Method for determining a temperature of at least one electrical conductor, computing unit and computer program, and electric drive system

Abstract

The invention relates to a method for determining the temperature of at least one electrical conductor (120) between a converter (110) and an electrical machine (130) in an electrical drive system (100), wherein the electrical machine (130) has a liquid cooling device (170) which is also intended for cooling the at least one electrical conductor (120), wherein the method (200) comprises energizing the electrical machine (130) with the converter (110) in operation, operating the liquid cooling device (170), measuring the temperature of a coolant used in the liquid cooling device by means of a temperature sensor (150), and determining the temperature of the at least one electrical conductor on the basis of the measured temperature of the coolant. Furthermore a computing unit (160) and a computer program for carrying out such a method and an electrical drive system (100) are proposed.

Description

Technical Field

[0001] The present invention relates to a method for determining the temperature of at least one electrical conductor between a converter and a motor, a computing unit and a computer program for implementing the method, and an electric drive system. Background Technology

[0002] In electric drive systems, such as electric vehicles, the motor is powered by electrical energy from the battery via an inverter, or electrical energy generated by the motor (e.g., regeneration) is fed into the battery via an inverter.

[0003] To protect power electronic equipment, it is typically necessary to monitor components that can become very hot due to high currents. In modern DC-AC converter electronics used for electric drives, busbars (so-called "AC rails" or "busbars," such as copper busbars) are used to conduct current from the final stage of the converter to the motor (e.g., a three-phase motor). Copper itself has a high maximum limiting temperature, but components in the environment (such as seals, PCBs, or current sensor chips) have lower limiting temperatures, for example, around 160°C. Taking into account manufacturing, aging, and software model tolerances, a maximum permissible temperature, the so-called derating temperature threshold, can be calculated, for example, from which the motor torque must be reduced so that the temperature does not exceed the critical temperature.

[0004] For sensorless thermal bus models (i.e., where there is no dedicated temperature sensor at the bus), the coolant temperature of the converter can be used as a temperature reference. Summary of the Invention

[0005] According to the present invention, a method for determining the temperature of at least one electrical conductor between a converter and a motor, a computing unit and a computer program for implementing the method, and an electric drive system, having the features of the independent patent claims, are provided. Advantageous designs are the subject matter of the dependent claims and the following description.

[0006] The present invention utilizes the following measures: particularly, detecting the temperature of the coolant in a sensing manner within the motor, and determining the temperature of at least one electrical conductor therefrom, wherein the coolant is used directly to cool at least one electrical conductor and to cool the motor.

[0007] Compared to solutions that use the converter's coolant temperature as a temperature reference, this offers the following advantages: in the case of liquid-cooled motors, it is possible to estimate the temperature of the electrical conductors more accurately. This is because the motor's cooling circuit is typically fluidically separated from the converter's cooling circuit, making it impossible to accurately detect the effects of liquid cooling on the motor (and its electrical conductors, whose temperature should be determined) based on the temperature of the cooling medium that cools the converter.

[0008] Specifically, according to the present invention, a method is proposed for determining the temperature of at least one electrical conductor between an inverter and a motor in an electric drive system, such as a vehicle that is at least partially electrically driveable, wherein the motor has a liquid cooling device, which is also used to cool at least one electrical conductor, wherein the method comprises: energizing the motor when using an inverter, operating the liquid cooling device, measuring the temperature of the coolant used in the liquid cooling device by means of a temperature sensor, and determining the temperature of at least one electrical conductor based on the measured temperature of the coolant.

[0009] In at least one design, the temperature sensor is disposed within the motor and / or downstream of the motor and / or downstream of the at least one electrical conductor. Typically, this sensor is already present, eliminating the need for additional components for this invention. This reduces the cost required for implementation.

[0010] In at least one design, the coolant includes thermal oil. Thermal oil is particularly suitable for cooling motors due to its electrical insulating properties and high temperature stability.

[0011] In at least one design, the method includes cooling the converter using a cooling system separate from the liquid cooling unit, wherein the cooling system specifically uses a cooling medium different from the coolant used in the liquid cooling unit. Typically, the converter can be cooled using water-based or air-based cooling, or it can be cooled directly by means of a refrigerant loop, which has the advantage of covering a wider temperature range and also provides heating, which can be particularly advantageous during the start-up and operation phases.

