Drive system with energy storage device and transverse flux machine and method for operating a transverse flux machine

Abstract

Electric drive system (100), with: a transverse flux machine (6) which has n phase input terminals for n phases of the transverse flux machine (6), where n ≥ 2; and an energy storage device (1) for generating an n-phase supply voltage for the transverse flux machine (6), wherein the energy storage device (1) comprises: n parallel connected power supply branches (10) each with a first output terminal (1a; 1b), which are each coupled to one of the n phase input terminals (6a; 6b) of the transverse flux machine (6), and a plurality of series connected energy storage modules (3), wherein the energy storage modules (3) each comprise: an energy storage cell module (5) comprising at least one energy storage cell (5a, 5k); and a coupling device (7) with active coupling elements (7a; 7b; 7c; 7d) which are designed to selectively switch the energy storage cell module (5) into the respective power supply branch (10) or to bypass it in the power supply branch (10), characterized by the fact that the energy supply branches (10) each have a second output connection (4a; 4b), which is each connected to separate phase output connections of the n phases of the transverse flux machine (6), so that the n phases of the transverse flux machine (6) can be supplied separately from each other from separate energy storage cells (5a, 5k).

Description

[0001] The invention relates to an electric drive system with an energy storage device and a transverse flux machine supplied by the energy storage device, as well as a method for operating a transverse flux machine, in particular a disc rotor machine, for example in electric drive systems of electrically operated vehicles such as hybrid and electric vehicles. State of the art

[0002] To supply electrical machines with a supply voltage, a conventional inverter, specifically a pulse-width modulated (PWM) inverter, converts a direct current (DC) voltage provided by a DC link into a multi-phase alternating current (AC) voltage. 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.

[0003] When transverse flux machines are used as electric machines, high power and torque density can be achieved with relatively low weight. Disc rotor motors, in particular, can be used advantageously due to their large available active area. For the same size as other machine types, the use of disc rotor motors can significantly reduce the investment in expensive magnet material.

[0004] Publication WO 2009 / 115247 A1, for example, discloses such a transverse flux disc rotor motor, which has a rotor made of carbon with segmented permanent magnets and stator housings pressed and sintered from soft magnetic components.

[0005] Feeding transverse flux machines using conventional inverters requires power electronics with two bridge arms or one full bridge circuit per phase. Therefore, for multiphase transverse flux machines, at least two full bridge circuits, i.e., at least one B8 bridge circuit, are necessary. Connecting to the neutral point of the transverse flux machine is not possible with such inverters, as inverters with B8 bridge circuits do not have a center tap or can only be implemented with considerable additional effort.

[0006] Document US 5,642,275 A1 describes a battery system with an integrated inverter function. Systems of this type are known as multilevel cascaded inverters or battery direct inverters (BDIs). Such systems comprise DC power sources in multiple energy storage module strings, which can be directly connected to an electric machine or an electrical grid. Single-phase or multi-phase supply voltages can be generated.The energy storage module strings comprise multiple energy storage modules connected in series, each containing at least one battery cell and an associated controllable coupling unit. This coupling unit allows, depending on control signals, the respective energy storage module string to be interrupted, the associated battery cell to be bridged, or the associated battery cell to be connected to the respective energy storage module string. By appropriately controlling the coupling units, for example, using pulse-width modulation, suitable phase signals can also be provided to control the phase output voltage, thus eliminating the need for a separate pulse inverter. The pulse inverter required for controlling the phase output voltage is therefore integrated into the battery.

[0007] BDIs typically exhibit higher efficiency and greater reliability compared to conventional systems. Reliability is ensured, among other things, by the ability to disconnect defective, failed, or underperforming battery cells from the power supply lines through appropriate bridging control of the coupling units.

[0008] German patent application DE 10 2011 076 571 A1 discloses a power supply device for inverter circuits. German patent application DE 10 2010 027 857 A1 discloses battery modules with an integrated pulse inverter. German patent application DE 10 2009 004474 A1 discloses transverse flux machines with disc- and drum-shaped rotors.

