Energy storage device and method for controlling an energy storage device in the event of a communication failure

Abstract

Energy storage device (10) for generating a supply voltage at output terminals (4a, 4b) of the energy storage device (10), comprising: at least one power supply line (10a; 10b) with one or more energy storage modules (3) connected in series in the power supply line (10a; 10b), each of which has an energy storage cell module (5) with at least one energy storage cell (5a, 5k) and a coupling device (7) with a plurality of coupling elements (7a, 7b, 7c, 7d), wherein the coupling device (7) is designed to selectively connect the energy storage cell module (5) to the respective power supply line (10a; 10b) or to bypass it in the respective power supply line (10a; 10b); a plurality of module control devices (13), each coupled to one of the energy storage modules (3) and designed to control the coupling device (7) of the respective associated energy storage module (3) and to detect the charge state of the energy storage module (3); and a control unit (11) which is coupled to the module control units (13) via a communication bus (12) and is designed to receive the charge states of the energy storage modules (3) from the module control units (13) and, depending on the received charge states of the energy storage modules (3), to output control signals for the energy storage modules (3) to the module control units (13), wherein the module control devices (13) are designed to control the coupling devices (7) of the respective assigned energy storage modules (3) in accordance with the charge states of the energy storage modules (3) recorded before the communication failure or communication disruption with the control device (11).

Description

[0001] The invention relates to an energy storage device and a method for controlling an energy storage device in the event of a communication failure, in particular in the case of modularly constructed energy storage devices in electric drive systems. State of the art

[0002] It is becoming clear that in the future, both in stationary applications, such as wind turbines or solar power plants, and in vehicles, such as hybrid or electric vehicles, electronic systems will increasingly be used that combine new energy storage technologies with electric drive technology.

[0003] To feed three-phase alternating current into an electric machine, a conventional inverter, specifically a pulse-width modulated inverter, converts the direct current (DC) supplied by a DC link into a three-phase alternating current (AC). The DC link is powered by a string of series-connected battery modules. To meet the power and energy requirements of a given application, several battery modules are often connected in series to form a traction battery. Such an energy storage system is frequently used, for example, in electric vehicles.

[0004] Connecting multiple battery modules in series presents the problem that if a single battery module fails, the entire string fails. Such a failure of the power supply string can lead to a failure of the entire system. Furthermore, temporary or permanent reductions in the performance of a single battery module can lead to performance reductions in the entire power supply string.

[0005] The publication DE 10 2010 060 305 A1 comprises at least one power supply line with one or more energy storage modules connected in series in the power supply line, each of which has an energy storage cell module with at least one energy storage cell and a coupling device with a plurality of coupling elements, wherein the coupling device is designed to selectively connect the energy storage cell module to the respective power supply line or to bypass it in the respective power supply line; a plurality of module control devices, each coupled to one of the energy storage modules and designed to control the coupling device of the respective assigned energy storage module and to detect the charge state of the energy storage module; and a control device which communicates with the energy storage module via a communication bus.coupled to the module control units and designed to receive the charge states of the energy storage modules from the module control units and, depending on the received charge states of the energy storage modules, to output control signals for the energy storage modules to the module control units.

[0006] The publication DE 10 2010 041 049 A1 discloses an energy storage device, and furthermore describes a fault-tolerant method in case of communication failure.

[0007] Documents DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1 disclose modularly connected battery cells in energy storage devices that can be selectively connected to or disconnected from the string of serially connected battery cells via suitable control of coupling units. Systems of this type are known as Battery Direct Converters (BDCs). Such systems comprise DC sources in an energy storage module string that can be connected to a DC link for the electrical power supply of an electric machine or an electrical network via a pulse inverter.

[0008] Battery converters (BDCs) exhibit higher efficiency and greater reliability compared to conventional systems in certain operating ranges. Reliability is ensured, among other things, by the ability to disconnect defective, failed, or underperforming battery cells from the power supply lines through appropriate bypass control of the coupling units. The overall output voltage of BDCs is determined by the control state of the coupling units and can be adjusted in steps, with the specific steps of the overall output voltage depending on the individual voltages of the energy storage modules.