[0012] In at least one design embodiment, the method includes controlling the motor and / or the converter based on a determined temperature of at least one electrical conductor. Furthermore, the method may specifically include limiting the electrical power supplied to the motor via the converter when the determined temperature of the at least one electrical conductor exceeds a predetermined threshold. Because the electrical power is reduced, for example, when the threshold is exceeded, and thus further heating of the electrical conductor is avoided, component protection can be achieved.

[0013] The computing unit according to the invention, such as the control device of a (electrically driven) motor vehicle, is particularly designed in terms of programming technology to implement the method according to the invention.

[0014] The electric drive system according to the invention includes a converter, a motor, at least one electrical conductor between the converter and the motor, a liquid cooling device for cooling the at least one electrical conductor and the motor (130), a temperature sensor for measuring the temperature of the coolant used in the liquid cooling device, and a calculation unit according to the invention.

[0015] It is also advantageous to implement the method according to the invention in the form of a computer program or computer program product having program code for implementing all method steps, because this results in particularly low costs, especially when the control device being executed is also used for other tasks and therefore already exists. Finally, a machine-readable storage medium is provided having the computer program as described above stored thereon. Suitable storage media or data carriers for providing the computer program are particularly magnetic, optical, and electrical memories, such as hard disks, flash memory, EEPROM, DVDs, etc. Downloading the program via a computer network (Internet, intranet, etc.) is also possible. Such downloading can be done wired or cabled or wirelessly (e.g., via WLAN networks, 3G, 4G, 5G, or 6G connections, etc.).

[0016] Other advantages and design solutions of the present invention will become apparent from the specification and the accompanying drawings.

[0017] The present invention is schematically illustrated in the accompanying drawings according to embodiments, and is described below with reference to the drawings. Attached Figure Description

[0018] Figure 1 The schematic block diagram illustrates one design of an electric drive system with a motor, which can be used in the design scheme of the present invention.

[0019] Figure 2 A design scheme of the present invention is schematically illustrated based on a simplified functional flowchart. Detailed Implementation

[0020] exist Figure 1 The block diagram schematically illustrates one design of an electric drive system with a motor, which can be used in the design scheme of the present invention, and is generally indicated by 100.

[0021] The drive system 100 includes a converter 110 (also technically known as an inverter or traction inverter) and at least one electrical conductor 120 (in this case, in the form of three buses for three phase windings of a motor 130), which connects the converter 110 to the phase terminals of the motor (represented here as 130). The electrical conductor 120, the busbar made of, for example, copper or other conductive material, is monitored by one or more other (particularly semiconductor) components, such as a current sensor 180, and is arranged in a housing 140 between the converter 110 and the end cap 132 of the motor 130, and is at least fluid-tightly positioned at the end cap 132. On the converter 110 side, the housing 140 may also be fluid-tightly positioned at the converter 110, or have fluid-tight sleeves for the electrical conductor 120.

[0022] The housing 140 is configured to allow the flow of a liquid coolant, such as heat transfer oil. For example, an inlet pipe 142 for introducing coolant may be provided for this purpose. In the example shown, an opening 134 is provided in the end cover 132 of the motor 130, through which the electrical conductor 120 or the phase terminal of the motor 130 is laid, and whereby coolant can flow from the housing into the motor 130, particularly into its stator windings, through the opening.

[0023] A temperature sensor 150 is provided in the motor 130, which detects the temperature of the coolant flowing through the stator and transmits the temperature to the computing unit 160. In the example shown, the coolant is circulated by means of a coolant pump 170. A heat exchanger may also be provided in the coolant circuit to better dissipate heat. However, for clarity, such a heat exchanger is not shown in this figure.

[0024] The computing unit 160 is connected to the temperature sensor 150, the current sensor 180, the coolant pump 170, and the converter 110 via data transmission.

[0025] exist Figure 2 The diagram illustrates a design scheme of the present invention schematically based on a simplified flowchart, and is generally denoted by 200. For example, this flowchart can be understood as a visualization of a design scheme of method 200 according to the present invention.

