Method for operating a battery-electric vehicle and drive system for a battery-electric vehicle

Abstract

The invention relates to a method for operating a battery-electric vehicle, wherein the vehicle has an HV battery, at least one traction drive machine which drives drive wheels of the vehicle, and a plurality of electrical auxiliary loads, the traction drive machine and the electrical auxiliary loads are supplied with electrical power from the HV battery in a normal mode, and the HV battery is connected via a main battery contactor to an electrical subsystem which comprises the at least one traction drive machine and the electrical auxiliary loads, the main battery contactor is closed during the normal mode in order to supply the electrical subsystem with electrical power from the HV battery and, in a battery protection mode, the HV battery is disconnected from the electrical subsystem by opening the main battery contactor. The method according to the invention is characterised in that, in the battery protection mode, the traction drive machine is operated as a generator and at least some of the electrical auxiliary loads are supplied with electrical power of the traction drive machine.

Description

[0001] Method for operating a battery electric vehicle and drive system for a battery electric vehicle

[0002] The present invention relates to a method for operating a battery-electric vehicle according to the preamble of claim 1 and a drive system for a battery-electric vehicle according to claim 11.

[0003] In motor vehicles with a battery-electric drive system, the so-called main battery contactor connects and disconnects the high-voltage battery (HV battery) from the rest of the electrical system, referred to here as the electrical subsystem. Such an electrical subsystem contains electrical consumers, including a traction motor that drives the vehicle's drive wheels and a variety of auxiliary electrical consumers, such as the vehicle's electrical system, electric power steering, an electric compressed air generator for the vehicle's compressed air system, and / or an electric heating system. During normal operation, when the vehicle is in a driving state with the main battery contactor closed, the electrical subsystem, comprising the traction motor and the auxiliary electrical consumers, is supplied with electrical power from the HV battery via the closed main battery contactor.For example, the main battery contactor is closed by a battery management system at the beginning of each vehicle operating cycle and reopened at the end of this cycle. However, such a main battery contactor is also used as part of a component protection function, in which the high-voltage battery is disconnected from the electrical subsystem, particularly by the battery management system, to prevent damage to the high-voltage battery if necessary. This operating state is referred to here as battery protection mode. One or more boundary conditions can be specified for this, depending on which the battery protection mode is activated by opening the main battery contactor. Activating the battery protection mode during vehicle operation has a significant impact on the driving behavior of the battery-electric vehicle.Conventionally, activating the battery protection mode by opening the main battery contactor not only prevents the vehicle from accelerating or decelerating using the traction motor, but also shuts down all electrical auxiliary consumers in the electrical subsystem. This leads to a failure of, for example, power steering, compressed air generation, and the vehicle's electrical system. The sudden failure of these auxiliary functions, in addition to the loss of drive and braking power, makes the battery-electric vehicle difficult for the driver to control.

[0004] The present invention is based on the objective of providing a method for operating a battery-electric vehicle and a drive system for a battery-electric vehicle, with which the aforementioned disadvantage is overcome.

[0005] The problem according to the invention is solved by a method with the features of claim 1 and a drive system with the features of claim 11. The dependent claims describe advantageous and particularly expedient embodiments of the invention.

[0006] The inventive method for operating a battery-electric vehicle, wherein the vehicle has an HV battery (high-voltage battery, for example with a voltage of more than 200 V), at least one traction drive motor which drives the drive wheels of the vehicle, and a plurality of electrical auxiliary consumers, the traction drive motor and the electrical auxiliary consumers are supplied with electrical power from the HV battery in normal operation, and the HV battery is connected via a main battery contactor to an electrical subsystem comprising the at least one traction drive motor and the electrical auxiliary consumers, provides that in normal operation the main battery contactor is closed in order to supply the electrical subsystem with electrical power from the HV battery, and in a battery protection mode the HV battery is disconnected from the electrical subsystem by opening the main battery contactor.

[0007] According to the invention, in battery protection mode the traction drive machine is operated as a generator and at least some or all of the electrical auxiliary consumers are supplied with electrical power from the traction drive machine, which it generates in generator mode driven by the drive wheels of the vehicle.

