WO2013124079A1

WO2013124079A1 - System and method for actuating an energy storage device

Info

Publication number: WO2013124079A1
Application number: PCT/EP2013/050085
Authority: WO
Inventors: Peter Feuerstack; Erik Weissenborn; Martin Kessler
Original assignee: Robert Bosch Gmbh
Priority date: 2012-02-24
Filing date: 2013-01-04
Publication date: 2013-08-29
Also published as: DE102012202863A1; CN104114403B; CN104114403A

Abstract

The invention relates to a method for actuating an energy storage device having a large number of energy storage modules, which are connected in series in an energy supply line and which each comprise an energy storage cell module, which has at least one energy storage cell, and a coupling device having coupling elements which are designed to selectively connect the energy storage cell module into the respective energy supply line or to bridge said energy storage cell module. In this case, the method comprises the steps of detecting operating parameters of an electrical machine, a pulse-controlled inverter, which is coupled to the electrical machine, and the energy storage device, of selecting a number of energy storage modules as a function of at least one of the detected operating parameters, of actuating the coupling elements of the coupling devices of the selected energy storage modules for connecting the energy storage cell modules of the selected energy storage modules into the energy supply line, and of providing a total output voltage of the energy supply line for a DC voltage intermediate circuit which feeds the pulse-controlled inverter.

Description

Description title

System and method for driving an energy storage device

The invention relates to a system and a method for driving a

Energy storage device, in particular in an energy storage device with a modular battery system for generating a stepped output voltage.

State of the art

It is becoming apparent that in the future both stationary applications, e.g. Wind turbines or solar systems, as well as in vehicles such as hybrid or

Electric vehicles, increasingly electronic systems are used, which combine new energy storage technologies with electric drive technology.

The feeding of multiphase electricity into an electric machine becomes

Usually accomplished by a converter in the form of a pulse inverter. For this purpose, one provided by a DC voltage intermediate circuit

DC voltage in a multi-phase AC voltage, for example, a three-phase AC voltage to be reversed. The DC link is fed by a string of serially connected battery modules. In order to meet the power and energy requirements of a particular application, multiple battery modules are often connected in series in a traction battery.

The publications DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1 disclose modularly connected battery cells in energy storage devices, which can be selectively connected or disconnected via a suitable control of coupling units in the strand of serially connected battery cells. Systems of this type are known as the Battery Direct Converter (BDC).

Such systems include DC sources in an energy storage module string connected to a DC link for supplying electrical power to an electrical machine or electrical network via a DC link

Pulse inverter can be connected. The energy storage module string has in this case a plurality of energy storage modules connected in series, each energy storage module having at least one battery cell and an associated controllable coupling unit, which allows depending on control signals to bridge the respectively associated at least one battery cell or the respectively associated at least one battery cell to switch the respective energy storage module string. Optionally, the coupling unit can be designed such that it additionally allows the respectively associated at least one battery cell with inverse polarity in the respective

Energy storage module strand to switch or the respective

Interrupt energy storage module string.

BDCs usually have higher efficiency and higher

Reliability against conventional systems. The reliability is ensured, inter alia, that defective, failed or not fully efficient battery cells by suitable bridging control of the

Coupling units can be switched out of the power supply line. The total output voltage of the energy storage module string can be varied by appropriate activation of the coupling units and in particular be set in stages. The gradation of the output voltage results from the voltage of a single energy storage module, the maximum possible

Total output voltage by the sum of the voltages of all

Energy storage modules of the energy storage module string is determined.

To set an output voltage of an energy storage module, a pulse width modulated (PWM) control of the coupling units can take place. This makes it possible to output a desired mean value as energy storage module voltage by specific variation of the on or off times.

Such BDCs have a need for control methods and control systems that can implement a control strategy that is optimal

Adjusting the voltage in the DC intermediate circuit while minimizing the system power loss, the power losses in individual system components and / or the stability of the voltage in the DC link independent of

Charge state of the battery cells of the BDCs guaranteed.