[0026] Method 200 utilizes a temperature model 280, by means of which the temperature 260 of at least one electrical conductor 120 and / or the temperature 270 of one or more other components, such as one or more current sensors 180 at the electrical conductor 120, can be determined.

[0027] In the example shown here, the DC current 211 supplied to the converter, the alternating current 212 provided by the converter (e.g., the total current of all phases or the average current of each phase), the thermal offset 213 (which typically occurs between the electrical conductor and the coolant, for example, determined empirically), and the coolant temperature 214 are used as input parameters for the temperature model 280, which can be provided in particular by the temperature sensor 150.

[0028] These input parameters constitute the input vector 210 for the state-space model 280. The state-space model 280 includes an input matrix 220, an integrator 230, a system matrix 240, and an output matrix 250.

[0029] Matrices 220, 230, 240, and 250 can be determined, for example, through thermal characterization measurements and subsequent parameter identification. In this case, it is advantageous if the structure at the test bench corresponds as well as possible to the target system.

[0030] Determine the temperatures 260, 270 of at least one electrical conductor 120 or one or more other components 180 from the output matrix 250.

[0031] In particular, the method 200 can be implemented essentially by the computing unit 160.

[0032] Based on the determined temperatures 260 and 270, the calculation unit 160 can manipulate the converter 110 and / or the coolant pump 170 such that the temperature 260 of at least one electrical conductor 120 or the temperature 270 of one or more other components does not exceed a predetermined temperature threshold. In particular, the electrical power supplied by the converter 110 can be limited (e.g., by limiting the maximum available current) and / or the delivery capacity of the coolant pump 170 can be adjusted according to the determined temperatures 260 and 270 (e.g., by means of corresponding speed adaptation).

[0033] As mentioned at the beginning, the accuracy of the temperature model 280 is significantly improved by using a coolant temperature 214, which involves the coolant flowing directly around the electrical conductor, compared to conventional solutions that use inverter temperature as an input parameter instead of coolant temperature. Therefore, the drive system 100, and in particular one or more current sensors 180, can be effectively protected from overheating without unnecessarily and prematurely limiting the power of the drive system 100.

Claims

1. A method (200) for determining the temperature (260) of at least one electrical conductor (120) between a converter (110) and a motor (130) in an electric drive system (100), wherein the motor (130) has a liquid cooling device (170) also configured to cool the at least one electrical conductor (120), wherein the method (200) comprises: When the motor (130) is energized using the converter (110), Operate the liquid cooling device (170). The temperature of the coolant used in the liquid cooling device is measured (214) by means of a temperature sensor (150), and The temperature (260) of the at least one electrical conductor is determined (250, 280) based on the measured temperature (214) of the coolant.

2. The method (200) according to claim 1, wherein the temperature sensor (150) is arranged inside the motor (130) and / or downstream of the motor (130) and / or downstream of the at least one electrical conductor (120).

3. The method (200) according to claim 1 or 2, wherein the coolant comprises heat transfer oil.

4. The method (200) according to any one of the preceding claims includes cooling the converter (110) using a cooling system separate from the liquid cooling device (170), wherein the cooling system uses a cooling medium different from the coolant used in the liquid cooling device.

5. The method (200) according to any one of the preceding claims, comprising controlling the motor (130) and / or the converter (110) based on a determined temperature (260) of the at least one electrical conductor (120).

6. The method (200) according to claim 5, comprising limiting the electrical power supplied to the motor (130) through the converter (110) when the determined temperature (260) of the at least one electrical conductor (120) exceeds a predetermined threshold.

7. A computing unit (160) configured to implement all method steps of the method (200) according to any one of the preceding claims.

8. An electric drive system (100) comprising: Converter (110) Motor (130) At least one electrical conductor (120) between the converter (110) and the motor (130). A liquid cooling device (170) for cooling the at least one electrical conductor (120) and the motor (130). A temperature sensor (150) for measuring the temperature of the coolant used in the liquid cooling device, and The computing unit (160) according to claim 7.

9. A computer program, when executed on a computing unit, causes the computing unit to perform all the method steps of the method according to any one of claims 1 to 6.

10. A machine-readable storage medium having a computer program according to claim 9 stored thereon.

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