[0009] There is a need for solutions for the power supply of transverse flux machines that can increase the voltage level at the input terminals of the transverse flux machine and ensure improved efficiency in controlling the transverse flux machine. Disclosure of the invention

[0010] According to one aspect of the present invention, an electric drive system is provided, comprising a transverse flux machine having n phase input terminals for n phases of the transverse flux machine, where n ≥ 2, and an energy storage device for generating an n-phase supply voltage for the transverse flux machine. The energy storage device has n parallel-connected power supply branches, each with a first output terminal coupled to one of the n phase terminals of the transverse flux machine, and a plurality of series-connected energy storage modules.The energy storage modules each comprise an energy storage cell module, which has at least one energy storage cell, and a coupling device with active coupling elements designed to selectively connect the energy storage cell module to the respective power supply branch or to bypass it within the power supply branch. Each power supply branch includes a second output terminal, which is connected to separate phase output terminals of the n phases of the transverse flux machine, so that the n phases of the transverse flux machine can be supplied separately from separate energy storage cells.

[0011] According to a further aspect, the present invention provides a method for operating a transverse flux machine, comprising the step of connecting first output terminals of n parallel-connected power supply branches of an energy storage device to each of n phase input terminals of a transverse flux machine, wherein the n parallel-connected power supply branches each have a plurality of series-connected energy storage modules, and wherein the energy storage modules each comprise: an energy storage cell module comprising at least one energy storage cell, and a coupling device with active coupling elements designed to selectively connect the energy storage cell module to the respective power supply branch or to bypass it in the power supply branch.

[0012] Each power supply branch includes a second output terminal, which is connected to separate phase output terminals of the n phases of the transverse flux machine, so that the n phases of the transverse flux machine can be supplied separately from separate energy storage cells. The method further includes the steps of controlling the coupling devices of one part of the energy storage modules to bypass the energy storage cell modules in the respective power supply branch, and controlling the coupling devices of another part of the energy storage modules to switch the energy storage cell modules into the respective power supply branch to provide phase voltages for the phase terminals of the transverse flux machine. Advantages of the invention

[0013] One idea of ​​the present invention is to supply a transverse flux machine with an energy storage device designed as a battery direct inverter (BDI), so that a flexibly adaptable energy supply branch with a variable number of energy storage modules can be used for each phase of the machine.

[0014] Such an energy storage device is particularly suitable for the voltage supply of transverse flux machines, as no adaptations of conventional inverter topologies are necessary, and no associated additional effort is required with regard to power electronic components, additional assembly and connection technology, required DC link capacity and installation space for the energy supply of the machine.

[0015] Furthermore, the switching frequency of the active switching elements used in the energy storage device can be significantly reduced compared to conventional inverters simply by increasing the number of energy storage modules. This is particularly noticeable with the already high fundamental frequencies of transverse flux machines, which, due to their considerably higher number of electrical poles compared to rotating field machines, exhibit higher fundamental frequencies of the electrical control variables. Reducing the switching frequencies in the energy storage device can lower the switching losses in the power electronics, reduce the iron losses in the machine, and thus decrease the required cooling capacity of the machine's cooling circuit.

[0016] The use of a modular energy storage device allows for the optimization of the electromagnetic design of the transverse flux machine, as the maximum terminal voltage can be significantly increased. This reduces the magnitude of the phase currents while maintaining the same power output, thereby decreasing the safety margins in the machine's thermal design. Furthermore, the sufficient control voltage reserves provided by the modular energy storage device prevent the machine from operating in the field weakening range, particularly at high speeds. This results in significantly improved efficiency, optimization of the transverse flux machine's power factor (cos φ), and a reduction in current consumption.These improvements in turn also increase the efficiency of the energy storage device by reducing switching losses in the power electronic components and optimizing the power output of the battery cells.

[0017] The modular design of the energy storage device also enables extremely fine gradation of the overall output voltage. This allows for advantageously higher degrees of freedom in the control of transverse flux machines, as the safety factor for dimensioning the magnetic circuit of the transverse flux machine can be significantly reduced. This, in turn, results in an increase in the efficiency and power density of the machine.

[0018] Alternatively, with the same output power of the transverse flux machine, the number of turns of the phase chokes can be adjusted to reduce the magnetomotive force (MAF) of the machine. This allows the use of cheaper and more readily available magnets based on ferrites or bonded materials in certain applications, instead of expensive and hard-to-find rare-earth magnets.

[0019] According to one embodiment of the drive system according to the invention, the active coupling elements can comprise power semiconductor switches. For example, according to a preferred embodiment, the active coupling elements can comprise metal oxide semiconductor field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs).