[0008] Because the traction drive machine is operated as a generator, an electrical voltage or an electrical power supply can be maintained in the electrical subsystem, which supplies all or selected electrical auxiliary consumers with electrical power, so that these electrical auxiliary consumers can maintain their function even when the main battery contactor is open.

[0009] For example, in battery protection mode, the vehicle operates in a coasting mode, which can be activated, for instance, by an electronic drive control system. Under normal operating conditions, this system controls the traction motor based on driver input or instructions from a vehicle assistance system. The driver expresses their input, for example, via an accelerator pedal and / or a brake pedal.

[0010] According to one embodiment of the invention, in battery protection mode the vehicle is operated in sailing mode, which means the traction motor is operated as a generator and produces slight braking torque.

[0011] It is conceivable that the generator operation in sailing mode is maintained until the vehicle comes to a standstill, thereby generating energy from the vehicle's kinetic energy to supply electrical auxiliary consumers, so that the vehicle remains controllable for the driver. According to the invention, until the vehicle comes to a standstill, the electrical auxiliary consumers can be supplied with electrical energy from the traction drive motor, so that the vehicle is not only gently decelerated, but also remains safely controllable for the driver during battery protection operation.

[0012] Preferably, the electrical subsystem comprises an electrical intermediate circuit with a variably adjustable intermediate circuit voltage. The traction motor, the electrical auxiliary loads, and, when the main battery contactor is closed, the high-voltage battery are electrically connected to the intermediate circuit. In battery protection mode, the intermediate circuit voltage is preferably regulated to a predetermined voltage setpoint using a braking torque absorbed by the traction motor as the control variable. This allows the level of the intermediate circuit voltage to be determined by the electrical auxiliary loads and the braking torque of the traction motor, even when the high-voltage battery, as a voltage-stabilizing component of the intermediate circuit, is disconnected by opening the battery contactor, in order to regulate the electrical voltage in the intermediate circuit to a defined value.

[0013] Setting a predetermined voltage setpoint in the DC link, even with the main battery contactor open, allows, for example, the main battery contactor to be closed again in the event of a recoverable battery fault, and normal operation to resume without having to switch off the auxiliary electrical loads for a pre-charging phase of the DC link. Preferably, the current voltage of the high-voltage battery is measured, and the DC link voltage setpoint is adjusted to this measured voltage. As explained, this can be achieved by selectively adjusting the drive torque or braking torque of the traction motor, taking into account the influence of the auxiliary electrical loads on the DC link voltage.Preferably, the HV battery is monitored for malfunctions and the battery protection mode is activated when one or more predefined malfunctions are detected.

[0014] If a malfunction is detected, its correction is preferably monitored, and if the malfunction is successfully corrected, the main battery contactor is closed again to end the battery protection operation and restore normal operation.

[0015] Preferably, at least one or more of the following electrical auxiliary consumers are supplied with electrical power from the generator-operated traction drive machine in battery protection mode:

[0016] - an electrical on-board network

[0017] - electric power steering

[0018] - an electric compressed air generator

[0019] - an electric heating device.

[0020] During the transition to battery protection mode, the sailing mode can be activated by an electric drive control, which is integrated in particular in a traction converter, via which the traction drive machine is supplied with electrical power, and in particular an overriding voltage control function can be activated, with which the voltage setpoint in the electrical intermediate circuit is regulated.

[0021] The main battery contactor is preferably closed at the beginning of each driving cycle of the motor vehicle, and reopened at the end of the same, particularly by means of a battery management system.

[0022] Particularly advantageous is the battery management system's activation of the main battery contactor based on the detection of predefined boundary conditions, such as a temperature in the HV battery, a voltage in the HV battery, a current value in the HV battery and / or a pressure in the HV battery, by opening the main battery contactor.

[0023] A drive system according to the invention for a battery-electric vehicle comprises accordingly an HV battery, at least one traction drive motor for driving the drive wheels of the vehicle and a plurality of electrical auxiliary consumers, wherein the traction drive motor and the electrical auxiliary consumers are arranged in an electrical subsystem and the HV battery is connected to the electrical subsystem via a main battery contactor.

