Motor rotor temperature estimation method, device and equipment

Abstract

The invention discloses a motor rotor temperature estimation method, and the method comprises the steps: obtaining a corresponding operation parameter of a motor at a current moment and the initial temperature of a rotor, inputting the operation transmission and the initial temperature of the rotor into a motor thermal model, and obtaining a first estimation temperature for the rotor; and obtaining a rotor flux linkage of the rotor under the zero-torque working condition, and obtaining a second estimated temperature of the rotor based on the rotor flux linkage and a preset corresponding relation. And if the difference value between the first estimated temperature and the second estimated temperature is greater than the first preset threshold value, taking the second estimated temperature as the temperature of the rotor at the current moment. And when the next estimation moment arrives, the operation parameters of the next estimation moment and the temperature of the rotor at the previous estimation moment (relative to the next estimation moment) are input into a motor thermal model, and the rotor estimation temperature output by the motor thermal model serves as the temperature of the rotor at the next estimation moment. Namely, the estimation accuracy is improved by correcting the estimated temperature of the rotor, so that the rotor is accurately protected.

Description

A method, apparatus and equipment for estimating motor rotor temperature Technical Field

[0001] This application relates to the field of new energy vehicle technology, specifically to a method, device, and equipment for estimating motor rotor temperature. Background Technology

[0002] Most current new energy vehicles use permanent magnet synchronous motors as their drive components. These motors mainly consist of a stator and a rotor. Temperature sensors are typically embedded in the stator windings to provide real-time feedback of the winding temperature to the controller for protection. The operating temperature of the rotor's permanent magnets also needs to be controlled within a certain range. However, due to the high speed of the rotor, installing temperature sensors is extremely difficult and costly, making it challenging to obtain the rotor temperature. Summary of the Invention

[0003] In view of this, this application provides a method, apparatus and equipment for estimating the rotor temperature of an electric motor, so as to obtain the rotor temperature and thereby protect the rotor.

[0004] To solve the above problems, the technical solution provided in this application is as follows:

[0005] In a first aspect of this application, a method for estimating the temperature of a motor rotor is provided, the method comprising:

[0006] The initial temperature of the rotor and the operating parameters of the motor at the current moment are obtained, including the speed, torque, water temperature and motor efficiency.

[0007] The operating parameters and the initial temperature are input into the motor thermal model to obtain the first estimated temperature of the rotor;

[0008] Obtain the rotor flux linkage under zero torque condition, and determine the second estimated temperature of the rotor based on the rotor flux linkage and the corresponding relationship, wherein the corresponding relationship includes the relationship between rotor flux linkage and rotor temperature;

[0009] If the difference between the first estimated temperature and the second estimated temperature is greater than the first preset threshold, the second estimated temperature is taken as the temperature of the rotor at the current moment.

[0010] When the next estimation time arrives, the operating parameters of the next estimation time and the rotor temperature at the current time are input into the motor thermal model, and the rotor estimation temperature output by the motor thermal model is used as the rotor temperature at the next estimation time.

[0011] In one possible implementation, obtaining the rotor flux linkage under zero torque conditions includes:

[0012] The voltage and speed of the rotor are obtained within a preset speed range with zero torque, and the rotor does not generate weak magnetic current within the preset speed range with zero torque;

[0013] The rotor flux linkage is determined based on the voltage and the rotational speed.

[0014] In one possible implementation, obtaining the initial temperature of the rotor during motor operation includes:

[0015] Get the current time and the time of the last motor power-off;

[0016] If the time difference between the current time and the most recent time the motor was powered off is less than or equal to the second preset threshold, the rotor temperature stored at the time the motor was powered off will be used as the initial temperature of the rotor.

[0017] If the time difference between the current time and the most recent time the motor was powered off is greater than the second preset threshold, the current ambient temperature will be used as the initial temperature of the rotor.

[0018] In one possible implementation, the method further includes:

[0019] If the difference between the first estimated temperature and the second estimated temperature is greater than the first preset threshold, the second estimated temperature is controlled to pass through a low-pass filter and then output to the control system.

[0020] In one possible implementation, the process of obtaining the motor thermal model includes:

[0021] Acquire test data of the motor under different operating conditions, including stator temperature and rotor temperature;

[0022] Obtain the motor's operating parameters under the target operating conditions, including speed, torque, water temperature, and motor efficiency;

[0023] The initial values ​​of the operating parameters and the parameters to be identified are input into the motor thermal model to obtain estimated data. The estimated data includes the estimated stator temperature and the estimated rotor temperature. The motor thermal model includes the parameters to be identified.

