DE102022106043A1 - Battery state-of-charge-dependent power requirement in a method for operating a hybrid vehicle powertrain, computer-readable storage medium and hybrid vehicle powertrain - Google Patents

Abstract

The invention relates to a method for operating a hybrid vehicle drive train (1), comprising at least one internal combustion engine (2), a (first) electrical machine (3) that can be operated as a motor and as a generator if necessary, and an electrical drive machine/second electrical machine (6), a (high-voltage -) Battery (9) and a control device (10) with power electronics, the energy source and the energy share provided by the selected energy source being selected for the drive depending on the current battery state of charge (SOC) of the (high-voltage) battery (9). . The invention also relates to a computer-readable storage medium and a hybrid vehicle drive train (1) in which the method according to the invention is implemented.

Description

The invention relates to a method for operating a hybrid vehicle drive train, comprising at least one internal combustion engine, a (first) electric machine that can be operated as a motor and as a generator if necessary, an optional clutch and an electric drive machine/second electric machine, a (high-voltage) battery and a control unit with a Power electronics.

In the case of hybrid-powered vehicles, the question arises as to the efficient distribution of the drive power during operation: For example, what proportion of the power required by the driver should be provided by the internal combustion engine and what proportion by the electric drive unit? An improvement should also be developed using the example of a multimode hybrid drive.

A multimode hybrid drive is characterized by the fact that, in addition to the purely electric mode (EV operation), the serial mode (serial mode) and the parallel mode (parallel mode) are also available. In purely electric mode, a clutch is opened and the vehicle is powered by the electric drive motor and the energy is provided exclusively by the (high-voltage) battery. In serial mode, the vehicle is also powered by the electric drive machine/second electric machine; the energy required is provided by both the (high-voltage) battery and the (first) electric machine/generator, whereby this (first) electric machine/generator is driven by the internal combustion engine. It should be emphasized that the first electrical machine is then operated as a generator.

In parallel mode, the clutch is closed and the drive energy is provided both by the (high-voltage) battery and directly by the internal combustion engine. The first electric machine does not deliver any power and is often operated in freewheeling mode for efficiency reasons.

Up to now, it has been common practice to plan the power requirement digitally, i.e. to use the electric drive machine exclusively and thus to supply the energy exclusively from the (high-voltage) battery until the battery state of charge (SOC) has fallen so low that further operation of the electric drive machine/second electric machine is no longer possible or efficient and the internal combustion engine must take over further operation. An alternative to this is to always cover a constant proportion of the required power by the electric drive machine and the rest by the internal combustion engine. However, this is quite inflexible and inefficient.

The object of the invention is to eliminate or at least mitigate the disadvantages of the prior art.

This is solved according to the invention by selecting, on the one hand, the energy source and, on the other hand, the energy share provided by the selected energy source for the drive, i.e. the electric drive machine and/or the internal combustion engine, depending on the current battery state (SOC) of the (high-voltage) battery .

A strategy for power distribution in a hybrid drive train is now presented, which prefers purely electric driving when the battery charge level is high, whereas operation of the internal combustion engine is increasingly preferred when the battery charge level is low.

1. 1. das Verhältnis der rein elektrischen Fahranteile zu verbrennerunterstützten Fahranteilen ändert sich abhängig vom SOC und somit langsam und kontinuierlich. Für den Fahrer gibt es keinen harten Übergang zwischen dem elektromotorischen und dem verbrennungsmotorischen Fahren, wie dies momentan jedoch bei so genannten Range Extendern der Fall wäre.
2. 2. Durch die SOC-abhängige Belastung der Batterie stabilisiert sich der SOC am Ende eines Zyklus (zum Beispiels WLTP; World Wide Harmonized Light-Duty Vehicles Test Procedure) unabhängig von dem Startwert des SOC's am Anfang des Zyklus.

