Electric drive system, control device and control method for such a drive system

Abstract

The invention proposes an electric drive system (1) comprising an electric storage device (10) having a first and a second battery (11, 12); a controllable multi-phase inverter (20) having a DC connection side (21) and an AC connection side (22); a multi-phase AC electric machine (30) comprising a winding arrangement (31) electrically coupled to the AC connection side (22) of the inverter (20); a connection arrangement (40) comprising electrical connection paths with controllable switches (SW1+, SW1-, SWs, SW2+, SW2-, SW3, SW4, SW5, SW6) for establishing and interrupting electrical connections, for providing a driving mode and a transfer mode of the electric drive system (1).In driving mode, one or both of the first and second batteries (11, 12) are electrically connected to the DC connection side (21) to supply electrical energy from the respective battery or both batteries (11, 12) via the inverter (20) to the electric motor (30) or vice versa. In transfer mode, the first battery (11) is electrically connected to the DC connection side (21), and the second battery (12) is electrically connected to the winding arrangement (31) of the electric motor (30) to transfer electrical energy from the first battery (11) via the inverter (20) and the winding arrangement (31) to the second battery (12) or vice versa. Advantageously, the invention enables battery self-heating as well as demand-based battery balancing. The invention further proposes a corresponding control device and a control method for such a drive system (1).

Description

[0001] The present invention relates to an electric drive system and a control device and a control method for such an electric drive system, in particular for use in a vehicle, such as a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV).

[0002] Such electric drive systems are known in the art and typically include the following components: - an electrical storage device comprising one or more batteries, - a controllable bidirectional multi-phase inverter having a DC connection side and an AC connection side, - a multi-phase AC electric machine comprising a winding arrangement (e.g. stator windings) electrically coupled to the AC connection side of the inverter, wherein in a driving mode of the electric drive system, the one or more batteries are electrically coupled to the DC connection side of the inverter for supplying electrical energy from the battery or batteries via the inverter to the electric machine (propulsion mode) or vice versa (regeneration mode).

[0003] Under cold conditions, the batteries of such a drive system must be preheated before operation, whether for operation in the above-mentioned driving mode or for operation in a charging mode (particularly when charging at high power) in which the batteries of the electric storage device are coupled to an electric charging device.

[0004] For this application, the prior art often used a large and expensive heater to perform preheating. In such cases, preheating is carried out, for example, by heating a cooling liquid, which then heats a cooling plate of the respective battery. To enable "self-heating" of batteries, another solution has been presented in which the energy storage is divided into two smaller packages or packs (batteries) and a DC-DC converter is inserted between them to transfer energy back and forth between the two battery packs. In this way, the electrical losses generated by the battery cells can heat the batteries without the need for external heating. Although this solution appears promising, the additional DC-DC converter disadvantageously adds cost and volume to the electric drive system or powertrain of a respective vehicle.

[0005] Particularly in autonomous driving (AD) applications, an electrical storage facility is typically split into two battery packs (batteries). The main reason for this is to increase system redundancy. In the event that one battery fails, the other can be used to power the vehicle. To increase DC charging flexibility, the two batteries can be connected either in series or in parallel. This means that the battery arrangement can supply two different voltage levels to a DC link of a charging device and can advantageously charge from different charging stations. Having two batteries that can be switched from series to parallel and vice versa is not a trivial task. Balancing the batteries (i.e., matching their charge levels and / or voltage levels) must be taken care of, especially when switching from series to parallel.Using conventional passive or active balancing techniques in the state of the art, this can take a long time because small and inexpensive electronics are used to achieve the balancing.

[0006] An object of the invention is to overcome the aforementioned disadvantages and to provide an electric drive system as well as a control device and a control method for such an electric drive system, which allow in a simple manner to heat and / or balance the batteries of an electrical storage device in the electric drive system.

[0007] This object is achieved by the features of the independent patent claims. Advantageous embodiments are specified in the dependent claims.

[0008] According to a first aspect, the problem is solved by an electric drive system. The electric drive system comprises: - an electrical storage device comprising a first battery and a second battery, - a controllable bidirectional multi-phase inverter having a DC connection side and an AC connection side, - a multi-phase AC electric machine comprising a winding arrangement electrically coupled to the AC connection side of the inverter, - a connection arrangement comprising electrical connection paths with controllable switches for establishing and interrupting electrical connections, for providing at least - a driving mode of the electric drive system in which the first battery or the second battery or a series arrangement of the first battery and the second battery or a parallel arrangement of the first battery and the second battery is electrically coupled to the DC connection side of the inverter for supplying electrical energy from the respective battery or battery arrangement via the inverter to the electric machine or vice versa, and - a transfer mode of the electric drive system in which the first battery is electrically coupled to the DC connection side of the inverter and the second battery is electrically coupled to the winding arrangement of the electric machine, for transferring electrical energy from the first battery via the inverter and the winding arrangement to the second battery or vice versa.

[0009] Advantageously, the invention enables battery self-heating and battery charge equalization using components that are at least largely typically provided as components of the electric drive system in vehicles of the type of interest here (e.g. BEV, HEV, etc.).

[0010] The invention is based on the concept of using the bidirectional inverter and the winding arrangement of the electric machine to perform DC / DC conversion to transfer electrical energy between the two batteries involved. This allows the aforementioned self-heating to be achieved through forward and reverse transfer in the inventive "transfer mode." Furthermore, balancing the two batteries in such a transfer mode can be achieved by transferring a suitable amount of energy from one of these batteries to the other.

[0011] In one embodiment, the DC terminal side of the inverter comprises a positive terminal (and a corresponding lead) of the inverter and a negative terminal (and a corresponding lead) of the inverter, and the AC terminal side of the inverter comprises a plurality of AC phase terminals (and corresponding leads), wherein the inverter comprises a plurality of series connections, each comprising an upper switch (e.g., MOSFET) connected to the positive terminal and a lower switch (e.g., MOSFET) connected to the negative terminal of the inverter, with a respective one of the AC phase terminals of the inverter formed therebetween. In this regard, the specific design of the inverter in the present invention can advantageously be based on well-established inverter designs known in the art.

[0012] In one embodiment, the electric machine is a synchronous machine in which the winding arrangement of the electric machine is formed by a plurality of stator windings of the electric machine. Furthermore, in this respect, the specific design of the electric machine can advantageously be based on well-established configurations known in the prior art.

[0013] In one embodiment, the connection arrangement comprises one or more, and in particular all, of the following connection paths: - a connection path with a controllable switch between a positive terminal of the first battery and a positive terminal of the inverter, - a connection path with a controllable switch between a negative terminal of the first battery and a negative terminal of the inverter, - a connection path with a controllable switch between the negative terminal of the first battery and a positive terminal of the second battery, - a connection path with a controllable switch between a positive terminal of the second battery and a connection node on the winding arrangement, - a connection path with a controllable switch between a negative terminal of the second battery and the negative terminal of the inverter, - a connection path with a controllable switch and a capacitor between the negative terminal of the second battery and the connection node on the winding arrangement.

[0014] The "connection node" on the winding may be a node in the electrical circuitry of the system that is electrically connected to one end (terminal) of at least one of the plurality of windings that make up the winding arrangement.

[0015] For example, in one embodiment, the winding arrangement of the electric machine is formed by several (for example three) stator windings in a star configuration, wherein the connection node on the winding arrangement is the star point of the star configuration.