[0024] The test data corresponding to the target working condition is compared with the estimated data. The value of the parameter to be identified is adjusted according to the comparison result until the error between the test data and the estimated data meets the preset condition, and the value of the parameter to be identified is obtained.

[0025] In one possible implementation, adjusting the data of the parameter to be identified based on the comparison result until the error between the test data and the estimated data meets a preset condition to obtain the value of the parameter to be identified includes:

[0026] Based on the prediction error minimization algorithm, the value of the parameter to be identified is adjusted according to the comparison results until the error between the test data and the estimated data is minimized, thereby obtaining the value of the parameter to be identified.

[0027] In one possible implementation, the parameters to be identified include thermal resistance, thermal capacity, and loss ratio, wherein the loss ratio refers to the ratio of rotor iron loss to sub-iron loss.

[0028] In one possible implementation, the step of inputting the initial values ​​of the operating parameters and the parameters to be identified into the motor thermal model to obtain estimation data includes:

[0029] The total motor loss is determined based on the speed, torque, and motor efficiency in the operating parameters.

[0030] Calculate the stator winding losses based on the motor's current;

[0031] The stator iron loss and the rotor iron loss are obtained by multiplying the difference between the total motor loss and the stator winding loss by the loss ratio.

[0032] The initial values ​​of thermal resistance, thermal capacity, stator iron loss, and rotor iron loss are input into the motor thermal model to obtain estimated data.

[0033] In a second aspect of this application, a motor rotor temperature estimation device is provided, the device comprising:

[0034] The first acquisition unit is used to acquire the initial temperature of the rotor and the operating parameters of the motor at the current moment, including the rotational speed, torque, water temperature and motor efficiency.

[0035] The second acquisition unit is used to input the operating parameters and the initial temperature into the motor thermal model to obtain the first estimated temperature of the rotor.

[0036] The third acquisition unit is used to acquire the rotor flux linkage of the rotor under zero torque conditions, and determine the second estimated temperature of the rotor based on the rotor flux linkage and the corresponding relationship, wherein the corresponding relationship includes the relationship between the rotor flux linkage and the rotor temperature.

[0037] The first determining unit is configured to, if the difference between the first estimated temperature and the second estimated temperature is greater than a first preset threshold, take the second estimated temperature as the temperature of the rotor at the current moment.

[0038] The second determining unit is used to input the operating parameters of the next estimation time and the rotor temperature at the current time into the motor thermal model when the next estimation time arrives, and to use the rotor estimation temperature output by the motor thermal model as the rotor temperature at the next estimation time.

[0039] In a third aspect of this application, an electronic device is provided, comprising: a processor and a memory;

[0040] The memory is used to store computer-readable instructions or computer programs;

[0041] The processor is configured to read the computer-readable instructions or the computer program to enable the electronic device to implement the motor rotor temperature estimation method as described in the first aspect.

[0042] Therefore, this application has the following beneficial effects:

[0043] In this application, to estimate the rotor temperature, the operating parameters of the motor at the current moment and the initial temperature of the rotor are obtained. This operating data and the initial rotor temperature are input into the motor thermal model to obtain a first estimated temperature for the rotor. Simultaneously, the rotor flux linkage under zero-torque conditions is obtained, and a second estimated temperature is obtained based on the rotor flux linkage and a preset correspondence. If the difference between the first and second estimated temperatures is greater than a first preset threshold, the second estimated temperature is taken as the rotor temperature at the current moment. When the next estimation moment arrives, the operating parameters for the next estimation moment and the rotor temperature at the previous estimation moment (relative to the next estimation moment) are input into the motor thermal model, and the rotor estimated temperature output by the motor thermal model is taken as the rotor temperature at the next estimation moment. That is, this embodiment improves the accuracy of the estimated rotor temperature by correcting it, thereby providing precise protection for the rotor. Attached Figure Description

[0044] Figure 1 is a schematic flowchart of a motor rotor temperature estimation method provided in an embodiment of this application;

[0045] Figure 2 is a schematic diagram showing the relationship between rotor flux and rotor temperature according to an embodiment of this application;

[0046] Figure 3 is a framework diagram for estimating motor rotor temperature according to an embodiment of this application;

[0047] Figure 4 is a flowchart of a method for obtaining a motor thermal model according to an embodiment of this application;

[0048] Figure 5 is a structural diagram of a motor rotor temperature estimation device provided in an embodiment of this application. Detailed Implementation

[0049] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0050] In practical applications, to obtain stator and rotor temperatures in a timely manner, these temperatures are typically estimated using software. However, stator and rotor temperature estimation algorithms are usually based on motor thermal models, and the calculation accuracy of these models is related to factors such as ambient temperature, initial temperature, and voltage. When the motor thermal model is running in a real vehicle, the calculation accuracy cannot be determined because there are no rotor temperature sensors. Moreover, since the calculated temperature value at one moment affects the temperature at the next moment, there is a cumulative effect in the temperature calculation, ultimately causing the calculated temperature to deviate from the true value.

