Method for determining the temperature of an electrical machine

Abstract

Method for determining a temperature of an electrical machine (2), in particular for a motor vehicle (1), wherein the temperature of the electrical machine (2), in particular a rotor temperature and / or a stator temperature, is determined by means of a thermal model, in particular based on at least one current parameter of the electrical machine (2) and / or a power loss parameter of the electrical machine (2), wherein a test temperature is determined by means of a test model that deviates from the thermal model and, depending on a deviation between the temperature determined by means of the thermal model and the test temperature, a temperature increment is determined and the thermal model is changed based on the temperature increment.

Description

[0001] The invention relates to a method for determining a temperature of an electrical machine, in particular for a motor vehicle, wherein the temperature of the electrical machine, in particular a rotor temperature and / or a stator temperature, is determined by means of a thermal model, in particular based on at least one current parameter of the electrical machine and / or a power loss parameter of the electrical machine.

[0002] Such methods for determining a temperature, in particular the rotor temperature and / or the stator temperature, of an electrical machine of a motor vehicle, in particular an electrical machine designed as a drive device of the motor vehicle, are generally known from the prior art. Typically, a thermal model is used for this purpose, which can basically be designed in any way, for example as a Kl model, node model or the like. Typically, the thermal model is based on the consideration of at least one electrical parameter of the electrical machine, in particular a current parameter and / or a parameter of the electrical machine describing the power loss. Alternatively or additionally, the thermal model can also be based on at least one cooling parameter, for example a temperature control medium temperature, in particular a cooling water temperature or an oil temperature.In other words, knowing the input variables, for example the current parameters and / or the power loss parameters, of the electrical machine, the temperature development in the electrical machine can be determined by the thermal model.

[0003] It is also known that when the temperature of an electrical machine is determined in this way, the temperature model depicts or models the behavior of the electrical machine. This assumes that the real electrical machine behaves, within certain limits, like the modeled electrical machine. Since the model behavior is based, for example, on historical or experimental data from a measured electrical machine, fluctuations that can occur in the manufacturing process of electrical machines and thus lead to a deviation of an individual electrical machine from the model behavior are usually not taken into account. This can lead to a deviation of the real behavior of the electrical machine from the model behavior due to manufacturing tolerances, component variation, and the like.Likewise, changes in the actual electrical machine can occur over its lifetime, for example, due to aging phenomena on the electrical machine's components, which can also lead to a deviation from the model behavior. This can lead to the specific temperature, which is determined based on the model as described, deviating from the actual temperature, and thus the determination error is reflected in the operation of the electrical machine.

[0004] The invention is based on the object of specifying a method for determining a temperature of an electrical machine which is improved compared to the method in question, in which, in particular, deviations from a model behavior can be taken into account.

[0005] The object is achieved by a method having the features of claim 1. Advantageous embodiments are the subject of the subclaims.

[0006] As described, the invention relates to a method for determining the temperature of an electrical machine, specifically an electrical machine of a motor vehicle. In particular, the electrical machine can be used as a traction drive or drive device in the motor vehicle. The temperature to be determined by the method can, in particular, relate to the rotor temperature and / or the stator temperature of the electrical machine. The temperature is generally determined using a thermal model, which is specifically based on at least one current parameter of the electrical machine and / or a power loss parameter of the electrical machine.

[0007] The invention is based on the realization that a test temperature is determined using a test model that differs from the thermal model, and that the thermal model is changed based on the temperature increment. The invention therefore proposes that, in addition to determining the temperature using the thermal model, a test model is used to determine a test temperature. The test model is different from the thermal model. If the real electrical machine corresponds to the model behavior, the test model and the thermal model obtain the same results. The test model can therefore determine the test temperature in a different way than is done by the thermal model. In other words, the same temperature of the electrical machine can be determined in different ways, and it can therefore be checked whether both models, i.e. the thermal model and the test model, deliver the same result.If the electrical machine deviates from the model behavior, the test temperature will deviate from the specified temperature. Depending on the deviation, a temperature increment can be determined, which can be used to modify the thermal model to account for the deviation between the model behavior and the actual behavior.

[0008] In other words, if the test temperature deviates from the specified temperature—i.e., if the test model and the thermal model produce different results—a temperature increment is determined, and the thermal model is modified based on the temperature increment, allowing the thermal model results to be better adapted to the behavior of the real electrical machine. In particular, this allows the thermal model to be used primarily to determine the temperature of the electrical machine, but the results to be adjusted based on the test model's determination.

