VEHICLE TRACTION SYSTEM

Description

[0001] The invention relates to a drive system for a vehicle, in particular for a rail vehicle.

[0002] Rail vehicles are predominantly powered by electrical energy from overhead lines. Since this is not possible on some routes, diesel propulsion can be used. However, this is undesirable due to pollutant and particulate emissions, so traction batteries are used instead. Hybrid vehicle traction systems eg for railways enable the use of electrical energy from the overhead line or alternatively from a traction battery.

[0003] Due to the high power requirements, battery-based traction systems typically use medium-voltage (MV) voltages. This requires that the battery voltage level, which is typically in the low-voltage (LV) range, be adapted to the intermediate circuit of the traction system.

[0004] A rail vehicle that does not have such a hybrid vehicle traction system is described in JP2001145201A. This system has a control power supply system that, in the event of a power failure in the overhead line, supplies DC loads such as an operational protection device and a brake control device using electrical storage devices.

[0005] The invention is based on the object of demonstrating an improved drive system for a vehicle.

[0006] This object is achieved by a drive system having the features of claim 1. Furthermore, the invention relates to advantageous uses of the drive system.

[0007] The drive system for a vehicle according to the invention comprises a first subsystem with a first electrical energy storage device and a first DC intermediate circuit, as well as a second subsystem with a second electrical energy storage device and a second DC intermediate circuit. Each DC intermediate circuit supplies at least one motor. The first DC intermediate circuit is connected to the first energy storage device via a battery controller such that the voltage level of the first DC intermediate circuit is higher than that of the first energy storage device, and the voltage level of the second DC intermediate circuit is equal to that of the second energy storage device.

[0008] The drive system is particularly suitable for larger rail vehicles such as trains. However, it can also be used for other larger drives, such as mining vehicles or stationary industrial applications.

[0009] The drive is provided – at least among other things, i.e., other forms of energy supply can also be provided – by means of electrical energy storage devices. These are preferably accumulators, i.e., rechargeable batteries that store energy in electrochemical form.

[0010] The drive system is divided into a first and a second subsystem. Both have a DC link from which one or more motors are supplied with electrical energy. The motors can be connected to the DC link in the conventional way using converters. The voltage levels of the two DC link circuits differ from each other. This is made possible by the fact that the first subsystem has a battery controller located between the first energy storage device and the DC link of the first subsystem, which is not required in the second subsystem. The battery controller is preferably a DC / DC converter, i.e. a DC-DC converter.

[0011] There is therefore a more powerful and a less powerful drive subsystem. This makes it possible to combine the advantages of both subsystems in one drive system. The first subsystem can indeed provide higher power than the second subsystem; however, this is accompanied by a higher outlay on the components required. Compared to a drive system with two powerful subsystems, money, space and weight are saved. Compared to a drive system with two less powerful subsystems, which is suitable for vehicle types such as trams, the drive system according to the invention can deliver significantly higher power and is therefore suitable for other applications.

[0012] Preferably, the voltage level of the first DC link is medium voltage, and the voltage level of the second DC link is low voltage. Low voltage refers to DC voltages up to 1500 volts, and medium voltage refers to 1500 volts and above.

[0013] The two electrical energy storage devices preferably each provide low voltage. The dimensions of the two energy storage devices can be the same or different. For example, the energy storage device of the first subsystem can provide a higher voltage than that of the second subsystem.

[0014] When the drive system is used in a rail vehicle, the first DC link can supply a first motor of a first motor bogie and a first motor of a second motor bogie, and the second DC link can supply a second motor of the first motor bogie and a second motor of the second motor bogie. This enables an evenly distributed power output to the two motor bogies.

[0015] It is particularly advantageous if, in addition to the components already mentioned, the first subsystem also has a filter choke and a braking controller, and the second subsystem has no battery controller, no filter choke, and preferably no braking controller either. This enables a simpler, more cost-effective, and more space-saving design of the second subsystem compared to the first subsystem.