[0051] Based on this, this application proposes a method for estimating motor rotor temperature. First, the operating parameters of the motor at the current moment and the initial temperature of the rotor are obtained. These operating parameters and initial temperature are then input into a motor thermal model to obtain a first estimated temperature for the rotor. Next, the rotor flux linkage under a specific operating condition (zero torque condition) is obtained, and a second estimated temperature of the rotor is determined based on this flux linkage and the correspondence between rotor flux linkage and rotor temperature. The difference between the first and second estimated temperatures is then determined. If the difference is significant, the second estimated temperature is used as the rotor temperature at the current moment. When the next estimation moment arrives, the operating parameters for the next estimation moment and the reference temperature (i.e., the temperature at the current moment) are input into the motor thermal model, and the estimated temperature output by the motor thermal model is used as the rotor temperature at that next estimation moment. That is, when the rotor temperature estimated by the motor thermal model differs significantly from the temperature estimated by the rotor back EMF, the rotor temperature estimated by the back EMF is used to correct the initial rotor temperature, thereby improving the reliability and confidence of the temperature estimated by the motor thermal model.

[0052] To facilitate understanding of the technical solution of this application, the following description will be provided in conjunction with the accompanying drawings.

[0053] Referring to Figure 1, which is a flowchart of a method for estimating the rotor temperature of a motor according to an embodiment of this application, as shown in Figure 1, the method includes:

[0054] S101: Obtain the initial temperature of the rotor and the current operating parameters of the motor.

[0055] S102: Input the operating parameters and initial temperature into the motor thermal model to obtain the first estimated temperature of the rotor.

[0056] In this embodiment, when the motor is running normally, the operating parameters corresponding to the motor's operation and the initial temperature of the rotor are acquired. These operating parameters include, but are not limited to, speed, torque, water temperature, and motor efficiency. Specifically, the types of parameters included in the operating parameters are related to the structure of the motor thermal model. The acquisition of the motor thermal model will be explained in subsequent embodiments.

[0057] It should be noted that when calculating rotor temperature, the rotor temperature at the previous moment will affect the rotor temperature at the next moment. Therefore, it is necessary to obtain the rotor temperature at the previous moment and use it as the base temperature to estimate the rotor temperature at the next moment. If the motor has just started, the rotor temperature at the previous moment is the rotor temperature at the moment the motor was powered off, i.e., the initial temperature.

[0058] The process of obtaining the initial rotor temperature during motor operation includes: obtaining the current time and the most recent motor shutdown time; if the time difference between the current time and the most recent motor shutdown time is less than or equal to a second preset threshold, the rotor temperature stored at the time of the most recent motor shutdown is used as the initial rotor temperature; if the time difference between the current time and the time of the most recent power-off is greater than the second preset threshold, the current ambient temperature is used as the initial rotor temperature. That is, each time the motor is powered off, the power-off time and the rotor temperature at that time are recorded. When the motor is powered on again, the time difference between the current time and the most recent power-off time is determined. If the time difference is less than or equal to the second preset threshold, it indicates that the time interval between the two is small, and the rotor temperature has not changed significantly; the temperature at the time of power-off can be used as the initial temperature for this power-on. If the time difference is greater than the second preset threshold, it indicates that the time interval between the two is large, and the rotor temperature is close to the ambient temperature; the current ambient temperature is then used as the initial rotor temperature.

[0059] After obtaining the motor's operating parameters and the rotor's initial temperature at the current moment, the above data is used as input parameters and input into the motor thermal model to obtain the first estimated temperature of the rotor output by the motor thermal model.

[0060] S103: Obtain the rotor flux linkage under zero torque conditions, and determine the second estimated temperature of the rotor based on the rotor flux linkage and the corresponding relationship.

[0061] In this embodiment, the rotor temperature is estimated based on the rotor's back electromotive force under specific operating conditions to obtain a second estimated temperature. Specifically, the rotor flux linkage under zero torque conditions is obtained, and the second estimated temperature of the rotor is determined based on this rotor flux linkage and its corresponding relationship. This corresponding relationship includes the relationship between the rotor flux linkage and the rotor temperature, which can be obtained through offline temperature measurement data. Specifically, based on the offline temperature measurement data, the rotor voltage value within a zero torque and preset speed range is extracted; the flux linkage value is obtained by dividing the voltage value by the speed. By extracting a large number of discrete rotor temperature and rotor flux linkage data points, a polynomial fitting method is used to obtain the temperature characteristic curve of the rotor flux linkage, as shown in Figure 2.