[0009] Therefore, there is no change to the basic determination of the temperature of the electrical machine, since the temperature is basically determined by the thermal model, although an adjustment of the results of the thermal model is permitted within certain limits. The test model is therefore only used in particular to check or to (slightly) correct the thermal model, namely by the temperature increment. The temperature increment can basically be positive or negative and can be incorporated into the modeling by the thermal model in a largely arbitrary manner or can change the thermal model accordingly. In particular, the temperature output by the thermal model is increased or decreased by the temperature increment. The temperature increment is particularly limited in its amount, meaning that no direct adjustment of the output temperature orthe specific temperature to the test temperature, but the change of the thermal model is only carried out in the direction of the test temperature by the temperature increment, for example limited to a maximum value, in particular 0.1 K to 2 K, preferably 0.5 K to 1 K. In other words, temperature increment and temperature difference are different.

[0010] As already described, the test model differs from the thermal model. In particular, the mechanisms by which the thermal model determines the temperature and the test model determines the test temperature are different from one another. The method can provide that the test model is based on a temperature flow observer, wherein the test temperature is determined based on a magnetic flux of the electrical machine. The thermal model can determine the specific temperature of the electrical machine in particular based on electrical parameters, in particular the currents flowing in the electrical machine or power loss parameters, i.e. the power loss prevailing in the electrical machine. In contrast, the test model considers the magnetic flux of the electrical machine, so that the test temperature can ultimately be determined based on the magnetic flux of the electrical machine.The magnetic flux in an electrical machine is known to be temperature-dependent, so the test temperature of the electrical machine can be determined based on the currently prevailing magnetic flux in the electrical machine, allowing the test model to determine the test temperature. The determined temperature can also be referred to as the model temperature in this application.

[0011] The advantage here is that, in addition to determining the temperature based on current parameters or power loss, component variation—i.e., tolerance-related deviations of the electrical machine and aging of the electrical machine—can also be taken into account in the test model. If such component variation or aging occurs, it changes the magnetic flux of the electrical machine and thus the test temperature determined by the test model in a specific operating state or at a specific magnetic flux.

[0012] This allows a change in the temperature behavior of the electrical machine over its service life to be taken into account by the test model. And because the thermal model, which is used to determine the actual temperature, can be modified by the test model, and thus the thermal model can also be adapted or adjusted over the service life of the electrical machine. In particular, a temporary model can be used as the test model, which can only be applied in certain operating ranges of the electrical machine, in particular certain speed ranges. The thermal model, on the other hand, can be applied globally, i.e., in all operating ranges of the electrical machine.

[0013] In a further development of the method, it can be provided that the test temperature is determined in a specific operating state of the electrical machine, in particular at at least one specific speed or in at least one specific speed range. In particular, it can be taken into account that, depending on the test model, this delivers optimal results in a specific operating state, for example in a specific speed range. The test model can further comprise at least two sub-models that are designed for specific operating states, for example a first sub-model for a specific first speed or a specific first speed range and a second sub-model for a specific second speed or a specific second speed range.

[0014] If the electric machine is operated at a specific speed or within a specific speed range, the thermal model determines the specific temperature. Furthermore, the test model determines the test temperature in the specific operating condition, i.e., at a specific speed or within a specific speed range. Changing the thermal model in the event of a deviation between the test temperature and the specific temperature can thus be carried out for specific operating conditions, for example, for different speeds or different speed ranges.

[0015] As already described at the beginning, the test temperature obtained from the test model and the determined temperature obtained from the thermal model are compared. This comparison allows a temperature difference to be determined if the test temperature deviates from the determined temperature. In other words, the temperature difference is zero if the test temperature corresponds to the determined temperature. According to a further development of the method, at least one temperature difference limit can be specified, whereby the thermal model is only changed if the test temperature deviates from the determined temperature by more than the temperature difference limit.This ensures that minor differences between the test temperature and the specified temperature do not directly lead to a change in the thermal model, but rather that the thermal model is only adapted when there is a significant difference between the results of the test model and the thermal model. For example, the temperature difference limit can be used symmetrically for an upper temperature difference limit and a lower temperature difference limit, or two different temperature difference limits can be specified for an upper temperature difference limit and a lower temperature difference limit. For example, a value in the range of 1-10 K, in particular 2-5 K, for example 3 K, can be used as the temperature difference limit.

[0016] The method can be further developed such that the thermal model is modified based on a characteristic map or a characteristic curve. As described, the temperature can be determined using the thermal model, as well as the test temperature can be determined using the test model for different operating conditions. The results can be stored accordingly in a characteristic map or a characteristic curve.