[0016] According to a further embodiment, the winding arrangement of the electric machine is formed by a plurality of (for example three) stator windings in a star configuration, wherein the connection arrangement further comprises a controllable switch in a phase line connecting one of the AC phase terminals of the inverter to a respective (winding terminal) of the stator windings of the electric machine, wherein the connection node on the winding arrangement is a node on the phase line between the controllable switch and the respective stator winding.

[0017] In yet another embodiment, the winding arrangement of the electric machine is formed by a plurality (e.g., three) stator windings in a delta configuration, wherein the connection arrangement further comprises a controllable switch in a phase line connecting one of the AC phase terminals of the inverter to a respective connection node (at a “delta corner”) of the winding arrangement, and wherein the connection node on the winding arrangement is the connection node of the winding arrangement.

[0018] According to a second aspect, the object is achieved by an electric drive system comprising: - an electrical storage device comprising the first battery and the second battery, - a first and a second controllable bidirectional multi-phase inverter, each having a DC connection side and an AC connection side, - a first and a second multi-phase AC electric machine, each comprising a winding arrangement electrically coupled to the AC connection side of a respective one of the first and second inverters, - a connection arrangement comprising electrical connection paths with controllable switches for establishing and interrupting electrical connections, for providing at least - the driving mode of the electric drive system in which the first battery is electrically coupled to the DC connection side of the first inverter for supplying electrical energy from the first battery via the first inverter to the first electric machine or vice versa and in which the second battery is electrically coupled to the DC connection side of the second inverter for supplying electrical energy from the second battery via the second inverter to the second electric machine or vice versa and - the transfer mode of the electric drive system, in which the first battery is electrically coupled to the DC connection side of the first inverter and the second battery is electrically coupled to the DC connection side of the second inverter, so that the second battery is electrically coupled indirectly via the second inverter and the winding arrangement of the second electric machine to the winding arrangement of the first electric machine, for transferring electrical energy from the first battery via the first inverter, the winding arrangement of the first electric machine, the winding arrangement of the second electric machine and the second inverter to the second battery, or vice versa.

[0019] According to an embodiment of the second aspect, the connection arrangement comprises - a connection path, optionally with a controllable switch between a positive terminal of the first battery and a positive terminal of the first inverter, - a connection path, optionally with a controllable switch between a negative terminal of the first battery and a negative terminal of the first inverter, - a connection path, optionally with a controllable switch between a positive terminal of the second battery and a positive terminal of the second inverter, - a connection path, optionally with a controllable switch between a negative terminal of the second battery and a negative terminal of the second inverter, - a connection path, optionally with a controllable switch between the negative terminal of the first inverter and the negative terminal of the second inverter, - a connection path with a controllable switch between a connection node on the winding arrangement of the first electric machine and a connection node on the winding arrangement of the second electric machine.

[0020] The above explanations about the (one) connection node in a system with an electric machine also apply analogously to each of the (two) connection nodes in the system with the first and the second electric machine, ie each connection node can be a node that is electrically connected to a winding terminal of at least one winding that forms the respective winding arrangement.

[0021] In an embodiment according to the second aspect, the winding arrangements of the first and the second electric machine are each formed by a plurality (for example three) stator windings in a respective star configuration, wherein the connection nodes on the winding arrangements are each the star point of the respective star configuration.

[0022] In an embodiment according to the second aspect, the winding arrangements of the first and the second electric machine are each formed by a plurality of (for example three) stator windings in a respective star configuration, wherein the connection arrangement further comprises a controllable switch in a phase line that connects one of the AC phase connections of the first inverter to a respective one (i.e. winding connection) of the stator windings of the first electric machine, wherein the connection arrangement further comprises a controllable switch in a phase line that connects one of the AC phase connections of the second inverter to a respective one (i.e. winding connection) of the stator windings of the second electric machine, and wherein the connection nodes on the winding arrangements are each a node on the phase line between the respective controllable switch and the respective stator winding.

[0023] In an embodiment according to the second aspect, the drive system further comprises a DC charging connection device comprising a positive charging terminal and a negative charging terminal, wherein the connection arrangement further provides a charging mode of the electric drive system in which the first battery or the second battery or a series arrangement of the first battery and the second battery or a parallel arrangement of the first battery and the second battery is electrically coupled to the DC charging connection device for supplying electrical energy from the DC charging connection device to the respective battery or the battery arrangement, or vice versa.

[0024] In an embodiment according to the second aspect, the connection arrangement of the drive system is designed such that more than one of the aforementioned coupling options, and in particular all of these coupling options (ie first battery, second battery, both batteries in series and both batteries in parallel electrically coupled to the charging connection device) can be implemented as desired.

[0025] For example, in one embodiment, the connection arrangement comprises - a connection path with a controllable switch between the positive charging terminal and the positive terminal of the first battery, - a connection path with a controllable switch between the negative charging terminal and the negative terminal of the first battery, - a connection path with a controllable switch between the positive charging terminal and the positive terminal of the second battery, - a connection path with a controllable switch between the negative charging terminal and the negative terminal of the second battery.

[0026] According to a third aspect, the above-mentioned object is achieved by a control device for controlling an electric drive system of the type described here. The control device comprises: - a communication interface for receiving information representing an operating mode of the drive system to be controlled, - a selection module for selecting an operating mode of the drive system to be controlled according to the received information, - a switch control module for controlling the controllable switches of the connection arrangement to provide the selected operating mode and - an inverter control module for controlling the inverter to provide electrical energy transmission according to the provided operating mode.

[0027] The selection module, the switch control module and the inverter module may be implemented as software modules each comprising one or more computer programs, wherein the computer programs may be executed by means of one or more processors / controllers or as hardware modules comprising one or more special electrical circuits or as hybrid modules comprising software components and hardware components.

[0028] Here, the operating modes from which a selection is made may, in addition to the aforementioned driving mode and the aforementioned transfer mode, include, in particular, for example, a charging mode.

[0029] In one embodiment, the control method for controlling an electric drive system comprises: - Receiving information representing an operating mode of the drive system to be controlled, - Selecting an operating mode of the drive system to be controlled according to the received information, - Controlling the controllable switches of the connection arrangement to provide the selected operating mode and - Controlling the inverter to deliver a transfer of electrical energy according to the provided operating mode.

[0030] According to a fourth aspect, the above-mentioned object is achieved by a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to the third aspect.

[0031] In the context of this document, mention of such a computer program is synonymous with the term program element and / or a computer program product containing instructions for controlling a computer to appropriately coordinate the operation of a system or method to achieve the effects associated with the inventive method. The computer program may be implemented as computer-readable instruction code in any suitable programming language, such as JAVA, C++, etc.

[0032] The computer includes a processor and program memory. Alternatively, the program memory may be linked to the computer. The processor may include a central processing unit (CPU). The processor may be a general-purpose processor, a microprocessor, a microcontroller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or the like.

[0033] According to a fourth aspect, the above-mentioned object is achieved by a computer-readable medium comprising instructions which, when executed by a control computer of a “high-voltage system of an electric vehicle”, cause the control computer to

[0034] The computer may be implemented by a program-controlled control device (of the type described here), for example, installed or available / usable in a vehicle. The computer program may be stored on a computer-readable storage medium (CD-ROM, DVD, Blu-ray Disc, memory stick, volatile or non-volatile memory, integrated memory / processor, etc.). The instruction code may program a computer or other programmable device, such as in particular a control unit for an electric vehicle, to perform the desired functions. Furthermore, the computer program may be provided on a network, such as the Internet, from which it can be downloaded by a user on demand.

