided at all times for at least a minimum period of, for example, 30 minutes (30-minute criterion). The minimum power profile can therefore be the nominally highest possible power flow for energy storage unit 15 and / or power electronics 16. The usage restriction enforces the provision of battery capacity or energy capacity that may only be charged / discharged at extreme grid frequency values ​​(the aforementioned extreme case). The minimum period multiplied by the highest primary control power to be provided results in the amount of energy that must be held in energy storage unit 15. Energy storage unit 15 must therefore have a minimum capacity 29. For illustration, a ratio V of the minimum capacity 29 to the storage capacity of energy storage unit 15 is shown on the abscissa.The minimum capacity 29 results at V=1. The ordinate represents the state of charge L, as it can be described by the state of charge signal 20.

[0038] If the energy storage device 15 only has the minimum capacity 29 (V=1), the energy storage device must always be charged to 50 percent (L = 50 percent). If, on the other hand, the ratio V of the capacity of the energy storage device to the minimum capacity 29 is greater than 1, this results in an upper operating limit 30 and a lower operating limit 31. In the range between the lower operating limit 31 and the upper operating limit 30, there is a margin of error 32 within which the state of charge L can fluctuate or be maintained without violating the aforementioned 30-minute criterion or the prequalification specification 28 in general. For a specific energy storage device 15, this always results in a specific ratio 33. In this case, an operating range 34 is available between the lower operating limit 31 and the upper operating limit 30, within which the state of charge L can fluctuate or be maintained.

[0039] Fig. Figure 3 again illustrates the specific ratio 33 for the specific energy storage device 15. It shows a curve of the state of charge L over time t. The curve can be controlled or maintained by the state of charge controller 18 between the lower operating limit 31 and the upper operating limit 30. It also illustrates that the respective operating limits 30, 31 can be offset by a respective tolerance value T from the actual values ​​for the state of charge that would actually be necessary to meet the prequalification specification. This compensates for or takes into account a response delay of the energy storage system 14.

[0040] In order to be able to provide electrical energy for the load management application 13 in a targeted manner by means of the energy storage system 14, it can be provided that the working range 34 is divided by providing or defining a charging limit 35 lying between the working limits 30, 31.

[0041] For the purposes of further explanation, it is assumed that the load management application 13 is an electrical load, i.e., a power consumer or energy load. The load limit 35 and the lower operating limit 31 define a buffer range 36, which corresponds to an amount of energy that is to be ensured or guaranteed for the load management application 13. Accordingly, a residual range 37 results in the operating range 34.

[0042] Fig. Figure 3 shows three phases of time t, namely two inactive phases 38 in which there is no power request from the load management application 13, and one phase of a power request 39 from the load management application 13, during which the load management application 13 requests electrical power from the energy storage device 15, which can be signaled by the described power request signal 21. Accordingly, during the power request 39, the state of charge L decreases starting from an initial state 40.

[0043] The charge state control 18 can now implement two different recharging strategies, depending on whether the phase 38 of the inactive load management application 13 or the power request 39 of the load management application 13 is present.

[0044] Fig. 4 illustrates how the described control power provision of the energy storage device 15 for the transmission network 10 is carried out continuously for the entire period in a step S 10.

[0045] Meanwhile, in a step S11, it can be checked whether the power request 39 of the load management application 13 is present.

[0046] If the power requirement 39 of the load management application 13 is present (in Fig. 4 symbolized by a "+" symbol), in a step S12 the state of charge L within the working range 34 can also be led into the buffer range 36 or can drop until the working limit delimiting the buffer range 36, here the lower working limit 31, is reached. This is because the energy from the buffer range 36 is reserved for the load management application 13. If a power request 39 still exists, the load management application 13 can be switched to inactive, i.e. it then fully utilizes the direct power flow 24 from the transmission grid 10 or is switched off. Thus, the state of charge L can then be led from the buffer range back into the remaining range 37 by recharging.

[0047] If, however, in step S11 the load management application 13 is inactive (phases 38), a recharge or a recharge 41 can already take place (see Fig. 3) if the load limit 35 is reached. This corresponds to Fig. 4 the case symbolized by a "-" symbol. Monitoring the charge level L for reaching the charge limit 35 and the subsequent recharging corresponds to step S13.

[0048] Fig. Figure 5 illustrates one way in which reloading can be performed.

[0049] For this purpose, the power source Q connected via the transmission grid 10 can be used. It may be possible to specifically request electrical charging power P from the power source Q, for which purpose, for example, an electricity exchange B can be provided for purchasing the charging power P from the power source Q.

