Method for monitoring temperature of electrical system

Abstract

The invention relates to a method for monitoring component temperatures in an electrical system having a plurality of components, comprising the following steps: measuring a reference temperature, which represents a temperature at a location in the electrical system, at the beginning of an operating phase of the electrical system; continuously modeling a component temperature of at least one component in the electrical system starting from a reference temperature as a starting value by means of a thermal equilibrium model modeled with a differential equation as a state model; continuously monitoring the component temperature of the at least one component on the basis of a preset threshold temperature for the at least one component; the method is characterized in that the monitoring is further carried out as a function of a temperature unreliability, the temperature unreliability being determined as a function of an end-reference temperature, which is a reference temperature at the end time of the previous operating phase, and the measured reference temperature.

Description

Field of the Invention

[0001] The present invention relates to temperature management of electrical systems, in particular electrical systems with sources of high power loss, such as drive systems with electric motors. Furthermore, the present invention relates to temperature monitoring of component temperatures after activation or switching on of the power supply without knowing the duration since the last cut-off. Background Art

[0002] Electrical systems, such as drive systems with electric motors, convert a significant portion of electrical energy into heat during operation, which may cause varying degrees of heating of the individual components of the system. For the purpose of protecting the components, it is necessary to monitor the individual components of the electrical system with respect to their temperature in order to identify and avoid overheating of the components.

[0003] Since it is not possible to equip each heated component with a temperature sensor due to high costs, temperature is often modeled using a thermal balance model. This enables thermal modeling based on energy input, energy output taking into account the heat transfer resistance, with which the component temperature can be continuously modeled and estimated. The modeled component temperature can be monitored using a threshold comparison with respect to temperature. However, for the modeling, a preset of the initial state of the component temperature is required.

[0004] However, for electrical systems that are not continuously switched on or supplied with energy, such as electrical systems that are only switched on for a short time according to the user's wish, the component temperature at the moment of switching on is not known, because it cannot be determined whether the components of the electrical system have the ambient temperature or are in a state of operating heat generation. Therefore, the initial state of the electrical system is not available for modeling the component temperature. Examples of such electrical systems are drive systems in electric window lifter systems, electric convertible roof systems, electric seat adjustment systems, etc. Summary of the Invention

[0005] The object of the present invention is to provide a method for temperature monitoring of at least one component in an electrical system, which method ensures robust and reliable temperature monitoring of at least one component without depending on the duration since the last disconnection and without depending on the operating intensity in the previous operating phase.

[0006] This object is solved by a method for temperature monitoring of components of an electrical system according to claim 1 and by a device and an electrical system according to the dependent claims.

[0007] Further design options are described in the dependent claims.

[0008] According to a first aspect, there is provided a method, in particular a computer-implemented method, for monitoring the component temperature in an electrical system having a plurality of components, the method having the following steps:

[0009] - At the start of the operating phase of the electrical system, a reference temperature is measured, which represents the temperature at a location in the electrical system;

[0010] - Starting from the reference temperature as the respective starting value, the component temperature of at least one component in the electrical system is continuously modeled by means of a heat balance model modeled as a differential equation for the state model;

[0011] - The component temperature of the at least one component is continuously monitored on the basis of a threshold temperature preset for the at least one component;

[0012] wherein furthermore the monitoring is carried out depending on the temperature unreliability, and the temperature unreliability is determined depending on the end-reference temperature, which is the reference temperature at the end of the previous operating phase, and the measured reference temperature.

[0013] Furthermore, the temperature unreliability can be determined depending on the end-component temperature, which is the component temperature modeled at the end of the previous operating phase, of at least one component and / or depending on the temperature fluctuation, which is the difference between the maximum and minimum component temperatures.

[0014] The electrical system, in particular a drive system having an electric motor and an integrated motor electronics, is compactly constructed. During operation, some components of the system, such as the coils, stator components, rotor components, and bearings contained therein, generate loss power due to energy input, and this loss power causes local heating. The heating of the individual components results in heat transfer to adjacent components due to the compact construction. The heat input of one or more components, the heat transfer between the components, and the heat dissipation from the electrical system, for example via a cooling body, to the surrounding environment can be modeled by means of a heat balance model. Such a heat balance model corresponds to a state model and is based on linear differential equations.