[0035] According to a further aspect of the invention, the use of an electric drive system of the type described here in a vehicle, such as, for example, a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV), is proposed. In this case, the electric drive system can form the drivetrain of the vehicle or at least a component of such a drivetrain.

[0036] The invention will now be described by way of exemplary embodiments, with reference to the accompanying drawings. They show: Fig. Figure 1 shows a first example of an electric drive system comprising an electric machine in star configuration and an inverter providing three-phase operation in a “transfer mode” of the electric drive system, Fig. 2 illustrates a “boost operation” in the transfer mode of the Fig. 1 shown system, Fig. 3 illustrates a “buck operation” in the transfer mode of the Fig. 1 shown system, Fig. Figure 4 shows a second example of an electric drive system which also has the electric machine in star configuration, but provides for two-phase operation in the transfer mode, Fig. Figure 5 shows a third example of an electric drive system having the electric machine configured in delta connection, illustrating the driving mode of the system, Fig. 6 illustrates the transfer mode of the Fig. 5 shown system, Fig. Figure 7 shows a fourth example of an electric drive system comprising two batteries, two inverters and two electric machines (according to a “dual drive” redundancy concept), both electric machines being in star configuration and providing three-phase operation in the transfer mode of the system, Fig. Figure 8 shows a fifth example of an electric drive system, similar to the fourth example, but providing two-phase operation in the transfer mode, Fig. 9 illustrates a basic concept of an electric drive system according to a sixth example, Fig. 10 shows the sixth example of an electric drive system, Fig. 11 illustrates the driving mode of the Fig. 10 shown electric drive system 1, Fig. 12 illustrates the transfer mode of the Fig. 10 shown electric drive system 1, Fig. 13 shows a flowchart illustrating an example of a method for controlling an electric drive system, and Fig. 14 shows a seventh example of an electric drive system.

[0037] Fig. 1 shows an electric drive system 1 installed in a vehicle for driving the same, according to a first example, comprising: - an electrical storage device 10 comprising a first battery 11 and a second battery 12; - a controllable bidirectional multi-phase inverter 20, having a DC connection side 21 with connection lines DC+ and DC- and an AC connection side 22 with AC phase lines U, V, W; - a multi-phase AC electric machine 30 comprising a winding arrangement 31 electrically coupled to the AC connection side 22 of the inverter 20; and - a connection arrangement 40 comprising electrical connection paths with controllable switches for making and breaking electrical connections, as in Fig. 1 is shown.

[0038] As in Fig. 1, the two connection lines DC+ and DC- can be connected via a capacitor (buffer capacitor) Cdc. In the example, the AC connection side 22 of the inverter 20 is formed by the three AC phase lines U, V, W for conducting corresponding (three) phase currents between the inverter 20 and the winding arrangement 31 (e.g., three stator windings in the example) of the electric machine. The winding arrangement 31 and thus the electric machine 30 in this example has a star configuration with a star connection point N, i.e., for each winding, a first winding terminal is connected to the star point N, whereas the second winding terminal is connected to a respective one of the plurality of AC phase lines U, V, and W.

[0039] In the example, the connection arrangement (40) comprises: - a connection path with a controllable switch SW1+ between a positive terminal of the first battery 11 and the positive terminal DC+ of the inverter 20, - a connection path with a controllable switch SW1- between a negative terminal of the first battery 11 and the negative terminal DC- of the inverter 20, - a connection path with a controllable switch SWs between the negative terminal of the first battery 11 and a positive terminal of the second battery 12, - a connection path with a controllable switch SW2+ between the positive terminal of the second battery 12 and a connection node C on the winding arrangement 31 (where the connection node C in the example is equivalent to the star connection point N), - a connection path with a controllable switch SW2- between a negative terminal of the second battery 12 and the negative terminal DC- of the inverter 20, - a connection path with a controllable switch SW3 and (in series) a capacitor Csp between the negative terminal of the second battery 12 and the connection node C on the winding arrangement 31.

[0040] With the connection arrangement 40, which includes the above-mentioned electrical connection paths, the electric drive system 1 can provide: - a driving mode of the electric drive system 1, in which a series arrangement of the first battery 11 and the second battery 12 is electrically coupled to the DC connection side 21 of the inverter 20, for supplying electrical energy from the battery arrangement 11, 12 via the inverter 20 to the electric machine 30 (propulsion mode) or vice versa (recuperation mode), and - a transfer mode of the electric drive system 1, in which the first battery 11 is electrically coupled to the DC connection side 21 of the inverter 20 and the second battery 12 is electrically coupled to the winding arrangement 31 of the electric machine 30, for transferring electrical energy from the first battery 11 via the inverter 20 and the winding arrangement 31 to the second battery 12 or vice versa.

[0041] In the Fig. 1, the winding arrangement 31 of the electric machine 30 is formed by several (in the example: three) stator windings in a star configuration, ie the electric machine 30 is configured in a star-point connection, wherein the connection node C on the winding arrangement 31 is the (equivalent to) star point N of the star configuration (since it is electrically connected thereto), as in Fig. 1 is shown.

[0042] The electric drive system 1 is controlled by a control device 2, comprising a communication interface for receiving information c* representing an operating mode of the drive system 1 to be controlled. During operation of the vehicle, the information c* is provided, for example, by a higher-level control device (e.g., a central control unit, ECU) of the vehicle, to which, for example, information relating to the operating state of the drive system 1 or operating parameters (voltages, currents, temperatures, etc.) detected by sensors in the drive system 1 can also be communicated to vehicle electronics via the same interface, for example back to such a higher-level control device.

[0043] The latter operating parameters may include, for example, information b* concerning an operating state of the batteries 11, 12 (e.g., their states of charge (SoC), voltage levels, temperature(s), etc.), information i* concerning an operating state of the inverter 20 (e.g., voltages and / or currents detected in the inverter), and information m* concerning an operating state of the electric machine 30 (e.g., its rotational speed, etc.).

[0044] The control device 2 further comprises a selection module for selecting an operating mode of the drive system 1 to be controlled according to the received information c*; a switch control module for controlling the controllable switches SW1+, SW1-, SW2+, SW2-, SWs, SW3 of the connection arrangement 40 to provide the selected operating mode; and an inverter control module for controlling the inverter 20 to provide electrical energy transmission according to the provided operating mode. The operating modes from which a selection is made include, in particular, the aforementioned drive and transfer modes.

[0045] In the example, the control device 2 is formed by a program-controlled electronic control device on which a control program (software) for controlling the system 1 runs. Accordingly, the aforementioned "modules" of the control device 2 are appropriately implemented here as partial functionalities of this control program.

[0046] To control the controllable switches SW1+, SW1-, SW2+, SW2-, SWs, SW3 of the connection arrangement 40, the control device 2 generates corresponding control signals sw* and outputs them to these switches (to provide the selected operating mode in the electric drive system 1).

[0047] As shown by Fig. As can be seen in Figure 1, the electrical storage device 10 comprises a high-voltage (HV) battery assembly (e.g., 800 V), divided into two battery packs, i.e., the first battery 11 and the second battery 12 (e.g., 400 V each). In the aforementioned driving mode (e.g., when the vehicle is being driven), according to the example shown, these batteries 11, 12 are connected in series to deliver the requested traction performance. In this case (driving mode), the switches SWs, SW1+, SW2- are closed, whereas SW1-, SW2+, SW3 are open.