Disclosure of the invention The present invention, in one aspect, provides a method of driving an energy storage device having a plurality of in one

Power supply string connected in series energy storage modules, each comprising an energy storage cell module, which has at least one energy storage cell, and a coupling device with coupling elements, which are adapted to selectively connect or bypass the energy storage cell module in the respective power supply line. The method has the steps of detecting operating parameters of an electrical machine, a pulse inverter coupled to the electrical machine and the energy storage device, selecting a number of energy storage modules depending on at least one of the detected operating parameters, driving the coupling elements of

Coupling devices of the selected energy storage modules for switching the energy storage cell modules of the selected energy storage modules in the

Power supply line, and providing a total output voltage of the power supply line for a pulse inverter feeding

DC voltage intermediate circuit.

According to another aspect, the present invention provides a system comprising an energy storage device having a plurality of energy storage modules connected in series in a power supply string, each of which

Energy storage cell module, which has at least one energy storage cell, and a coupling device with coupling elements, which are adapted to selectively switch the energy storage cell module in the respective power supply line or to bridge. The system also has a

DC link, which is coupled to the energy storage device, a pulse inverter, which is coupled to the DC link, and which is fed from the DC link with an input voltage, an electric machine, which is coupled to the pulse inverter, and which supplies from the pulse inverter with a phase voltage is, and a control device which is coupled to the coupling means, and which is adapted to a method according to the invention for driving the

Perform energy storage device.

Advantages of the invention

It is an idea of the present invention to control an energy storage device which has a modular series in a string of serially connected battery cells, such that the intermediate circuit voltage of a powered by the energy storage device DC intermediate circuit is optimized, in particular with regard to

Power loss in the entire system, in individual system components or the state of charge of the battery cells of the energy storage device. This can be done by capturing various relevant operating parameters in the system and in the

System components happen whose evaluation allows a selection of a suitable number of zuzuschaltenden battery cells and thus the setting of a suitable output voltage of the energy storage device.

According to one embodiment of the method according to the invention, the detection of operating parameters may comprise detecting the rotational speed of the electric machine and the torque of the electric machine, and selecting the number of energy storage modules depending on the detected rotational speed and the detected torque. In accordance with a further embodiment of the method according to the invention, the recording of operating parameters can be the detection of the state of charge of

Energy storage cells include, and selecting the number of

Energy storage modules depending on the state of charge done. According to a further embodiment of the method according to the invention, the selection of a number of energy storage modules can be done by determining a number of energy storage modules

predetermined number of energy storage modules carried out in a spanned by the detected speed and the detected torque map. According to another embodiment of the method according to the invention, the method may further comprise the steps of detecting an operating mode of the electric machine, and limiting the selected number of energy storage modules to a maximum number depending on the detected operating mode. According to one embodiment of the system according to the invention, the

Coupling devices have power MOSFET switches or IGBT switches.

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

Show it: Fig. 1 is a schematic representation of a system with a

Energy storage device according to an embodiment of the

present invention;

Fig. 2 is a schematic representation of an embodiment of a

Energy storage module of an energy storage device according to Fig. 1; a schematic representation of another embodiment of an energy storage module of an energy storage device of FIG. 1; a schematic representation of a diagram for the efficiency of an energy storage device as a function of the number of connected energy storage modules; a schematic representation of a diagram for the power loss in a system with an energy storage device in dependence on the number of connected energy storage modules; a schematic representation of a map for the loss-optimal number switched energy storage modules a

Energy storage device according to another embodiment of the present invention; and a schematic representation of a method for driving an energy storage device according to another embodiment of the present invention.

1 shows a system 100 for voltage conversion of DC voltage provided by energy storage modules 3 into an n-phase AC voltage. The system 100 comprises an energy storage device 1 with energy storage modules 3, which are connected in series in a power supply train. The power supply line is coupled between two output terminals 1a and 1b of the energy storage device 1, which are each coupled to a DC voltage intermediate circuit 2b.

By way of example, the system 100 in FIG. 1 is used to supply a three-phase electrical machine 6. However, provision may also be made for the energy storage device 1 to be used for generating electrical current for a power supply network 6. For this purpose, the energy storage device 1 via a coupling inductance 2a with the

DC intermediate circuit 2b coupled. The coupling inductance 2a can

For example, be a selectively connected between the DC voltage intermediate circuit 2b and the output terminal 1a of the energy storage device 1 inductive throttle. Alternatively, it may also be possible for the coupling inductance 2 a to be present through parasitic inductances in the interconnection that are present anyway

Energy storage device 1 and DC intermediate circuit 2b is formed. The DC voltage intermediate circuit 2b feeds a pulse inverter 4, which from the DC voltage of the DC intermediate circuit 2b a three-phase

AC voltage for the electric machine 6 provides.