[0015] For an electrical system used, for example, in a mechanism operable by a motor vehicle driver in a drive system, the operation is often carried out by manual input or in the case of being controlled by a superior system, such that the time intervals between the operating phases are different and usually unknown. Therefore, there may be frequently activated time periods of the electrical system, whereby the individual components of the electrical system may heat up correspondingly strongly. In addition, the ambient temperature in summer may also cause heating of the components or the entire electrical system.

[0016] Since the duration since the end of the previous operating phase or the time period between the disconnection and reconnection of a control means, such as a control device / microcontroller, is usually unknown, there is usually no starting value for modeling the component temperature from which further temperature modeling can be carried out with the aid of a state model. This can lead, in particular, in the case of a high ambient temperature or a short duration since the previous operating phase, to the situation that the component temperature is near the threshold temperature for monitoring when the electrical system is switched on, and this cannot be recognized by the state model.

[0017] It is therefore provided that the component temperature of at least one component is temperature-monitored based on a temperature uncertainty taking into account the likelihood of a high component temperature, in order to thus reduce the risk of non-recognition of an excess of the threshold temperature.

[0018] For this purpose, the method described above proposes measuring a reference temperature at a location in the electrical system at the start of a new operating phase of the electrical system. This is usually done with the aid of a temperature sensor, which can preferably be arranged in the control device of the electrical system. An "operating phase" in this context means the time period during which the component temperature can be tracked or modeled by the electrical system.

[0019] With the aid of a heat balance model, the modeling of the component temperature is carried out continuously starting from an initial component temperature assumed to be the reference temperature, in such a way that the heat balance model corresponding to a linear differential equation is calculated discretely in successive time steps.

[0020] Thus, at the beginning, that is, at the start of the current operating phase, the component temperature of at least one component is set to the measured reference temperature due to the lack of general information about the duration elapsed since the end of the last operating phase. This reference temperature is measured by at least one temperature sensor in the electrical system. Then, through modeling, the modeled component temperature is available during the course of the operating phase.

[0021] It can be provided that, in addition, the temperature uncertainty is taken into account only for a predetermined duration after the start of the operating phase. In particular, the temperature uncertainty can be taken into account in a decreasing manner starting from a base value at the start of the operating phase. In particular, the temperature uncertainty can be taken into account in a linearly decreasing or exponentially decreasing manner for a predetermined duration after the start of the operating phase.

[0022] Furthermore, at corresponding times after the start time, a temperature unreliability is determined for at least one component, which results from a base value of the temperature unreliability assigned to the component and in particular from a time-dependent factor function, which provides a curve of the temperature unreliability that decreases to zero, in particular decreases towards zero, starting from the duration since the start time of the current operating phase.

[0023] It can be provided that after a predetermined duration has elapsed, a preset value for the temperature unreliability is continuously assumed.

[0024] Here, the base value of the temperature unreliability can be determined depending on a reference temperature (end-reference temperature) at the end time of the previous operating phase, a component temperature (end-component temperature) modeled for the at least one component at the end time of the previous operating phase, and, if necessary, based on the expansion and contraction amount of the component temperature of the at least one component during the previous operating phase.

[0025] Thus, the higher the end-reference temperature, the higher the base value of the temperature unreliability can be selected. Furthermore, the lower the temperature expansion and contraction amount during the last operating cycle, the lower the base value of the temperature unreliability can be selected. Furthermore, the higher the end-component temperature, the higher the base value of the temperature unreliability can be selected. Furthermore, the smaller the temperature difference between the currently measured reference temperature and the end-reference temperature while the temperature expansion and contraction amount during the previous operating phase is small (for example, the temperature expansion and contraction amount is below a preset threshold), the smaller the unreliability scale can be selected. As an alternative, the smaller the product of the temperature difference between the currently measured reference temperature and the end-reference temperature and the temperature expansion and contraction amount during the previous operating phase, the smaller the base value of the temperature unreliability can be selected.