[0009] For optimal control of the individual energy storage modules, it is necessary to continuously monitor their operating parameters. Monitoring devices with microprocessors and corresponding current or voltage sensors can be used for each energy storage module, which can report to a central control unit. A communication failure between the monitoring devices or with the central control unit can lead to a forced shutdown of the entire system, as control-relevant parameters are no longer known.

[0010] In the event of communication failures affecting individual energy storage modules, these modules can be excluded from the overall control strategy in BDCs by permanently switching them to a bridging or bypass state. However, the current energy content of the excluded modules at the time of the communication failure can no longer be used in this case. Therefore, there is a need for solutions for modular energy storage systems that allow the continued operation of the overall system in the event of a communication failure of individual modules, thus ensuring both operational reliability and the availability of the entire energy storage system for as long as possible. Disclosure of the invention

[0011] According to one aspect of the present invention, an energy storage device for generating a supply voltage at the output terminals of the energy storage device is provided, comprising at least one parallel-connected energy supply line with one or more energy storage modules connected in series in the energy supply line, each of which has an energy storage cell module with at least one energy storage cell and a coupling device with a plurality of coupling elements, wherein the coupling device is designed to selectively connect the energy storage cell module to the respective energy supply line or to bypass it in the respective energy supply line, and a plurality of module control devices, each coupled to one of the energy storage modules and designed toto control the coupling device of the respective assigned energy storage module and to detect the state of charge and, if applicable, the output voltage of the energy storage module, and a control device which is coupled to the module control devices via a communication bus and is designed to receive the state of charge and, if applicable, the output voltage of the energy storage modules from the module control devices and, depending on the received state of charge and, if applicable, the output voltages of the energy storage modules, to output control signals for the energy storage modules to the module control devices, wherein the control device is designed toIn the event of a communication failure or communication malfunction with one or more of the module control units, the module control units are to be used to control the respective energy storage modules according to the charge states and, if applicable, output voltages of the energy storage modules recorded before the communication failure or communication malfunction.

[0012] According to a further aspect, the present invention provides a method for controlling an energy storage device according to the invention, comprising the steps of detecting a charge state and optionally the output voltage of each of the energy storage modules by a module control unit assigned to the energy storage module, communicating the charge states and optionally the detected output voltages of the energy storage modules via the communication bus to the respective other module control units, and monitoring whether a communication failure or a communication fault occurs between at least one of the module control units and the control unit.and the control of the coupling devices of the respective assigned energy storage modules depending on the charge states recorded before the communication failure or communication disturbance and, if applicable, output voltages of the energy storage modules after the occurrence of a communication failure or communication disturbance by the module control devices. Advantages of the invention

[0013] An idea of ​​the present invention is to increase the availability of an energy storage device with one or more modularly constructed energy supply strings consisting of a series connection of energy storage modules in the event of a communication failure or communication disturbance between the central control of the energy storage device and the module controls assigned to the respective energy storage modules by accessing the last known state of the distribution of the charge states of the individual energy storage modules in order to locally control the energy storage modules in the module controls to provide a proportionate share of the total required output voltage of the energy storage device.This allows the energy content of the individual energy storage modules to be optimally utilized without the local module controls having to communicate with the other module controls or the central control.

[0014] Advantageously, the modular design of the energy supply strings allows for a uniform discharge of the energy storage modules according to their residual charge, without this having any influence on the total voltage of the energy storage device provided to the outside.

[0015] Furthermore, in such modular systems, the local control units can independently monitor critical operating parameters and operate their respective assigned energy storage modules within permissible operating limits. Because each module storage unit already knows how the other modules will react in the event of a communication failure, thanks to a common operating strategy defined for all modules, the energy content of the assigned energy storage modules can be optimally utilized, taking into account the local operating strategy of the other modules, without requiring further communication with the other modules.

[0016] According to one embodiment of the energy storage device according to the invention, the module control devices can be designed to control the coupling devices of the respective assigned energy storage modules using a pulse width modulation method such that the set pulse widths depend on the charge state of the respective energy storage module as detected before the communication failure or communication disturbance. The use of pulse width modulation makes the distribution of the contributions of the individual energy storage modules to the total output voltage of the energy storage device particularly simple and flexible.