[0016] In a further development of the invention, a circuit arrangement is provided with which, for driving the vehicle, the second DC intermediate circuit can be connected selectively to the first or the second electrical energy storage device, and at the same time the first DC intermediate circuit can be connected to the other electrical energy storage device via the battery controller. This corresponds to the possibility of switching the responsibilities of the energy storage devices for supplying energy to the two subsystems. By switching between the responsibilities, an identical or similar discharge of the two energy storage devices can be achieved. Alternatively, it is also possible for either the first or the second DC intermediate circuit to be connected to both the first and the second electrical energy storage device. This enables a higher power output from the DC intermediate circuit that is supplied simultaneously by both energy storage devices.Alternatively, it is also possible for both DC intermediate circuits—the first DC intermediate circuit via the battery controller and the second DC intermediate circuit—to be connected to both energy storage systems simultaneously. The latter is a situation in which both energy storage systems operate both subsystems in parallel.

[0017] This circuit arrangement enables the following operation of the drive system according to the invention: when the vehicle initially accelerates from a standstill or near standstill, the power is delivered to the motor(s) by the first and second subsystems, preferably to the same or almost the same extent, and / or when accelerating further after the initial acceleration of the vehicle, the power is delivered to the motor(s) to a greater extent by the first subsystem, and / or when the vehicle is traveling at a constant speed or with a low power output, this power is delivered to the motor(s) exclusively or almost exclusively by the second subsystem.

[0018] Alternatively or in addition to the circuit arrangement described for driving the vehicle, a circuit arrangement for charging the two electrical energy storage devices can also be provided, with which the following four states can be set as desired: 1) only the first electrical energy storage device is charged, i.e. the first energy storage device is charged simultaneously via the first and second DC intermediate circuits, or 2) only the second electrical energy storage device is charged, i.e. the second energy storage device is charged simultaneously via the first and second DC intermediate circuits, or 3) each DC intermediate circuit is responsible for charging one energy storage device, i.e. the first electrical energy storage device is charged via the first DC intermediate circuit and at the same time the second electrical energy storage device is charged via the second DC intermediate circuit, or vice versa, or 4) both DC intermediate circuits are responsible for charging both energy storage devices at the same time, i.e. the first and second electrical energy storage devices are charged simultaneously via the first and second DC intermediate circuits.

[0019] This circuit arrangement enables the following preferred operation of the drive system according to the invention: First, in a first step, the first electrical energy storage device is charged via the first DC intermediate circuit and, at the same time, the second electrical energy storage device is charged via the second DC intermediate circuit, or vice versa. Then, in an optional second step, only one of the electrical energy storage devices is charged, i.e. either the first or the second electrical energy storage device simultaneously via the first and the second DC intermediate circuit. Finally, in a third step, the first and the second electrical energy storage device are charged simultaneously via the first and the second DC intermediate circuit.

[0020] Alternatively, you can proceed as follows: In a first step, only one of the electrical energy storage devices is charged, i.e. either the first or the second electrical energy storage device simultaneously via the first and the second DC intermediate circuit, and then, in a second step, the first and the second electrical energy storage devices are charged simultaneously via the first and the second DC intermediate circuit.

[0021] The invention is explained in more detail below using an exemplary embodiment. The following shows: Figure 1: a rail vehicle, Figure 2: a traction system according to the prior art, Figure 3: a traction system according to an embodiment of the invention, Figure 4: a schematic representation of the traction system of the Figure 3, Figures 5a, b: a cross-connection of traction subsystems to batteries, Figure 6: a temporal progression of tractive force and power of a traction system, Figure 7: a connection of traction subsystems to batteries, Figures 8a to 8d: various charging situations.

[0022] Figure 1shows a rail vehicle with two mechanical traction drive components in the form of motor bogies TDG1 and TDG2. The two motors M1 and M2 are located on the front motor bogie TDG1, and the two motors M3 and M4 are located on the rear motor bogie TDG2, which drive the respective wheel sets. The rail vehicle, e.g. a train, has a hybrid vehicle traction system. This means that the rail vehicle can be supplied with electrical energy via current from the overhead line on the one hand, and from traction batteries on the other. For this purpose, the traction battery BAT1 is located near the motor bogie TDG1, and the traction battery BAT2 is located near the motor bogie TDG2.