[0048] In the event that the battery arrangement needs to be preheated (for example, under cold conditions before driving the vehicle), the two batteries 11, 12 are electrically separated from each other in the aforementioned transfer mode by opening the switches SWs and SW2-. Rather, in the transfer mode, the first battery 11 is connected via the switches SW1+ and SW1- to the DC link side 21, i.e., the connecting lines DC+, DC- of the inverter 20, whereas the second battery 12 is connected via the switches SW2+ and SW3 to the connection node C and the capacitor Csp, wherein the capacitor Csp is also connected to the connection node C and thus to the star point connection N of the electric machine 30, as in Fig. 1 is shown.

[0049] Then, in the transfer mode, using the inductances of the three windings of the winding arrangement 31 of the electric machine 30 and the three-phase half bridges of the inverter 20, a DC / DC conversion can be achieved to transfer electrical energy from the first battery 11 via the inverter 20 and the winding arrangement 31 to the second battery 12 or vice versa.

[0050] The energy transfer is controlled by the inverter control module of control device 2, which generates and outputs appropriate control signals uvw* to inverter 20 (for appropriate switching of the half-bridges shown in inverter 20). Using this circuit arrangement and by adjusting the voltage operating point from each side by the inverter control module of control device 2, inverter 20 and electric machine 30 are capable of transferring electrical energy back and forth between the two batteries 11, 12.

[0051] First, to begin moving the energy from battery 12 to battery 11, a “boost mode” operation of inverter 20 is used, as shown in Fig. 2 (by current flow arrows). This function allows the batteries 11, 12 to be heated. Next, the energy is shoveled back to the battery 11 using the "buck mode" functionality, as shown in Fig. 3 (shown by current flow arrows).

[0052] The performance of the DC / DC conversion is approximately the same as in the drive mode. This allows the two batteries 11, 12 to be heated very quickly and without the need for any additional devices. Advantageously, reusing the powertrain components enables battery self-heating. Additionally, the two batteries 11, 12 can be symmetrical at the end of the preheating process (and / or during the preheating process) using the inverter 20 and the electric machine 30. The controllable switches (SW1+, SW1-, ...) can comprise, for example, switching transistors (e.g., MOSFETs) or, for example, relays or the like.

[0053] In short, the operations for transmitting electrical energy are controlled by the control device 2, which defines the operating mode of the electric drive system 1, including the direction of the corresponding energy flow (by appropriately adjusting the voltage operating points of the inverter 20).

[0054] Instead of preheating the batteries 11, 12, the transfer mode can also be used to balance the two batteries 11, 12. This also applies to all other examples described here.

[0055] In the first example, which is Fig. As shown in Figures 1 to 3, three-phase operation of the inverter 20 is provided for implementing the transfer mode using an electric machine 30 formed in a star configuration. However, as will become apparent from further embodiments (examples) described below, such details can also be modified.

[0056] In the following description of further embodiments, the same reference numerals are used for the same components. Basically, only the differences from the embodiment(s) described above are discussed here, and furthermore, explicit reference is made to the description of the preceding embodiments.

[0057] For the sake of simplicity, a control device used to control the respective drive system is omitted in the figures of the following examples. However, such a control device can be used, in particular as described with reference to Fig. 1 already described, designed and functioning.

[0058] Fig. Figure 4 shows an electric drive system 1 according to a second example, in which the winding arrangement 31 of the electric machine 30 is also formed by several stator windings in star configuration, as in the example of Fig. 1 to 3.

[0059] However, in this example, Fig. 4, the connection arrangement 40 further includes a controllable switch SW4 in an AC phase line (in the example, W) that connects one of the AC phase terminals of the inverter 30 to a respective one of the stator windings of the electric machine 30. A further modification to the first example is that the connection node C on the winding arrangement 31 is a node on this AC phase line W between the controllable switch SW4 and the respective stator winding.

[0060] In this example, a “two-phase operation” of the inverter 20 is provided to carry out the transfer mode, with one inverter branch (W in Fig. 4) is disconnected from the inverter 20 by the controllable switch SW4, and the corresponding (W)-AC phase terminal of the electric machine 30 (winding arrangement 31) is connected to the second battery 12, as in Fig. 4. Furthermore, the same concept can also be extended to a "single-phase" operation for performing the transfer mode.

[0061] Fig. 5 shows an electric drive system 1 according to a third example, in which the electric machine 30 is configured in delta connection, ie, the winding arrangement 31 thereof is formed by several (three) stator windings in delta configuration.

[0062] Furthermore, the connection arrangement 40, in addition to the switches SW1+, SW1-, SW2+, SW2-, SWs, SW3 provided in the first and second examples (star connection topology), further comprises a controllable switch SW4 in an AC phase line (V in the example) that connects one (V) of the AC phase terminals of the inverter 20 to a respective connection node (“delta corner”) of the winding arrangement 31. The connection node C on the winding arrangement 31 in this example is the connection node of the winding arrangement 31, as shown in Fig. 5 is shown.

[0063] With this topology, as in Fig. As shown in Figure 5, the switches SW1+, SWs, SW2- and SW4 are closed in drive mode, whereas SW1-, SW2+, SW3 are open.

[0064] In transfer mode, switches SW1+, SW1-, SW2+ and SW3 are closed, whereas SW2- and SW4 are open.

[0065] Fig. Figure 6 illustrates the transfer mode of the electric drive system 1 in the third example. In this transfer mode, for example, a heating mode during a standstill of the vehicle, as in Fig. As shown in Figure 6, one inverter branch (phase line V in this example) is disconnected from the corresponding (V) terminal of the delta sides of the winding assembly 31. Accordingly, to allow energy transfer from one of the batteries 11, 12 to the other, switches SW1+, SW1-, SW2+, SW3 are closed.

[0066] Thus, in short, in the third example ( Fig. 5 and Fig. 6) a two-phase operation of the inverter 20 for performing the transfer mode using an electric machine 30 configured in delta connection is provided.

[0067] In the future, a redundancy concept will be required for many electric vehicles, especially to meet challenging requirements for autonomous driving. One option is to use an electric storage facility comprising (at least) two batteries and (at least) two electric drive units, each comprising an electric machine. To reuse the two drivetrain components for heating and / or balancing the two batteries, a Fig. 7 shown electric drive system 1 can be used.

[0068] Fig. 7 shows an electric drive system 1 according to a fourth example, comprising: - the electrical storage device 10, which comprises the first battery 11 and the second battery 12, - a first and a second controllable bidirectional multi-phase inverter 20-1, 20-2, each having a DC connection side 21 (with DC lines DC+ and DC-) and an AC connection side 22 (with AC phase lines U, V, W in the example), - a first and a second multi-phase AC electric machine 30-1, 30-2, each comprising a winding arrangement 31-1, 31-2, electrically coupled to the AC connection side 21 of a respective one of the first and second inverters 20-1, 20-2, - the connection arrangement 40, comprising electrical connection paths with controllable switches for establishing and interrupting electrical connections, for providing the drive mode and the transfer mode.