The system 100 may further include a controller 8, which is connected to the energy storage device 1, and by means of which the

Energy storage device 1 can be controlled to the desired

Total output voltage of the energy storage device 1 to the respective

Output terminals 1a, 1 b provide. In addition, the control device 8 can be designed to charge the energy storage cells during charging

Energy storage device 1, the respective active switching elements of

To drive energy storage device 1.

The power supply line of the energy storage device 1 has at least two energy storage modules 3 connected in series. By way of example, the number of energy storage modules 3 in FIG. 1 is four, but any other number of

Energy storage modules 3 is also possible. The energy storage modules 3 each have two output terminals 3a and 3b, via which a

Module output voltage of the energy storage modules 3 can be provided. Since the energy storage modules 3 are primarily connected in series, add up the

Module output voltages of the energy storage modules 3 to the

Total output voltage, which at the output terminals 1 a, 1 b the

Energy storage device 1 is provided.

Two exemplary construction forms of the energy storage modules 3 are shown in greater detail in FIGS. 2 and 3. The energy storage modules 3 each comprise a coupling device 7 with a plurality of coupling elements 7a, 7c and 7b and 7d. The

Energy storage modules 3 furthermore each comprise an energy storage cell module 5 with one or more energy storage cells 5a to 5k connected in series. The energy storage cell module 5 can, for example, have cells 5a to 5k connected in series, for example lithium-ion cells. In this case, the number of energy storage cells 5 a to 5 k in those shown in Fig. 2 and Fig. 3

Energy storage modules 3 exemplified two, but any other number of

Energy storage cells 5a to 5k is also possible. The energy storage cell modules 5 have a terminal voltage of U _M and are connected via connecting lines with input terminals of the associated coupling device 7. To the

Input terminals of the associated coupling device 7 is thus the voltage U _M on.

In Fig. 2, the series-connected coupling elements 7a and 7c, the center tap is connected to the output terminals 3a, the so-called left branch of

Full bridge and it form the series-connected coupling elements 7b and 7d, whose center tap is connected to the output terminal 3b, the so-called right branch of the full bridge. The coupling device 7 is formed in Fig. 2 as a full bridge circuit with two coupling elements 7a, 7c and two coupling elements 7b, 7d. The

Coupling elements 7a, 7b, 7c, 7d can each have an active switching element, for example a semiconductor switch, and a free-wheeling diode connected in parallel therewith. It may be provided that the coupling elements 7a, 7b, 7c, 7d are designed as MOSFET switches, which already have an intrinsic diode.

The coupling elements 7a, 7b, 7c, 7d can be controlled in such a way, for example with the aid of the control device 9 shown in FIG

Energy storage cell module 5 is selectively connected between the output terminals 3a and 3b or that the energy storage cell module 5 is bridged. For example, referring to FIG. 2, the power storage cell module 5 may be connected in the forward direction between the output terminals 3a and 3b by putting the active switching element of the coupling element 7d and the active switching element of the coupling element 7a in a closed state, while the other two active switching elements of FIG Coupling elements 7b and 7c are set in an open state. In this case, the voltage U _M is present between the output terminals 3a and 3b of the coupling device 7. A lock-up state can be set, for example, by putting the two active switching elements of the coupling elements 7a and 7b in the closed state, while keeping the two active switching elements of the coupling elements 7c and 7d in the open state. A second

Bridging state, for example, be set by the two active switches of the coupling elements 7c and 7d are placed in the closed state, while the active switching elements of the coupling elements 7a and 7b in open Condition are kept. In both bridging states, the voltage 0 is present between the two output terminals 3a and 3b of the coupling device 7. Similarly, the energy storage cell module 5 in the reverse direction between the

Output terminals 3a and 3b of the coupling device 7 are switched by the active switching elements of the coupling elements 7b and 7c are placed in the closed state, while the active switching elements of the coupling elements 7a and 7d are set in the open state. In this case, the voltage -U _M is applied between the two output terminals 3a and 3b of the coupling device 7. By suitable activation of the coupling devices 7 can therefore individual

Energy storage cell modules 5 of the energy storage modules 3 targeted in the

Series connection of the power supply line to be integrated. This can be achieved by a selective control of the coupling devices 7 for selective switching of the energy storage cell modules 5 of the energy storage modules 3 in the

Power supply line, a total output voltage can be provided, which depends on the individual output voltages of the energy storage cell modules 5 of the

Energy storage modules 3 is dependent. The total output voltage can be set in each case in stages, wherein the number of stages with the number of

Energy storage modules 3 scaled. For a number of n energy storage modules 3, the total output voltage of the power supply string can be set in 2n + 1 stages between -n-U _M , ..., 0, ..., + n ^■ U _M.

