Method for operating drive device of motor vehicle, drive device and computer program product

Abstract

The invention relates to a method for operating a power transmission device (2) of a motor vehicle, the power transmission device (2) having a power battery (1) comprising a plurality of cell modules (3) and a power unit designed as a power motor, the power unit being electrically connected to electrical connections (4, 5) of the power battery (1) via a converter, the cell modules (3) can be electrically connected in different ways between the connection ends (4, 5). According to the invention, the cell modules (3) are divided into battery modules (6), each comprising the same number of cell modules (3) electrically connected in parallel and electrically connected in series between the connections (4, 5), the number of battery modules (6) being adapted during operation of the drive unit (2) such that the voltage present at the connections (4, 5) corresponds at least to the operating voltage of the drive motor. The invention further relates to a drive device (2) for a motor vehicle and to a computer program product.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for operating a drive train of a motor vehicle, wherein the drive train has a power battery comprising a plurality of cell modules and a power unit designed as a power electric machine, the power unit being electrically coupled to electrical connection terminals of the power battery via a converter, wherein the cell modules can be electrically connected / wired in different ways between the connection terminals. Furthermore, the invention relates to a drive train for a motor vehicle and to a computer program product. BACKGROUND

[0002] For example, the document DE 10 2019 212 860 A1 is known from the prior art. This document describes a battery system for a motor vehicle, wherein for the battery components of the battery system a switching unit is respectively provided, which is adapted to determine one of a plurality of possible connection schemes / wiring schemes between the battery components depending on its respective switching state, wherein a processor device is adapted to switch the respective switching state of the switching unit of at least one of the battery components into a predetermined target state, in a shift register for the respective battery component, a predetermined enable level is respectively adjusted at a Flip Flop output end of the shift register assigned to one of the battery components by means of an enable signal, and a predetermined blocking level is adjusted at every remaining Flip Flop output end, and a selection signal for the target state is generated in at least one common selection line.

[0003] Furthermore, the document DE 10 2021 119 607 A1 discloses an energy storage device having at least one connection terminal for coupling the energy storage device to an electrical grid and a cell for storing energy and a cell contact device, the cell contact device being adapted to connect the cell to the at least one connection terminal. It is provided here that the cell contact device is designed as a multilayer cell contact device, wherein the multilayer cell contact device has at least one layer system for a respective voltage level, wherein the at least one layer system comprises at least one respective conductor layer for connecting the cell to the at least one connection terminal of the energy storage device, the multilayer cell contact device has a switching device having a control unit and a plurality of actuatable switching units, wherein the control unit is adapted to connect the cell to the respective layer system in one of at least two predetermined circuit configurations of the switching units in order to provide the respective voltage level in the at least one layer system. SUMMARY

[0004] It is an object of the invention to propose a method for operating a drive train of a motor vehicle, which has advantages compared to known methods, in particular enables a continuous provision of as high a drive train drive power as possible.

[0005] According to the application, this is achieved by a method for operating a powertrain of a motor vehicle having the features of claim 1. It is provided here that the electric cell modules are divided into battery modules, which each comprise an identical number of electrically parallel electric cell modules and are electrically connected in series between connection terminals, wherein the number of battery modules is adjusted during operation of the powertrain such that the voltage present at the connection terminals is not lower than the operating voltage of the electric motor.

[0006] Advantageous embodiments of the application and suitable extensions thereof are given in the dependent claims. It is pointed out that the examples set forth in the description are not restrictive; rather, any variant of the features disclosed in the description, claims and drawings is possible.

[0007] The method serves to operate a powertrain. The powertrain is set up and designed for driving a motor vehicle, i.e. for providing a drive torque which is intended to drive the motor vehicle. In order to provide the drive torque, the powertrain has a power unit in the form of an electric motor. Preferably, the powertrain is an integral part of the motor vehicle, but of course can also exist independently of the motor vehicle, in particular before the powertrain is installed on or in the motor vehicle.

[0008] The electric motor is electrically coupled to the power battery, i.e. via a converter. The electric motor is operated at least temporarily using electrical energy extracted from the power battery. Conversely, it can be provided that electrical energy provided in the use of the electric motor is stored in the power battery at least temporarily. The converter serves to convert a direct current provided by the power battery into an alternating current for the electric motor, or conversely to convert an alternating current provided by means of the electric motor into a direct current supplied to the power battery. Preferably, the converter is designed as a pulse-controlled / pulse-width-modulated converter.