[0069] In the example shown, the connection arrangement comprises 40 - a connection path with a controllable switch SW1+ between a positive terminal of the first battery 11 and a positive terminal (DC+ line) of the first inverter 20-1, - a connection path with a controllable switch SW1- between a negative terminal of the first battery 11 and a negative terminal (DC- line) of the first inverter 20-1, - a connection path, optionally with a controllable switch SW2+ between a positive terminal of the second battery 12 and a positive terminal (DC+ line) of the second inverter 20-2, - a connection path with a controllable switch SW2- between a negative terminal of the second battery 12 and a negative terminal (DC- line) of the second inverter 20-2, - a connection path with a controllable switch SW3 between the negative terminal (DC- line) of the first inverter 20-1 and the negative terminal (DC- line) of the second inverter 20-2, - a connection path with a controllable switch SW4 between a connection node on the winding arrangement 31 of the first electric machine 30-1 and a connection node on the winding arrangement 31 of the second electric machine 30-2.

[0070] In this example, the winding assemblies 31 of the first and second electric machines 30-1, 30-2 are each formed by a plurality of stator windings in a respective star configuration, and the aforementioned "connection nodes" (connected via the connection path including the switch SW4) on the winding assemblies 31 are the star points of the respective star configurations.

[0071] In the driving mode of the electric drive system 1, the two electric machines 30-1, 30-2 are kept separate by keeping switches SW3 and SW4 open. In this mode, the first battery 11 is electrically coupled to the DC connection side 21 of the first inverter 20-1 for supplying electrical energy from the first battery 11 via the first inverter 20-1 to the first electric machine 30-1 or vice versa, whereas the second battery 12 is electrically coupled to the DC connection side 21 of the second inverter 20-2 for supplying electrical energy from the second battery 12 via the second inverter 20-2 to the second electric machine 30-2 or vice versa.

[0072] In the transfer mode of the electric drive system 1, switches SW3 and SW4 are closed. In this mode, the first battery 11 remains electrically coupled to the DC connection side 21 of the first inverter 20-1, and the second battery 12 remains electrically coupled to the DC connection side 21 of the second inverter 20-2.

[0073] However, in the transfer mode, the second battery 12 is electrically coupled indirectly, namely via the second inverter 20-2 and the winding arrangement 31 of the second electric machine 30-2, and the paths with the (closed) switches SW3 and SW4, to the winding arrangement 31 of the first electric machine 30-1.

[0074] Therefore, in the transfer mode, electrical energy can be transferred from the first battery 11 via the first inverter 20-1, the winding arrangement 31 of the first electric machine 30-1, the winding arrangement 31 of the second electric machine 30-2 and the second inverter 20-2 to the second battery 12, or vice versa.

[0075] In this way, the first and second drives operate in transfer mode as step-down converters and buck-boost converters, respectively (through appropriate control of inverters 20-1, 20-2). To transfer electrical energy from battery 11 to battery 12, the first drive (with first inverter 20-1 and first electric machine 30-1) operates as a buck DC / DC converter, whereas the second drive (with second inverter 20-2 and second electric machine 30-2) operates as a boost DC / DC converter. The two buck and boost DC / DC converters add high flexibility to the operation.

[0076] One (in Fig. 7) used to control the drive system 1 can be configured as already described with reference to Fig. 1 described, but in this case ( Fig. 7) (with output signals uvw*) both inverters 20-1, 20-2 in a coordinated manner.

[0077] It should be noted that the provision of switches SW1+, SW1-, SW2+ and SW2- is useful here mainly for other reasons, including safety reasons (which is also the case in other examples described here), but for example in the example of Fig. 7 is not absolutely necessary for the basic functionality of the drive system 1.

[0078] Thus, in short, in the fourth example according to Fig. 7, three-phase operation of the two inverters 20-1, 20-2 is provided for implementing the transfer mode using two electric machines 30-1, 30-2, each configured in a star connection. Two-phase operation would also be possible for efficiency and operational improvements. A corresponding example is shown in Fig. 8 shown.

[0079] Fig. Figure 8 shows an electric drive system 1 according to a fifth example. As in the previous example ( Fig. 7) the winding arrangements 31 of the first and second electric machines 30-1, 30-2 are each formed by a plurality of stator windings in a respective star configuration.

[0080] In contrast to the previous example ( Fig. 7) the connecting arrangement 40 in the fifth example according to Fig. 8 however - a controllable switch SW5 in a phase line (W in the example) connecting one (W) of the AC phase terminals of the first inverter 20-1 to a respective one (W) of the stator windings of the first electric machine 30-1, and - a controllable switch SW6 in a phase line (W in the example) connecting one (W) of the AC phase terminals of the second inverter 20-2 to a respective one (W) of the stator windings of the second electric machine 30-2.

[0081] A further difference is that the connection nodes C (at the ends of the connection path comprising the switch SW4) on the winding assemblies 31 are each a node on the aforementioned AC phase line W, between the respective controllable switches SW5 or SW6 and the stator winding of the respective winding assemblies 31.

[0082] Thus, in this example, Fig. 8 the switches SW5 and SW6 are used to disconnect an inverter branch (AC phase line W in the example) of the first inverter 20-1 and the second inverter 20-2 in the transfer mode.

[0083] In short, in the fifth example according to Fig. 8 a two-phase operation of two inverters 20-1, 20-2 for performing the transfer mode using two electric machines 30-1, 30-2, each configured in star connection, is provided.

[0084] As mentioned above, in autonomous driving (AD) applications, a high-voltage (HV) battery can be split into two batteries to increase system redundancy. In the event of one battery failing, the other can be used to drive the vehicle to its destination.

[0085] Furthermore, such a battery arrangement divided into two batteries (first and second battery) can advantageously also provide increased DC charging flexibility, as described later herein with reference to Fig. 9 to 12.

[0086] Fig. 9 illustrates a basic concept of an electric drive system 1 according to another example, further comprising a DC charging terminal device 50 comprising a positive charging terminal and a negative charging terminal connected to the DC terminal side 21 of the inverter 20, i.e., the DC+ and DC- lines, via connection paths comprising controllable switches Ch+ and Ch-.

[0087] The DC charging connector 50 of the vehicle can be used, for example, to charge (or discharge) the electrical storage device 10 by means of an external charging station when the connector 50 is connected to such a charging station.

[0088] In the example shown, the inverter 20 and the electric motor 30 are connected in a delta configuration as an example of the electric drivetrain in a vehicle. This can also be modified.

[0089] In the Fig. 9, a connection arrangement 40 of the electric drive system 1 provides the following: a charging mode of the electric drive system 1, in which the first battery 11 or the second battery 12 or a series arrangement of the first battery 11 and the second battery 12 or a parallel arrangement of the first battery 11 and the second battery 12 is electrically coupled to the DC charging connection device 50 for supplying electrical energy via the DC charging connection device 50 to the respective battery or battery arrangement (serial arrangement or parallel arrangement), or vice versa.

[0090] For this purpose, in the example shown, the connection arrangement 40 - a connection path with a controllable switch SW1+ between the positive charging terminal (or switch Ch+ in the example) and the positive terminal of the first battery 11, - a connection path with a controllable switch SW1- between the negative charging terminal (or switch Ch- in the example) and the negative terminal of the first battery 11, - a connection path with a controllable switch SWs between the negative terminal of the first battery and the positive terminal of the second battery, - a connection path with a controllable switch SW2+ between the positive charging terminal and the positive terminal of the second battery 12 and - a connection path with a controllable switch SW2- between the negative charging terminal and the negative terminal of the second battery 12.

[0091] Since the DC charging terminal device 50 is connected to the electrical storage device 10 via the switches Ch+ and Ch- (for connecting / disconnecting the electrical storage device 10 to / from the DC charging terminal device 50), the switches Ch+ and Ch- must be closed in the charging mode.