[0017] In other words, a temperature increment can be defined for the different operating conditions and the thermal model modified accordingly, with the change being stored in the characteristic map or characteristic curve. Specifically, for each operating condition, for example, each specific speed or each specific speed range, the test temperature can be compared with the specific temperature. This means that if the temperature difference limit is exceeded, the thermal model can be adapted, specifically for this speed range or speed. If the speed or speed range is re-established during further operation of the electric machine, the modified thermal model can be used to determine the temperature.

[0018] The method can further provide for a change limit to be specified, wherein the thermal model, in particular the determined temperature, can only be changed from a base value within the change limit, in particular + / - 10 K or between -5 K and +10 K or -10 K and +5 K. The "base value" can be understood in particular as the temperature determined by the thermal model for the operating state without adaptation of the thermal model. The thermal model can only be changed by the test model to such an extent that, after changing the thermal model, the determined temperature in the operating state deviates from the base value by the change limit.The change limit specifically prevents the test model, which is inherently less accurate than the thermal model used to determine the specific temperature, from causing a change in the thermal model within defined limits. In other words, the thermal model used to determine the specific temperature of the electrical machine is generally trusted. A tendency for the test model to change the thermal model, for example, due to component variation or aging of the electrical machine, is permitted, but the thermal model cannot be changed beyond the change limit.

[0019] Furthermore, the method can generate status information for the electrical machine based on the number of temperature increments. For example, it is possible to determine how many temperature increments were generated to adapt the thermal model. The number of temperature increments or the temperature increments can, for example, be stored in a control unit of the electrical machine and read out again from there. If there are several temperature increments by which the thermal model was adapted during operation, it can be assumed that the electrical machine deviates significantly from the model behavior, which was corrected by the test model. As described, the deviation can generally occur due to component variation or aging.In this case, the corresponding phenomena that lead to a change in the thermal model can also reverse or compensate for each other, so that, for example, when the electrical machine is put into operation, a change in the thermal model occurs due to component variation, which is then reversed or compensated for due to aging phenomena by appropriate adaptation of the thermal model, so that the basic value of the thermal model is returned.

[0020] Furthermore, the method can generate state information based on time information of at least one temperature increment. The time information indicates in particular when the temperature increment or when the individual temperature increments were generated or when the thermal model was changed based on the temperature increment. This enables in particular further precision of the state information, since the time information of the temperature increments can be used to determine at what point in time, for example in relation to the lifetime of the electrical machine, the temperature increment was generated and the thermal model was changed. This makes it possible to distinguish whether the temperature increment is based on component variation or a manufacturing tolerance, or whether it only became necessary over the course of the electrical machine's operation due to aging of the components of the electrical machine.

[0021] In addition to the described method, the invention relates to a determination device for determining a temperature of an electrical machine, in particular for a motor vehicle, wherein the determination device is designed to determine the temperature of the electrical machine, in particular a rotor temperature and / or a stator temperature, by means of a thermal model, in particular based on at least one current parameter of the electrical machine and / or a power loss parameter of the electrical machine, wherein the determination device is designed to determine a test temperature by means of a test model that deviates from the thermal model and to determine a temperature increment depending on a deviation between the temperature determined by means of the thermal model and the test temperature and to change the thermal model based on the temperature increment.The determination device can in particular be designed as part of a control device or computing device or can comprise such a device.

[0022] Furthermore, the invention relates to a motor vehicle comprising an electric machine and a determination device as described above.

[0023] All advantages, details and features described with regard to the method are fully transferable to the motor vehicle and the destination device.

[0024] The invention is explained below using exemplary embodiments with reference to the figures. The figures are schematic representations and show: Fig. 1 a schematic diagram of a motor vehicle; and Fig. 2 a schematic diagram of a flow chart of a method for determining a temperature of an electrical machine of a motor vehicle.

[0025] Fig. 1 schematically shows a motor vehicle 1 comprising an electric machine 2 and a determination device 3. The determination device 3 can be designed as a component of a control device or computing device of the motor vehicle 1 or alternatively can be connected thereto or have such a device. The determination device 3 is designed to determine the temperature of the electric machine 2, in particular to determine a rotor temperature and / or a stator temperature of the electric machine 2. The determination device 3 is fundamentally designed to carry out the method described herein for determining the temperature of the electric machine 2. The method is described below with reference to Fig. 2. The description is accordingly applicable to the destination device 3 or the motor vehicle 1 of Fig. 1 transferable.