[0023] The use of battery-powered trains is advantageous because they can replace diesel vehicles, which would otherwise be used on non-electrified lines. This avoids the undesirable pollutant emissions of diesel vehicles. Battery-powered electric traction has similar characteristics to diesel traction, namely high tractive effort with relatively low power. This corresponds to the possibility of rapid acceleration and traveling at a moderately high constant speed after acceleration. This requirement is placed on many regional trains that run on remote, non-electrified lines where high speeds are not possible.

[0024] Figure 2shows a schematic diagram of a traction system for such a rail vehicle according to the state of the art. The supply network, which can be based on direct current (DC) or alternating current (AC), as well as the pantograph and associated components of the rail vehicle, are collectively referred to as NET. The railway network can, for example, operate at a voltage level of 15 or 25 kV, which the rail vehicle's transformer steps down to the intermediate circuit voltage.

[0025] To increase clarity, both in Figure 2 Both in the following figures, the single-line diagram representation is used. In this representation, multiple power lines are represented as a single line; for example, the three lines supplying the motors are replaced by a single line.

[0026] The BAT 1 and BAT 2 traction battery systems typically have a voltage level of less than 1000V. This is achieved by connecting 2-3V cells in series. These individual cells are stacked so that the output voltage of the BAT 1 and BAT 2 traction battery systems is in the LV (low voltage) range. Since the LV standard range, which extends up to a maximum of 1.5 kV, is suitable for batteries for service and safety purposes—this correlates, for example, with the requirements for the skilled personnel required for service and repair and the required insulation class—this dimensioning of the traction batteries is preferred.

[0027] Instead of the BAT 1 and BAT 2 traction battery systems, other types of energy storage devices can also be used. High-performance capacitors, for example, are possible options.

[0028] The hybrid vehicle traction system of the Figure 2, which is particularly suitable for railways, but also for larger vehicles such as special trucks, e.g. dump trucks used in mining, comprises two medium-voltage systems MV-SYS. Both have a DC intermediate circuit DC-ZK, the voltages of which are 2 kV, for example. This higher voltage than the battery voltage is necessary to prevent excessively high currents from occurring due to the high power required. For this reason, the battery voltage level, which, as described, lies in the low-voltage range, is adapted to the intermediate circuit DC-ZK of the traction subsystem. This stepping up of the direct voltage provided by the batteries BAT1 or BAT2 is carried out by means of the battery controller BAT-STELL. This is usually a DC / DC converter, via which the intermediate circuit DC-ZK of the drive is connected to the battery BAT1 or BAT2.

[0029] Further components of the MV-SYS medium-voltage systems are the filter chokes with smoothing capacitor FT for smoothing the current ripple, which are necessary in conjunction with the BAT-STELL battery controller, as well as the B-STELL brake controller, which are used to destroy excess energy, for example during transient processes or during braking, the E-STELL input controllers, such as 4-quadrant controllers, which bring the feed-in voltage supplied by the current collector to the voltage level of the DC intermediate circuit DC-ZK, as well as the M-CONV motor converters, such as PWR (pulse inverters), which provide the AC voltage required by the motors.

[0030] According to the state of the art, two identical traction subsystems are available in the form of the two MV systems (MV-SYS). The left of the two systems supplies the two motors M1 and M2 of one motor bogie, and the right of the two systems supplies the two motors M3 and M4 of another motor bogie. The two MV systems (MV-SYS) can jointly provide traction for the rail vehicle, and in the event of a failure, either of them is sufficient.

[0031] Other components not relevant for understanding the invention, such as the absorption circuit choke, input filter, intermediate circuit capacitance, are not shown for reasons of clarity. Figure 2 and the following figures.