[0026] Now, when monitoring the temperature based on a threshold temperature preset for at least one component, the thus determined base value of the temperature unreliability can be taken into account and the current temperature unreliability can be taken into account by means of a time-dependent factor function. Thus, the temperature unreliability can be added to the modeled component temperature and then a threshold comparison with the threshold temperature can be carried out. As an alternative, before carrying out the threshold comparison with a reduced threshold temperature, the temperature unreliability can be subtracted from the threshold temperature determined for at least one component. In this way, different thresholds can be generated for monitoring in the case of multiple modeled component temperatures.

[0027] It can be provided that a thermal equilibrium model is used to determine the component temperatures for multiple components, where one or more corresponding threshold temperatures are provided for each component.

[0028] In addition, the fault response can include a limitation or interruption of power delivery or a disconnection of the electrical system.

[0029] According to another aspect, there is provided an apparatus configured to perform the above method.

[0030] According to another aspect, there is provided an electrical system comprising:

[0031] - a plurality of components arranged in a structural assembly so as to effect heat transfer between at least two of said components;

[0032] - the above apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The embodiments will be explained in detail hereinafter with reference to the drawings. Among them:

[0034] Figure 1 A schematic diagram of a drive system as an example for an electrical system is shown; and

[0035] Figure 2 Shows a method for Figure 1 monitoring the component temperatures in an electric drive system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] Figure 1 A drive system 1 is shown as an example for an electrical system, which has an electric machine 2 and a control device 3 for the electric machine 2.

[0037] The control device 3 and the electric machine 2 are compactly arranged in a structural unit.

[0038] The electric machine 2 can have a stator 21 and a rotor 22. The rotor 22 has a rotor shaft 23, which is supported in the housing 24 of the electric machine 2 by a suitable bearing structure 25. Electrical energy is supplied to the electric machine 2 via a control wire 26.

[0039] The control is carried out by means of a drive circuit 31 in the control device 3. The drive circuit 31 is controlled by a control signal from a control unit 32. The control unit can include a microprocessor or a microcontroller, which adjusts the control signal in a manner known per se according to a preset rotational speed or load preset and thus operates the electric machine 2 by means of regulation or control.

[0040] In the drive system, a sensor 33 is provided to, for example, determine the motor current, in particular the phase current, or to model it, measure the motor voltage, measure the rotational speed of the motor (such as a Hall sensor), measure or determine the supply voltage applied to the drive circuit, and measure a reference temperature by means of a temperature sensor 34 arranged at a suitable position in the drive system.

[0041] Based on the motor current and rotational speed estimated as necessary, the electrical loss power of the electric machine 2 can be determined. In addition, based on the rotational speed and the estimated motor current (or torque), the mechanical loss power, for example, in the bearing structure 25 of the rotor shaft 23 can be determined in a manner known per se.

[0042] The start of operation of the drive system 1 can be activated manually via an operating unit (not shown) or by the control of a superior system. When such a drive system is used in user comfort applications in a motor vehicle, such as, for example, an electric window lift system, an electric sliding roof system, or an electric seat adjustment system, it is used irregularly, so that the electric machine is operated frequently during certain periods and the electric machine 2 is not operated at all during other periods.

[0043] In principle, in the control device 3, there is no information in a start of operation about how much time has passed since the end of the previous operating phase.

[0044] Temperature monitoring is performed in the control unit 32, and this temperature monitoring ensures that no components 21, 22, 23, 25, 26 of the electric machine 2 experience heating exceeding a preset threshold temperature. This temperature monitoring is carried out by means of a temperature model that can be formed in the form of a heat balance model. The temperature balance model takes into account the heat sources and heat sinks in the components and the heat transfer resistances between the individual components in the form of linear differential equations of a state model. For this purpose, electrical and mechanical operating parameters are monitored and the energy input is calculated according to physical model equations, where the energy input into the electrical system and the energy output from the electrical system are carried out by means of the electrical and mechanical operating parameters.

[0045] It is possible to model the temperature of the components in the electric drive system 1 based on the heat balance model represented by the state model in the form

[0046] . The vector T here corresponds to the estimated state of the system determined by the component temperatures T1…Tn, and A and B correspond to system matrices that, on the one hand, represent the reaction to the heat gradient (A) and, on the other hand, represent the reaction to the loss power u that is coupled into the component due to contact with adjacent components.