[0020] According to a further embodiment of the drive system according to the invention, the energy storage cells can be lithium-ion batteries, lithium-polymer batteries, lithium-titanate batteries, lithium iron phosphate batteries, lithium-sulfur batteries, nickel-iron batteries, nickel-metal hydride batteries, nickel-hydrogen batteries or nickel-zinc batteries.

[0021] The drive system according to the invention has the advantage that the n phases of the transverse flux machine can be supplied separately from separate energy storage cells. Furthermore, different zero levels of the voltage levels can be selected for the n phases of the transverse flux machine, depending on the requirements.

[0022] According to a further embodiment of the drive system according to the invention, the coupling devices can comprise active coupling elements in a half-bridge configuration. This allows for a reduction in the number of necessary coupling elements, which is particularly advantageous in the case of separate phase connection for the transverse flux machine. This eliminates the need for the possibility of reversing the polarity of the respective power supply branch, i.e., the possibility of providing negative voltage levels for the phases.

[0023] Alternatively, the coupling devices can include active coupling elements in a full bridge configuration. While this increases the number of required active coupling elements, it also allows for the generation of negative voltage levels, thus enabling the connection of the output terminals of the power supply branches to a common neutral point of the transverse flux machine.

[0024] According to a further embodiment of the drive system according to the invention, the transverse flux machine can comprise a transverse flux disc rotor machine. This embodiment is particularly advantageous because, with disc rotors, the available active area for permanent magnets can be maximized.

[0025] According to one embodiment, the transverse flux disc rotor machine can be constructed as a permanent magnet machine using rare earth magnets, ferrite magnets, or bonded magnets. These materials are particularly readily available and cost-effective.

[0026] 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

[0027] They show: Fig. 1 a schematic representation of an exemplary disc rotor of a transverse flux engine; Fig. 2 a schematic representation of an exemplary construction of a transverse flux machine; Fig. 3 a schematic representation of an electric drive system with an energy storage device according to an embodiment of the present invention; Fig. 4 a schematic representation of an electric drive system with an energy storage device according to a further embodiment of the present invention; Fig. 5 A schematic representation of an exemplary energy storage module for an energy storage device in an electric drive system according to one of the Fig. 3 and Fig. 4 according to a further embodiment of the present invention; Fig. 6 A schematic representation of another exemplary energy storage module for an energy storage device in an electric drive system according to one of the Fig. 3 and Fig. 4 according to a further embodiment of the present invention; and Fig. 7 a schematic representation of a method for operating a transverse flux machine according to a further embodiment of the present invention.

[0028] Fig. Figure 1 shows a schematic representation of an exemplary disc rotor R of a transverse flux machine. The disc rotor R consists, for example, of a support ring made of non-magnetic material, such as fiber-reinforced plastic (FRP), in which permanent magnets PM are arranged concentrically around the center of the rotor R. Examples of permanent magnets PM include ferrites, bonded materials, or rare-earth magnetic materials.

[0029] Fig. 2 shows the use of a in Fig. Figure 1 shows a disc rotor R in a transverse flux machine. The disc rotor R is embedded between two stator blocks Sa and Sb, which can be made, for example, of soft magnetic material, for instance by pressing and sintering. In an advantageous embodiment, the stator blocks Sa and Sb completely or almost completely cover the active area of ​​the disc rotor R, meaning that the stator blocks Sa and Sb have a circular cross-sectional area. Stator windings, forming the inductances La and Lb of the transverse flux machine, are embedded in groove-like recesses in the stator blocks Sa and Sb. In the example of the Fig. Figure 2 shows two phase windings, although more windings are possible. It is possible to implement an angular offset of half a pole pitch between the stator blocks Sa and Sb by arranging the slot-like recesses of the stator blocks Sa and Sb accordingly.

[0030] Fig. Figure 3 shows a schematic representation of an electric drive system 100 with an energy storage device 1 which feeds a transverse flux machine 6, for example a transverse flux machine 6 as in connection with Fig. 1 and Fig. 2 explained. The transverse flux machine 6 can be designed as a synchronous machine, an asynchronous machine or a switched reluctance machine.