[0092] Advantageously, with the Fig. 9, the two batteries 11, 12 may be connected / connected either in series or in parallel to perform the charging mode.

[0093] Namely, in case the switches SW1+, SWs, SW2- are closed and the switches SW1- and SW2+ are open, the batteries 11, 12 are connected in series and the DC link voltage (at the charging connection device 50) is the sum of the voltages of both batteries 11 and 12 (for example, 2 x 400 V = 800 V).

[0094] If switches SW1+, SW1-, SW2+, and SW2- are closed and switch SWs is open, the two batteries 11 and 12 are connected in parallel. In this case, the voltages of the two batteries 11 and 12 should be equal (for example, both 400 V).

[0095] This means that the electrical storage device 10 can supply two voltage levels to the DC link of the charging connection device 50 and can therefore advantageously be charged (or discharged) at different charging stations (providing, for example, 400 V or 800 V).

[0096] Having two batteries 11, 12 switched from series to parallel and vice versa is no trivial task. Balancing the batteries 11, 12 is essential, especially when switching from series to parallel. The states of charge (SoCs) of the two batteries must be more or less balanced before switching to parallel. Using state-of-the-art passive or active balancing techniques (within a battery pack forming a respective battery), this can take a long time, especially when small and inexpensive electronics are used to achieve such charge balancing. During charging of the two batteries, SoCs may deviate due to differences in internal resistance, capacity, and temperature. Even after a full charge, for example, one cannot directly connect two battery packs in parallel and drive the vehicle.A voltage mismatch between the two batteries can cause hazards and safety problems. Therefore, after charging (whether in series or parallel), balancing of batteries 11 and 12 must be achieved. This, however, takes time. To reduce the balancing time required, high-performance electronics can be used to allow high energy transfer between the two batteries. However, this will increase costs. To overcome these disadvantages of the prior art, a method based on the method described in . Fig. 9 shown concept, an electric drive system, as in Fig. 10 to 12 shown.

[0097] Fig. Fig. 10 shows an electric drive system 1 according to a sixth example, in which a DC charging connection device 50 is provided (as described above) and in which the winding arrangement 31 of the electric machine 30 is formed by several (three in the example) stator windings in delta configuration, as in the Fig. 9 shown (exemplary) basic concept.

[0098] However, the connection arrangement 40 in this sixth example ( Fig. 10) furthermore - a connection path with a controllable switch SW3 and a capacitor Csp between the negative line DC- of the DC connection side 21 of the inverter and a connection node C on the winding arrangement 31 and - a connection path with a controllable switch SW4 in one of the AC phase lines (V in the example), which connects a respective (V) AC phase terminal of the inverter 20 to a respective (V) connection node (“delta corner” in the delta configuration shown) of the winding arrangement 31, wherein the connection node C on the winding arrangement 31 is identical to the connection node of the winding arrangement 31 (since electrically connected).

[0099] In this case, in the transfer mode, by disconnecting an AC phase terminal (the AC phase line V in the example) of the electric machine 30 through the switch SW4 and connecting the additional capacitor Csp via the switch SW3 between the AC phase terminal of the electric machine and the battery assembly (batteries 11, 12), as shown in Fig. 10, the winding arrangement 31 and the inverter 20 can advantageously be used to preheat or balance the two batteries 11, 12 very quickly and efficiently.

[0100] Fig. 11 illustrates the driving mode of the Fig. 10. In drive mode (e.g., when the vehicle is being driven), switches SW1+, SW2-, SW5, and SW4 are closed, and switches Ch+, Ch-, SW1-, SW2+, and SW3 are open. Switch SW3 is open and switch SW4 is closed so as not to interrupt the normal (driving) operation of system 1.

[0101] Fig. 12 illustrates the transfer mode of the Fig. 10 shown electric drive system 1. In this transfer mode, the switches SW1+, SW1-, SW2+, SW2- and SW3 are closed and the switches Ch+, Ch-, SWs and SW4 are open.

[0102] This reconfiguration by appropriate control of the connection arrangement 40 allows the electric machine 30 and the inverter 20 to operate as a buck / boost DC / DC converter. In the example of Fig. 12, the first battery 11 is connected to the DC link side 21 of the inverter, and the second battery 12 is connected to the aforementioned AC phase connection (connection node C) of the electric machine. By adjusting the voltage operating point of the thus formed DC / DC converter, the control device 2 defines (in Fig. 12 not shown) the operating mode of the converter and the current flow direction, ie from the battery 11 to the battery 12 or vice versa.

[0103] The transfer mode can be executed, for example, after completion of a charging operation, such as fast charging, in which the electrical storage device 10 was charged while connected in series (or parallel) to the batteries 11, 12. After such a charging operation, the two batteries 11, 12 must be balanced before being connected / connected in parallel.

[0104] In a charging mode for charging / discharging the electrical storage device 10, the switches Ch+ and Ch- are closed. In this case, the switch SW3 is open and the switch SW4 is closed. Regarding the status of the remaining switches, reference is made to the above description of the concept with reference to Fig. 9. These switches can be connected differently depending on whether the batteries are to be connected in series or parallel in the charging mode.

[0105] In brief, the electric drive system 1 in the sixth example according to Fig. 10 to 12 depict an electric machine in a delta configuration, with two-phase operation being used in the transfer mode. However, it should be noted that single-phase operation would also be possible by disconnecting one of the inverter phase branches.

[0106] In all the examples described here, a control device such as in Fig. 1, for controlling the respective electric drive system 1. Such a control device can, for example, execute a control method comprising the following: - Receiving information (see c* in Fig. 1) representing an operating mode (including at least one driving mode and a transfer mode) of the drive system to be controlled, i.e., the received information may include a temperature of the first battery and / or the second battery. For example, if the temperature is below 15°C when the vehicle is started, preheating of the battery (transfer mode) is required. Preferably, the received information includes all of the information required to select the operating mode appropriate for the situation. - Selecting an operating mode of the drive system to be controlled according to the received information, - Controlling the controllable switches in the connection arrangement to provide the selected operating mode and - Controlling the inverter (or both inverters) to deliver a transfer of electrical energy according to the provided operating mode. Fig. Figure 13 is a flowchart illustrating an example of such a control method and the various operating modes of the drive system affected by this method. In this example, it is assumed that the control method provides the following: - a driving mode for supplying electrical energy from the electrical storage device 10, which comprises the batteries 11, 12, to the electric machine 30 (propulsion mode) or vice versa (recuperation mode), - a transfer mode for transferring electrical energy from the first battery 11 to the second battery 12 or vice versa, and a charging mode for supplying electrical energy from a DC charging terminal device 50 to the electrical storage device 10 (charging the electrical storage device 10) or vice versa (discharging the electrical storage device 10).

[0107] In Fig. 13, the procedure performed by the control device 2 begins at a step S1. In a subsequent step S2, a received information (such as c* in Fig. 1) is used to check whether the drive system 1 should be put into drive mode. If so, the procedure proceeds to step S3; otherwise, to step S4.

[0108] In step S3, the connection arrangement 40 is controlled such that the drive system 1 can be operated in the driving mode.

[0109] In the example for drive system 1 of Fig. 10 to 12, this means that switches SW1+, SW2-, SWs, and SW4 are closed, while switches SW1-, SW2+, SW3, Ch+, and Ch- are open. For the other examples, refer to the drive mode description given for each of these.

