Junction temperature estimation method, electronic equipment and storage medium

Abstract

The invention discloses a junction temperature estimation method, electronic equipment and a storage medium, and relates to the technical field of electronic power, and the method comprises the steps: obtaining the rotating speed of a motor in an operation process; if the rotating speed is smaller than the preset speed threshold value, transient loss of each switching power module in the motor is determined, and the transient loss is jointly used as power loss of the motor in the operation process; if the rotating speed is greater than or equal to a preset speed threshold value, determining respective average loss of each switching power module, and taking each average loss as power loss of the motor in an operation process; and estimating the target junction temperature of the motor according to the power loss and a preset junction temperature conduction model. The technical problem of low junction temperature estimation accuracy is solved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of power electronics technology, and in particular, to a method for estimating junction temperature, an electronic device, and a storage medium. Background Art

[0002] In the field of new energy technology, improving the service life of IGBT (Insulated Gate Bipolar Transistor) power modules is the current research focus, and the key lies in accurately modeling the power electronic system and accurately estimating the junction temperature of the IGBT power module. The principle of estimating the junction temperature of IGBT power devices is as follows: The joule heat generated by the electric power loss diffuses to the chip junction area through the internal heat conduction path of the device, ultimately resulting in the change of the junction temperature of the power device.

[0003] Although this principle provides a theoretical basis for junction temperature estimation, in practical applications, there is still a situation where the accuracy of estimating the junction temperature of power devices is low. The junction temperature of power devices will affect the thermal field distribution of the motor, so the estimation error of power devices will further be transmitted to the junction temperature estimation of the motor, thereby reducing the accuracy of the junction temperature estimation of the motor. Therefore, there is currently a technical problem of low accuracy in junction temperature estimation.

[0004] The above content is only used to assist in understanding the technical solution of the embodiments of the present application, and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main purpose of the embodiments of the present application is to provide a method for estimating junction temperature, an electronic device, and a storage medium, aiming at the technical problem of low accuracy in junction temperature estimation.

[0006] To achieve the above object, the embodiments of the present application provide a method for estimating junction temperature, which obtains the rotation speed of the motor during operation;

[0007] If the rotation speed is less than the preset speed threshold, determine the respective transient losses of each switching power module in the motor, and use the transient losses together as the power loss of the motor during operation; if the rotation speed is greater than or equal to the preset speed threshold, determine the respective average losses of each switching power module, and use the average losses together as the power loss of the motor during operation; estimate the target junction temperature of the motor according to the power loss and the preset junction temperature conduction model.

[0008] In addition, to achieve the above object, an embodiment of the present application provides a junction temperature estimation device, which includes: an acquisition module for acquiring the rotational speed of the motor during operation; a transient determination module for determining the respective transient losses of each switching power module in the motor if the rotational speed is less than a preset speed threshold, and taking the transient losses together as the power loss of the motor during operation; an average determination module for determining the respective average losses of each switching power module if the rotational speed is greater than or equal to the preset speed threshold, and taking the average losses together as the power loss of the motor during operation; and a junction temperature estimation module for estimating the target junction temperature of the motor based on the power loss and a preset junction temperature conduction model.

[0009] In addition, to achieve the above object, an embodiment of the present application further provides an electronic device, which includes: a memory, a processor, and a program of the junction temperature estimation method stored on the memory and executable on the processor. When the program of the junction temperature estimation method is executed by the processor, the steps of the junction temperature estimation method as described above can be implemented.

[0010] In addition, to achieve the above object, an embodiment of the present application further provides a computer-readable storage medium, on which a program for implementing the junction temperature estimation method is stored. When the program of the junction temperature estimation method is executed by the processor, the steps of the junction temperature estimation method as described above are implemented. In addition, to achieve the above object, an embodiment of the present application further provides a computer program product, including a computer program, and when the computer program is executed by the processor, the steps of the junction temperature estimation method as described above are implemented.

[0011] One or more technical solutions proposed in the embodiments of the present application have at least the following technical effects: By acquiring the rotational speed of the motor, the present application can dynamically select different loss calculation methods according to the operating state (low speed or high speed) of the motor, thereby improving the accuracy of power loss calculation. Specifically, when the rotational speed is less than the preset speed threshold, it indicates that the motor is in a low-speed operating state. At this time, the number of switching times in the electrical cycle of the motor is relatively large, and each switching operation will generate switching losses, and the switching losses will increase with the increase in the number of switching times. Therefore, in the low-speed operating state, the present application determines the respective transient losses of each switching power module, so as to achieve the cumulative calculation of the transient losses of the switching power modules, improve the accuracy of the losses, and avoid the situation of underestimating the losses of the switching power modules caused by determining the losses in the low-speed operating state in the way of average losses. Furthermore, the transient losses can be taken together as the power loss of the motor during operation, and the target junction temperature of the motor can be estimated based on the power loss and the preset junction temperature conduction model, improving the accuracy of junction temperature estimation in the low-speed operating state of the motor.