[0017] According to a further embodiment of the energy storage device according to the invention, the module control devices can be designed to transmit the charge state and, if applicable, the output voltage of the respective associated energy storage module to the other module control devices via the communication bus.

[0018] According to a further embodiment of the energy storage device according to the invention, the control unit can be configured to cease generating control signals for the energy storage modules to the module control units in the event of a communication failure or communication malfunction. Additionally, according to a further embodiment of the energy storage device according to the invention, the control unit can also be configured to output a control signal to those module control units not affected by the communication failure or malfunction, which instructs the module control units to control the coupling devices of the respective assigned energy storage modules according to the charge states of the energy storage modules detected before the communication failure or malfunction.This advantageously ensures that all module control units participate equally in the operational fault strategy, especially if only some of the module control units experience communication faults.

[0019] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Brief description of the drawings

[0020] They show: Fig. 1 a schematic representation of an energy storage device according to an embodiment of the present invention; Fig. 2 a schematic representation of an embodiment of an energy storage module of an energy storage device according to a further embodiment of the present invention; Fig. 3 a schematic representation of a further embodiment of an energy storage module of an energy storage device according to a further embodiment of the present invention; Fig. 4 a schematic representation of exemplary control state diagrams of energy storage modules of an energy storage device according to a further embodiment of the present invention; Fig. 5 a schematic representation of exemplary control state diagrams of energy storage modules of an energy storage device according to a further embodiment of the present invention; and Fig. 6 a schematic representation of a method for controlling an energy storage device in the event of a communication failure according to a further embodiment of the present invention.

[0021] Fig. Figure 1 shows an energy storage device 10 for providing a supply voltage by means of parallel-connected energy supply strands 10a, 10b between two output terminals 4a and 4b of the energy storage device 10. The energy supply strands 10a, 10b each have strand terminals 1a and 1b. The energy storage device 1 has at least two parallel-connected energy supply strands 10a, 10b. By way of example, the number of energy supply strands 10a, 10b is Fig. 1 two, however any other larger number of energy supply strands 10a, 10b is equally possible. It is equally possible to connect only one energy supply strand 10a between the strand terminals 1a and 1b, which in this case can form the output terminals 4a, 4b of the energy storage device 10.

[0022] The power supply lines 10a, 10b can each be coupled to the output terminal 4a of the energy storage device 10 via storage inductors 2a, 2b. The storage inductors 2a, 2b can be, for example, concentrated or distributed components. Alternatively, parasitic inductances of the power supply lines 10a, 10b can also be used as storage inductors 2a, 2b. By appropriately controlling the power supply lines 10a, 10b, the current flow can be directed, for example, into a DC link connected to the output terminals 4a, 4b. The maximum current is limited by the storage inductors 2a, 2b in conjunction with the DC link.

[0023] A string coupling device 2c may also be provided, which can be coupled between the storage inductors 2a, 2b and the output terminal 4a of the energy storage device 10. The string coupling device 2c can, for example, comprise contactors or circuit breakers by means of which the power supply strings 10a, 10b can be selectively disconnected from the output terminal 4a of the energy storage device 10. In the case of a single power supply string 10a, the storage inductors 2a and 2b, as well as the string coupling device 2c, can also be omitted, so that the power supply string 10a is directly coupled between the output terminals 4a, 4b of the energy storage device 10.

[0024] Each of the energy supply strings 10a, 10b has at least two energy storage modules 3 connected in series. For example, the number of energy storage modules 3 per energy supply string is... Fig. 1. Two, but any other number of energy storage modules 3 is also possible. Preferably, each of the energy supply strings 10a, 10b comprises the same number of energy storage modules 3, but it is also possible to provide a different number of energy storage modules 3 for each energy supply string 10a, 10b. The energy storage modules 3 each have two output terminals 3a and 3b, via which an output voltage of the energy storage modules 3 can be provided.