[0110] In step S4, a check is again made based on the received information to determine whether the drive system 1 should be put into charging mode. If so, the procedure proceeds to step S5; otherwise, it proceeds to step S6.

[0111] In step S5, the connection arrangement 40 is controlled such that the drive system 1 can be operated in the charging mode.

[0112] In the example for drive system 1 of Fig. For batteries 10 to 12, this means that switches SW1+, SW1-, SW2+, SW2-, SW4, Ch+, Ch- are closed, while switches SW5, SW3 are open when batteries 11, 12 are to be connected in parallel in charging mode. Of course, charging batteries 11, 12 connected in parallel is also possible (by controlling the switches accordingly).

[0113] In step S6, the connection arrangement 40 is controlled such that the drive system 1 can be operated in the transfer mode.

[0114] In the example for drive system 1 of Fig. 10 to 12, this means that switches SW1+, SW1-, SW2+, SW2-, and SW3 are closed, while switches SWs, SW4, Ch+, and Ch- are open. For the other examples, refer to the transfer mode description given for each of these.

[0115] Furthermore, in steps S3, S5 and S6, after the aforementioned respective control of the connection arrangement 40, the inverter 20 (or the inverters 20-1, 20-2 respectively) is / are operated accordingly in each case, so that the driving mode, the charging mode or the transfer mode is executed respectively.

[0116] When the driving mode is executed, the control device 2 can then control the inverter 20 (or the inverters 20-1, 20-2, respectively) and thus the transmission of electrical energy between the electrical storage device 10 and the electric machine 30 (or electric machines 30-1, 30-2, respectively), in particular depending on, for example, a position of an accelerator pedal of the respective vehicle (or depending on corresponding control data in the case of an autonomous vehicle).

[0117] When the charging mode is executed, the control device 2 can deactivate the inverter (or inverters) so that energy transfer occurs only between the storage device 10 and a charging connection device 50. For example, the charging mode can be aborted when a measured actual value of a state of charge, e.g., "SoC," of the storage device 10, reaches a setting value specified for charging operation.

[0118] When the transfer mode is executed for the purpose of balancing, the control device 2 can control the inverter (or inverters) and thus the energy transfer between the two batteries 11, 12 of the storage device 10, in particular depending on measured charge states and / or voltage levels of the two batteries 11, 12.

[0119] When executing the transfer mode for the purpose of preheating the storage device 10, the control device 2 controls the inverter (or inverters) for energy transfer back and forth between the two batteries 11, 12 until the preheating is completed. This can be assumed, for example, by the control device 2 after a predetermined period of preheating operation. Alternatively or additionally, the control device 2 can provide for termination of the transfer mode, for example, when a predetermined temperature has been reached in the area of ​​the storage unit 10 (e.g., equipped with at least one temperature sensor that communicates with the control device 2).

[0120] Fig. 14 shows an electric drive system 1 according to a seventh example, comprising an electrical storage device 10 with a first battery 11 and a second battery 12, a first and a second inverter 20-1, 20-2 and a first and a second electric machine 30-1, 30-2 according to a redundancy concept (as in the Fig. 7 shown fourth example).

[0121] In addition, the electric drive system includes 1 of Fig. 14 a DC charging connection device 50 and a connection arrangement 40 (as in the Fig. 10 shown sixth example).

[0122] The first and second electric machines 30-1, 30-2 are each configured with a star configuration, and this is described above with reference to Fig. The concept described in section 7 can be implemented without the need for switch SW3 ( Fig. 7).

[0123] In the case of Fig. In the electric drive system 1 shown in Figure 14, each inverter 20-1, 20-2 and each associated electric machine 30-1, 30-2 represents a buck / boost DC / DC converter. The two electric drives are connected via a switch SW4 to allow successive buck / boost DC / DC conversion. The electrical energy can be moved from one battery (11 or 12) to the other (12 or 11, respectively) very quickly and efficiently, basically in the same way as in the fourth example ( Fig. 7). This allows the two batteries 11, 12 to be heated very quickly and without the need for any additional device.

[0124] As in the other examples described here, reusing existing powertrain components in the vehicle enables battery self-heating (or balancing of the batteries).

[0125] In brief, the main idea of ​​this invention is to reuse some powertrain components (such as the HV inverter and electric machine(s)) in a vehicle by adding some switches (e.g., semiconductor switches or relays) to realize a special "transfer mode," for example, to achieve battery self-heating at standstill (while the vehicle is parked). This idea helps reduce the overall development costs and the total cost of ownership. The HV battery is divided into (at least) two batteries to allow back-and-forth power transfer between them. The invention can be adapted to various configurations (star-connected electric machine, delta-connected electric machine, powertrain with two electric drives, etc.) to allow energy transfer from one battery pack to the other. List of reference symbols: 1 electric drive system 2 Control device 10 Electrical storage device 11 first battery 12 second battery 20 bidirectional multiphase inverters 21 DC connection side (of the inverter) 22 AC connection side (of the inverter) 30 multi-phase AC electric machine 31 Winding arrangement (of the electric machine) 40 Connection arrangement 50 DC charging connector

