Method for controlling a drive train for a battery-electric motor vehicle

Abstract

The invention relates to a method for controlling a drive train for a battery-electric motor vehicle, in particular for a bus, the drive train comprising an HV on-board electrical system having an HV battery and an electrical DC link, and the HV battery being connected to the electrical DC link via a main contactor; a main drive converter being arranged in the electrical DC link, via which main drive converter a traction drive machine of the drive train is fed with electrical power from the HV on-board electrical system in order to drive drive wheels of the motor vehicle; the HV battery being electrically coupled to the electrical DC link at the beginning of an operating cycle of the drive train by closing the main contactor and being electrically decoupled from the electrical DC link at least at the end of the operating cycle by opening the main contactor. The method according to the invention is characterized in that, when the main contactor is open, the electrical DC link is discharged via the main drive converter and / or via at least one additional electrical control unit which is arranged in the electrical DC link and comprises at least one electrical switch and at least one capacitor.

Description

[0001] Method for controlling a powertrain for a battery-electric vehicle

[0002] The present invention relates to a method for controlling a powertrain for a battery-electric motor vehicle, in particular for a bus, according to the preamble of claim 1.

[0003] The powertrains of battery-electric vehicles have a high-voltage electrical system – hereinafter referred to as HV electrical system – which comprises an HV battery and an intermediate circuit, the HV battery being connected to the intermediate circuit via a main contactor. For the purposes of this document, high voltage (HV) is defined as an electrical voltage in accordance with Regulation No. 100 of the United Nations Economic Commission for Europe (UNECE) as amended on the filing date, in particular an electrical voltage of at least 200 volts.

[0004] A main drive converter is arranged in the electrical intermediate circuit, through which a traction motor is supplied with electrical power from the high-voltage (HV) vehicle electrical system to drive the vehicle's drive wheels. In addition, further power electronic actuators are arranged in the electrical intermediate circuit, which have their own capacitors in the circuit to stabilize their input voltage. Such power electronic actuators, which represent an interface between the HV component, for example an electric drive, and its power supply from the HV battery, and which include devices for controlling, guiding, and converting the energy flow from the HV battery to the HV component or vice versa, are referred to here as an electrical control unit, comprising at least one electrical switch and at least one capacitor.The total DC link capacitance, referred to here as the DC link capacitance, is the sum of all capacitances connected in parallel within the electrical DC link, i.e., the capacitances in the control units and any external capacitances. Typically, the high-voltage battery is electrically connected via the main contactor at the beginning of a drivetrain operating cycle and disconnected from the electrical DC link again at the end. Due to the DC link capacitance, a residual voltage remains in the electrical DC link. There are normative requirements for a passive discharge of the electrical DC link after the main contactor has been opened. The duration of such a passive discharge is comparatively long.

[0005] Due to safety functions integrated into the electrical control units, it is regularly necessary to ensure a voltage-free environment at the electrical input of the respective electrical control unit at the start of a new operating cycle. This is problematic in the case of a passive discharge of the intermediate circuit, because the switch-on time of the high-voltage electrical system is delayed.

[0006] To increase electrical safety in the event of a vehicle accident or during maintenance, discharge resistors with discharge contactors can be installed in the electrical intermediate circuit. However, this has the disadvantage of requiring additional components, which increase manufacturing costs and may be subject to failure during the vehicle's service life.

[0007] The present invention is based on the objective of providing a method for controlling a drive train for a battery-electric motor vehicle, in particular for a bus, with which the switching-on time of the HV on-board network can be shortened and the electrical safety can be improved, preferably without additional components.

[0008] The problem according to the invention is solved by a method with the features of claim 1. The dependent claims describe advantageous and particularly expedient embodiments of the invention.According to the inventive method for controlling a drive train for a battery-electric vehicle, in particular for a bus, wherein the drive train comprises a high-voltage electrical system with a high-voltage battery and an electrical intermediate circuit, and the high-voltage battery is connected to the electrical intermediate circuit via a main contactor, a main drive converter is arranged in the electrical intermediate circuit, via which a traction drive machine of the drive train is supplied with electrical power from the high-voltage electrical system to drive drive wheels of the vehicle, the high-voltage battery is electrically coupled to the electrical intermediate circuit at the beginning of an operating cycle of the drive train by closing the main contactor and is electrically decoupled from the electrical intermediate circuit at least at the end of the operating cycle by opening the main contactor.

[0009] According to the invention, when the main contactor is open, the electrical intermediate circuit is discharged via the main drive converter and / or via at least one further electrical control unit arranged in the electrical intermediate circuit, which comprises at least one electrical switch and at least one capacitor.

[0010] This means that discharge is only possible when the electric motor is not inducing a voltage and the contactor is open. Therefore, the electrical intermediate circuit can only be discharged when the system is at rest.