In other words, the invention consists in defining a continuous battery charge-dependent (SOC-dependent) characteristic curve which, as a result, provides a percentage K _{of battery share} . This percentage is multiplied by the maximum battery power P _BattMax that should be available. The advantage of such a characteristic curve consists of two points:

1. 1. The ratio of purely electric driving components to combustion-assisted driving components changes depending on the SOC and therefore slowly and continuously. For the driver, there is no hard transition between electric motor and combustion engine driving, as would currently be the case with so-called range extenders.
2. 2. Due to the SOC-dependent load on the battery, the SOC stabilizes at the end of a cycle (for example WLTP; World Wide Harmonized Light-Duty Vehicles Test Procedure) regardless of the starting value of the SOC at the beginning of the cycle.

Advantageous embodiments are claimed in the subclaims and are explained in more detail below.

It is therefore advantageous if both the internal combustion engine and the (high-voltage) battery are selected as the energy source between a minimum battery state of charge limit and a maximum battery state of charge limit. In this way, if the combustion power machine is switched on, the energy of which is used either for direct propulsion, namely by branching off as mechanical energy, and / or as an energy supplier by operating the first electrical machine and either storing it in the (high-voltage) battery or for feeding the electric drive machine / second electric machine. A variety of energy-efficient operating modes can then be implemented.

In order to be able to react particularly well to customer requirements, it has proven to be positive if the minimum battery charge state limit value is 20% +/-2.5% or +/-5% of the maximum possible battery charge state and/or as the maximum Battery charge state limit value 95% +/-2.5% or +/-5%, preferably exactly 100% of the maximum possible battery charge state is selected. Through such a needs-based definition of the minimum battery state of charge limit values and/or the maximum battery state of charge limit values, the expected driving behavior can be specifically influenced.

A further embodiment is also characterized in that a fixed/constant ratio between the two energy sources is selected between the minimum battery state of charge limit and the maximum battery state of charge limit or, depending on the exact battery state of charge value, according to a linear and/or staggered and/or progressive and/or or degressive and/or exponential function the ratio between the two energy sources is selected.

In order to be well prepared for cross-country journeys and inner-city traffic, it is advantageous if operation in parallel or serial mode is selected. In principle, it is also conceivable to operate the first electrical machine in parallel operation in freewheeling mode.

It is advantageous if the first electrical machine is operated in generator mode in serial mode.

Furthermore, it is expedient if the first electric machine is operated in motor mode in parallel mode.

It is also advantageous if one of the clutches is closed in parallel mode.

The invention also relates to a computer-readable storage medium arranged and prepared for carrying out control and/or regulation steps for enforcing said method.

The invention also relates to a hybrid vehicle drive train with an internal combustion engine and a first electric machine / first electric machine assigned to it, which is prepared for motor and generator operation and an electric drive machine / second electric machine / second electric machine that can be connected, for example via a clutch, further comprising a control device with power electronics and a computer-readable storage medium and a (high-voltage) battery, the computer-readable storage medium being set up and prepared for executing control and / or regulation steps to enforce the method according to the invention.

• 1 einen schematischen Aufbau eines Hybridfahrzeugantriebsstrangs gemäß der Erfindung,
• 2 ein Steuer- / Regelungsdiagramm gemäß einer ersten Ausführungsform des erfindungsgemäßen Verfahrens,
• 3 ein weiteres Steuer- / Regelungsdiagramm zum Durchführen des erfindungsgemäßen Verfahrens einer zweiten Ausführungsform,
• 4 ein weiteres Diagramm zum Erklären des Ablaufs des erfindungsgemäßen Verfahrens, und
• 5 ein weiteres Diagramm zum Belegen einer weiteren Steuer- / Regelstrategie gemäß einer weiteren Ausführungsform.

The invention is explained in more detail below with the aid of a drawing. Show it:

• 1 a schematic structure of a hybrid vehicle drive train according to the invention,
• 2 a control/regulation diagram according to a first embodiment of the method according to the invention,
• 3 a further control/regulation diagram for carrying out the method according to the invention of a second embodiment,
• 4 another diagram to explain the sequence of the method according to the invention, and
• 5 a further diagram to demonstrate a further control/regulation strategy according to a further embodiment.