[0012] Further, when the rotational speed is less than the preset speed threshold, it indicates that the motor is in a high-speed operation state. At this time, the number of switchings is small and the switching loss is low. Therefore, the average loss of each switching power module in the motor can be determined by the average loss method to improve the accuracy of the loss. Furthermore, the average losses can be jointly used as the power loss of the motor during operation, and the target junction temperature of the motor can be estimated based on the power loss and the preset junction temperature conduction model, improving the accuracy of the junction temperature estimation of the motor in the high-speed operation state. Therefore, this application can solve the technical problem of low accuracy of junction temperature estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings herein are incorporated into the specification and form a part of this specification, showing embodiments that comply with the embodiments of this application, and are used together with the specification to explain the principles of the embodiments of this application. In order to more clearly illustrate the embodiments of this application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0014] Figure 1 It is a schematic flowchart of an embodiment of the junction temperature estimation method of this application;

[0015] Figure 2 It is a schematic curve diagram of the collector-emitter voltage of the IGBT varying with the collector current and the junction temperature in the junction temperature estimation method of this application;

[0016] Figure 3 It is a schematic curve diagram of the switching loss energy of the IGBT varying with the collector current and the junction temperature in the junction temperature estimation method of this application;

[0017] Figure 4 It is a schematic curve diagram of the reverse recovery loss energy of the diode varying with the collector current and the junction temperature in the junction temperature estimation method of this application; Figure 5 It is a schematic flowchart of an example in the junction temperature estimation method of this application;

[0018] Figure 6 It is a schematic diagram of the upper and lower bridge arms in the junction temperature estimation method of this application;

[0019] Figure 7 It is a schematic structural diagram of an example in the junction temperature estimation method of this application;

[0020] Figure 8 It is a schematic diagram of the module structure of the junction temperature estimation device of this application;

[0021] Figure 9It is a schematic diagram of the device structure of the hardware operating environment involved in the junction temperature estimation method in this application. The implementation, functional characteristics, and advantages of the embodiments of this application will be further described with reference to the accompanying drawings in combination with the embodiments. Detailed implementation manners

[0022] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the embodiments of this application and are not used to limit the embodiments of this application. To better understand the technical solutions of the embodiments of this application, the following will be described in detail in combination with the accompanying drawings of the specification and specific implementation manners. With the increasing development of new energy technologies, the reliability of a large number of power electronic systems has received much attention. Among them, semiconductor switching devices are particularly important. The uncertainty of different road conditions and drivers' driving habits will lead to complex mission conditions of electric vehicles and unstable operating states of IGBT power modules. Therefore, to improve the service life of power modules, modeling the power electronic system and estimating the temperature of IGBT power modules are the key to current new energy technology research. The principle of IGBT power device junction temperature estimation is based on the conversion of electrical power loss into Joule heat, and the transfer of Joule heat in the environment causes the chip junction temperature to change. Currently, the accuracy of power device junction temperature estimation is low, which in turn will also affect the accuracy of motor junction temperature estimation.

[0023] Therefore, the embodiment of the present application provides a junction temperature estimation method, which can improve the accuracy of the loss of the switching power module in the motor, and further improve the accuracy of the motor junction temperature estimation. In the embodiment of the present application, a transient calculation method is adopted when the motor is running at a low speed to determine the respective transient losses of the switching power modules in the motor. When the motor is running at a high speed, an average power consumption calculation method is adopted to determine the respective average losses of the switching power modules in the motor, thereby improving the accuracy of the losses. Specifically, when the rotational speed is less than the preset speed threshold, it indicates that the motor is in a low-speed operation state. At this time, the number of switching times within the electrical cycle of the motor is relatively large, and each switching operation will generate switching losses. The switching losses will increase with the increase in the number of switching times. Therefore, in the low-speed operation state of the present application, the respective transient losses of the switching power modules are determined, so as to realize the cumulative calculation of the transient losses of the switching power modules, improve the accuracy of the losses, and avoid underestimating the losses of the switching power modules due to determining the losses in the low-speed operation state in the way of average losses. Furthermore, the respective transient losses can be jointly used as the power losses during the operation of the motor, and the target junction temperature of the motor can be estimated based on the power losses and the preset junction temperature conduction model, improving the accuracy of the junction temperature estimation in the low-speed operation state of the motor. Further, when the rotational speed is greater than the preset speed threshold, it indicates that the motor is in a high-speed operation state. At this time, the number of switching times is small and the switching losses are small. Therefore, the average losses of the switching power modules in the motor can be determined by the average loss method to improve the accuracy of the losses. Furthermore, the respective average losses can be jointly used as the power losses during the operation of the motor, and the target junction temperature of the motor can be estimated based on the power losses and the preset junction temperature conduction model, improving the accuracy of the junction temperature estimation in the high-speed operation state of the motor. Therefore, the present application can solve the technical problem of low accuracy of junction temperature estimation.