Fig. 3 shows a schematic representation of another exemplary

Embodiment for an energy storage module 3. In this case, the coupling device 7 comprises only the coupling elements 7a and 7c, the half-bridge circuit as the

Energy storage cell module 5 can be switched either in a bridging state or a switching state in the forward direction in the power supply line. Incidentally, similar control rules apply as explained in connection with FIG. 3 for the energy storage module 3 shown in full bridge circuit.

In the region of low rotational speeds of the electric machine 6, the full voltage on the electric machine 6 is usually not required. Therefore, it is sufficient to set the voltage of the DC intermediate circuit 2b to a correspondingly lower value. The lower value can be obtained, for example, by appropriately selecting a reduced number of energy storage modules 3 in the

Energy storage device 1 done. On the one hand, this results in that the switching losses in the pulse-controlled inverter 4, which are generated, for example, by the switching of IGBT switches in the pulse-controlled inverter 4 and corresponding freewheeling currents in the diodes assigned to the IGBT switches, are reduced, since these losses are approximated scale the applied input voltage to the pulse inverter 4. For another

Eddy current losses in the electric machine 6 are reduced because the occurrence of Wrbelströmen is significantly dependent on the harmonic content of the total output voltage of the energy storage device 1. In addition, the sink

AC losses in the Wcklungen the electric machine 6 due to this law.

In contrast, there are increased conductivities in the energy storage device 1, since the DC component in the energy storage device 1 increases with a reduced number of connected energy storage modules 1. Since the direct current component is included quadratically in the calculation of the conduction losses in the energy storage device 1, the losses on the energy storage cell modules 5 will increase as the number of connected energy storage modules 3 decreases.

4 shows a schematic representation of a diagram 40 for the efficiency η of an energy storage device 1 as a function of the number N of connected energy storage modules 3. In the diagram 40, two characteristic curves 41 and 42 for various operating parameters of the system 100 are entered in qualitative form.

By way of example, a certain state of charge of all energy storage cells 5a to 5k is assumed, as well as a load claimed by the electric machine 6. The

Curve 41 now shows the decrease of the efficiency η with increasing number N of connected energy storage modules 3 at low speed D of the electric machine 6. For example, the speed D for the characteristic 41 may be about 500 rpm. Conversely, the characteristic 42 shows the increase of the efficiency η with increasing number N of connected energy storage modules 3 at high speed D of the electric machine 6. For example, the speed D for the characteristic 42 may be about 10000 rpm.

Similarly, FIG. 5 shows a schematic representation of a diagram 50 for the power loss P in a system 100 with an energy storage device 1 in FIG

Dependent on the number N of connected energy storage modules 3. The characteristic curve 52 shows, by way of example, the switching losses of the pulse-controlled inverter 4, which increase as the number of connected energy storage modules 3 increases. In contrast, the shows Characteristic 51, the switching losses within the energy storage device 1, which decrease with increasing number of connected energy storage modules 3, since the current load on the coupling devices of the individual energy storage modules 3 by the distribution to several energy storage modules 3 decreases overall. The characteristic curve 53 shows an exemplary overall switching loss curve, which depends inter alia on the sum of the characteristic curves 51 and 52. This characteristic 53 has a minimum for a certain number N of energy storage modules 3, in which the sum of all power losses in the system 100 is minimal. From this behavior can be a first driving strategy for the

Derive energy storage device 1 by, to minimize the system power loss or to optimize the system efficiency in each case depending on the instantaneous speed D, current load of the electric machine 6 and / or the

Charge state of the energy storage cells 5a to 5k an optimal number of zuzuschaltenden energy storage modules 3 in the power supply line of the energy storage device 1 is selected.