[0009] The power battery has a plurality of electric cell modules which are electrically connected between the electrical connection terminals of the power battery. An electric cell module is understood to mean a power battery element which comprises at least one electric cell of the power battery, respectively. In this regard, each electric cell module has at least one electric cell of the plurality of electric cells of the power battery. Preferably, each electric cell module has a plurality of electric cells, in particular an identical number of electric cells. For example, the electric cells of each electric cell module are electrically connected in series with one another. Preferably, each electric cell module comprises at least 10, in particular at least 30 or at least 50 electric cells, in particular electric cells in series.

[0010] The cell modules can be electrically connected between the two connection terminals of the traction battery in different ways. For example, it can be provided that a part of the cell modules is connected electrically in series between the connection terminals and another part is connected electrically in parallel. By means of the different connection schemes of the cell modules between the connection terminals, different voltages can be provided at the cell modules. In the case of a series connection of the cell modules, a higher voltage is achieved than in the case of a parallel connection.

[0011] The drive power of the electric motor depends to a large extent on the voltage of the current provided by the traction battery on the electrical connection terminals. This voltage can also be referred to as the battery voltage. The battery voltage, in turn, depends on the voltage of the individual cell modules or individual cells. Since the voltage of the cell modules and the corresponding battery voltage changes as a function of the state of charge of the traction battery, the available drive power available for driving the motor vehicle by means of the electric motor also changes. In particular, the drive power decreases significantly as the state of charge of the traction battery decreases.

[0012] In general, the cell modules are electrically connected between the connection terminals in such a way that, in the case of a fully charged traction battery, i.e. in the case of a state of charge of approximately or almost 100%, the battery voltage corresponds to the rated voltage of the electric motor. Starting from the rated power of the electric motor provided in the case of the rated voltage, the drive power of the electric motor decreases as the state of charge decreases, for example to a maximum of 50%, a maximum of 40% or a maximum of 30% of the rated power. This is perceived as uncomfortable by the user of the motor vehicle.

[0013] For this reason, it is provided in accordance with the application that the cell modules are divided into battery modules. That is, each cell module is assigned to one of the battery modules, so that each battery module ultimately contains at least one of the cell modules. The use of the term "battery modules" in the plural does not mean that the battery modules are quantified, but rather that there can be any number of battery modules, i.e. for example there can be one battery module or a plurality of battery modules. The term "battery modules" therefore stands for at least one battery module, preferably a plurality of battery modules.

[0014] The division of the cell modules into battery modules is such that each battery module contains the same number of cell modules. The cell modules of each battery module are electrically connected in parallel. In contrast, the battery modules are electrically connected in series between the connection terminals, so that the battery voltage corresponds to the sum of the individual voltages of the battery modules. The division of the cell modules into battery modules and the connection of the cell modules between the connection terminals takes place during the operation of the drive train. That is, it can be provided that, during the operation of the drive train, the cell modules are electrically connected to one another in different ways between the connection terminals, so that sometimes a first connection of the cell modules is established and sometimes a second connection.

[0015] The cell modules are divided into battery modules and the respective connections between the cell modules in the battery modules and between the battery modules are established in such a way that a voltage which at least corresponds to the operating voltage of the electric machine, i.e. for example exactly corresponds to the operating voltage or is higher than the operating voltage, is present at the connection end. The operating voltage of the electric machine is understood to mean the voltage which is currently used or should be used for operating the electric machine. For example, the operating voltage is preset by a controller of the drive train.

[0016] It is particularly preferred that the cell modules are divided into battery modules and are electrically connected in such a way that the operating voltage at least corresponds to the rated voltage of the electric machine, in particular independently of the state of charge of the traction battery. This means that, during operation of the drive train, the cell modules are divided into battery modules in accordance with the state of charge in such a way that a voltage which at least corresponds to the rated voltage of the electric machine is thereby present at the connection end.

[0017] Before the cell modules are divided into battery modules, the number of battery modules is determined. Here, the number of battery modules is selected in such a way that the required voltage is achieved at the connection end, i.e. for example the voltage at least corresponds to the operating voltage of the electric machine or at least corresponds to the rated voltage of the electric machine. By the described approach, it is ensured that, at least partially independently of the state of charge of the traction battery, a high driving power can be provided using the traction machine.

[0018] An improved embodiment of the application provides that the number of battery modules is selected in such a way that the voltage present at the connection end is in a voltage range which includes the operating voltage, wherein the voltage range is bounded in the direction of a lower voltage by a first threshold value and in the direction of a higher voltage by a second threshold value. The voltage range includes the operating voltage of the electric machine, bounded on the one hand by the first threshold value and on the other hand by the second threshold value. For example, the operating voltage is in the centre of the voltage range, i.e. is the intermediate value between the first threshold value and the second threshold value. In addition to the operating voltage, the voltage range can also include the rated voltage of the electric machine.