[0062] The process of obtaining the rotor flux linkage under zero torque conditions includes: acquiring the voltage and speed of the rotor within a preset speed range at zero torque, where the rotor does not generate weak electromagnetic fields; and determining the rotor flux linkage based on the voltage and speed. After acquiring the rotor flux linkage, the corresponding rotor temperature can be calculated using Figure 2. The preset speed range can be determined based on the actual operating conditions of the rotor, for example, a speed of 1000-6000 rpm. It should be noted that requiring the rotor to be within the preset speed range at zero torque is to eliminate the influence of dead zones and speed fluctuations; therefore, the speed cannot be too low. Additionally, it is necessary to ensure that there is no weak magnetic current under zero torque, as weak magnetic current will couple with parameters, leading to reduced voltage accuracy. To ensure the accuracy of voltage and speed, and thus obtain a more accurate rotor temperature, the speed cannot be too high. Based on the above considerations, an upper and lower limit for the speed needs to be set.

[0063] It should be noted that the execution order of S102 and S103 is not limited as described above. S101 and S102 can be executed first, followed by S103; or S103 can be executed first, followed by S101 and S102; or S102 and S103 can be executed simultaneously. This embodiment does not impose any limitations on this.

[0064] S104: If the difference between the first estimated temperature and the second estimated temperature is greater than the first preset threshold, the second estimated temperature is taken as the rotor temperature at the current moment.

[0065] S105: When the next estimation time arrives, input the operating parameters of the next estimation time and the rotor temperature at the current time into the motor thermal model, and use the rotor estimated temperature output by the motor thermal model as the rotor temperature at the next estimation time.

[0066] After obtaining the first and second estimated temperatures for the rotor, the temperature difference between the two estimated temperatures is compared. If the temperature difference is less than or equal to a first preset threshold, the first estimated temperature is used as the rotor's operating temperature at the current moment; if the temperature difference is greater than the first preset threshold, the second estimated temperature is used as the rotor's operating temperature at the current moment. That is, when the difference between the two estimated temperatures is less than or equal to the first preset threshold, the control system uses the rotor estimated temperature output by the motor thermal model to protect the rotor at the current moment.

[0067] When the next estimation time arrives, the operating parameters corresponding to the next estimation time are obtained, and the operating parameters and the rotor temperature of the previous time (the current time mentioned above) are input into the motor thermal model. The estimated temperature output by the motor thermal model is used as the rotor temperature of the rotor at the next estimation time.

[0068] For example, if the current time is t1 and the next estimated time is t2, at time t1, the first estimated temperature output by the motor thermal model is T1, and the second estimated temperature determined based on the rotor flux linkage is T2. If the absolute value of the temperature difference between T1 and T2 is less than a first preset threshold, then the rotor temperature at time t1 is T1; otherwise, the rotor temperature at time t1 is T2. When time t2 is reached, the motor's operating parameters at time t2 and the rotor temperature at time t1 are obtained. These parameters are input into the motor thermal model to obtain the estimated temperature output by the motor thermal model, and this estimated temperature is used as the rotor temperature at time t2.

[0069] In some applications, to prevent sudden changes in control system capabilities caused by temperature fluctuations, it is necessary to limit the rate of temperature change. Specifically, if the difference between the first estimated temperature and the second estimated temperature is greater than a first preset threshold, the second estimated temperature is output to the control system through a low-pass filter.

[0070] To facilitate understanding of this application, refer to the framework diagram shown in Figure 3. To estimate the rotor temperature, the operating parameters of the motor at the current moment and the initial temperature of the rotor are obtained. These operating parameters and the initial temperature of the rotor are input into the motor thermal model to obtain a first estimated temperature for the rotor. Simultaneously, the rotor flux linkage under zero-torque conditions is obtained, and a second estimated temperature of the rotor is obtained based on the rotor flux linkage and a preset correspondence. If the difference between the first and second estimated temperatures is less than a first preset threshold, the first estimated temperature is taken as the rotor's operating temperature at the current moment; if the difference between the first and second estimated temperatures is greater than the first preset threshold, the second estimated temperature is taken as the rotor's operating temperature at the current moment. When estimating the temperature at the next moment, the rotor's operating temperature at the previous moment and the operating parameters for the next moment will be used for estimation.