[0011] The method according to the invention thus allows for active discharge of the electrical intermediate circuit when required, for example, every time the main contactor opens and / or when, in particular with at least one acceleration sensor, the involvement of the motor vehicle in an accident is detected and / or when a malfunction, for example an impermissible electrical voltage and / or an impermissible temperature, in particular in the HV battery, is detected.No additional components are required in the high-voltage electrical system, especially in the electrical intermediate circuit; instead, active discharge takes place via the main drive converter already provided and / or an electrical control unit already located in the electrical intermediate circuit, for example, an air conditioning compressor, an air compressor for a vehicle compressed air system, an electric heater, a voltage converter for a low-voltage electrical system, and / or an electric charging device.

[0012] Preferably, the electrical intermediate circuit comprises two conductors between which, when the main contactor is closed and connected to the high-voltage battery, an intermediate circuit voltage is applied, which is, for example, more than 200 volts, and in particular more than 300 volts. This intermediate circuit voltage, or the portion thereof that is not immediately discharged, is preferably reduced to a residual voltage of a maximum of 36 volts, 24 volts, or 12 volts during the active discharge of the electrical intermediate circuit according to the invention, or the two conductors are de-energized during the active discharge.

[0013] According to one embodiment of the invention, to discharge the electrical intermediate circuit, the traction drive motor is controlled by the main drive converter in such a way that a torque-free magnetic field is generated in the traction drive motor. Thus, only a magnetic field-generating current component is impressed into the traction drive motor, and a magnetic field is produced without generating any torque. In this way, the electrical energy from the electrical intermediate circuit is converted into the magnetic field. The resulting ohmic losses cause the electrical energy to be converted into heat, and the voltage of the electrical intermediate circuit decreases accordingly. The mathematical models that can be used for controlling the traction drive motor are known to those skilled in the art, for example, the d / q transformation, particularly in field-oriented control.

[0014] In principle, according to one embodiment of the invention, it is also possible that a torque, in particular a torque limited compared to a maximum possible torque, is generated in or with the traction drive motor via the main drive converter, but the output-side portion of the drive train of the traction drive motor is braked, so that no drive to the drive wheels occurs. The magnetic field generated in the traction drive motor in this case also leads to a discharge of the electrical intermediate circuit.

[0015] According to an alternative embodiment of the invention, which can also be combined with the aforementioned embodiment, wherein the main drive converter has a three-phase connection with three phases for the traction drive motor and at least one electrical switch between each phase, i.e., the conductor of each phase, and at least one of the conductors or each conductor of the intermediate circuit, a pulsed electrical short circuit is created via the switch(es), which are closed in a pulsed manner, to discharge the intermediate circuit. The electrical short circuit can be created via a capacitor in the main drive converter. In this way, electrical energy from the intermediate circuit is also converted into heat and thereby discharged from the intermediate circuit.

[0016] The clocked circuit prevents a harmful short circuit from occurring.

[0017] The at least one electrical switch and the at least one capacitor of the control unit and / or the electrical switches and the at least one capacitor of the main drive converter can preferably be formed by semiconductors. This allows for particularly efficient power electronics.

[0018] The electrical intermediate circuit may contain, for example, an air conditioning compressor, an air compressor for a vehicle's compressed air system, an electric heater, and / or an electric charging device, each with an electrical control unit, and these components are supplied with electrical power via the high-voltage electrical system. A voltage converter for a low-voltage electrical system, advantageously located in the electrical intermediate circuit, can also include such an electrical control unit.

[0019] The invention will below be described by way of example using an embodiment and the figures.

[0020] They show:

[0021] Figure 1 shows a drive train according to the invention for a battery-electric motor vehicle;

[0022] Figure 2 shows an exemplary representation of the main drive converter with the traction drive machine connected to it;

[0023] Figure 3 shows a schematic representation of an embodiment of an electrical control unit in the electrical intermediate circuit.

[0024] Figure 1 schematically depicts a drive train for a battery-electric vehicle, in particular for a bus, comprising a high-voltage electrical system 1 with a high-voltage battery 2 and an electrical intermediate circuit 3. The high-voltage battery 2 is connected to the electrical intermediate circuit 3 via a main contactor 4, so that it can be electrically disconnected from the electrical intermediate circuit 3 by opening the main contactor 4 and connected to the electrical intermediate circuit 3 by closing the main contactor 4.

[0025] A main drive converter 5 is arranged in the electrical intermediate circuit 3, which supplies a traction drive motor 6 with electrical power from the electrical intermediate circuit 3, so that the traction drive motor 6 drives the drive wheels 7 of the vehicle. During braking operation of the vehicle, the traction drive motor 6 can be operated as a generator and feed electrical power into the electrical intermediate circuit 3 accordingly.