[0025] Exemplary configurations of the energy storage modules 3 are shown in the Fig. 2 and Fig. Figure 3 is shown in greater detail. The energy storage modules 3 each comprise a coupling device 7 with several coupling elements 7a and 7c, and optionally 7b and 7d. The energy storage modules 3 also each comprise an energy storage cell module 5 with one or more energy storage cells 5a, 5k connected in series.

[0026] The energy storage cell module 5 can, for example, comprise batteries 5a to 5k connected in series, such as lithium-ion batteries or accumulators. The number of energy storage cells 5a to 5k in the module is... Fig. The energy storage module 3 shown is an example of two, but any other number of energy storage cells 5a to 5k is also possible.

[0027] The energy storage cell modules 5 are connected to input terminals of the associated coupling device 7. The coupling device 7 is in Fig. Figure 2 shows an example of a full bridge circuit with two coupling elements 7a, 7c and two coupling elements 7b, 7d. Each coupling element 7a, 7b, 7c, 7d can have an active switching element, for example a semiconductor switch, and a freewheeling diode connected in parallel. The semiconductor switches can, for example, be field-effect transistors (FETs). In this case, the freewheeling diodes can also be integrated into the semiconductor switches.

[0028] The coupling elements 7a, 7b, 7c, 7d in Fig. 2 can be controlled in this way, for example using the control unit 11 in Fig. 1. The energy storage cell module 5 is selectively connected between the output terminals 3a and 3b, or the energy storage cell module 5 is bridged or bypassed. By appropriately controlling the coupling devices 7, individual energy storage cell modules 5 of the energy storage modules 3 can therefore be selectively integrated into the series connection of an energy supply string 10a, 10b.

[0029] With reference to Fig. 2. For example, the energy storage cell module 5 can be connected in the forward direction between the output terminals 3a and 3b by setting the active switching element of coupling element 7d and the active switching element of coupling element 7a to a closed state, while setting the two remaining active switching elements of coupling elements 7b and 7c to an open state. A first bridging or bypass state can be set, for example, by setting the two active switching elements of coupling elements 7a and 7b to a closed state, while keeping the two active switching elements of coupling elements 7c and 7d in an open state.A second bypass state can be set, for example, by closing the two active switches of coupling elements 7c and 7d while keeping the active switching elements of coupling elements 7a and 7b open. In both bypass states, the voltage between the two output terminals 3a and 3b of coupling device 7 is zero. Similarly, the energy storage cell module 5 can be connected in reverse between the output terminals 3a and 3b of coupling device 7 by closing the active switching elements of coupling elements 7b and 7c while opening the active switching elements of coupling elements 7a and 7d.

[0030] The total output voltage of a power supply line 10a, 10b can be adjusted in steps, with the number of steps scaling with the number of energy storage modules 3. Intermediate levels of the output voltage of an energy storage module 3 can be set, for example, by controlling the coupling elements 7a, 7b, 7c, 7d of the coupling device 7 using pulse-width modulation. The output voltage scales with the selected pulse width of the control signal. In this way, a number of energy storage modules 3 can be continuously controlled to set a coarse gradation of the total output voltage of a power supply line 10a, 10b. The fine gradation of the total output voltage of a power supply line 10a, 10b can, in turn, be set via an energy storage module 3 that is controlled using pulse-width modulation.

[0031] The control of the coupling elements 7a, 7b, 7c, 7d can, for example, be a module control unit, such as the module control unit 13 in Fig. 1, which is designed, for example, to perform current control with a subordinate voltage control, so that individual energy storage modules 3 can be switched on or off in stages. Each of the module control units 13 in Fig. 1 is assigned to one of the energy storage modules 3 in the energy supply line. For the sake of clarity, in Fig. 1. Module control units 13 assigned to the energy storage modules 3 are shown only for the energy supply line 10a. However, it is understood that the energy supply line 10b can also have corresponding module control units 13 assigned to the energy storage modules 3 it contains.

[0032] Fig. Figure 3 shows another exemplary embodiment of an energy storage module 3. The one in Fig. The energy storage module shown in Figure 3 differs from the one in Figure 3. Fig. The energy storage module 3 shown in Figure 2 differs only in that the coupling device 7 has two coupling elements instead of four, which are connected in a half-bridge circuit instead of a full-bridge circuit.