[0031] The energy unit 1 serves to convert direct current supplied by energy storage modules 3 into an n-phase alternating current. The energy storage modules 3 are connected in series in parallel-connected energy supply branches 10. Examples are shown in Fig. Figure 3 shows two power supply branches 10, which are suitable for generating a two-phase alternating voltage, for example for the two-phase transverse flux machine 6. However, it is clear that any other number of power supply branches 10 is equally possible, just as any other number n of phases is equally possible for the transverse flux machine 6. The energy storage device 1 has a first output terminal 1a, 1b on each power supply branch 10, which are each connected to phase input terminals 6a and 6b of the transverse flux machine 6, respectively. By way of example, the transverse flux machine 6 can be a disc rotor transverse flux machine 6.

[0032] The drive system 100 can further comprise a control device 11 which is connected to the energy storage device 1 and by means of which the energy storage device 1 can be controlled to provide the desired output voltages at the respective first output terminals 1a, 1b of the power supply branches 10.

[0033] The power supply branches 10 can be coupled to the phase output terminals of the transverse flux machine 6 at second output terminals 4a and 4b. This creates a separate circuit for each phase. Therefore, twice as many separate motor cables as phases are required to operate a transverse flux machine 6 in an electric drive system 100.

[0034] Fig. Figure 4 shows a schematic representation of an electric drive system 100 with an energy storage device 1, whose power supply branches are coupled at their second output terminals 4a, 4b to a star point S of the transverse flux machine 6. In this case, the required number of motor cables in an electric drive system 100 can be reduced to n+1, where n represents the number of phases of the transverse flux machine 6.

[0035] In both cases of the Fig. 3 and Fig. 4 Each of the energy supply branches 10 has at least two energy storage modules 3 connected in series. For example, the number of energy storage modules 3 per energy supply branch 10 is Fig. 1 two, however any other number of energy storage modules 3 is also possible. Preferably, each of the energy supply branches 10 comprises the same number of energy storage modules 3, although it is also possible to provide a different number of energy storage modules 3 for each energy supply branch 10.

[0036] 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. Since the energy storage modules 3 are connected in series at the primary end, the output voltages of the energy storage modules 3 add up to a total output voltage, which can be provided at the respective first output terminals 1a, 1b of the energy storage device 1.

[0037] An exemplary configuration of the energy storage modules 3 is shown in Fig. Figure 5 shows in greater detail. The energy storage modules 3 each comprise a coupling device 7 with active coupling elements 7a, 7b, 7c, and 7d, which are coupled in a full-bridge circuit between the two output terminals 3a and 3b. The active coupling elements 7a and 7c, as well as the active coupling elements 7b and 7d, each form a half-bridge branch of the full-bridge circuit. The active coupling elements 7a, 7b, 7c, and 7d can be configured as power semiconductor switches, for example, as metal-oxide-semiconductor field-effect transistors (MOSFETs), which already incorporate an intrinsic diode.

[0038] Alternatively, the active coupling elements 7a, 7b, 7c and 7d can also be formed by insulated gate bipolar transistors (IGBTs), each with a diode connected in parallel.

[0039] The energy storage modules 3 each further 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, contain series-connected batteries 5a to 5k, such as lithium-ion batteries, lithium-polymer batteries, lithium-titanate batteries, lithium iron phosphate batteries, lithium-sulfur batteries, nickel-iron batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, nickel-zinc batteries, or other suitable battery types. The number of energy storage cells 5a to 5k in the module is specified in the module 5. Fig. The energy storage module 3 shown in section 5 is an example of two, but any other number of energy storage cells 5a to 5k is also possible.

[0040] The energy storage cell modules 5 are connected via connecting lines to input terminals of the associated coupling device 7, so that the active coupling elements 7a, 7b, 7c and 7d can be controlled, for example using the Fig. 3 and Fig. The control device 11 shown in Figure 4 ensures that the respective energy storage cell module 5 is selectively connected between the output terminals 3a and 3b, or that the energy storage cell module 5 is bypassed or circumvented in the power supply branch 10. With reference to Fig. 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. A bridging state or bypass state can be set, for example, by setting both active switching elements of coupling elements 7a and 7b or both active switching elements of coupling elements 7c and 7d to a closed state. A freewheeling state can be set, for example, by setting one of the two active switching elements of coupling elements 7a and 7d to an open state and the other to a closed state.

[0041] 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 branch 10.