[0050] Fig. 5 illustrates how, in step S10, the primary control power can continue to be provided even during recharging of the energy storage device 15. Fig. 5 shows, over time t for different times in a diagram 42, the temporal progression of a control power requirement for the primary control power, as may be signaled by the request signal 22. Furthermore, the power control signal 23 for controlling the power electronics 16 is shown. For the sake of clarity and without loss of generality, it is assumed here that there is no power request from the load management application 13. To recharge the energy storage device 15, a schedule transaction 43 can now be concluded with the power source Q via the energy exchange B, by which the power source Q is obliged or controlled to feed charging power P into the transmission grid 10 for a charging period 44. For the charging period 44, the operating point for the power control signal 23 is then offset by an offset 45 according to diagram 42, the amount of which corresponds to the charging power P.As a result, part of the control power is now provided by the power source Q. By means of the energy storage device 15, only control power is provided according to a difference signal 46 or exchanged with the transmission grid 10. The difference signal 46 describes the difference between the request signal 22 for the control power and the charging power P.

[0051] A diagram 47 illustrates how this can prevent the state of charge L from, for example, crossing or falling below the lower operating limit 31 (step S12) or the charging limit 35 (step S13). When the respective operating limit 31, 35 is reached, a stabilization 48 results from the additional charging power P fed into the transmission grid 10. Shifting the operating point by the offset 45 results in a charging process 49 (see diagram 42), during which the portion of the charging power not required as control power flows from the transmission grid 10 into the energy storage device 15, which is thus recharged and the state of charge L can thus be brought into the residual range 37.

[0052] This results in four operating modes: 1) Provision of primary control power PRL: If the load management application 13 is equal to 0 and the state of charge is within the residual signal, the power control signal 23 results from the request signal 22 of the control power provision. 2) PRL plus discharge: If the upper operating limit 30 is exceeded, a discharge schedule is triggered to return the state of charge (L) to the operating range. Power control signal 23 results from request signal 22 and the discharge schedule. 3) PRL plus load management: If the state of charge L is in the residual range 37 and there is a power request 39 from the load management application 13, the power control signal 23 results from the request signal 22 for the PRL and the power request 39 for the load management application 13. 4) PRL plus recharging: If the state of charge L is in the buffer range and there is no load management request or the lower working limit 31 is undershot, a recharging schedule is activated, as for example in Fig. 4 is given, and the power control signal 23 results from PRL plus recharging schedule.

[0053] The unloading schedule can be adjusted according to Fig. 4 can be realized by trading negative charging power on the energy exchange instead of positive charging power P.

[0054] Overall, this results in a state of charge control for the simultaneous provision of primary control power for a power grid or transmission grid 10 operating at a nominal grid frequency and a power request from another electricity consumer / generator of a load management application 13 using an energy storage device 15. This considers the transmission grid 10, the energy storage device 15, and the load management application 13. The energy storage device 15 continuously provides control power as requested by the operator of the transmission grid 10. This results in the four operating modes described: PRL, PRL + discharging, PRL + load management, and PRL + recharging.The energy storage system 15 consistently meets the prequalification specification for the provision of control power, in particular the described 30-minute criterion, by defining a buffer capacity or buffer area 36, ​​which may be used when the energy storage system is used in PRL + load management mode (active load management application 13 with power demand 39) and is ensured by early recharging of the energy storage system 15, which is defined or specified by the charging limit 35. When the storage system is used in the PRL + load management operating mode, this buffer capacity of the buffer area 36 may be used until the operating limit 30, 31 limiting the buffer area is reached, as defined by the prequalification specification.When this working limit 30, 31 is reached, no more power can be provided for the load management application and the energy storage device 15 is recharged instead (operating mode PRL + recharge).

[0055] Overall, this results in a division of the permitted operating range of the state of charge of an energy storage device into different areas and a definition of different operating modes to ensure that the requirement of the operating range is not violated.

[0056] In addition to the revenues from the provision of control power, the system can generate further revenues through the provision of power, for example for peak shaving (reduction of peak load; reduction of network charges) or fast charging (provision of high charging power) with a battery system.

[0057] Simultaneously with the grid service control power at the transmission grid level, the battery can avoid peak loads in the grids and thus simultaneously provide a service for the distribution grid operator.

[0058] The energy storage system can be flexibly adapted by dividing the operating range or the recharging limit and thus react spontaneously to price changes on the control power market or to changes in demand for load management (e.g.: more electric vehicles want to charge).

[0059] The use of a battery can significantly reduce the cost of grid connection power when investing in a fast charging system.

[0060] Dividing the permissible operating range of the state of charge of energy storage devices into different areas. Defining different operating modes to ensure that the operating range requirement is never violated.

[0061] Advantages of the invention are in particular the following: In addition to the revenue from the provision of control power, the system can generate further revenue by providing power, for example, for peak shaving (reducing peak loads and thus reducing grid fees) or fast charging (particularly with the provision of high charging power) with a battery system. Simultaneously with the grid service of control power at the transmission grid level, the battery can avoid peak loads in the grids and thus simultaneously provide a service for the distribution grid operator.

[0062] The system can be flexibly adapted by dividing the operating range or the recharging limits and can thus react spontaneously to price changes on the control power market or to changes in demand for load management (e.g.: more electric vehicles want to charge).