[0026] In the Fig.In the flowchart schematically illustrated in Figure 2, block 4 represents the thermal model, or rather, the thermal model is executed in block 4, which is executed, for example, by the determination unit 3. The thermal model is fundamentally arbitrary and can, for example, comprise a Cl model, a node model, and the like, and is based, for example, on cooling parameters and / or current parameters of the electrical machine 2, in particular on power loss parameters. The thermal model is designed in block 4 to determine the temperature of the electrical machine 2.

[0027] Furthermore, block 5 in the flowchart shows a test model that is designed to determine a test temperature. The test model differs from the thermal model and deviates from it. The test model is based in particular on a temperature flow observer or on a signal injection model, so that the test temperature determined by the test model in block 5 can be based on the magnetic flux of the electrical machine 2. The test temperature determined by the test model in block 5 is fed to a block 6, to which the determined temperature from the thermal model is also fed. Furthermore, the determined temperature from the thermal model from block 4 is fed to a block 7, which exemplifies the control or regulation of the operation of the electrical machine 2.This makes it clear that only the thermal model is relevant for the operation of the electrical machine 2, which means that only the specific temperature from the thermal model is used for the control or regulation of the electrical machine 2.

[0028] The test temperature supplied to block 6 and the specified temperature supplied to block 6 are compared in block 6. In particular, the temperature difference is calculated. Depending on the temperature difference, block 6 branches to one of blocks 8-10. Specifically, a temperature difference limit is set in block 6. If the test temperature differs from the specified temperature by less than the temperature difference limit, i.e., if the temperature difference is smaller than the temperature difference limit, block 6 branches to block 9, where no change to the thermal model occurs.

[0029] If the temperature difference exceeds the temperature difference limit, the program branches from block 6 to block 8 if the test temperature is lower than the specified temperature, and from block 6 to block 10 if the test temperature is higher than the specified temperature. The same temperature difference limit can be used for both cases, for example -3K and +3K, or a first temperature difference limit and a second temperature difference limit can be specified, i.e. different temperature difference limits can be defined for positive and negative temperature differences. In any case, the program branches from block 6 to block 9 if the temperature difference limit is not exceeded, and optionally, depending on the positive or negative temperature difference, the program branches from block 6 to block 8 or from block 6 to block 10.

[0030] In blocks 8 and 10, the corresponding temperature increments are defined or generated by which the thermal model is to be modified. The temperature increments are therefore limited in magnitude. Regardless of how much the determined temperature differs from the test temperature in block 6, either a positive temperature increment is generated in block 8 or a negative temperature increment in block 10. The temperature increment can be, for example, 0.1 K to 2 K, specifically 0.5 K to 1 K.

[0031] For example, it can be determined in block 6 that the test temperature is 10 K lower than the specific temperature, whereby the temperature difference limit has been exceeded. As described, a branch is then made from block 6 to block 8, in which a positive temperature increment, for example 0.5 K, is generated to change the thermal model. If it is determined in block 6 that the test temperature is, for example, 20 K higher than the specific temperature, a branch can be made from block 6 to block 10, as described, in which a negative temperature increment, for example -0.5 K, is generated to change the thermal model accordingly. This ensures that the thermal model is only changed to a small extent by generating the temperature increments, so that an iterative run of the method described herein is possible in order to make slow changes to the thermal model.

[0032] Subsequently, the program branches from block 6 or block 10 to block 11, where the thermal model is modified based on a map or characteristic curve. Alternatively, the thermal model adaptation can also branch directly from block 8 or block 10 to block 4 to adapt the thermal model directly.

[0033] Optionally, the temperature increment for the currently existing operating state can be stored in block 11 so that the thermal model can be modified for this specific operating state, for example a specific speed or a specific speed range. When the electric machine 2 is operated again in the specific operating state, the thermal model is already operated taking the temperature increment into account. The method described here can be executed across all operating states of the electric machine 2 so that corresponding temperature increments can be stored in block 11 for a wide variety of operating states. In this case, a selection of various submodels of the test model can be made in block 5. The submodels of the test model are, in particular, temporary models that are suitable for specific operating states.Depending on the current operating state, for example, the appropriate submodel can be selected as a test model.