[0024] Furthermore, an electric drive control system is provided, which is configured to execute a method according to the invention as described herein. The electric drive control system can be provided in a single electronic control device within the drive system or distributed across various electronic control devices. In particular, the electric drive control system is at least partially integrated into a traction converter, via which the traction drive motor is supplied with electrical energy, especially from the electrical intermediate circuit.

[0025] The invention ensures that even if the main energy source of the drive system, namely the HV battery, is lost, the vehicle remains controllable and, if necessary, a fully automatic restart is possible while driving.

[0026] The invention will below be described by way of example using an embodiment and the figure.

[0027] Figure 1 shows an exemplary drive system according to the invention for a battery-electric vehicle, comprising a high-voltage battery 1, a traction drive motor 2, and a plurality of electrical auxiliary consumers 3. The traction drive motor 2 and the electrical auxiliary consumers 3 are arranged in an electrical subsystem 5, which includes an electrical intermediate circuit 6 with a variably adjustable electrical intermediate circuit voltage. The high-voltage battery 1 is connected to the electrical subsystem 5, or rather to the electrical intermediate circuit 6, via a main battery contactor 4, which acts as a voltage-stabilizing component for the electrical intermediate circuit 6.

[0028] The traction drive motor 2, which drives the vehicle's drive wheels 10, is connected to the electrical intermediate circuit 6 via a traction inverter 8. The traction inverter 8 includes an electric drive control unit 7, which, depending on a driver request or a signal from a vehicle assistance system 13, controls the traction drive motor 2 via its electrical power supply, which is preferably designed as a three-phase supply, in order to set a desired drive torque in the rotary operation of the traction drive motor 2 or a desired braking torque in the regenerative operation of the traction drive motor 2. The driver can input their driving request via suitable actuators 14, such as an accelerator pedal, a brake pedal, a gear selector, or the like, which are shown here as a black box.

[0029] The HV battery 1 is connected to the electrical subsystem 5 or the electrical intermediate circuit 6 via the main battery contactor 4, so that the HV battery 1 can be electrically disconnected from the electrical subsystem 5 in the event of a fault.

[0030] The opening and closing of the main battery contactor 4 is carried out by means of a battery management system 9, which preferably continuously monitors the operating status of the HV battery 1.

[0031] Preferably, the HV battery 1, the traction drive motor 2 and the electrical auxiliary consumers 3, as well as a charging port 12 are electrically connected to each other via a power distribution unit 11, wherein the power distribution unit 11 is arranged in the electrical intermediate circuit 6.

[0032] The electrical auxiliary consumers 3 include, for example, an electrical on-board network 3.1, an electric power steering system 3.2, an electric compressed air generator 3.3 and / or an electric heating device 3.4.

[0033] For example, a central electronic control device 15 is provided which is connected via control lines to the function-specialized electronic control devices, which form the battery management system 9, the driving control 7 and in particular a charging management system 16, and the vehicle assistance system 13 and the actuators 14, in order to act, for example, as a master control device.

[0034] Whenever the high-voltage battery 1 is disconnected from the electrical subsystem 5 by opening the main battery contactor 4 and the vehicle is in coasting mode, the traction motor 2 is switched to generator mode, the so-called coasting mode, by means of the electric drive control 7. In this mode, the vehicle is more or less decelerated, and electrical power is generated. This power is supplied to the auxiliary electrical consumers 3 via the intermediate circuit 6. An intermediate circuit voltage can be specifically set in the intermediate circuit 6 to match the electrical voltage of the high-voltage battery 1. This allows the main battery contactor 4 to be closed after a fault in the high-voltage battery 1 has been rectified, without having to pre-charge the intermediate circuit 6, which would require switching off the auxiliary electrical consumers 3. (Reference symbol list)

[0035] HV battery traction drive motor auxiliary consumer

[0036] electrical system

[0037] electric power steering, electric compressed air generator, electric heating device, main battery contactor

