Method for determining a system performance indicator of an electric drivetrain

Abstract

The invention relates to a method for operating a hybrid vehicle which is operated using an internal combustion engine, an electric machine, and a gearbox, wherein the gearbox is connected to the internal combustion engine via an input shaft, and has a first electrical network and a second electrical network acting as an onboard network operating at a lower voltage level than the first electrical network; wherein the following components are coupled to the first electrical network: - the electric machine, which is operated either as a motor or as a generator, - an electric energy storage device, - a power converter which transmits electrical power at least from the first electrical network to the second electrical network, wherein the first electrical network is designed as part of a gearbox system which, together with the components coupled to it, is controlled via a gearbox control unit, wherein power is generated by the electric machine when operated as a generator.

Description

[0001] Method for determining a system performance indicator of an electric drive train

[0002] The invention relates to a method for determining a system performance indicator of an electric drive train.

[0003] When operating motor vehicles with mild hybrid drives or other electric drive systems, the aging of the system is a feature that has so far received little attention.

[0004] The aging phenomena of the many required components such as cables, cable connections, inverters, DC / DC converters, electric motors, batteries, etc. can develop very differently over the course of their service life. This can affect their function and lead to functional limitations.

[0005] Electrical components have operating limits that, for example, restrict their operating range to certain voltage limits. If these limits are exceeded, the components can only operate at limited performance, which generally leads to increased energy loss.

[0006] Due to the aging of the system, the resulting electrical resistance also increases. When energy is recovered through braking with the electric motor (regeneration), this results in a higher voltage level in the components, resulting in a reduction in energy yield.

[0007] In mild hybrid applications, the reduction in storage capacity, which is usually expressed by a “state of health” value (SOH value), plays a minor role, since even a reduced storage capacity of the battery is sufficient to enable operation without functional restrictions.

[0008] The StdT is basically known from EP 3 515 741 A1. The electrical

[0009] The on-board electrical system is supplied with power from the hybrid system, for example, by an energy converter, particularly a DC / DC converter, converting power from the voltage level of the hybrid drive's electrical network to the voltage level of the electrical network used as the on-board electrical system. Overall, this generally requires a comparatively large energy storage device in the hybrid system to meet the requirements for supplying power to the on-board electrical system while simultaneously performing the tasks involved in hybridizing the vehicle.In the case of a comparatively heavier commercial vehicle, this requires very large and therefore expensive and heavy energy storage devices, which is a disadvantage if the vehicle's hybrid system is to be designed as a so-called mild hybrid, i.e. a hybrid system that is only suitable for supporting the on-board electrical system but not for exclusively electric driving of the vehicle, since such a system is typically used in order to prevent the energy storage device from becoming too large.

[0010] The control of the hybrid vehicle is integrated into the transmission system, with the electric motor and the electrical energy storage unit of the first electrical network also being part of this transmission system. The energy storage unit is further integrated into the transmission system in such a way that operation is possible even if the energy storage unit fails. This is possible because the second electrical network has two potential energy suppliers connected in parallel: the first electrical network with the electric motor and the energy storage unit, which can be controlled independently of each other by the transmission control unit.

[0011] DE 102016217 955 A1 discloses a method for operating a hybrid vehicle having a first and a second electrical network, the first electrical network being operated at a higher voltage level than the second electrical network. Furthermore, an energy converter is provided which transfers electrical power at least from the first electrical network to the second electrical network. DE 10 2021 211 631 A1 discloses a method for operating an electrical machine having a computing unit. An electrical machine connected to the drive without a clutch can be controlled or operated via the controller in such a way that smooth starting or acceleration without reversing or stopping is possible.

[0012] Rolling backwards is guaranteed when a static torque is applied to the drive.

[0013] The object of the invention is to propose a method that allows a better assessment of an electric drive train.

[0014] The object is achieved according to the invention by an embodiment according to the independent claim. Further advantageous embodiments of the present invention can be found in the subclaims.