6 shows a schematic representation of a map 60 for the

loss-optimal number of connected energy storage modules 3 a

Energy storage device 1. The map 60 can be formed, for example, depending on the two system parameters speed D and torque M (i.e., power consumption) of the electric machine 6. For each point of the map 60 can be an optimal number of zuzuschaltenden energy storage modules 3 in the

Energy supply strand of the energy storage device 1 can be determined. By way of example, four areas 61, 62, 63 and 64 are entered in the map 60. For example, in region 61, it may be optimal to switch on only two energy storage modules 3 while in region 64 it is optimal to switch on four energy storage modules 3. It should be understood that the illustration in FIG. 6 is merely exemplary in nature and actual map lines may differ from the selected illustration.

To determine the map lines 61 to 64 in advance can simulations

be carried out or rasterized by measurements, the map. The determined map 60 with the corresponding drive strategy can then

stored for example in the control device 8 of FIG. 1.

It may also be possible to set up in the control device 8 a loss model in the form of functional relationships between operating parameters of the system 100, so that the calculation of the energy storage modules 3 to be switched on optimally in the Control device 8 at run time of the system 100, that is, online can be performed. For determining the operating parameters of the system 100, the control device 8 can determine the operating parameters of the respective system components, for example the energy storage device 1, the pulse-controlled inverter 4 and / or the electric machine 6, for example via sensor device or measuring devices.

Another criterion in the selection of the zuzuschaltenden energy storage modules 3, the setting of a voltage stabilization of the voltage in the

DC intermediate circuit 2b be. This can be advantageous insofar as the design of the electric machine 6 is based on the minimum input voltage. When fully discharged energy storage cells 5a to 5k is the

Output voltage of a single energy storage cell only about 60% of the maximum possible rated voltage. When the electric machine 6 is designed for a lower minimum voltage level, fewer turns are usually provided to keep the induced Polradspannung low.

However, if the total output voltage of the energy storage device 1 can be maintained at a constant, in particular higher level, the

Winding number of the electric machine 6 can not be reduced or the electric machine 6 can be designed for a higher minimum voltage level. As a result, the current load on the energy storage device 1, the

Pulse inverter 4 and all other electrical connection components such as plugs, leads, connections and the like. In addition, the transition from the basic area to the field weakening area of the electric machine 6 can be kept independent of the state of charge of the energy storage device 1. In addition, the voltage spread of the components that are fed by the DC voltage intermediate circuit 2b, for example vehicle electrical system voltage converter or similar components, low, so that the design of these components can be made simpler or more efficient.

Therefore, there is a second drive strategy for the energy storage device 1 is that for stabilizing the voltage level in the DC voltage intermediate circuit 2b in response to the state of charge of the energy storage cells 5a to 5k in the energy storage modules 3 an optimal number zuzuschaltenden

Energy storage modules 3 in the power supply of the

Energy storage device 1 is selected so that the total output voltage of the energy storage device 1 with respect to the state of charge of the

Energy storage modules 3 remains constant. Even at low charge state of Energy storage modules 3 to be able to offer a constant (high) voltage, the number of energy storage modules 3 can be selected to be higher. For example, the number of energy storage modules 3 can be selected such that when the charge state of all energy storage modules 3 is full, the total output voltage of the energy storage device 1 is higher than necessary for the operation of the pulse inverter 4. This can with decreasing charge state of

Energy storage modules 3, the number of zuzuschapenden energy storage modules 3 are successively increased by the energy storage modules 3 held in reserve. Finally, switching off energy storage modules 3 in operating modes of electric machine 6, in which only a low input voltage or a low rotational speed is required, brings about an advantage in terms of switching losses in pulse-controlled inverter 4. For example, in electric vehicles, an operating mode in which electric motor 6 has a low speed, starting on a slope. In these operating modes, the pulse-controlled inverter 4 limits the permissible maximum phase current.

A third driving strategy is therefore the number of zuzuschaltenden

Energy storage modules 3 in predetermined operating modes of the electric machine 6 to limit so that the input voltage to the pulse inverter 4 is reduced so much that it no longer limits the maximum permissible phase current. As a result, the switching losses decrease, in particular in the pulse inverter 4, which leads in consequence to an improved design of the electric machine 6, since the axial length of the electric machine 6 for the realization of a sufficiently high torque, for example, for starting on the mountain, no longer to the limited phase current of the pulse inverter 4 must be adjusted.