[0038] Subsystem

[0039] Intermediate circle

[0040] Driving control

[0041] Traction inverter, battery management system, drive wheel, power distribution unit, charging port, vehicle assistance system

[0042] Actuators

[0043] central electronic control unit charging management

Claims

Patent claims 1. A method for operating a battery-electric vehicle, wherein the vehicle has a high-voltage battery (1), at least one traction drive motor (2) that drives the vehicle's drive wheels (10), and a plurality of electrical auxiliary consumers (3), the traction drive motor (2) and the electrical auxiliary consumers (3) are supplied with electrical power from the high-voltage battery (1) during normal operation, and the high-voltage battery (1) is connected via a main battery contactor (4) to an electrical subsystem (5) comprising the at least one traction drive motor (2) and the electrical auxiliary consumers (3), the main battery contactor (4) being closed during normal operation to supply the electrical subsystem (3) with electrical power from the high-voltage battery (1), and the high-voltage battery (1) being disconnected from the electrical subsystem (5) by opening the main battery contactor (4) during battery protection operation, characterized in that In battery protection mode, the traction drive machine (2) is operated as a generator and at least some of the electrical auxiliary consumers (3) are supplied with electrical power from the traction drive machine (2).

2. Method according to claim 1, characterized in that the vehicle is operated in a sailing mode during battery protection operation.

3. Method according to claim 2, characterized in that in battery protection mode the vehicle is maintained in sailing mode with the traction drive machine (2) until it comes to a standstill.

4. Method according to one of claims 1 to 3, characterized in that the electrical subsystem (5) comprises an electrical intermediate circuit (6) with a variably adjustable electrical intermediate circuit voltage, to which the traction drive motor (2), the electrical auxiliary consumers (3) and, when the main battery contactor (4) is closed, the HV battery (1) are connected, wherein in battery protection mode the intermediate circuit voltage is regulated to a predetermined voltage setpoint using a braking torque absorbed by the traction drive motor (2) as a control variable.

5. Method according to claim 4, characterized in that the current electrical voltage of the HV battery (1) is detected and the voltage setpoint of the intermediate circuit voltage is set to the currently detected electrical voltage of the HV battery (1).

6. Method according to one of claims 1 to 5, characterized in that the HV battery (1) is monitored for malfunctions and the battery protection operation is activated in the event of one or more predefined detected malfunctions.

7. Method according to claims 5 and 6, characterized in that, in the event of a detected malfunction, its rectification is monitored and, in the event of rectification, the main battery contactor (4) is closed to terminate the battery protection operation and to commence normal operation.

8. Method according to one of claims 1 to 7, characterized in that at least one or more of the following electrical auxiliary consumers (3) are supplied with electrical power from the generator-operated traction drive machine (2) in battery protection mode: - an electrical on-board network (3.1) - an electric power steering system (3.2) - an electric compressed air generator (3.3) - an electric heating device (3.4).

9. Method according to one of claims 2 to 8, characterized in that, during the transition to battery protection mode by an electric drive control (7), which is in particular integrated in a traction converter (8), the traction drive machine (2) is supplied with electrical power, the sailing mode is activated and in particular a superimposed voltage control function is activated, with which the voltage setpoint in the electrical intermediate circuit (6) is controlled.

10. Method according to one of claims 1 to 9, characterized in that the main battery contactor (4), in particular by means of a battery management system (9), is closed at the beginning of each driving cycle of the motor vehicle and opened again at the end of the same, and in particular the battery management system (9) activates the battery protection operation depending on a detection of predetermined boundary conditions by opening the main battery contactor (4).

11. Drive system for a battery-electric vehicle with an HV battery (1), with at least one traction drive motor (2) for driving drive wheels (10) of the vehicle, with a large number of electrical auxiliary consumers (3) and with an electrical subsystem (5) comprising the at least one traction drive motor (2) and the electrical auxiliary consumers (3), wherein the HV battery (1) is connected to the electrical subsystem (5) via a main battery contactor (4), and with an electric drive control (7), characterized by the fact that the electric drive control (7) is set up to carry out a method according to one of claims 1 to 10.

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