[0034] In blocks 8, 10 or 11, a change limit can also be specified. In this case, changes to the thermal model are only permitted within the change limit. For example, a base value can be specified for a specific operating state, in particular the temperature output by the thermal model in the operating state, provided the thermal model has not been changed by temperature increments. The change limit can be 10 K, for example. This means that using the method described here, in particular using the test model, the thermal model can only be changed by a maximum of + / - 10 K in order to take component variation or aging or other changes to the electrical machine 2 into account. This ensures, in particular, that the thermal model cannot be changed excessively by the test model.

[0035] Further optionally, the generated temperature increments can be stored in block 11. Specifically, each temperature increment can be assigned a timestamp, allowing the time and date of each temperature increment to be read throughout the operation of the electric machine 2 in order to adapt the thermal model. This allows state information of the electric machine 2 to be determined in block 11, indicating how the state of the electric machine 2 has changed or how it deviates from a model behavior.

[0036] For example, the number of temperature increments can be taken into account to determine the extent to which the thermal model has been changed. The state information, in particular the number of temperature increments, is ultimately a measure of the deviation of the real electrical machine 2 from standard behavior or model behavior. Furthermore, based on time information, in particular the timestamp of each temperature increment, it can be determined whether the change in the thermal model or the generation of the temperature increments occurred at the beginning of the operation of the electrical machine 2, so that this is based on component variation of the electrical machine 2, or whether the temperature increments were generated over the course of the operation of the electrical machine 2, so that the corresponding cause may lie in aging of the electrical machine 2.

[0037] The method shown can, in particular, be performed continuously, so that the determined temperature output by the thermal model can always be compared with the corresponding test temperature from the test model. If temperature increments are generated or stored in the characteristic curve or map, these are then fed to block 4 so that the thermal model can be modified accordingly, and the modified determined temperature can then be fed to block 7 for the control or regulation of the electric machine 2.

[0038] As described, the thermal model determines a temperature, in particular the rotor temperature and the stator temperature. The test model is able to determine the rotor temperature as the test temperature, particularly based on the magnetic flux under consideration. This allows, in particular, the rotor temperature determined by the thermal model to be changed based on the test temperature, as previously described. In this case, feedback between the rotor temperature and the stator temperature is possible in the thermal model, or a change in the rotor temperature can be at least indirectly converted into a change in the stator temperature. Reference symbol 1 motor vehicle 2 electric machine 3 Destination device 4-11 Block

Claims

[1] Method for determining a temperature of an electrical machine (2), in particular for a motor vehicle (1), wherein the temperature of the electrical machine (2), in particular a rotor temperature and / or a stator temperature, is determined by means of a thermal model, in particular based on at least one current parameter of the electrical machine (2) and / or a power loss parameter of the electrical machine (2), characterized by that a test temperature is determined by means of a test model that deviates from the thermal model and, depending on a deviation between the temperature determined by means of the thermal model and the test temperature, a temperature increment is determined and the thermal model is changed based on the temperature increment. [2] Method according to claim 1, characterized bythat the test model is based on a temperature flow observer and / or on a signal injection model, wherein the test temperature is determined based on a magnetic flux of the electrical machine (2). [3] Method according to claim 1 or 2, characterized by that the test temperature is determined in a specific operating state of the electrical machine (2), in particular at at least one specific speed or in at least one specific speed range. [4] Method according to one of the preceding claims, characterized by that at least one temperature difference limit is specified, whereby the thermal model is only changed if the test temperature deviates from the specified temperature by more than the temperature difference limit. [5] Method according to one of the preceding claims, characterized by that the change in the thermal model is carried out based on a map or a characteristic curve. [6] Method according to one of the preceding claims, characterized by that a change limit is specified, whereby the thermal model, in particular the specific temperature, can be changed starting from a base value only within the change limit, in particular + / -10K. [7] Method according to one of the preceding claims, characterized by that status information of the electrical machine (2) is generated based on a number of temperature increments. [8] Method according to claim 7, characterized by that the state information is generated based on time information of at least one temperature increment. [9] Determination device (3) for determining a temperature of an electrical machine (2), in particular for a motor vehicle (1), wherein the determination device is designed to determine the temperature of the electrical machine (2), in particular a rotor temperature and / or a stator temperature, by means of a thermal model, in particular based on at least one current parameter of the electrical machine (2) and / or a power loss parameter of the electrical machine (2), characterized by that the determining device is designed to determine a test temperature by means of a test model that deviates from the thermal model and to determine a temperature increment as a function of a deviation between the temperature determined by means of the thermal model and the test temperature and to change the thermal model based on the temperature increment. [10] Motor vehicle (1) comprising an electric machine (2) and a determining device (3) according to the preceding claim.

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