[0071] It should be noted that this embodiment also applies to the stator. Specifically, the operating parameters corresponding to the motor's operation at the current moment and the initial temperature of the stator are obtained. These operating parameters and the initial temperature of the stator are input into the motor thermal model to obtain the third estimated temperature of the stator. The stator temperature detected by the stator temperature sensor is obtained. The difference between the third estimated temperature and the detected stator temperature is determined. If the difference is greater than a third preset threshold, the detected stator temperature is taken as the temperature of the stator at the current moment; otherwise, the third estimated temperature is taken as the temperature of the stator at the current moment. When the next estimated moment arrives, the operating parameters for the next estimated moment are obtained, and these operating parameters and the stator temperature of the previous moment (relative to the next estimated moment) are input into the motor thermal model to obtain the temperature of the stator at the next estimated moment.

[0072] In other words, the motor thermal model in this embodiment can estimate not only the rotor temperature but also the stator temperature. The acquisition of the motor thermal model will be explained below.

[0073] Referring to Figure 4, which is a flowchart of a method for obtaining a motor thermal model provided in this application, the method includes:

[0074] S401: Obtain test data for the motor under different operating conditions.

[0075] In this embodiment, to determine the values ​​of the parameters to be identified in the motor thermal model, the stator and rotor temperatures corresponding to the actual operation of the motor will first be obtained. That is, test data corresponding to the motor under different operating conditions will be obtained, including stator and rotor temperatures. Specifically, under a fixed voltage, the stator and rotor temperatures of the motor can be tested at different speeds and torques with a fixed step size.

[0076] Under the test conditions, the stator temperature can be obtained using a stator temperature sensor, and the rotor temperature can be obtained using a rotor temperature sensor. If a rotor temperature sensor is unavailable, the back electromotive force (EMF) generated by the rotor at zero torque can be measured at fixed time steps (e.g., 1 minute), and the rotor temperature can then be determined based on this back EMF value. In specific testing, when the torque is below the rated capacity, the motor needs to run for 40 minutes to allow the stator temperature to stabilize; when the torque is above the rated capacity, the running time of the motor under this condition decreases as the torque and speed increase, in order to reach the maximum safe temperature that the motor's stator and rotor can withstand.

[0077] When acquiring test data, it is also necessary to obtain the corresponding test conditions, such as speed and torque. Specifically, during the test, data such as speed, torque, stator temperature, rotor temperature, motor efficiency, input DC current, input voltage, and cooling water temperature will be recorded.

[0078] S402: Obtain the operating parameters of the motor under the target operating conditions, including speed, torque, water temperature and motor efficiency.

[0079] S403: Input the initial values ​​of the operating parameters and the parameters to be identified into the motor thermal model to obtain estimated data.

[0080] The target operating condition is a specific operating condition under which the motor operates during the test. The operating parameters of the motor under the target operating condition are obtained, such as speed, torque, water temperature (cooling water temperature), and motor efficiency. These operating parameters, along with the initial values ​​of the parameters to be identified, are input into the motor thermal model to obtain temperature estimates for the stator and rotor, i.e., estimated data.

[0081] To facilitate understanding, the motor thermal model will be explained below. In this embodiment, the number of nodes included in the motor thermal model is determined by the motor's body structure. Specifically, the nodes in the motor thermal model may include auxiliary stator node x1, stator node x2, stator iron node x3, auxiliary rotor node x4, rotor node x5, and water temperature node T. water Please refer to Figure 2 for the equivalent circuit diagram of the motor thermal model. Specifically, a first thermal resistance R6 is provided between auxiliary stator node x1 and stator node x2; a second thermal resistance R4 is provided between stator node x2 and stator iron node x3; a third thermal resistance R5 is provided between stator iron node x3 and rotor node x5; a fourth thermal resistance R7 is provided between rotor node x5 and auxiliary rotor node x4; and a fourth thermal resistance R7 is provided between auxiliary stator node x1 and water temperature node T. water A first heat capacity C is provided between them. NTCT Stator node x2 and water temperature node T water A fifth thermal resistance R1 and a second thermal capacity C are provided between them. NTC Stator iron node x3 and water temperature node T water A sixth thermal resistance R2 and a third thermal capacity C are provided between them. sta Rotor node x5 and water temperature node T water A fourth heat capacity C is provided between them. rotT The fifth heat capacity C of the equipment between auxiliary rotor node x4 and water temperature node x6 rot Water temperature node T water Grounding.

[0082] In this method, the stator winding loss is equivalent to the first current source Pwinding connected to the auxiliary stator node, the temperature of each node is equivalent to the potential, the stator iron loss is equivalent to the second current source Psta connected to the stator iron node x3, and the rotor iron loss is equivalent to the third current source Prot connected to the auxiliary rotor node x4.