The figures are only of a schematic nature and only serve to understand the invention. The same elements are given the same reference numbers.

In the 1 a hybrid vehicle drive train 1 according to the invention is shown. There is an internal combustion engine 2, a first electrical machine 3 that can be operated as a motor and as a generator, and a transmission 4 arranged between them. After an (optional) clutch 5, an electric drive machine 6 and a transmission 7 connect to a wheel 8 to be driven. There is also a (high-voltage) battery 9, which is connected to a control unit 10 with power electronics. The control unit is connected to the first electrical machine 3 and the electrical drive machine 6.

In 2 the SOC% value is entered on the abscissa, where the abscissa is referenced with the reference number 11. The ordinate is referenced with the reference numeral 12 and indicates the battery share (K _{battery share} ).

The solid stepped line 13 indicates the control curve/control curve.

In the range from 70% to 100% SOC, only the (high-voltage) battery 9 is used to propel the vehicle. Below 20% SOC, only the internal combustion engine is used for propulsion. Between 20% and 70% SOC, a consistent distribution of the internal combustion engine driving force and the battery driving force is selected. An area 14 shows the internal combustion engine drive area and the area 15 shows the battery drive area.

The SOC minimum value is referenced by reference number 16, and the SOC maximum value is referenced by reference number 17. Different than in 2 and the regulation/control strategy there, according to the embodiment 3 The same ratio of internal combustion engine driving force to battery driving force is not always used, but a linearly changing ratio is selected.

The SOC minimum value thus corresponds to a minimum battery state of charge limit and the SOC maximum value 17 corresponds to a maximum battery state of charge limit.

In the diagrams of the 4 and 5 The SOC% value 11 is again entered on the abscissa, but the power in kW is entered on the ordinate. The ordinate is therefore referenced with the reference number 18.

In the 3 Performance characteristics are shown for speeds below V _VehParMin . So the minimum speed V _VehParMin is relevant there. A characteristic curve P _Max is provided with the reference number 19. The line P _ICESR is marked with reference number 20.

P _BattMaxVLow is identified by reference number 21. The line P _BattMaxVHigh is marked with reference number 22. The P _PARMax marked with the reference number 23 also lies on this line. The line P _target is marked with reference number 24. There is also the line P _ICEPAR , which is referenced with the reference number 25. The reference numbers 11 and 18 to 25 are also in 5 used.

In 4 Performance characteristics are shown with respect to the minimum speed. The characteristic curve 19 represents the maximum possible performance, which is made up of the maximum battery and combustion engine performance (in serial mode). The maximum performance of the internal combustion engine in serial and parallel modes differ from each other because the engine speed in serial mode is freely selectable (clutch is open), while in parallel mode it is tied to the vehicle speed (clutch 5 is closed). For low SOC values, i.e. when the charge state of the battery is very low, the P _Max characteristic curve 19 must be reduced so that it is below the maximum internal combustion engine engine power and so that operation of the vehicle is only possible with the internal combustion engine, without it To take power from the battery 9. The characteristic curve 21 corresponds to the already described characteristic curve K _{Battery proportion} x P _BattMax . If the drive power P _target 24 required by the driver is below the characteristic curve P _BattMaxVLow 21, then the EV mode becomes active, otherwise the serial mode is activated.

If the vehicle speed exceeds the limit of V _VehParMin , then the parallel mode can also be activated and thus the performance characteristics are chosen as shown in 5 shown. Furthermore, if the power P _target 24 required by the driver is below the P _BattMaxVHigh 22 characteristic curve, then the EV mode is activated and the electric drive machine 6 will draw its power exclusively from the battery 9 and the internal combustion engine 2 will remain off.