[0019] The number of cell modules into which the cell modules are divided is determined in such a way that the voltage provided at the connection end, i.e. the battery voltage, is in the voltage range. Preferably, the voltage range is constant during operation of the drive train, i.e. the two threshold values likewise remain constant. It is preferably provided that, in the case of a battery voltage which is in the voltage range, the connection scheme of the traction battery is not changed and the number of battery modules remains unchanged. In the case of a battery voltage which is below the first threshold value, the number of battery modules is adjusted or changed, i.e. is adjusted or changed in such a way that the battery voltage is increased.

[0020] The number of battery modules is thus selected and the cell modules are thus divided into battery modules such that the battery voltage is increased. In particular, the number of battery modules is thus selected such that the battery voltage is greater than a first threshold value but less than a second threshold value. The change in the number of battery modules thus ultimately results in the battery voltage again being in the voltage range. The voltage range comprises, for example, a voltage difference which corresponds to at least 30%, at least 40% or at least 50% and / or at most 70%, at most 60% or at most 50% of the rated voltage of the electric machine. The use of this voltage range enables the number of battery modules to be selected flexibly and a voltage to be achieved which is sufficient for the electric machine to be operated.

[0021] An improved embodiment of the application provides that, in order to adjust the number of battery modules, one of a plurality of connection variants of the battery modules is selected and set on the traction battery, wherein, in a first connection variant of the connection variants, the number of battery modules corresponds to a first number of battery modules and the number of cell modules per battery module corresponds to a first number of cell modules, and in a second connection variant of the connection variants, the number of battery modules corresponds to a second number of battery modules which differs from the first number of battery modules and the number of cell modules per battery module corresponds to a second number of cell modules which differs from the first number of cell modules.

[0022] The connection variants correspond to different electrical connection variants of the battery modules between the connection terminals of the traction battery and accordingly also to different numbers of battery modules. In the first connection variant, there are the first number of battery modules and in each battery module there are the first number of cell modules, and in the second connection variant, there are the second number of battery modules and in each battery module there are the second number of cell modules. The total number of cell modules thus always remains the same, the product of the first number of battery modules and the first number of cell modules being equal to the product of the second number of battery modules and the second number of cell modules. At a given state of charge, different voltages are achieved between the connection terminals by means of the different numbers of battery modules.

[0023] One refinement of the application provides that, as one of the connection variants, a third connection variant is used in which the number of battery modules corresponds to a third battery module number and the number of cell modules per battery module corresponds to a third cell module number, wherein the third battery module number differs not only from the first battery module number but also from the second battery module number and the third cell module number differs not only from the first cell module number but also from the second cell module number. There are thus at least three different connection variants from which one connection variant is selected and which is set on the traction battery. The traction battery is thus sometimes operated in the first connection variant, sometimes in the second connection variant and sometimes in the third connection variant. Particularly high flexibility is thereby achieved and the required battery voltage is reliably achieved.

[0024] One refinement of the application provides that the number of battery modules is determined depending on the state of charge of the traction battery and / or the discharge current of the traction battery. It has been shown that the voltage between the connection terminals is inter alia related to the state of charge. However, in addition, a correlation with the discharge current can also be present. In particular, the greater the discharge current at which the traction battery is discharged in order to operate the electric traction machine, the lower the voltage. In this regard, by determining the number of battery modules depending on the state of charge and / or the discharge current, it is ensured that the voltage present on the connection terminals at least corresponds to the operating voltage of the electric traction machine.

[0025] One refinement of the application provides that, in the case of a state of charge within a first state of charge range, a first connection variant is selected as the connection variant and, in the case of a state of charge within a second state of charge range adjoining the first state of charge range, a second connection variant is selected as the connection variant, wherein the voltage in the first connection variant in the case of a state of charge corresponding to a range boundary of the first state of charge range facing the second state of charge range is proportional to the voltage in the second connection variant in the case of a state of charge corresponding to a range boundary of the second state of charge range facing the first state of charge range, the proportionality corresponding to the proportion of the first battery module number to the second battery module number.

[0026] The two state of charge ranges, namely the first state of charge range and the second state of charge range, directly adjoin one another, such that the (first) range boundary of the first state of charge range facing the second state of charge range directly adjoins the (second) range boundary of the second state of charge range, which delimits the second state of charge range on its side facing the first state of charge range. The first connection variant is used in the case of a state of charge within the first state of charge range and the second connection variant is used in the case of a state of charge within the second state of charge range.