[0042] Fig. Figure 6 shows a schematic representation of another exemplary energy storage module 3 for an energy storage device 1 in an electric drive system, for example the drive system 100 in Fig. 3 and Fig. 4. The difference to the energy storage module 3 is that the coupling device 7 has only two active coupling elements 7a and 7c, which are connected in a half-bridge configuration. Therefore, the energy storage cell module 5 can only be integrated into the respective power supply branch 10 in one polarity direction.

[0043] For transverse flux machines 6, it is advantageous to have the highest possible voltage reserve in order to be able to exert sufficient influence on the current shaping, especially at high machine speeds 6. With the drive systems 100 of the Fig. 3 and Fig. With the 4 energy storage devices 1 employed, this is particularly easy, since firstly no intermediate circuit capacitor is required and secondly, each of the active semiconductor switches only has to withstand a limited maximum voltage. This allows the number of energy storage modules 3 to be flexibly adapted to the requirements of the transverse flux machine 6 without having to change the basic topology of the energy storage devices 1 or the voltage withstand capability of the semiconductor switches used.

[0044] The number of energy storage modules 4 can be adjusted in this way to increase the terminal voltage at the phase connections 6a, 6b of the transverse flux machine 6. This leads to a reduction in the field weakening range of the transverse flux machine 6, particularly at high speeds. As a result, with a constant output torque at the shaft of the transverse flux machine 6, the power factor cos φ increases, thus reducing the phase currents in the phases of the transverse flux machine 6. Overall, the efficiency of the transverse flux machine 6 can be optimized in this way.

[0045] Alternatively, while maintaining the same output power, the number of turns of the inductors La and Lb of the transverse flux machine 6 can be reduced, thus decreasing the magnetomotive force of the transverse flux machine 6. Furthermore, the number of turns can be adjusted to the voltage ratio such that the flux linkage in the stator and the required coercive field strength in the air gap of the transverse flux machine 6 are optimized. This also allows for a lower quality of permanent magnets PM, enabling the use of significantly cheaper magnets such as ferrites or bonded magnets instead of more expensive alternatives like rare earth magnets.

[0046] The switching frequency of the coupling devices 7 of the individual energy storage modules 3 decreases proportionally with the square of the number of energy storage modules 3 per energy supply branch 10. This means, firstly, a significantly lower amplitude and number of harmonics that are fed into the phases of the transverse flux machine 6, and secondly, it increases the efficiency of the energy storage device 1.

[0047] The coupling of energy storage device 1 and transverse flux machine 6 according to the invention can be used not only in mobile systems such as electric or hybrid vehicles, but also in stationary systems, for example in power plants, in electrical energy generation plants such as wind turbines, photovoltaic systems or combined heat and power plants, in energy storage systems such as compressed air energy storage plants, battery storage plants, flywheel energy storage systems, pumped storage plants or similar systems. Another possible application is in passenger or freight transport vehicles designed for movement on or under water, for example ships, motorboats or the like.

[0048] Fig. Figure 7 shows a schematic representation of a method 20 for operating a transverse flux machine 6. The method 20 can, for example, be used in an electric drive system 100 as in connection with the Fig. 1 to 6 are explained and used.

[0049] In a first step 21, the first output terminals 1a and 1b of n parallel-connected power supply branches 10 of an energy storage device 1 are connected to one of n phase input terminals 6a, 6b of a transverse flux machine 6, wherein the n parallel-connected power supply branches 10 each have a plurality of series-connected energy storage modules 3. The energy storage modules 3 each comprise an energy storage cell module 5, which has at least one energy storage cell 5a, 5k, and a coupling device 7 with active coupling elements 7a to 7d, which are designed to selectively switch the energy storage cell module 5 into the respective power supply branch 10 or to bypass or bridge it in the power supply branch 10.

[0050] In further steps 22 and 23, the coupling devices 7 of a part of the energy storage modules 3 are then controlled to bypass the energy storage cell modules 5 in the respective energy supply branch 10, and the coupling devices 7 of another part of the energy storage modules 3 are controlled to switch the energy storage cell modules 5 into the respective energy supply branch 10 to provide phase voltages for the phase connections 6a; 6b of the transverse flux machine 6.