[0026] In the electrical intermediate circuit 3, further electrical control units 8 are arranged, which supply further HV components not shown in detail with electrical power from the HV on-board power supply 1 or the electrical intermediate circuit 3, or, if it is the electrical control unit 8 of an electrical charging device 16, feed electrical power into the electrical intermediate circuit 3.

[0027] In the embodiment shown in Figure 1, the HV components include, for example, an air conditioning compressor 14, an air compressor 15 for a vehicle compressed air system and an electric charging device 16.

[0028] In the illustrated embodiment, a voltage converter 17 is also arranged in the electrical intermediate circuit 3 as a high-voltage component. This converter supplies a low-voltage electrical system 18, comprising a low-voltage battery 19 and electrical loads 20, with electrical power from the high-voltage electrical system 1. The electrical voltage of the low-voltage electrical system is, for example, a maximum of 36 volts, 24 volts, or 12 volts. The voltage converter 17 can also include a corresponding electrical control unit 8, although this is not shown in detail.

[0029] The electrical connections in the intermediate circuit 3 between the terminals for the HV battery 2, the main drive inverter 5, the electrical control units 8 and / or the voltage converter 7 can preferably be made by means of an electrical power distribution unit 21. This allows for particularly convenient wiring.

[0030] The electrical intermediate circuit 3 has two electrical conductors 3.1 and 3.2, between which, when the main contactor 4 is closed, the electrical intermediate circuit voltage U is applied by means of the HV battery 2, in particular more than 200 volts. When the main contactor 4 is opened, this intermediate circuit voltage U is actively discharged according to the invention.

[0031] The main drive converter 5 and the electrical control units 8 each comprise their own capacitances 10, 13, which can also be referred to as DC link partial capacitances. These add up, optionally with further capacitances in the electrical DC link 3, to the DC link capacitance of the electrical DC link 3. This DC link capacitance ensures that the DC link voltage U is maintained for a comparatively long time even when the main contactor 4 is open, provided that the electrical DC link 3 is not actively discharged, as proposed by the invention.

[0032] If it is defined here that the main drive converter 5 and an electrical control unit 8 comprise at least one capacitance 10, 13, it is not absolutely necessary that this capacitance 10, 13 be directly integrated into a housing of the main drive converter 5 or the control unit 8. Rather, it is sufficient if the capacitance 10, 13 is electrically assigned to the function of the main drive converter 5 or the control unit 8.

[0033] Three possible active discharges of the electrical intermediate circuit 3 are explained below with reference to Figures 2 and 3.

[0034] Figure 2 shows further details of the main drive converter 5. In addition to the capacitor 13, it has electrical switches 12 between the three phases 11.1, 11.2 and 11.3 of the three-phase connection 11 for the traction drive machine 6 and the two conductors 3.1, 3.2 of the electrical intermediate circuit 3.

[0035] A total of six switches 12 are provided, one switch each between phase 11.1, 11.2, 11.3 and the first conductor 3.1, and one switch 12 between each phase 11.1, 11.2, 11.3 and the second conductor 3.2. The switches between the first conductor 3.1 and the second conductor 3.2 and each of phases 11.1, 11.2, 11.3 are connected in series with each other and in parallel with the capacitor 13.

[0036] This allows a short circuit in the main drive converter 5 to be achieved by clocked closing of at least two switches 12 connected in series, in particular via the capacitor 13, but also alternatively via the switches 12 of two phases 11.1 , 11.2 , 11 .3, with which the electrical voltage U between the two conductors 3.1 and 3.2 is reduced.

[0037] Another way to actively discharge the electrical intermediate circuit 3 and reduce the electrical voltage U, as shown in Figure 2, is to control the traction drive motor 6 with the main drive converter 5 in such a way that an electric magnetic field is generated in the motor, but no torque is produced that sets the traction drive motor 6 in motion. Finally, it would also be conceivable that a limited torque is generated by the traction drive motor 6 via the main drive converter 5, but the output side of the drive train is braked, so that the drive wheels 7 are not driven. The magnetic field generated in the traction drive motor 6 in this way also leads to a discharge of the electrical intermediate circuit 3.

[0038] In the embodiment shown in Figure 3, an electrical short circuit across the capacitor 10 can also be pulsed using the two electrical switches 9 of the electrical control unit 8 connected in series to each other and in parallel to the capacitor 10, in order to reduce the voltage U between the two conductors 3.1 , 3.2 of the electrical intermediate circuit 3.