[0032] Figure 3 shows an embodiment of the invention. The same components are the same as in Figure 2 In contrast to Figure 2The second traction subsystem is not an MV system, but the LV system LV-SYS. Compared to the MV system MV-SYS, the LV system LV-SYS can only provide lower power levels. These lower power levels enable the DC-ZK intermediate circuit of the LV system LV-SYS to be operated at the voltage level of the BAT2 battery. For example, the DC-ZK intermediate circuit of the LV system LV-SYS can be operated at 0.8 kV, while the voltage level of the DC-ZK intermediate circuit of the MV system MV-SYS is 2 kV. This allows the voltage level in the MV system MV-SYS to be Figure 2explains that the BAT-STELL battery controller with the FT filter element is no longer required in the LV-SYS system. The BAT-STELL battery controller is typically an expensive component, which also results in electrical energy losses of up to 3% during operation with each energy conversion. Furthermore, space must be provided for the BAT-STELL battery controller with the FT filter element, and they increase the overall weight and therefore indirectly contribute negatively to increasing the acceleration mass and driving resistance. Furthermore, the B-STELL brake controller is also not required. The component costs saved by not requiring the aforementioned components are on the order of magnitude of the M-CONV motor converter.

[0033] As already mentioned, the Low Voltage System LV-SYS is not operated at the same power levels as the Medium Voltage System MV-SYS. This is because the lower voltage of the intermediate circuit DC link of the LV-SYS system would otherwise result in excessively high currents. This allows the components of both traction subsystems to be designed for the same maximum current, e.g., 500 or 700 A. However, the components of the LV-SYS system can be designed for lower voltages, which is why they can be technically simpler and more cost-effective than those of the MV-SYS system.

[0034] In Figure 3 The LV system LV-SYS and the MV system MV-SYS are connected to the traction motors in such a way that in each motor bogie, one motor is powered by the MV system MV-SYS and another motor is powered by the LV system LV-SYS. This has the advantage that the tractive effort and power are the same in each of the two motor bogies.

[0035] The traction system of the Figure 3 is schematically in Figure 4 Thus, a combination of an LV system (LV-SYS) and an MV system (MV-SYS) is envisaged as the drive for a rail vehicle. Both subsystems can generate a similarly high tractive force when starting, e.g., 75 kN per motor, but with different power outputs, e.g., 0.5 MW per motor for operation with the MV system (MV-SYS) and 0.3 MW per motor for operation with the LV system (LV-SYS).

[0036] The energy storage units BAT1 and BAT2 assigned to the LV system LV-SYS and the MV system MV-SYS can be dimensioned in different sizes to meet the different energy requirements of the traction subsystems. Alternatively or additionally, the batteries BAT1 and BAT2 can be assigned alternately to the two traction subsystems LV-SYS and MV-SYS by providing cross-connections between the systems. This is illustrated in the two schematic diagrams of the Figure 5 shown: In Figure 5a The switches that enable the cross-connection of batteries BAT1 and BAT2 to the two traction subsystems LV-SYS and MV-SYS are open. In this way, each battery BAT1 or BAT2 supplies the system assigned to it, i.e., battery BAT1 supplies the MV-System MV-SYS and battery BAT2 supplies the LV-System LV-SYS. Figure 5bHowever, these switches are closed. In this way, each battery BAT1 or BAT2 supplies the other system, i.e., battery BAT2 supplies the MV system MV-SYS and battery BAT1 supplies the LV system LV-SYS. This configuration according to Figure 5 allows for a uniform discharge of the two energy storage devices BAT1 and BAT2. It is also possible to Figure 5a and 5b close all switches. In this case, both batteries BAT1 and BAT2 operate both systems in parallel; this corresponds to the charging situation that will later lead to Figure 8d is explained.

[0037] Figure 6shows an example of the temporal progression of tractive effort F and power P. In the first phase, the rail vehicle accelerates, in the second phase it travels at a constant speed, and in the third phase it brakes until the rail vehicle comes to a standstill. The line F-LV-SYS shows the tractive effort generated by the LV system, the line F-MV-SYS shows the tractive effort generated by the MV system, and the line F-TOTAL shows the total tractive effort, which corresponds to the sum of the two tractive forces F-LV-SYS and F-MV-SYS of the LV system and the MV system. Furthermore, the line P-LV-SYS shows the power output or input by the LV system, and the line P-MV-SYS shows the power output or input by the MV system.