[0051] This control can, on the one hand, involve the temporary and permanent integration of a specific number of energy storage modules 3 into the respective power supply branch 10 to provide a specific branch output voltage. By selectively and periodically changing the integrated energy storage modules 3, a periodically fluctuating branch output voltage, for example a sinusoidal waveform, can be approximated. Additionally, individual energy storage modules 3 can, for example, be controlled using a pulse-width modulation (PWM) method to achieve finer gradations of the branch output voltage and to approximate the sinusoidal waveform even more closely.

Claims

[1] Electric drive system (100), with: a transverse flux machine (6) which has n phase input terminals for n phases of the transverse flux machine (6), where n ≥ 2; and an energy storage device (1) for generating an n-phase supply voltage for the transverse flux machine (6), wherein the energy storage device (1) comprises: n parallel connected power supply branches (10) each with a first output terminal (1a; 1b), which are each coupled to one of the n phase input terminals (6a; 6b) of the transverse flux machine (6), and a plurality of series connected energy storage modules (3), wherein the energy storage modules (3) each comprise: an energy storage cell module (5) comprising at least one energy storage cell (5a, 5k); and a coupling device (7) with active coupling elements (7a; 7b; 7c; 7d) which are designed to selectively switch the energy storage cell module (5) into the respective power supply branch (10) or to bypass it in the power supply branch (10), characterized by , that the energy supply branches (10) each have a second output connection (4a; 4b), which is each connected to separate phase output connections of the n phases of the transverse flux machine (6), so that the n phases of the transverse flux machine (6) can be supplied separately from each other from separate energy storage cells (5a, 5k). [2] Electric drive system (100) according to claim 1, wherein the active coupling elements (7a; 7b; 7c; 7d) comprise power semiconductor switches. [3] Electric drive system (100) according to claim 2, wherein the active coupling elements (7a; 7b; 7c; 7d) comprise metal oxide semiconductor field-effect transistors, MOSFETs, or insulated gate bipolar transistors, IGBT. [4] Electric drive system (100) according to one of claims 1 to 3, wherein the energy storage cells (5a, 5k) comprise lithium-ion batteries, lithium-polymer batteries, lithium-titanate batteries, lithium iron phosphate batteries, lithium sulfur batteries, nickel-iron batteries, nickel-metal hydride batteries, nickel-hydrogen batteries or nickel-zinc batteries. [5] Electric drive system (100) according to one of claims 1 to 4, wherein the coupling devices (7) comprise active coupling elements (7a; 7c) in half-bridge configuration. [6] Electric drive system (100) according to one of claims 1 to 5, wherein the coupling devices (7) comprise active coupling elements (7a; 7b; 7c; 7d) in full bridge configuration. [7] Electric drive system (100) according to one of claims 1 to 6, wherein the transverse flux machine (6) comprises a transverse flux disc rotor machine. [8] Electric drive system (100) according to claim 7, wherein the transverse flux disc rotor machine is constructed as a permanent magnet machine with magnets made of rare earths, ferrites or bonded magnets. [9] Method (20) for operating a transverse flux engine (6), comprising the steps: Connecting (21) first output terminals (1a; 1b) of n parallel connected power supply branches (10) of an energy storage device (1) to each of n phase input terminals (6a; 6b) of a transverse flux machine (6), wherein the n parallel connected power supply branches (10) each have a plurality of series connected energy storage modules (3), and wherein the energy storage modules (3) each comprise: an energy storage cell module (5) comprising at least one energy storage cell (5a, 5k); and a coupling device (7) with active coupling elements (7a; 7b; 7c; 7d) which are designed to selectively switch the energy storage cell module (5) into the respective power supply branch (10) or to bypass it in the power supply branch (10), wherein the energy supply branches (10) each have a second output terminal (4a; 4b) which is each connected to separate phase output terminals of the n phases of the transverse flux machine (6), so that the n phases of the transverse flux machine (6) can be supplied separately from each other from separate energy storage cells (5a, 5k); Controlling (22) the coupling devices (7) of a part of the energy storage modules (3) to bypass the energy storage cell modules (5) in the respective power supply branch (10) and controlling (23) the coupling devices (7) of another part of the energy storage modules (3) to switch the energy storage cell modules (5) into the respective power supply branch (10) to provide phase voltages for the phase terminals (6a; 6b) of the transverse flux machine (6). [10] Method (20) according to claim 9, wherein the transverse flux machine (6) comprises a transverse flux disc rotor machine.

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