7 shows a schematic representation of a method 70 for activating an energy storage device, for example the energy storage device 1 in FIG. 1. The method 70 can be implemented by the control device 8 in FIG. 1, for example. In the method, the above-mentioned three

Ansteuerstrategien considered. For this purpose, the control device 8 via

Have detection lines 8a, 8b and 8c, with which the control device 8 with the energy storage modules 3, the pulse inverter 4 and the electric machine 6 are connected, and which operating parameters of the respective components can be detected.

The method 70 may include, as a first step 71, detecting operating parameters of an electric machine coupled to the electric machine Pulse inverter and the energy storage device 1 have. The operating parameters may include the speed of the electric machine and the torque of the electric machine. Furthermore, the state of charge of the energy storage cells of the energy storage device 1 can be detected as an operating parameter.

In a second step 72, a number is selected from

Energy storage modules depending on at least one of the detected

Operating parameters, whereupon in a step 73, driving the coupling elements of the coupling devices of the selected energy storage modules for switching the energy storage cell modules of the selected energy storage modules in the

Power supply string done. Thereby, in step 74, providing a total output voltage of the power supply string for one

Pulse inverter feeding DC voltage intermediate circuit done.

Optionally, detection of an operating mode of the electric machine and limiting of the selected number of energy storage modules to a maximum number depending on the detected operating mode can continue to take place. This is particularly advantageous in special operating modes, such as a low speed, high torque operating mode of the electric machine. Limiting the maximum number may be prioritized over the number of energy storage modules selected in step 72, that is, the number of energy storage modules is capped over a maximum function depending on the detected operating mode.

Claims

Claims 1. A method (70) for driving an energy storage device (1) having a plurality of energy storage modules (3) connected in series in a power supply string, each comprising:

an energy storage cell module (5), which at least one energy storage cell

(5a, 5k), and

a coupling device (7) with coupling elements (7a, 7b; 7c, 7d), which are designed to selectively connect or bypass the energy storage cell module (5) in the respective power supply line,

the method (70) comprising the steps of:

Detecting (71) operating parameters of an electric machine (6), a pulse inverter (4) coupled to the electric machine (6), and the

Energy storage device (1);

Selecting (72) a number of energy storage modules (3) in response to at least one of the detected operating parameters;

Driving (73) of the coupling elements (7a, 7b, 7c, 7d) of the coupling devices (7) of the selected energy storage modules (3) for switching the

Energy storage cell modules (5) of the selected energy storage modules (3) in the power supply line; and

Providing (74) a total output voltage of the power supply line for a the DC inverter (4) DC voltage intermediate circuit (2b).

The method (70) of claim 1, wherein detecting (71) operating parameters comprises detecting the rotational speed of the electric machine (6) and the torque of the electric machine (6), and wherein selecting (72) the number of energy storage modules (3) depending on the detected speed and the detected torque.

The method (70) of any one of claims 1 and 2, wherein detecting (71) of

Operating parameters comprises detecting the state of charge of the energy storage cells (5a, 5k), and wherein the selecting (72) the number of

Energy storage modules (3) takes place in dependence on the state of charge.

The method (70) of claim 2, wherein selecting (72) a number of

Energy storage modules (3) by determining a predetermined number of Energy storage modules (3) in a spanned by the detected speed and the detected torque map (60) takes place.

The method (70) of any one of claims 1 to 4, further comprising the steps of:

Detecting an operating mode of the electric machine (6); and

Limiting the selected number of energy storage modules (3) to a maximum number depending on the detected operating mode.

6. System (100), with:

an energy storage device (1) having a plurality of in one

Power supply string connected in series energy storage modules (3), each comprising:

an energy storage cell module (5) which has at least one energy storage cell (5a, 5k), and

a coupling device (7) with coupling elements (7a, 7b; 7c, 7d) which are designed to selectively switch or bypass the energy storage cell module (5) in the respective power supply line;

a DC voltage intermediate circuit (2b), which with the

Energy storage device (1) is coupled;

a pulse inverter (4) which is coupled to the DC intermediate circuit (2b) and which is fed from the DC intermediate circuit (2b) with an input voltage;

an electric machine (6) which is coupled to the pulse inverter (4) and which is supplied by the pulse inverter (4) with a phase voltage; and

a control device (8), which is coupled to the coupling devices (7), and which is adapted to a method (70) for driving the

Energy storage device (1) according to one of claims 1 to 5 perform.

7. System (100) according to claim 6, wherein the coupling devices (7) comprise power MOSFET switches or IGBT switches.