[0015] A method for operating a hybrid vehicle is proposed, which

[0016] 1.1 is operated with an internal combustion engine, an electric machine and a transmission,

[0017] 1 .2 wherein the transmission is connected to the internal combustion engine via an input shaft,

[0018] 1.3 a first electrical network,

[0019] 1 .4 a second electrical network which is operated as an on-board network at a lower voltage level than the first electrical network, wherein coupled to the first electrical network:

[0020] 1 .5.1 the electrical machine is operated as a motor or generator,

[0021] 1 .5.2 an electrical energy storage device is operated,

[0022] 1 .5.3 an energy converter is operated which transfers electrical power at least from the first electrical network to the second electrical network,

[0023] 1 .6 wherein the first electrical network is designed as part of a transmission system which, together with the components coupled to it, is controlled via a transmission control unit, 1 .7 wherein power is generated by the electric machine in generator mode.

[0024] According to the invention, it is proposed that the transmission control unit is designed to record system data and measured values ​​and to calculate a desired performance and an actual performance from these data and to determine therefrom a current SP I value, system performance value, which corresponds to the quotient of desired performance and actual performance.

[0025] The SPI (System Performance Indicator) indicates the vehicle's system performance. This value depends on the vehicle's driving profile and is not limited to battery condition, which significantly improves the assessment of a vehicle's usability.

[0026] Furthermore, it can be provided that a current SPI value is recalculated if all of the following conditions are met:

[0027] - at least the following components,

[0028] Frequency converter and battery are ready for operation

[0029] - the recuperation mode is active

[0030] - the temperatures of the battery, frequency converter,

[0031] Electric motor must be within the specified temperature range.

[0032] Furthermore, it can be provided that a new SPI value, which replaces the current SPI value, is based on the following additional calculation steps:

[0033] - Calculation and storage of the current desired power based on: a setpoint of the frequency converter or a setpoint of the DCDC controller

[0034] - Calculation and storage of an actual power based on: a battery actual power or a DCDC controller actual power

[0035] - Calculation of a new quotient based on the calculated desired performance and the calculated actual performance, which forms the new SPI value.

[0036] Furthermore, it can be provided that a further calculation step takes place:

[0037] - Calculation of several microscopic SPI values ​​on

[0038] Based on several calculated desired and actual services

[0039] According to another aspect, a further calculation step can be carried out:

[0040] - Calculation of the new SP l value by averaging the microscopic SPI values.

[0041] According to a further aspect, at least one of the following further calculation steps can be carried out:

[0042] - Calculation of the actual transmission power = power limit

[0043] - Calculation of the actual vehicle power = power limit, whereby a microscopic SPI value is calculated from the respective desired power and the actual power.

[0044] The invention is explained below with reference to figures:

[0045] Fig 1 : basic representation of a hybrid vehicle

[0046] Fig 2: Flow chart

[0047] Figure 1 shows a detailed schematic diagram of a hybrid vehicle. The hybrid vehicle is powered by an internal combustion engine 2, for example a diesel engine or a gas engine. This is connected via an input shaft 3 to a transmission system 4, which contains and controls the entire functionality of the hybrid drive except for the internal combustion engine 2. This transmission system 4 is connected via an output shaft 5 to two indicated driven wheels 6. Part of the transmission system 4 is an electric motor 7 and a transmission 8, for example an automatic transmission with a differential converter. The transmission 8 can have a hydrodynamic retarder T9 as a wear-free continuous brake. Another part of the transmission system 4 is the electrical control system.For this purpose, a transmission control unit 9 is provided, which is connected to a vehicle control unit (not shown here) via a bus system 10, preferably a CAN bus. Another part of the transmission system 4 is a frequency converter 11, which serves to control the electric motor. Furthermore, the transmission system 4 includes an electrical energy storage device 12, which is also referred to below as a hybrid battery. The electrical energy storage device 12 does not have to be configured as a battery. It can also be implemented, for example, in the form of capacitors.