[0038] Regarding the distribution of tractive effort between the LV system and the MV system, it can be seen that during acceleration, the high tractive effort at low speeds is provided by both systems. Once the maximum deliverable power is reached, as indicated by the horizontal shape of the power curves during the acceleration phase, the rail vehicle continues to accelerate at this maximum power. The same applies to power consumption during deceleration. When traveling at a constant speed, the power and tractive effort can be provided exclusively by the LV system to balance the energy output of the batteries.The plan is therefore to provide the high tractive force at low speeds with the LV system and the MV system together, then to cover the traction requirement at high power during further acceleration predominantly with the MV system, and when driving at a constant speed only or mainly with the LV system. When driving at a constant speed, neither high tractive force nor high power is required, so the LV system alone is sufficient. In the partial load range, the LV system can therefore be subjected to greater strain, so that different energy levels (state of charge) of the batteries are balanced out due to the greater power output during acceleration by the MV system. This is because in the previous full load range, the MV system performed better than the LV system, so its battery was drained more rapidly.

[0039] During "steady-state operation," a different approach to the one described above can be used. This operation corresponds to driving at a constant speed, or generally to driving at low power levels where the high tractive effort required during acceleration is not required. This does not necessarily have to be driving at a constant speed, but also applies to gentle acceleration or even sharp acceleration downhill. In this case of driving at partial load, it may be advantageous, as described above, to cover the traction requirement with the LV system if possible, since it lacks loss-generating components such as the battery regulator (BAT-STELL) and the filter element (FT) when powered from the energy storage system. However, this difference does not apply when driving with power from the grid. Furthermore, it can be considered whether the LV system or the MV system has the better efficiency at the partial load point.Furthermore, other criteria may also play a role that justify a different distribution of the load between the LV system and the MV system during steady-state operation, such as (spontaneous) thermal differences. Using primarily or exclusively the LV system during partial load operation is therefore only one possible option, which can be used in particular for battery leveling, i.e., balancing the battery charge levels.

[0040] Since the MV system delivers significantly higher power during the acceleration phase than the LV system, it is advantageous to design the motors connected to the MV system with higher power than those supplied by the LV system.

[0041] When dividing traction and power according to Figure 6 This is an example. Different allocations are possible. In particular, the allocation according to Figure 6in the event that the batteries of the MV system and the LV system are of the same design and charge. Accordingly, in the event of a deviation from the distribution of the Figure 6 the charge level of the batteries of the LV system and the MV system must be taken into account.

[0042] The charging process is explained in more detail below.

[0043] As with the interconnection principle of the Figure 7 As shown, the energy storage units can also be redistributed for the charging process only. This connection is suitable for cases where there are not enough cross connections in the form of busbars or cables between the traction subsystems possible or practical. With this simple connection according to Figure 7 It is therefore not possible to achieve a simultaneous cross-connection of both energy storage units to the other traction subsystem. The various interconnection principles of the Figure 7possible switching states for charging purposes are shown in the Figure 8a to 8d shown.

[0044] Alternatively to Figure 7 The more complex wiring according to Figure 5 This - not in Figure 8 shown - enables a simultaneous cross-connection of both energy storage units to the respective other traction subsystem. This can be advantageous, for example, if battery BAT2 requires more energy than battery BAT1, so that battery BAT2 can be charged by the MV system MV-SYS, which provides a higher feed-in power, and battery BAT1 can be charged by the LV system LV-SYS, which provides a lower feed-in power.

[0045] The Figure 8a , 8b , 8c and 8dshow four different charging situations with different power levels. The MV system MV-SYS enables faster battery charging compared to the LV system LV-SYS, e.g., with a power of 1 MW for the MV system MV-SYS compared to 0.6 MW for the LV system LV-SYS. This different power consumption is in Figure 8 symbolized by the arrows of different thicknesses that lead to the batteries.

[0046] Figure 8a shows the case where the MV system MV-SYS charges the battery BAT 1 assigned to it, and at the same time the LV system LV-SYS charges the battery BAT 2 assigned to it. Figure 8b shows the case where both the MV system MV-SYS and the LV system LV-SYS charge the battery BAT 2 assigned to the LV system LV-SYS, and Figure 8c shows the case where both the MV system MV-SYS and the LV system LV-SYS charge the battery BAT 1 assigned to the MV system MV-SYS.