Claims

[1] Electric drive system (1), comprising: - an electrical storage device (10) comprising a first battery (11) and a second battery (12), - a controllable bidirectional multi-phase inverter (20) having a DC connection side (21) and an AC connection side (22), - a multi-phase AC electric machine (30) comprising a winding arrangement (31) electrically coupled to the AC connection side (22) of the inverter (20), - a connection arrangement (40) comprising electrical connection paths with controllable switches (SW1+, SW1-, SWs, SW2+, SW2-, SW3, SW4, SW5, SW6) for establishing and interrupting electrical connections for providing - a driving mode of the electric drive system (1), in which the first battery (11) or the second battery (12) or a serial arrangement of the first battery (11) and the second battery (12) or a parallel arrangement of the first battery (11) and the second battery (12) is electrically coupled to the DC connection side (21) of the inverter (20) for supplying electrical energy from the respective battery or battery arrangement via the inverter (20) to the electric machine (30) or vice versa and - a transfer mode of the electric drive system (1), in which the first battery (11) is electrically coupled to the DC connection side (21) of the inverter (20) and the second battery (12) is electrically coupled to the winding arrangement (31) of the electric machine (30), for transferring electrical energy from the first battery (11) via the inverter (20) and the winding arrangement (31) to the second battery (12) or vice versa. [2] Drive system (1) according to claim 1, wherein the DC connection side (21) of the inverter (20) comprises a positive terminal of the inverter (20) and a negative terminal of the inverter (20), and the AC connection side (22) of the inverter (20) comprises a plurality of AC phase terminals, wherein the inverter (20) comprises a plurality of series connections each comprising an upper switch connected to the positive terminal and a lower switch connected to the negative terminal of the inverter (20), with a respective one of the AC phase terminals of the inverter (20) being formed therebetween. [3] Drive system (1) according to claim 1 or 2, wherein the electric machine (30) is a synchronous machine in which the winding arrangement (31) of the electric machine (30) is formed by a plurality of stator windings of the electric machine (30). [4] Drive system (1) according to one of the preceding claims, wherein the connection arrangement (40) comprises: - a connection path with a controllable switch (SW1+) between a positive terminal of the first battery (11) and a positive terminal of the inverter (20), - a connection path with a controllable switch (SW1-) between a negative terminal of the first battery (11) and a negative terminal of the inverter (20), - a connection path with a controllable switch (SWs) between the negative terminal of the first battery (11) and a positive terminal of the second battery (12), - a connection path with a controllable switch (SW2+) between a positive terminal of the second battery (12) and a connection node on the winding arrangement (31), - a connection path with a controllable switch (SW2-) between a negative terminal of the second battery (12) and the negative terminal of the inverter (20), - a connection path with a controllable switch (SW3) and a capacitor (Csp) between the negative terminal of the second battery (12) and the connection node on the winding arrangement (31). [5] Drive system (1) according to claim 4, wherein the winding arrangement (31) of the electric machine (30) is formed by a plurality of stator windings in a star configuration, and wherein the connection node on the winding arrangement (31) is the star point of the star configuration. [6] Drive system (1) according to claim 4, wherein the winding arrangement (31) of the electric machine (30) is formed by a plurality of stator windings in a star configuration, wherein the connection arrangement (40) further comprises a controllable switch (SW4) in a phase line connecting one of the AC phase terminals of the inverter (20) to a respective one of the stator windings of the electric machine (30), and wherein the connection node on the winding arrangement (31) is a node on the phase line between the controllable switch (SW4) and the respective stator winding. [7] Drive system (1) according to claim 4, wherein the winding arrangement (31) of the electric machine (30) is formed by a plurality of stator windings in delta configuration, wherein the connection arrangement (40) further comprises a controllable switch (SW4) in a phase line connecting one of the AC phase terminals of the inverter (20) to a respective connection node of the winding arrangement (31), and wherein the connection node on the winding arrangement (31) is the connection node of the winding arrangement (31). [8] Drive system (1), comprising - an electrical storage device (10) comprising the first battery (11) and the second battery (12), - a first and a second controllable bidirectional multi-phase inverter (20-1, 20-2), each having a DC connection side (21) and an AC connection side (22), - a first and a second multi-phase AC electric machine (30-1, 30-2), each comprising a winding arrangement (31) electrically coupled to the AC connection side (22) of a respective one of the first and second inverters (20-1, 20-2), - a connection arrangement (40) comprising electrical connection paths with controllable switches (SW1+, SW1-, SWs, SW2+, SW2-, SW3, SW4, SW5, SW6) for establishing and interrupting electrical connections for providing - a driving mode of the electric drive system (1), in which the first battery (11) is electrically coupled to the DC connection side (21) of the first inverter (20-1), for supplying electrical energy from the first battery (11) via the first inverter (20-1) to the first electric machine (30-1) or vice versa, and in which the second battery (12) is electrically coupled to the DC connection side (21) of the second inverter (20-2), for supplying electrical energy from the second battery (12) via the second inverter (20-2) to the second electric machine (30-2) or vice versa, - the transfer mode of the electric drive system (1), in which the first battery (11) is electrically coupled to the DC connection side (21) of the first inverter (20-1) and the second battery (12) is electrically coupled to the DC connection side (21) of the second inverter (20-2), so that the second battery (12) is electrically coupled indirectly, via the second inverter (20-2) and the winding arrangement (31) of the second electric machine (30-2), to the winding arrangement (31) of the first electric machine (30-1), for transmitting electrical energy from the first battery (11) via the first inverter (20-1), the winding arrangement (31) of the first electric machine (30-1), the winding arrangement (31) of the second electric machine (30-2) and the second inverter (20-2) to the second battery (12), or vice versa. [9] Drive system (1) according to claim 8, wherein the connection arrangement (40) comprises: - a connection path, optionally with a controllable switch (SW1+) between a positive terminal of the first battery (11) and a positive terminal of the first inverter (20-1), - a connection path, optionally with a controllable switch (SW1-) between a negative terminal of the first battery (11) and a negative terminal of the first inverter (20-1), - a connection path, optionally with a controllable switch (SW2+) between a positive terminal of the second battery (12) and a positive terminal of the second inverter (20-2), - a connection path, optionally with a controllable switch (SW2-) between a negative terminal of the second battery (12) and a negative terminal of the second inverter (20-2), - a connection path, optionally with a controllable switch (SW3) between the negative terminal of the first inverter (20-1) and the negative terminal of the second inverter (20-2), - a connection path with a controllable switch (SW4) between a connection node on the winding arrangement (31) of the first electric machine (30-1) and a connection node on the winding arrangement (31) of the second electric machine (30-2). [10] Drive system (1) according to claim 9, wherein the winding arrangements (31) of the first and the second electric machine (30-1, 30-2) are each formed by a plurality of stator windings in a respective star configuration, and wherein the connection nodes on the winding arrangements (31) are each the star point of the respective star configuration. [11] Drive system (1) according to claim 9, wherein the winding arrangements (31) of the first and second electric machines (30-1, 30-2) are each formed by a plurality of stator windings in a respective star configuration, wherein the connection arrangement (40) further comprises a controllable switch (SW5) in a phase line connecting one of the AC phase terminals of the first inverter (20-1) to a respective one of the stator windings of the first electric machine (30-1), wherein the connection arrangement (40) further comprises a controllable switch (SW6) in a phase line connecting one of the AC phase terminals of the second inverter (20-2) to a respective one of the stator windings of the second electric machine (30-2), and wherein the connection nodes on the winding arrangements (31) are each a node on the phase line between the respective controllable switch (SW5, SW6) and the respective stator winding. [12] Drive system (1) according to one of the preceding claims, further comprising a DC charging terminal device comprising a positive charging terminal and a negative charging terminal, wherein the connection arrangement (40) further provides: - a charging mode of the electric drive system (1) in which the first battery (11) or the second battery (12) or a series arrangement of the first battery (11) and the second battery (12) or a parallel arrangement of the first battery (11) and the second battery (12) is electrically coupled to the DC charging connection device for supplying electrical energy from the DC charging connection device to the respective battery or battery arrangement, or vice versa. [13] Drive system (1) according to claim 12, wherein the connection arrangement (40) comprises: a connection path with a controllable switch (SW1+) between the positive charging terminal and the positive terminal of the first battery (11), - a connection path with a controllable switch (SW1-) between the negative charging terminal and the negative terminal of the first battery (11), - a connection path with a controllable switch (SW2+) between the positive charging terminal and the positive terminal of the second battery (12), - a connection path with a controllable switch (SW2-) between the negative charging terminal and the negative terminal of the second battery (12), [14] Control device for controlling an electric drive system (1) according to one of the preceding claims, comprising: - a communication interface for receiving information representing an operating mode of the drive system (1) to be controlled, - a selection module for selecting an operating mode of the drive system (1) to be controlled according to the received information, - a switch control module for controlling the controllable switches (SW1+, SW1-, SWs, SW2+, SW2-, SW3, SW4, SW5, SW6) of the connection arrangement (40) to provide the selected operating mode and - an inverter control module for controlling the inverter (20) to provide a transmission of electrical energy according to the provided operating mode. [15] Control method for controlling an electric drive system (1) according to one of the preceding claims, comprising: - receiving information representing an operating mode of the drive system (1) to be controlled, - selecting an operating mode of the drive system (1) to be controlled according to the received information, - controlling the controllable switches (SW1+, SW1-, SWs, SW2+, SW2-, SW3, SW4, SW5, SW6) of the connection arrangement (40) to provide the selected operating mode and - controlling the inverter (20) to provide a transfer of electrical energy according to the provided operating mode. [16] A computer program comprising instructions which, when executed by a computer, cause the computer to perform the method of claim 15.

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