[0033] In the illustrated implementation variants, the active switching elements can be designed as power semiconductor switches, for example in the form of IGBTs (Insulated Gate Bipolar Transistors), JFETs (Junction Field-Effect Transistors) or MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors).

[0034] The energy storage device 10 with the energy supply strings 10a, 10b can, for example, be used to power a single-phase electric machine. However, it can also be used to generate electricity for a power grid. For example, the energy storage device 10 can power a synchronous or asynchronous machine, a reluctance machine, or a brushless DC motor (BLDC). It is also possible to use the energy storage device 10 in stationary systems, such as power plants, electrical energy generation plants like wind turbines, photovoltaic systems, or combined heat and power plants, and energy storage systems like compressed air energy storage plants, battery storage plants, flywheel energy storage systems, pumped storage plants, or similar systems.

[0035] The energy storage device 10 can further comprise a control unit 11, which is connected to the module control units 13 via a communication bus 12, and by means of which the module control units 13 can be centrally controlled to provide the desired total output voltage of the energy storage device 10 at the respective output terminals 4a, 4b. In addition, the control unit 11 can be configured to control the respective coupling elements or active switching elements of the energy storage modules 3 of the power supply strings 10a, 10b when the energy storage cell modules 5 of the energy storage device 10 are being charged.

[0036] Fig. Figure 4 shows schematic diagrams of exemplary control states of four energy storage modules 3 of a power supply line 10a, 10b of an energy storage device 10, as in connection with Fig. 1 to 3 explained. The control states in Fig. 4 can correspond to the control states in the normal state of the energy storage device 10, that is, when there is no communication failure or communication disturbance. Accordingly, it shows Fig. 5 schematic diagrams of exemplary control states of the four energy storage modules 3 in Fig. 4, after a communication failure or communication disruption has been detected. The situation in Fig. 5 therefore corresponds to an emergency running strategy for the energy storage device 10. The number of energy storage modules shown is 3 in Fig. 4 and Fig. 5 is only an example of four, and it is clear that any other number is possible taking into account the appropriate adjustments.

[0037] In the normal state of Fig. In section 4, the energy storage modules (b) and (c) are in a permanently switched-on state, as represented by the logic high control signals P2 and P3. The energy storage module (d) is permanently disconnected from the power supply line in its normal state, as represented by the logic low control signal P4. To achieve fine-tuning of the desired overall output voltage of the power supply line, the energy storage module (a) can be controlled in a clocked operating state, for example, pulse-width modulated (PWM), as represented by the example PWM control signal P1. In the example of the Fig. Let 4 be the control level of the PWM control signal P1 0.4, so that the total output voltage U of the power supply line in the Fig. In the operating situation shown in section 4, 2.4 / 4 = 60% of the maximum possible total output voltage U max amounts.

[0038] It is possible to use alternative control methods to pulse width modulation, which can generate a variable effective voltage by providing a control signal pattern.

[0039] If a communication failure or malfunction occurs or is detected between the module control units 13 or between the module control units 13 and the control unit 11, an emergency running program can be activated in all module control units 13. For this purpose, all module control units 13 are aware of the current charge states of all energy storage modules 3. For example, let us assume that the charge state of energy storage module (a) is 80%, the charge state of energy storage module (b) is 20%, the charge state of energy storage module (c) is 40%, and the charge state of energy storage module (d) is 60%. This results in an average charge state of 50% across all energy storage modules (a) to (d).

[0040] In the event of a detected communication failure or communication disruption, the following can be used instead of the control strategy in Fig. 4 the approach strategy in Fig. 5 can be selected. For this purpose, all module control units 13 can control their respective assigned energy storage module 3 such that each of the energy storage modules (a) to (d) is operated in a pulse-width modulated operating state. This can be done depending on the desired total output voltage U or the ratio of the desired total output voltage U to the maximum possible voltage U. max in the energy supply line. In the example in Fig. 4 let this ratio U / U max = 2.4 / 4 = 60%. Furthermore, the pulse widths of the control signals Q1 to Q4 for the energy storage modules (a) to (d) can be selected such that they reflect the relative charge state or energy content E of the energy storage modules (a) to (d) compared to the average charge state or energy content E. mittelacross all energy storage modules (a) to (d). For this purpose, the pulse widths of the control signals Q1 to Q4 for the energy storage modules (a) to (d) can be multiplied by a factor E / E. mittel weighted.