[0047] According to Figure 8b The energy storage unit BAT 2 assigned to the LV system LV-SYS can be temporarily charged by the more powerful MV system MV-SYS with the lower power of the LV charging system, thus supplying more energy than the ratio of the dimensions of the two charging devices (MV / LV). This is achieved by controlled connection or disconnection of the batteries to the partial traction systems. Conversely, as in Figure 8c As shown, the battery system BAT1 can be charged by the LV system LV-SYS in case it requires more charging energy. Figure 8b and 8c show how the energy levels of the battery systems BAT1 and BAT2 can be adjusted. This serves to prepare the Figure 8d As an alternative to voltage level compensation, the Figure 8b and 8c the possibility of fully charging one of the battery systems BAT1 or BAT2 as quickly as possible.

[0048] If the voltages of the two battery systems are equalized, it is Figure 8d It is also possible to charge both batteries simultaneously without having to separate the two traction subsystems MV-SYS and LV-SYS using the switch. This equal charging distribution can generally only be carried out if the voltages of the two battery systems BAT1 and BAT2 are uniform, either already or as a result of previous charging phases. The total charging power in the constellation of Figure 8d is set by controlling the battery controller BAT-STELL of the MV system MV-SYS and the input controller E-STELL of the LV system LV-SYS.

[0049] The flexible assignment of batteries and charging systems is advantageous because the differences between the two traction subsystems, MV-SYS and LV-SYS, result in different behavior regarding battery discharge. However, if two MV systems or two LV systems were present, this difference in battery discharge would not be significant. The difference may also be due to the fact that the two batteries are not designed the same.

[0050] Generally, it is desirable to achieve the fastest possible charging of all battery packs. Since excessively high currents are generally not desired, an even distribution of the charging power among the batteries is generally advisable. Therefore, an allocation to the charging devices based on the current charge level of the batteries proves advantageous. Rapid charging of both batteries can be achieved, for example, by first charging according to Figure 8a Both batteries can be charged simultaneously. To equalize the voltage levels of the batteries or to quickly charge one battery, the batteries can also be charged individually according to Figure 8b or Figure 8c be loaded.

[0051] Once the battery voltages are equalized, a uniform charge according to Figure 8d After one of the two batteries has been fully charged, the remaining battery that is not yet fully charged can be charged according to Figure 8b or 8c Alternatively, the batteries can generally not be charged in parallel, but one after the other, i.e. first according to Figure 8b and subsequently according to Figure 8c or vice versa.

[0052] As in the Figure 5 and 7As shown, different allocations or assignments of batteries to traction subsystems are possible, both in terms of battery power output and battery charging. Switching between the different assignments should be performed with or near-de-energized, e.g., when stopping at a station.

[0053] The invention has been described above using an exemplary embodiment. It is understood that numerous changes and modifications are possible without departing from the scope of the invention, which is defined in the claims.

Claims

1. Drive system for a vehicle, comprising a first subsystem (MV-SYS) having a first electrical energy store (BAT1) and a first DC link (DC-ZK), a second subsystem (LV-SYS) having a second electrical energy store (BAT2) and a second DC link (DC-ZK), wherein each DC link (DC-ZK) respectively supplies power to at least one traction motor (M1, M2, M3, M4), wherein the motors are connected to the DC links by means of converters, wherein the voltage level of the two DC links (DC-ZK) differs from one to the other and the first subsystem (MV-SYS) can provide a higher power than the second subsystem (LV-SYS), wherein the first DC link (DC-ZK) is connected to the first energy store (BAT1) via a battery actuator (BAT-STELL) in such a way that the voltage level of the first DC link (DC-ZK) is higher than that of the first energy store (BAT1), and the voltage level of the second DC link (DC-ZK) is equal to that of the second energy store (BAT2).

2. Drive system according to Claim 1, in which the voltage level of the first DC link (DC-ZK) corresponds to a medium voltage, and the voltage level of the second DC link (DC-ZK) corresponds to a low voltage.

3. Drive system according to either of Claims 1 and 2, in which the first (BAT1) and second (BAT2) electrical energy stores each provide low voltage.