[0083] The state equations for the motor thermal model based on the nodal method are shown in Figure 3. G1, G2, G3, G4, G5, G6, and G7 are the reciprocals of R1, R2, R3, R4, R5, R6, and R7, respectively. These state equations describe the relationship between the temperature of each node and its thermal resistance, heat capacity, heat loss, and water temperature. Given the thermal resistance, heat capacity, heat loss, and water temperature under different operating conditions, the temperature of each node can be calculated.

[0084] For electric motors, water temperature is a known quantity, acquired through sensors; thermal resistance, thermal capacity, and heat loss are parameters to be identified. Typically, heat loss is not directly used as the parameter to be identified. Instead, the total motor loss is calculated from the speed and torque, and the stator winding loss is calculated from the input current. Subtracting the stator winding loss from the total motor loss yields the sum of stator iron loss and rotor iron loss. The ratio of these two losses is then used as the parameter to be identified. In other words, the parameters to be identified include thermal resistance, thermal capacity, and the loss ratio, which refers to the ratio of stator iron loss to rotor iron loss.

[0085] Specifically, the total motor loss is determined based on the operating parameters such as speed, torque, and motor efficiency; the stator winding loss is calculated based on the motor current; the difference between the total motor loss and the stator winding loss is multiplied by the loss ratio to obtain the stator iron loss and the rotor iron loss; the initial values ​​of thermal resistance, thermal capacity, stator iron loss, and rotor iron loss are input into the motor thermal model to obtain estimated data.

[0086] It should be noted that when determining the value of the parameter to be identified, the input voltage value will be collected. The purpose of collecting the input voltage is to determine the voltage level at which the operation is performed, because the value of the parameter to be identified will be different under different voltage levels.

[0087] S404: Compare the test data and estimated data corresponding to the target working condition, adjust the value of the parameter to be identified according to the comparison result, until the error between the test data and the estimated data meets the preset condition, and obtain the value of the parameter to be identified.

[0088] After obtaining estimated data through the motor thermal model, the test data under the same operating conditions is compared with the estimated data to obtain the comparison result (the error between the test data and the estimated data). If the comparison result meets the preset conditions, the value of the parameter to be identified under the current condition is determined as the final value; if the comparison result does not meet the preset conditions, the value of the parameter to be identified is adjusted according to the comparison result until the error between the test data and the estimated data meets the preset conditions. The value of the parameter to be identified when the preset conditions are met is determined as the final value, thus obtaining the motor thermal model. Specifically, based on the prediction error minimization algorithm, the data of the parameter to be identified is adjusted according to the comparison result until the error between the test data and the estimated data is minimized, thus obtaining the value of the parameter to be identified.

[0089] In practical implementation, the range and initial values ​​of the parameters to be identified can be given based on experience. Under these conditions, combined with a set of test data and estimated data from the motor thermal model, the values ​​of the parameters to be identified that meet the conditions for each operating condition are determined. After each iteration, the values ​​of the parameters to be identified are obtained and substituted into the motor thermal model to calculate the stator node temperature x2 and rotor node temperature x5 under the corresponding operating condition as predicted values. The termination condition is that the error between the predicted value and the test data is less than a preset threshold. If the error of a single prediction cannot meet the requirements, the values ​​of the parameters to be identified are adjusted within the range until the accuracy requirements are met.

[0090] As can be seen, to determine the motor thermal model, the first step is to acquire offline test data of the motor under different operating conditions, including stator and rotor temperatures. For a specific operating condition, the corresponding operating parameters of the motor are acquired, such as motor speed, motor torque, water temperature, and motor efficiency. These operating parameters, along with the initial values ​​of the parameters to be identified, are input into the motor thermal model to obtain estimated data, including estimated stator and rotor temperatures. The test data and estimated data under the same operating condition are compared to obtain the comparison results. Based on these results, the values ​​of the parameters to be identified are adjusted until the error between the test data and the estimated data meets a preset condition. This process yields the values ​​of the parameters to be identified, thus determining the motor thermal model. This model can then be used to predict stator and rotor temperatures, thereby providing protection for the stator and rotor.

[0091] Based on the above method embodiments, this application also provides a motor rotor temperature estimation device, which will be described below with reference to the accompanying drawings.

[0092] Referring to Figure 5, which is a structural diagram of a motor rotor temperature estimation device provided in an embodiment of this application, the device 500 may include:

[0093] The first acquisition unit 501 is used to acquire the initial temperature of the rotor and the operating parameters of the motor at the current moment. The operating parameters include speed, torque, water temperature and motor efficiency.

[0094] The second acquisition unit 502 is used to input the operating parameters and the initial temperature into the motor thermal model to obtain the first estimated temperature of the rotor.