[0063] Using a battery can significantly reduce the investment costs for a fast-charging system, including the cost of connecting to the grid. Batteries are currently very expensive. Multiple revenue streams enable greater cost-effectiveness.

[0064] There is no need to aggregate multiple battery systems to continuously provide control power in accordance with the requirements of the transmission system operators. List of reference symbols 10 Transmission network 11 Connection point 12 Balance sheet area 13 Load management application 14 Energy storage system 15 energy storage 16 Power electronics 17 Control device 18 Charge level control 20 Charge level signal 21 Power demand signal 22 Request signal 23 Power control signal 24 Power flow 25 Provision of control power 26 Power flow 27 Power flow 28 Prequalification specification 29 Minimum capacity 30 Working limit 31 Working limit 32 Scope for action 33 ratio 34 Work area 35 loading limit 36 Buffer area 37 remaining area 38 Phase 39 Performance requirement 40 Initial state 41 Reloading 42 Diagram 43 Timetable business 44 Loading time 45 offset 46 Differential signal 47 Diagram 48 Stabilization 49 Charging process

Claims

[1] Method for operating an electrical energy storage device (15) with which a control power provision is carried out in an electrical transmission network (10), wherein, according to a predetermined prequalification specification (28), a lower operating limit (31) and an upper operating limit (30) are provided for a state of charge (L) of the energy storage device (15), by which it is guaranteed in each case that the energy storage device (15) is able to provide a predetermined minimum power profile for at least a predetermined minimum period of time when said lower operating limit is reached, characterized bythat in a working range (34) limited by the lower working limit (31) and the upper working limit (30), a charging limit (35) is provided for a predetermined additional load management application (13) which is independent of the control power provision, wherein the charging limit (35) on the one hand and one of the two working limits (30, 31) on the other hand define a buffer range (36) which corresponds to an amount of energy guaranteed for the load management application (13), thus resulting in a remaining range (37) of the working range (34) reduced by the buffer range (36), and by a charge state control (18) of the energy storage device (15): - when the load management application (13) is inactive, if there is no power request (39) from the load management application (13), the charge state (L) is maintained in the residual range (37) by recharging and / or discharging the energy storage device (15), and - when the load management application (13) is active, if the power requirement (39) of the load management application (13) is present, the state of charge (L) is also led into the buffer area (36). [2] Method according to claim 1, wherein the load management application (13) is deactivated if the state of charge (L) is in the buffer area (36) and the state of charge (L) reaches the working limit (30, 31) delimiting the buffer area (36). [3] Method according to one of the preceding claims, wherein in the event that the state of charge (L) is in the buffer area (36) and the state of charge (L) reaches the working limit (30, 31) delimiting the buffer area (36) and / or the load management application (13) is inactive, in the case of the lower working limit (31) by recharging and / or in the case of the upper working limit (30) by discharging the energy storage device (15), the state of charge (L) is led into the remaining area (37). [4] Method according to one of the preceding claims, wherein the recharging and / or discharging takes place by controlling at least one power source (Q) different from the energy storage device (15) and / or at least one power consumer within a predetermined charging time period (44) to exchange a predetermined charging power (P) with the transmission network (10) or directly with the energy storage device (15), and the charge state control (18) sets (45) a target power flow of the energy storage device (15) offset by the power amount of the charging power (P) during the charging time period (44). [5] Method according to claim 4, wherein the control of the at least one power source (Q) and / or the at least one power consumer is carried out by means of a schedule transaction of an energy exchange (B), by the charge state control (18) signaling a bid to the energy exchange (B) according to the predetermined charging power (P), and / or by controlling a flexible power source and / or a flexible power consumer in the same balancing group (12). [6] Method according to claim 4 or 5, wherein during the charging period (44) a difference signal (46) signalling a difference between a request signal (22) for the provision of control power and a course signal of the charging power (P) is generated by the charging state control (18), and a power exchange carried out between the transmission network (10) and the energy storage device (15) for recharging and / or discharging is modulated as a function of the difference signal (46). [7] Method according to one of the preceding claims, wherein, when the load management application (13) is active, the charge state controller (18) generates a power control signal (23) which controls a power exchange of the energy storage device (15) with the transmission network (10) and the load management application (13) both as a function of the power request (39) of the load management application (13) and as a function of a control power requirement. [8] Method according to one of the preceding claims, wherein the minimum time period specified by the prequalification specification (28) is in a range from 10 minutes to 60 minutes, in particular 30 minutes. [9] Control device (17) for a charge state control (18) in an electrical energy storage device (15) operated on an electrical transmission network (10), wherein the control device (17) has a computing device which is designed to carry out a method according to one of the preceding claims. [10] Energy storage system (14) with an electrical energy storage device (15) for operation on an electrical transmission network (10) and with a control device (17) according to claim 9.

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