[0041] In the example of the Fig. 5 thus results in a control level of U / U for the control signal Q1. max * E / E mittel= 60% * 80% / 50% = 96%. Accordingly, the control signal Q2 has a value of 24%, the control signal Q3 a value of 48%, and the control signal Q4 a value of 72%. These values ​​can be limited to a maximum control level of 100%, meaning that instead of pulse width modulation, continuous activation of the energy storage module is used. In this case, the respective energy storage module can be operated continuously, and the pulse widths of the other energy storage modules can be controlled according to their remaining charge level. If further energy storage modules are to be controlled with a maximum control level of 100%, the pulse width adjustment procedure for the remaining energy storage modules can be performed iteratively.

[0042] With such a pulse width setting, the entire power supply line can be used with maximum remaining runtime without having to accept any losses in the setting of the maximum total voltage.

[0043] If, after a communication failure or malfunction, the control unit 11 can still communicate with at least some of the module control units 13, the control unit 11 can be configured to cease generating control signals for the energy storage modules 3 to the module control units 13 in order to enable the module control units 13 to operate in an undisturbed emergency mode. Furthermore, the control unit 11 can also output a control signal to those module control units 13 that are not affected by the communication failure or malfunction, instructing the module control units 13 to control the coupling devices 7 of the respective assigned energy storage modules 3 according to the charge states of the energy storage modules 3 detected before the communication failure or malfunction.

[0044] Fig. Figure 6 shows a schematic representation of an exemplary method 20 for controlling an energy storage device, in particular an energy storage device 10, as in connection with the Fig. 1 to 3 explained. In one variant, method 20 can be used to control an energy storage device 10 in the event of a communication failure or communication disruption between the module control units 13 and the control unit 11, in order to increase the availability of the energy storage device 10 by means of an emergency running strategy. Method 20 can, for example, use the methods associated with the Fig. 4 and Fig. Implement the emergency running strategy outlined in step 5.

[0045] In a first step 21, the state of charge and, if applicable, the output voltage of each of the energy storage modules 3 is detected by a module control unit 13 assigned to each energy storage module 3. This can be done, for example, by detecting operating parameters of the energy storage module 3 or the energy storage cells 5a to 5k, from which the state of charge of the energy storage cells 5a to 5k can be calculated or at least estimated. For example, the output voltage of the energy storage cells 5a to 5k, the output current of the energy storage cells 5a to 5k, the temperature of the energy storage cells 5a to 5k, or the operating time since the last charge can be detected as operating parameters.

[0046] In a second step 22, the charge states and, if applicable, the output voltages of the energy storage modules 3 are communicated via the communication bus 12 to the respective other module control units 13 and, if applicable, to the control unit 11. In a third step 23, it is continuously monitored whether a communication failure or a communication fault occurs between at least one of the module control units 13 and the control unit 11. This could be, for example, a fault in the communication bus 12, a defect in the control unit 11, or a loss of connection to the module control units 13. A communication failure or a communication fault can occur between individual module control units 13 and the control unit 11 or between all of the aforementioned components.

[0047] If a communication failure or communication fault has been detected, in step 24 the coupling devices 7 of the respective assigned energy storage modules 3 can be controlled by the module control devices 13, depending on the charge states and, if applicable, the output voltages of the energy storage modules 3 detected before the communication failure or communication fault occurred. In this process, for example, energy storage modules 3 that were not initially involved in providing the total output voltage of the energy storage device 10 can be switched on.All energy storage modules 3 can be operated by their respective module control units 13 using a pulse width modulation (PWM) method, in which the set pulse widths depend on the charge state detected before the communication failure or communication disturbance and, if applicable, the output voltage of the respective energy storage module 3. Since all module control units 13 were informed about all charge states of the energy storage modules 3 at the time of the communication failure, the set pulse width can correspond to the ratio of the current charge state of the respective energy storage module 3 to the sum of the current charge states of all energy storage modules 3. This ensures that all energy storage modules 3 are loaded according to their remaining energy content and can provide energy for essentially the same remaining time.Thus, the provision of the desired total output voltage of the energy storage device 10 is ensured for the longest possible period of time, without the need for an emergency shutdown of the energy storage device 10 in the event of a communication failure.