[0095] The third acquisition unit 503 is used to acquire the rotor flux linkage of the rotor under zero torque conditions, and determine the second estimated temperature of the rotor based on the rotor flux linkage and the corresponding relationship, wherein the corresponding relationship includes the relationship between the rotor flux linkage and the rotor temperature.

[0096] The first determining unit 504 is used to determine the second estimated temperature as the temperature of the rotor at the current moment if the difference between the first estimated temperature and the second estimated temperature is greater than a first preset threshold.

[0097] The second determining unit 505 is used to input the operating parameters of the next estimation time and the rotor temperature at the current time into the motor thermal model when the next estimation time arrives, and to use the rotor estimation temperature output by the motor thermal model as the rotor temperature at the next estimation time.

[0098] In one possible implementation, the acquisition unit 503 is specifically used to acquire the voltage and speed of the rotor within a zero torque and preset speed range, wherein the rotor does not generate a weak magnetic current within the zero torque and preset speed range; and to determine the rotor flux linkage based on the voltage and the speed.

[0099] In one possible implementation, the acquisition unit 501 is specifically used to acquire the current time and the most recent motor power-off time; if the time difference between the current time and the most recent motor power-off time is less than or equal to a second preset threshold, the rotor temperature stored at the time of the most recent motor power-off is used as the initial temperature of the rotor; if the time difference between the current time and the most recent motor power-off time is greater than the second preset threshold, the current ambient temperature is used as the initial temperature of the rotor.

[0100] In one possible implementation, the device further includes: a control unit;

[0101] The control unit is configured to, if the difference between the first estimated temperature and the second estimated temperature is greater than the first preset threshold, control the second estimated temperature to pass through a low-pass filter and then output it to the control system.

[0102] In one possible implementation, the process of obtaining the motor thermal model includes:

[0103] Acquire test data of the motor under different operating conditions, including stator temperature and rotor temperature;

[0104] Obtain the motor's operating parameters under the target operating conditions, including speed, torque, water temperature, and motor efficiency;

[0105] The initial values ​​of the operating parameters and the parameters to be identified are input into the motor thermal model to obtain estimated data. The estimated data includes the estimated stator temperature and the estimated rotor temperature. The motor thermal model includes the parameters to be identified.

[0106] The test data corresponding to the target working condition is compared with the estimated data. The value of the parameter to be identified is adjusted according to the comparison result until the error between the test data and the estimated data meets the preset condition, and the value of the parameter to be identified is obtained.

[0107] In one possible implementation, adjusting the data of the parameter to be identified based on the comparison result until the error between the test data and the estimated data meets a preset condition to obtain the value of the parameter to be identified includes:

[0108] Based on the prediction error minimization algorithm, the value of the parameter to be identified is adjusted according to the comparison results until the error between the test data and the estimated data is minimized, thereby obtaining the value of the parameter to be identified.

[0109] In one possible implementation, the parameters to be identified include thermal resistance, thermal capacity, and loss ratio, wherein the loss ratio refers to the ratio of rotor iron loss to sub-iron loss.

[0110] In one possible implementation, the step of inputting the initial values ​​of the operating parameters and the parameters to be identified into the motor thermal model to obtain estimation data includes:

[0111] The total motor loss is determined based on the speed, torque, and motor efficiency in the operating parameters.

[0112] Calculate the stator winding losses based on the motor's current;

[0113] The stator iron loss and the rotor iron loss are obtained by multiplying the difference between the total motor loss and the stator winding loss by the loss ratio.

[0114] The initial values ​​of thermal resistance, thermal capacity, stator iron loss, and rotor iron loss are input into the motor thermal model to obtain estimated data.

[0115] It should be noted that the specific implementation of each unit in this embodiment can be found in the relevant descriptions in the above method embodiments, and will not be repeated here.

[0116] Additionally, embodiments of this application provide an electronic device, including: a processor and a memory;

[0117] The memory is used to store computer-readable instructions or computer programs;

[0118] The processor is configured to read the computer-readable instructions or the computer program so that the electronic device implements the motor rotor temperature estimation method.

[0119] This application provides a computer-readable storage medium, including instructions or a computer program, which, when run on a computer, causes the computer to execute the motor rotor estimation method described above.

[0120] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0121] It should be understood that in this application, "at least one (item)" means one or more, and "more than one" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0122] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0123] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0124] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for estimating the temperature of a motor rotor, characterized in that, The method includes: acquiring the initial temperature of the rotor and the operating parameters of the motor at the current moment, the operating parameters including speed, torque, water temperature, and motor efficiency; inputting the operating parameters and the initial temperature into a motor thermal model to obtain a first estimated temperature of the rotor; acquiring the rotor flux linkage under zero torque conditions, and determining a second estimated temperature of the rotor based on the rotor flux linkage and a corresponding relationship, the corresponding relationship including the relationship between rotor flux linkage and rotor temperature; if the difference between the first estimated temperature and the second estimated temperature is greater than a first preset threshold, using the second estimated temperature as the temperature of the rotor at the current moment; when the next estimated moment arrives, inputting the operating parameters of the next estimated moment and the temperature of the rotor at the current moment into the motor thermal model, and using the rotor estimated temperature output by the motor thermal model as the temperature of the rotor at the next estimated moment.