[0047] By means of the form of the state model, it is necessary to define the initial state that exists at the start of the operating phase, i.e., at the start time. However, since it is not known how much time has passed since the previous operating phase and the component temperatures may therefore differ significantly from the ambient temperature, the resulting unreliability of the temperature determination of the component temperatures is taken into account by the following method in order to perform temperature monitoring for all components 21, 22, 23, 25.

[0048] The method for temperature monitoring is shown in Figure 2 the flow chart of. The method is preferably implemented in the control unit and can be implemented there as software and / or hardware.

[0049] First, in step S1, it is checked whether the operating phase should be started. The operating phase is characterized by actively operating the motor 2. The operating phase can be carried out, for example, by manually operating the corresponding operating element or by external control by a superior system. Generally speaking, the operating phase is characterized by a start time and an end time, where the system is passive and has no initiative, especially does not achieve any power, between the end time and the immediately following start time.

[0050] If the start of the operating phase is recognized (alternative: yes), the method is continued with step S2, otherwise it jumps back to step S1. Once the control device is switched on, the operating phase starts, regardless of whether the motor has been operated or not.

[0051] In step S2, the reference temperature at the start time is determined by means of the temperature sensor 34.

[0052] In step S3, this reference temperature is assumed as the starting temperature for all components 21, 22, 23, 25 of the electric drive system 1 to be monitored. This is especially true when the components are cooled to the ambient temperature.

[0053] Furthermore, in step S4, continuously, that is, periodically, starting from the reference temperature of the components, the temperature is determined by means of the above-mentioned state model taking into account the detected or modeled operating parameters, so as to periodically, that is, with the corresponding time step, determine the component temperature for each component.

[0054] In the next step S5, the reference temperature at the end time of the previous operating phase as the end-reference temperature, the component temperature at the end time of the previous operating phase as the end-component temperature, and / or the temperature fluctuation during the previous operating phase, that is, the difference between the maximum component temperature and the minimum component temperature, are called from the permanent memory, and the temperature unreliability value is determined accordingly. The temperature unreliability values T for different components unsicher can be determined, for example, by the weighted sum of the reference temperature at the start time of the current operating phase, the end-reference temperature, the end-component temperature of the relevant component, and the temperature fluctuation of the relevant component.

[0055]

[0056] where g1, g2, g3, g4 represent preset weighting factors.

[0057] However, immediately after the start of the operation phase, there is increased unreliability in determining the component temperature, which decreases as the duration since the start time increases, because the component temperature at the start of the current operation phase has an increasingly smaller weight in the modeled component temperature.

[0058] In particular, it is stipulated for this purpose that the temperature unreliability is only taken into account for a specific duration during monitoring, because it can be assumed that after a specific duration, the temperature model correctly determines the component temperature, since the influence of the component temperature at the start time becomes increasingly smaller. Thus, it can be stipulated that, on the one hand, the temperature unreliability is only taken into account for a predetermined duration. After the end of the predetermined duration, the temperature unreliability can have a value of 0 or a predefined value, with which the basic measurement unreliability can be taken into account.

[0059] As an alternative, it is stipulated that the temperature unreliability decreases as the duration since the start of the current operation phase increases, preferably linearly, or according to the e-function as follows:

[0060]

[0061] Here, the time constants τ1…τ for the different components to be monitored by means of temperature monitoring can be selected differently. n 。T unsicher_1 …T unsicher_n T corresponds to the temperature unreliability for different components, and t corresponds to the evaluation time determined by the time step.

[0062] Now, in addition, it is stipulated in step S6 that a threshold comparison is carried out, in which the modeled component temperature of each monitored component is compared with the threshold temperature preset for the relevant component at each time step. Here, the component temperature must always be lower than the preset threshold temperature for the relevant component.

[0063] In principle, in the method presented here, the unreliability does not explicitly enter into the temperature estimation, but is considered separately with its own dynamics. Therefore, the temperature unreliability is taken into account accordingly during the threshold comparison. This can be done by adding the temperature unreliability to the determined component temperature before the threshold comparison or subtracting it from the corresponding threshold temperature of the temperature unreliability.