[0048] A further component of the transmission system 4 is an energy converter 13, preferably a DC / DC converter. This converts the electrical energy from the voltage level of a first electrical network 14, which is, for example, 48 V, to that of a second electrical network 15, which in particular represents the on-board electrical system of the hybrid vehicle 1 including its consumers 17, of which only one is indicated here. This on-board electrical system 15 of the hybrid vehicle can operate, in particular, at a voltage level of 24 V when used in a commercial vehicle. In addition to the consumers 17 of the on-board electrical system, it also has a battery 18, which will be referred to below as the vehicle battery to distinguish it from the hybrid battery 12.

[0049] This design of the hybrid vehicle 1 can now be used for the primary provision of electrical energy for the second electrical network 15 by the first electrical network 14 and the electrical machine 7 coupled to it. To implement this prioritization of the supply to the second electrical network 15, it may now be the case, in particular, that operating variants are selected for certain driving situations of the hybrid vehicle 1, which ensure the electrical energy supply to the second electrical network 15, which is also referred to below as the on-board electrical system 15.

[0050] Figure 2 shows a flow chart with several condition steps 23 a to c and subsequently several optional calculation steps 21 a to c and several necessary calculation steps 22 a to d, wherein a new SPI value 20b is calculated from the optional calculation steps 21 a to c and the necessary calculation steps 22 a to d, which replaces the current SPI value 20a.

[0051] Conditional steps 23a to c are system-dependent steps that run sequentially, with the current SPI value 20a retained if the condition is not met. The following is checked:

[0052] Condition 23a: Are the components, frequency converter 11 and battery 12, ready for operation

[0053] Condition 23b: If the recuperation mode is present

[0054] Condition 23c: Are the temperatures of battery 12, frequency converter 11, electric motor 7 in the specified temperature range

[0055] When testing conditions 23a and 23c, other components may also be tested for their operational readiness or temperature.

[0056] If all conditions are met, a new SPI value 20b is calculated, whereby the SPI value 20b is based on optional and necessary calculations.

[0057] The optional calculations are the following calculation steps:

[0058] - 21 a: Calculation of the transmission-side power limit: e.g. torque limit during gear shifts, limits at transmission input, torque ramps, etc.) P_lim_Get= M_Emot_max_Get *n1 / 9.55

[0059] - 21 b: Calculation of the vehicle-side power limit: e.g. blocking of recuperation, limiting of the current of the DCDC controller 13

[0060] - 21 c: Minimum value formation between desired performance and

[0061] Transmission and vehicle performance limits The necessary calculations are the following calculation steps:

[0062] - 22a: Calculation of the current desired performance from the

[0063] Setpoint of the frequency converter 1 or battery power control and the setpoint of the DCDC controller 13.

[0064] Voltage-related limits of the converter 11 and the DCDC controller 13 are not taken into account.

[0065] - 22b: Calculation of the actual battery power and the actual power of the DCDC controller 12 Possibly - calibration value,

[0066] - Consider offset value

[0067] - 22c: Calculation of at least one microscopic SPI value:

[0068] Formation of the quotient over

[0069] Energy container (data set value) by a temporal integration of the desired power taking into account the limits as set by the transmission control unit 9, e.g. the TCU, Transmission Control Unit, integrated in the transmission control unit 9, the vehicle, and by a temporal integration of the actual power.

[0070] - 22d: Calculation of the SPI value by averaging the microscopic SPI values ​​(number of micro SPI values ​​adjustable via a data set value)

[0071] The current SPI value 20a is replaced by the calculated new SPI value 20b, i.e. stored or saved in the controller, it becomes the current SPI value 20a.