[0027] A first battery voltage exists in the case that the state of charge corresponds to the first range limit and a second battery voltage exists in the case that the state of charge corresponds to the second range limit. The two connection variants are chosen such that the first voltage and the second voltage are in such a ratio to one another that this ratio corresponds to the ratio of the first number of battery modules to the second number of battery modules. In this regard, the connection variants do not lead to a significant jump in the voltage present at the connection end, but rather provide the voltage in accordance with the described rules. Thereby, a reliable operation of the powertrain is ensured.

[0028] An improvement of the application provides that the number of battery modules is chosen at least temporarily such that the voltage present at the connection end is greater than the rated voltage of the electric machine, and the inverter is operated such that the output voltage of the inverter is at most equal to the rated voltage. This means that the battery voltage provided by the traction battery, which represents the output voltage of the inverter, is reduced at least temporarily in the case of use of the inverter, i.e. at least to the rated voltage of the electric machine.

[0029] For example, it is provided that the number of battery modules is chosen at least temporarily such that the battery voltage is at least 30%, at least 40% or at least 50% greater than the rated voltage. Preferably, the number of battery modules in the different connection variants is chosen such that the battery voltage is greater than the rated voltage, in particular by exactly one of the aforementioned percentages. Nonetheless, a reliable operation of the electric machine in its technical conditions is achieved by means of the inverter, so that a sufficiently high driving power is ensured by the different connection variants of the cell modules, regardless of the state of charge of the traction battery.

[0030] Furthermore, the application relates to a powertrain for a motor vehicle, in particular for carrying out the method according to the embodiments in the scope of the description, wherein the powertrain has an electric machine comprising a plurality of cell modules and a power unit designed as the electric machine, the power unit being electrically coupled via an inverter to an electrical connection end of a traction battery, wherein the cell modules can be electrically connected in different ways between the connection ends.

[0031] The powertrain is provided and designed such that the cell modules are divided into battery modules, the battery modules each comprising the same number of electrically parallel connected cell modules and being electrically connected in series between the connection ends, wherein the number of battery modules is adjusted during operation of the powertrain such that the voltage present at the connection end is at least equal to the operating voltage of the electric machine.

[0032] The advantages of this type of approach or this type of design of the powertrain have already been indicated. Not only the powertrain for a motor vehicle but also the method for its operation can be improved in accordance with the explanations made in the scope of the description, reference being made to these explanations.

[0033] Furthermore, the present application relates to a computer program product comprising commands which cause a powertrain to perform the explained method according to the embodiments of the description. For the advantages and possible advantageous refinements, full reference is made to the description.

[0034] The features and feature combinations described in the description, in particular in the description of the following figures, and / or shown in the figures can be used not only in the respectively indicated combinations, but also in other combinations or individually, without leaving the scope of the present application. Therefore, embodiments which are not explicitly shown or explained in the description and / or the figures, but which can be derived or inferred from the explained embodiments, are also considered to be included in the present application. BRIEF DESCRIPTION OF DRAWINGS

[0035] The present application is explained below on the basis of embodiments shown in the figures without restricting the present application. Herein,

[0036] Figure 1 A schematic representation of a part of a powertrain for a motor vehicle, i.e. a power battery, is shown for three different connection schemes of the cell modules. DETAILED DESCRIPTION

[0037] Figure 1 A highly schematic representation of a power battery 1 is shown, which is a component of a powertrain 2 of a motor vehicle. Herein, the power battery 1 is shown for three different connection schemes of the cell modules 3, i.e. a first connection scheme is shown on the far left, a second connection scheme is shown in the middle, and a third connection scheme is shown on the far right. Also, the electrical connection terminals 4 and 5 of the power battery are only shown very schematically, by means of which the cell modules 3 provide a voltage between the electrical connection terminals.

[0038] The cell modules are divided into battery modules 6, wherein, by way of example, there are two battery modules in the first connection scheme, three battery modules 6 in the second connection scheme, and four battery modules 6 in the third connection scheme. Exemplarily, a total of 12 cell modules 3 are shown, which are always all divided into battery modules 6, i.e. divided in such a way that each battery module 6 has the same number of cell modules 3. The cell modules 3 of each battery module 6 are electrically parallel to one another in the battery module. While the battery modules 6 are electrically serial to one another between the connection terminals 4 and 5. Accordingly, a different battery voltage of the power battery 1 between the connection terminals 4 and 5 results in the case of the same voltage of the cell modules 3.