If the power required by the driver is between the characteristics 23 and 22, for example by increasing the required drive power, then the parallel mode is activated. The internal combustion engine 2 is started and after the rotational speed of the two electric machines 3 and 6 has been synchronized, the clutch 5 is closed. The torque of the internal combustion engine 2 should always be at the most efficient point; the battery power creates the balance between the driver's desired drive power P _target 24 and the power of the internal combustion engine P _ICEPAR set for efficiency reasons. For P _target greater than P _ICEPAR 25, the battery 9 supplies the additional power required; for P _target 24 smaller than P _ICEPAR 25, the excess power of the internal combustion engine 2 is stored in the battery 9. The first electric machine 3 does not deliver any power in this mode and is operated in freewheeling mode for efficiency reasons.

Since the drive power in parallel mode can always be generated more efficiently than in serial mode due to the elimination of losses in the first electrical machine 3, parallel mode should always be preferred over serial mode, unless the power requirement is too high or the state of charge is too low Battery 9 doesn't allow it. If the driver demands so much power that the battery power does not limit the performance of the Internal combustion engine can be covered in parallel mode, the serial mode must be activated, in which the performance of the internal combustion engine is greater than in parallel mode due to the free rotation speed determination.

Reference symbol list

1

Hybrid vehicle powertrain

2

Internal combustion engine

3

first electric machine

4

transmission

5

coupling

6

electric drive machine

7

transmission

8th

wheel

9

(High-voltage) battery

10

Control unit

11

SOC% value

12

K _{battery share}

13

Regulation/control curve

14

Internal combustion engine drive area

15

Battery drive area

16

SOC minimum value

17

SOC maximum value

18

Performance / Power

19

P _Max

20

P _ICESER

21

P _BattMaxVLow

22

P _BattMaxVHigh

23

P _{PAR Max}

24

P _should

25

P _ICEPAR

Claims (10)

Method for operating a hybrid vehicle drive train (1), comprising at least one internal combustion engine (2), a (first) electrical machine (3) that can be operated as a motor and as a generator if necessary, and an electrical drive machine/second electrical machine (6), a (high-voltage) battery ( 9) and a control device (10) with power electronics, the energy source and the energy share provided by the selected energy source being selected for the drive depending on the current battery state of charge (SOC) of the (high-voltage) battery (9). Procedure according to Claim 1 , characterized in that both the internal combustion engine (2) and the (high-voltage) battery (9) are selected as the energy source between a minimum battery state of charge limit and a maximum battery state of charge limit. Procedure according to Claim 1 or 2 , characterized in that 20% of the maximum possible battery state of charge is selected as the minimum battery state of charge limit and/or 95% of the maximum possible battery state of charge is selected as the maximum battery state of charge limit. Procedure according to one of the Claims 1 until 3 , characterized in that a fixed (constant) ratio between the two energy sources is selected between the minimum battery state of charge limit and the maximum battery state of charge limit or, depending on the exact battery state of charge value, according to a linear and / or stepped and / or progressive and / or degressive and /or exponential function the ratio between the two energy sources is selected. Procedure according to one of the Claims 1 until 4 , characterized in that operation in parallel and/or serial mode is selected. Procedure according to Claim 5 , characterized in that in serial mode the first electrical machine (3) is operated in generator mode. Procedure according to Claim 5 , characterized in that in parallel mode the first electrical machine (3) is operated in motor mode. Procedure according to Claim 7 , characterized in that one clutch (5) is closed in parallel mode. Computer-readable storage medium, set up and prepared for carrying out control and/or regulation steps for enforcing the method according to one of the preceding claims. Hybrid vehicle drive train (1) with an internal combustion engine (2) and a first electric machine / electric machine (3) assigned to it, which is prepared for motor and generator operation and a connectable electric drive machine / second electric machine machine / second electrical machine (6), further comprising a control device (10) with power electronics and a computer-readable storage medium Claim 9 , as well as a (high-voltage) battery (9).

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