[0064] If it is determined in step S6 that the corresponding threshold temperature has been exceeded (alternative: yes), then a fault reaction is carried out in step S10. Otherwise, the method is continued with step S7.

[0065] In step S7, it is checked whether the running phase should be ended. If this is the case (alternative: yes), the method is continued with step S8, otherwise it jumps back to step S4. It can be determined that the running phase ends if the manual operation ends or if the corresponding signal is received by the superior system.

[0066] At the end time, then in step S8 the reference temperature is measured with a temperature sensor, and the temperature expansion / contraction amount determined based on the temperature difference between the maximum reference temperature and the minimum reference temperature during the current just-ended running phase and the component temperature of the monitored component are stored in the permanent memory in order to use them for determining temperature unreliability when activating the next running phase.

[0067] According to another embodiment, a plurality of threshold temperatures can be preset for the component. These threshold temperatures are taken into account in the corresponding threshold comparison as described above. For example, a threshold factor between 0.1 and 1 can be loaded onto the temperature unreliability, and this threshold factor is taken into account during temperature monitoring in the threshold comparison, so that first the operating state is restricted when the lower threshold temperature is exceeded, and the operation of the electric drive system 1 is completely stopped when a higher threshold temperature is exceeded, in a graded manner.

Claims

1. A method for monitoring the temperature of a component in an electrical system (1) having a plurality of components (21, 22, 23, 25, 26), comprising the following steps: - at the start of an operating phase (S1) of the electrical system (1), measuring (S2) a reference temperature, said reference temperature representing the temperature at a location in the electrical system (1); - starting from a reference temperature as a starting value, continuously modeling (S3, S4) the component temperature of at least one component (21, 22, 23, 25, 26) in the electrical system (1) by means of a heat balance model modeled with differential equations as a state model; - continuously monitoring (S6) the component temperature of at least one component (21, 22, 23, 25, 26) based on a threshold temperature preset for at least one component (21, 22, 23, 25, 26); It is characterized in that Furthermore, the monitoring relies on temperature uncertainty. The temperature uncertainty is determined in this case as a function of an end reference temperature, which is a reference temperature at the end of a preceding operating phase, and a measured reference temperature.

2. The method according to claim 1, wherein the temperature uncertainty is further determined as a function of an end-component temperature of at least one component as a component temperature modeled at the end of a previous operating phase and / or as a temperature expansion as a difference between a maximum and a minimum component temperature. 3 . The method according to claim 1 , wherein the temperature uncertainty is also taken into account only for a predetermined period of time after the start-up phase. 4 . The method according to claim 3 , wherein the temperature uncertainty is taken into account in a reduced manner starting from a value at the start of an operating phase. 5 . The method according to claim 4 , wherein the temperature uncertainty is taken into account in a linearly decreasing manner or in an exponentially decreasing manner over a predetermined period of time after the start-up phase. 6 . The method according to claim 3 , wherein a predefined value for the temperature uncertainty is continuously assumed after a predetermined period of time has elapsed.

7. The method according to any one of claims 1 to 6, wherein a plurality of component temperatures are ascertained for a plurality of components (21, 22, 23, 25, 26) with the aid of a thermal balance model, wherein one or more corresponding threshold temperatures are provided for each of the components (21, 22, 23, 25, 26).

8. The method according to any one of claims 1 to 7, wherein the fault reaction (S10) comprises a restriction of power delivery or a shutdown of the electrical system (1).

9. An apparatus configured to perform the method according to any one of claims 1 to 8.

10. An electrical system (1), comprising: - a plurality of components (21, 22, 23, 25, 26) arranged in a structural assembly so that heat transfer occurs between at least two of the components (21, 22, 23, 25, 26). - Device according to claim 9.

11. A computer program product comprising instructions which, when the program is executed by at least one data processing mechanism, cause it to perform the steps of the method according to any one of claims 1 to 8.

12. A machine-readable storage medium comprising instructions which, when executed by at least one data processing mechanism, cause the program to execute the steps of the method according to any one of claims 1 to 8.

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