Claims

[1] Energy storage device (10) for generating a supply voltage at output terminals (4a, 4b) of the energy storage device (10), comprising: at least one power supply line (10a; 10b) with one or more energy storage modules (3) connected in series in the power supply line (10a; 10b), each of which has an energy storage cell module (5) with at least one energy storage cell (5a, 5k) and a coupling device (7) with a plurality of coupling elements (7a, 7b, 7c, 7d), wherein the coupling device (7) is designed to selectively connect the energy storage cell module (5) to the respective power supply line (10a; 10b) or to bypass it in the respective power supply line (10a; 10b); a plurality of module control devices (13), each coupled to one of the energy storage modules (3) and designed to control the coupling device (7) of the respective associated energy storage module (3) and to detect the charge state of the energy storage module (3); and a control unit (11) which is coupled to the module control units (13) via a communication bus (12) and is designed to receive the charge states of the energy storage modules (3) from the module control units (13) and, depending on the received charge states of the energy storage modules (3), to output control signals for the energy storage modules (3) to the module control units (13), wherein the module control devices (13) are designed to control the coupling devices (7) of the respective assigned energy storage modules (3) in accordance with the charge states of the energy storage modules (3) recorded before the communication failure or communication disruption with the control device (11). [2] Energy storage device (10) according to claim 1, wherein the module control devices (13) are designed to control the coupling devices (7) of the respective associated energy storage modules (3) in a pulse width modulation method such that the set pulse widths depend on the charge state of the respective energy storage module (3) detected before the communication failure or communication disturbance. [3] Energy storage device (10) according to claim 1, wherein the module control devices (13) are designed to control the coupling devices (7) of the respective associated energy storage modules (3) with an adjustable control signal pattern to provide an effective voltage, wherein the control signal pattern depends on the charge state of the respective energy storage module (3) detected before the communication failure or communication disturbance. [4] Energy storage device (10) according to one of claims 1 to 3, wherein the module control devices (13) are designed to transmit the charge state of the respective associated energy storage module (3) to the other module control devices (13) via the communication bus (12). [5] Energy storage device (10) according to any one of claims 1 to 4, wherein the control device (11) is designed to stop the generation of control signals for the energy storage modules (3) to the module control devices (13) in the event of a communication failure or communication disturbance. [6] Energy storage device (10) according to claim 5, wherein the control device (11) is further designed to output a control signal to those module control devices (13) which are not affected by the communication failure or communication disruption in the event of a communication failure or communication disruption, which instructs the module control devices (13) to control the coupling devices (7) of the respective associated energy storage modules (3) according to the charge states of the energy storage modules (3) detected before the communication failure or communication disruption. [7] Energy storage device (10) according to any one of claims 1 to 6, wherein the module control devices (13) are designed to detect the output voltages of the energy storage modules (3), and wherein the control device (11) is further designed to receive the output voltages of the energy storage modules (3) from the module control devices (13) and to output the control signals for the energy storage modules (3) to the module control devices (13) depending on the received output voltages of the energy storage modules (3). [8] Method (20) for controlling an energy storage device (10) according to any one of claims 1 to 7, comprising the steps: Detection (21) of a charge state of each of the energy storage modules (3) by a module control unit (13) assigned to the energy storage module (3); Communicating (22) the charge states of the energy storage modules (3) via the communication bus (12) to the respective other module control units (13); Monitor (23) whether a communication failure or communication disturbance occurs between at least one of the module control units (13) and the control unit (11); and Control (24) the coupling devices (7) of the respective assigned energy storage modules (3) depending on the charge states of the energy storage modules (3) recorded before the communication failure or communication disturbance after the occurrence of a communication failure or communication disturbance by the module control devices (13).

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