[0072] Recuperation, also known as brake energy recovery, involves the generation of energy through the regenerative use of the electric motor during braking and coasting. The recovered energy can be used to charge a 12- or 18-volt battery and / or to provide auxiliary electrical power, i.e., to supply auxiliary electrical consumers. The battery can be a 24V and / or 48V system.

[0073] The system allows for a very efficient implementation of an automatic start-stop system, reducing noise and fuel consumption when stationary. The system can also be used effectively as an alternator replacement and / or for electric boosting, the use of the electric motor as a motor.

[0074] List of reference symbols

[0075] 1 hybrid vehicle

[0076] internal combustion engine

[0077] 3 Input shaft

[0078] Transmission system

[0079] 5 Output shaft

[0080] Wheels

[0081] 7 electric motor

[0082] 8 gearboxes

[0083] 9 Transmission control unit

[0084] 10 Bus system

[0085] 11 frequency converters

[0086] 12 batteries

[0087] 13 DCDC controller or energy converter unit

[0088] 14 First electrical network

[0089] 15 Second electrical network

[0090] 16 retarders

[0091] 17 consumers

[0092] 18 Battery subsystem

[0093] 19 Retarder 0a, b SPI - current / new value 1 ac optional calculation steps 2a-d necessary calculation steps

[0094] 23a-c Process steps

Claims

Patent claims 1 . Method for operating a hybrid vehicle (1 ), which 1.1 is operated with an internal combustion engine (2), an electric machine (7) and a transmission (8), 1 .2 wherein the transmission (8) is connected to the internal combustion engine (2) via an input shaft (3); 1 .3 with a first electrical network (14), 1.4 with a second electrical network (15) which is operated as an on-board network at a lower voltage level than the first electrical network (14, 1 .5 wherein coupled to the first electrical network (14): 1 .5.1 the electrical machine (7) is operated as a motor or generator, 1 .5.2 an electrical energy storage device (12) is operated, 1 .5.3 an energy converter (13) is operated, which transmits electrical power at least from the first electrical network (14) to the second electrical network (15), 1 .6 wherein the first electrical network (14) is designed as part of a transmission system (4) which, together with the components (7, 11, 12, 13) coupled to it, is controlled via a transmission control unit (9), 1 .7 wherein power is generated by the electric machine (7) in generator mode, characterized in that the transmission control unit (9) is designed to record system data and measured values ​​and to calculate a desired power and an actual power from these data and to determine therefrom a current SPI value (20a), system performance value, which corresponds to the quotient of desired power and actual power.

2. Method according to claim 1, characterized in that a current SPI value (20a) is recalculated if all of the following conditions are met: - Condition (23a): at least the following components, Frequency converter 11 and battery 12 are ready for operation - Condition (23b): the recuperation mode is present - Condition (23c): the temperatures of battery 12, frequency converter 11, Electric machine 7 is in the specified temperature range 3. Method according to claim 2, characterized in that a new SPI value (20b) replacing the current SPI value (20a) is determined on the basis of the following calculation steps: - Step (22a): Calculate and save the current desired power based on: a setpoint of the frequency converter (11) or a setpoint of the DCDC controller (13) - Step (22b): Calculating and storing an actual power based on: a battery (12, 18) actual power or a DCDC controller (13) actual power - Calculation of a new quotient based on the calculated desired performance and the calculated actual performance, which forms the new SPI value (20b).

4. Method according to claim 3, characterized in that a further calculation step is carried out: - Step (22c): Calculation of several microscopic SP I values ​​based on several calculated desired and actual performances.

5. Method according to claim 3 or 4, characterized in that a further calculation step is carried out: - Step (22d): Calculation of the new SP l value (20b) by averaging the microscopic SPI values.

6. Method according to claim 5, characterized in that at least one of the following further calculation intermediate steps takes place: - Step (21a): Calculation of the actual transmission power = power limit - Step (21b): Calculation of the vehicle's actual power = power limit, whereby a microscopic SPI value is calculated from the respective desired power and the actual power.

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