[0039] Different connection schemes are used at different states of charge of the traction battery, so that a battery voltage is achieved which is sufficiently large to supply the traction motor of the drive device 2 with a sufficiently large operating voltage, despite the different states of charge and the different voltages of the cell modules 3 resulting therefrom. Overall, by means of the approach sketched here, it is ensured that a similar voltage is always provided for operating the traction motor, despite the different states of charge.

[0040] List of reference signs

[0041] 1 traction battery

[0042] 2 drive device

[0043] 3 cell module

[0044] 4 connection

[0045] 5 connection

[0046] 6 battery module

Claims

1. A method for operating a powertrain (2) for a motor vehicle, wherein, The powertrain (2) has a power battery (1) comprising a plurality of cell modules (3) and a power unit designed as a power electric machine, the power unit being electrically coupled to electrical connection terminals (4, 5) of the power battery (1) via a converter, wherein the cell modules (3) can be electrically connected in different ways between the connection terminals (4, 5), characterized in that the cell modules (3) are divided into battery modules (6), the battery modules each comprising the same number of electrically parallel cell modules (3) and being electrically connected in series between the connection terminals (4, 5), wherein the number of battery modules (6) is adapted during operation of the powertrain (2) such that the voltage present at the connection terminals (4, 5) corresponds at least to the operating voltage of the power electric machine.

2. The method of claim 1, wherein, The number of battery modules (6) is selected such that the voltage present at the connection terminals (4, 5) lies in a voltage range comprising the operating voltage, the voltage range being delimited in the direction of lower voltages by a first threshold value and in the direction of higher voltages by a second threshold value.

3. The method according to any of the preceding claims, characterized in that, In order to adapt the number of battery modules (6), one of a plurality of connection variants of the battery modules (6) is selected and set at the power battery (1), wherein in a first connection variant the number of battery modules (6) corresponds to a first battery module number and the number of cell modules (3) per battery module (6) corresponds to a first cell module number, and in a second connection variant the number of battery modules (6) corresponds to a second battery module number different from the first battery module number and the number of cell modules (3) per battery module (6) corresponds to a second cell module number different from the first cell module number.

4. The method according to any of the preceding claims, characterized in that, As one of the connection variants, a third connection variant is used in which the number of battery modules corresponds to a third battery module number and the number of cell modules per battery module (6) corresponds to a third cell module number, wherein the third battery module number differs both from the first battery module number and from the second battery module number and the third cell module number differs both from the first cell module number and from the second cell module number.

5. The method according to any of the preceding claims, characterized in that, The number of battery modules (6) is determined depending on the state of charge of the power battery (1) and / or the discharge current of the power battery (1).

6. The method according to any of the preceding claims, characterized in that, In the case of a state of charge lying in a first state of charge range, the first connection variant is selected as the connection variant, and in the case of a state of charge lying in a second state of charge range adjoining the first state of charge range, the second connection variant is selected as the connection variant, wherein the voltage in the first connection variant in the case of a state of charge corresponding to the range boundary of the first state of charge range facing the second state of charge range is proportional to the voltage in the second connection variant in the case of a state of charge corresponding to the range boundary of the second state of charge range facing the first state of charge range, the proportion corresponding to the proportion of the first battery module number to the second battery module number.

7. The method according to any of the preceding claims, characterized in that, The number of battery modules (6) is selected at least for a short time such that the voltage present at the connection terminals (4, 5) is greater than the rated voltage of the electric machine, and the inverter is operated such that the output voltage of the inverter corresponds at most to the rated voltage.

8. The method according to any of the preceding claims, characterized in that, A sodium-ion battery is used as the traction battery (1).

9. A powertrain (2) for a motor vehicle, in particular for carrying out the method according to any one of the preceding claims, wherein The powertrain (2) has a traction battery (1) comprising a plurality of cell modules (3) and a power unit designed as an electric machine, which is electrically coupled to the electrical connection terminals (4, 5) of the traction battery (1) via an inverter, wherein the cell modules (3) can be electrically connected in different ways between the connection terminals (4, 5), characterized in that the powertrain (2) is designed and configured to divide the cell modules (3) into battery modules (6), which each comprise the same number of electrically parallel-connected cell modules (3) and are electrically connected in series between the connection terminals (4, 5), wherein the number of battery modules (6) is adapted during operation of the powertrain (2) such that the voltage present at the connection terminals (4, 5) corresponds at least to the operating voltage of the electric machine.

10. Computer program product comprising commands which cause the powertrain (2) according to claim 9 to carry out the method according to any one of claims 1 to 8.

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