[0039] An HV component 22, which is, for example, one of the components shown in Figure 1, is controlled via the electrical control unit 8. Reference numeral

[0040] 1 HV-Bordz

[0041] 2 HV batteries

[0042] 3 electrical intermediate circuit

[0043] 3.1 Ladder

[0044] 3.2 Ladder

[0045] 4 Main gate

[0046] 5 main drive converters

[0047] 6 Traction drive machine

[0048] 7 drive wheel

[0049] 8 electrical control unit

[0050] 9 electrical switches

[0051] 10 capacity

[0052] 11 Three-phase connection

[0053] 11.1 electrical phase

[0054] 11.2 electrical phase

[0055] 11.3 electrical phase

[0056] 12 electrical switches

[0057] 13 Capacity

[0058] 14 Air conditioning compressor

[0059] 15 air compressor

[0060] 16 electric charging device

[0061] 17 voltage converters

[0062] 18 Low-voltage electrical system

[0063] 19 Low-voltage battery

[0064] 20 electrical consumers

[0065] 21 electrical power distribution unit

[0066] 22 HV components

[0067] U DC circuit voltage

Claims

Patent claims 1. Method for controlling a powertrain for a battery-electric vehicle, in particular for a bus, wherein the powertrain comprises a high-voltage electrical system (1) with a high-voltage battery (2) and an electrical intermediate circuit (3), and the high-voltage battery (2) is connected to the electrical intermediate circuit (3) via a main contactor (4); a main drive inverter (5) is arranged in the electrical intermediate circuit (3), via which a traction drive motor (6) of the powertrain is supplied with electrical power from the high-voltage electrical system (1) to drive drive wheels (7) of the vehicle; wherein the high-voltage battery (2) is electrically coupled to the electrical intermediate circuit (3) at the beginning of an operating cycle of the powertrain by closing the main contactor (4) and is electrically decoupled from the electrical intermediate circuit (3) at least at the end of the operating cycle by opening the main contactor (4);characterized in that the electrical intermediate circuit (3) is discharged via the main drive converter (5) and / or via at least one further electrical control unit (8) arranged in the electrical intermediate circuit (3), which comprises at least one electrical switch (9) and at least one capacitor (10).

2. Method according to claim 1, characterized in that the electrical intermediate circuit (3) has two conductors (3.1, 3.2) between which, when the main contactor (4) is closed, an electrical intermediate circuit voltage (U) is applied to the HV battery (2), which is reduced to a residual voltage of a maximum of 36 volts, 24 volts or 12 volts when the electrical intermediate circuit (3) is discharged, or the two conductors (3.1, 3.2) are switched off during discharge.

3. Method according to one of claims 1 or 2, characterized in that, for the discharge of the electrical intermediate circuit (3), the traction drive machine (6) is controlled with the main drive converter (5) in such a way that a torque-free magnetic field is formed in the traction drive machine (6).

4. Method according to one of claims 2 or 3, characterized in that the main drive converter (5) has a three-phase connection (11) with three phases (11.1, 11.2, 11.3) for the traction drive machine (6) and at least one electrical switch (12) between each phase (11.1, 11.2, 11.3) 11.2, 11.3) and includes at least one of the conductors (3.1, 3.2) or each of the conductors (3.1, 3.2) via which a pulsed electrical short circuit is made to discharge the electrical intermediate circuit (3) via the switch(es) (12) which are closed in a pulsed manner.

5. Method according to claim 4, characterized in that the pulsed electrical short circuit is produced via at least one capacitor (13) of the main drive converter (5).

6. Method according to one of claims 1 to 5, characterized in that the at least one electrical switch (9) and the at least one capacitor (10) of the electrical control unit (8) and / or the electrical switches (12) and the at least one capacitor (13) of the main drive converter (5) are formed by semiconductors.

7. Method according to one of claims 1 to 6, characterized in that at least one air conditioning compressor (14), one air compressor (15) for a motor vehicle compressed air system, one electric heater, one voltage converter (17) for a low-voltage electrical system (18) and / or one electric charging device (16), each with an electrical control unit (8), is / are arranged in the electrical intermediate circuit (3) and is / are supplied with electrical power via the HV electrical system (1).

8. Method according to one of claims 1 to 7, characterized in that the motor vehicle, in particular with acceleration sensors, is monitored for involvement in an accident and, upon detection of involvement in an accident, the main contactor (4) is opened and the electrical intermediate circuit (3) is discharged accordingly.

9. Method according to one of claims 1 to 8, characterized in that the occurrence of at least one malfunction, in particular an impermissible electrical voltage and / or an impermissible The temperature, especially in the HV battery (2), is monitored and, if a malfunction is detected, the main contactor (4) is opened and the electrical intermediate circuit (3) is discharged accordingly.

10. Method according to one of claims 1 to 9, characterized in that the electrical intermediate circuit (3) is discharged accordingly each time the main contactor (4) is opened.

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