2. The method according to claim 1, characterized in that, Obtaining the rotor flux linkage under zero torque conditions includes: obtaining the voltage and speed of the rotor within a preset speed range with zero torque, wherein the rotor does not generate a weak magnetic current within the preset speed range with zero torque; and determining the rotor flux linkage based on the voltage and the speed.

3. The method according to claim 1, characterized in that, The step of obtaining the initial temperature of the rotor during motor operation includes: obtaining the current time and the most recent time the motor was powered off; if the time difference between the current time and the most recent time the motor was powered off is less than or equal to a second preset threshold, the rotor temperature stored at the time the motor was powered off is taken as the initial temperature of the rotor; if the time difference between the current time and the most recent time the motor was powered off is greater than the second preset threshold, the current ambient temperature is taken as the initial temperature of the rotor.

4. The method according to claim 1, characterized in that, The method further includes: if the difference between the first estimated temperature and the second estimated temperature is greater than the first preset threshold, controlling the second estimated temperature to pass through a low-pass filter and then output to the control system.

5. The method according to claim 1, characterized in that, The process of acquiring the motor thermal model includes: acquiring test data of the motor under different operating conditions, the test data including stator temperature and rotor temperature; acquiring operating parameters of the motor under a target operating condition, the operating parameters including speed, torque, water temperature, and motor efficiency; inputting the operating parameters and the initial values ​​of the parameters to be identified into the motor thermal model to obtain estimated data, the estimated data including stator estimated temperature and rotor estimated temperature, the motor thermal model including the parameters to be identified; comparing the test data corresponding to the target operating condition with the estimated data, and adjusting the value of the parameters to be identified according to the comparison result until the error between the test data and the estimated data meets a preset condition, thereby obtaining the value of the parameters to be identified.

6. The method according to claim 5, characterized in that, The step of adjusting the data of the parameter to be identified based on the comparison results until the error between the test data and the estimated data meets the preset condition to obtain the value of the parameter to be identified includes: adjusting the value of the parameter to be identified based on the comparison results using a prediction error minimization algorithm until the error between the test data and the estimated data is minimized to obtain the value of the parameter to be identified.

7. The method according to claim 5, characterized in that, The parameters to be identified include thermal resistance, thermal capacity, and loss ratio, wherein the loss ratio refers to the ratio of rotor iron loss to sub-rotor iron loss.

8. The method according to claim 7, characterized in that, The step of inputting the initial values ​​of the operating parameters and the parameters to be identified into the motor thermal model to obtain estimated data includes: determining the total motor loss based on the speed, torque and motor efficiency in the operating parameters; calculating the stator winding loss based on the motor current; multiplying the difference between the total motor loss and the stator winding loss by the loss ratio to obtain the stator iron loss and the rotor iron loss; and inputting the initial values ​​of the thermal resistance, thermal capacity, stator iron loss and rotor iron loss into the motor thermal model to obtain estimated data.

9. A device for estimating the temperature of a motor rotor, characterized in that, The device includes: a first acquisition unit for acquiring the initial temperature of the rotor and the operating parameters of the motor at the current moment, the operating parameters including speed, torque, water temperature, and motor efficiency; a second acquisition unit for inputting the operating parameters and the initial temperature into a motor thermal model to obtain a first estimated temperature of the rotor; a third acquisition unit for acquiring the rotor flux linkage under zero torque conditions and determining a second estimated temperature of the rotor based on the rotor flux linkage and a corresponding relationship, the corresponding relationship including the relationship between the rotor flux linkage and the rotor temperature; a first determination unit for using the second estimated temperature as the temperature of the rotor at the current moment if the difference between the first estimated temperature and the second estimated temperature is greater than a first preset threshold; and a second determination unit for inputting the operating parameters of the next estimated moment and the temperature of the rotor at the current moment into the motor thermal model when the next estimated moment arrives, and using the rotor estimated temperature output by the motor thermal model as the temperature of the rotor at the next estimated moment.

10. An electronic device, characterized in that, Includes: processor, memory; The memory is used to store computer-readable instructions or computer programs; the processor is used to read the computer-readable instructions or computer programs so that the electronic device implements the motor rotor temperature estimation method as described in any one of claims 1-8.

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