4. Drive system according to one of Claims 1 to 3, in which the first DC link (DC-ZK) supplies power to a first traction motor (M1) of a first drive bogie (TGD1) and to a first traction motor (M3) of a second drive bogie (TGD2) of a rail vehicle, and the second DC link (DC-ZK) supplies power to a second traction motor (M2) of the first drive bogie (TGD1) and to a second traction motor (M4) of the second drive bogie (TGD2).

5. Drive system according to one of Claims 1 to 4, wherein the first subsystem (MV-SYS) comprises: a filter inductor (FT) and a brake actuator (B-STELL), and the second subsystem (LV-SYS) does not comprise: a battery actuator (BAT-STELL) and a filter inductor (FT).

6. Drive system according to one of Claims 1 to 5, having a circuit arrangement with which, in order to drive the vehicle, the second DC link (DC-ZK) is optionally able to be connected to the first (BAT1) or the second (BAT2) electrical energy store, and the first DC link (DC-ZK) is able to be simultaneously connected to the respective other electrical energy store (BAT1, BAT2) via the battery actuator (BAT-STELL).

7. Drive system according to one of Claims 1 to 5, having a circuit arrangement with which, in order to drive the vehicle, alternatively the second DC link (DC-ZK) is able to be connected to the first (BAT1) and the second (BAT2) electrical energy store simultaneously, or the first DC link (DC-ZK), via the battery actuator (BAT-STELL), is able to be connected to the first (BAT1) and the second (BAT2) electrical energy store simultaneously, or the first DC link (DC-ZK), via the battery actuator (BAT-STELL), and the second DC link (DC-ZK) are able to be connected to the first (BAT1) and the second (BAT2) electrical energy store simultaneously.

8. Drive system according to one of Claims 1 to 7, having a circuit arrangement with which, in order to charge the two electrical energy stores (BAT1, BAT2), optionally - the first electrical energy store (BAT1) is charged via the first DC link (DC-ZK) and the second DC link (DC-ZK) simultaneously, or - the second electrical energy store (BAT2) is charged via the first DC link (DC-ZK) and the second DC link (DC-ZK) simultaneously, or - the first electrical energy store (BAT1) is charged via the first DC link (DC-ZK) and the second electrical energy store (BAT2) is charged via the second DC link (DC-ZK) simultaneously, or - the first electrical energy store (BAT1) is charged via the second DC link (DC-ZK) and the second electrical energy store (BAT2) is charged via the first DC link (DC-ZK) simultaneously, or - the first and second electrical energy stores (BAT1, BAT2) are charged via the first and the second DC link (DC-ZK) simultaneously.

9. Use of a drive system according to Claim 8, wherein - firstly, the first electrical energy store (BAT1) is charged via the first DC link (DC-ZK) and the second electrical energy store (BAT2) is charged via the second DC link (DC-ZK) simultaneously, - optionally, the first (BAT1) or the second (BAT2) electrical energy store is then charged via the first DC link (DC-ZK) and the second DC link (DC-ZK) simultaneously, and - afterwards, the first and second electrical energy stores (BAT1, BAT2) are charged via the first and the second DC link (DC-ZK) simultaneously.

10. Use of a drive system according to Claim 8, wherein - firstly, the first (BAT1) or the second (BAT2) electrical energy store is charged via the first DC link (DC-ZK) and the second DC link (DC-ZK) simultaneously, and - afterwards, the first and second electrical energy stores (BAT1, BAT2) are charged via the first and the second DC link (DC-ZK) simultaneously.

11. Use of a drive system according to one of Claims 1 to 8, wherein when the vehicle is initially accelerated, the power output to the one or more traction motors (M1, M2, M3, M4) is provided by the first (MV-SYS) and the second (LV-SYS) subsystem, and / or as the vehicle continues to accelerate, the power output to the one or more traction motors (M1, M2, M3, M4) is provided to a greater extent by the first subsystem (MV-SYS), and / or when the vehicle is driven at a constant speed or in the case of a low power output, this power output to the one or more traction motors (M1, M2, M3, M4) is provided exclusively by the second subsystem (LV-SYS).