[0024] Based on this, the embodiment of the present application provides a junction temperature estimation method, referring to Figure 1 , Figure 1 which is a schematic flowchart of the first embodiment of the junction temperature estimation method in the embodiment of the present application. The junction temperature estimation method includes steps S10 to S40:

[0025] Step S10, obtaining the rotational speed of the motor during operation;

[0026] Step S20, if the rotational speed is less than the preset speed threshold, determining the respective transient losses of the switching power modules in the motor, and jointly using the respective transient losses as the power losses during the operation of the motor;

[0027] It should be noted that the rotational speed is the speed at which the motor operates. The preset speed threshold can be determined based on the actual situation. For example, the preset speed threshold can be determined based on actual requirements. When the rotational speed is less than the preset speed threshold, it can be indicated that the motor is operating at a low speed. The switching power module is a power module provided on the motor. The switching power module can include an IGBT and a diode. In the same switching power module, the IGBT and the diode are connected in parallel. The motor includes multiple switching power modules. Specifically, the motor includes three phases. For example, the three phases include U, V, and W. Each phase includes an upper bridge arm and a lower bridge arm. A switching power module is provided on each upper bridge arm, and a switching power module is also provided on each lower bridge arm. Therefore, there are multiple switching power modules in the motor. Each switching power module has its own corresponding transient loss. The transient loss is the loss generated by the switching power module during the low-speed operation of the motor. The transient loss includes IGBT transient loss and diode transient loss. The loss of the IGBT mainly includes static loss, switching loss, and drive loss (negligible). The static loss mainly includes conduction loss and forward cut-off loss (negligible); the switching loss mainly includes turn-on loss and turn-off loss. Therefore, the loss of the IGBT mainly considers conduction loss and switching loss. So, the IGBT transient loss can reflect the transient switching loss and transient conduction loss generated by the IGBT during the low-speed operation of the motor.

[0028] The loss of the diode mainly includes conduction loss and reverse recovery loss, and turn-on loss (very small and negligible). So, the diode transient loss can reflect the transient conduction loss and transient reverse recovery loss generated by the diode during the low-speed operation of the motor. In the switching power module, there is an instantaneous power change at the moment of the switching action. This instantaneous power is accumulated during the entire switching action to obtain the transient loss. Power loss is the energy loss that occurs during the operation of the motor. When the motor is in the low-speed operation state, the power loss is the transient loss corresponding to each switching power module.

[0029] Exemplarily, obtain the rotational speed of the motor during operation. When the rotational speed is less than the preset speed threshold, determine that the motor is in the low-speed operation state. When the motor is in the low-speed operation state, determine the transient loss of each switching power module in the motor. When the rotational speed is greater than or equal to the preset speed threshold, determine that the motor is in the high-speed operation state.

[0030] In a feasible embodiment, the switching power module includes an IGBT and a diode, and the transient loss includes IGBT transient loss and diode transient loss; step S20 further includes steps S21 to S24:

[0031] Step S21, for each switching power module, determine the first transient conduction loss of the IGBT in the switching power module and the second transient conduction loss of the diode in the switching power module;

[0032] It should be noted that the first transient conduction loss is characterized as the conduction loss generated by the IGBT during the low-speed operation of the motor. The second transient conduction loss is characterized as the conduction loss generated by the diode during the low-speed operation of the motor. In the same switching power module, when the IGBT is conducting, the diode is turned off, and when the IGBT is turned off, the diode is conducting. Exemplarily, for each switching power module, the first transient conduction loss of the IGBT and the second transient conduction loss of the diode are calculated by means of transient calculation. Additionally, it should be noted that both the first transient conduction loss and the second transient conduction loss are losses at a preset junction temperature. The preset junction temperature is the temperature set by default in the system to which the junction temperature estimation method is applied, and the preset junction temperature can vary dynamically. For example, the preset junction temperature can be iteratively updated.

[0033] In a feasible embodiment, step S21 further includes steps S211 to S214:

[0034] Step S211, obtain the instantaneous collector current when the IGBT is conducting and the IGBT conduction duty cycle, and determine the initial conduction voltage drop of the IGBT at the preset junction temperature and the IGBT conduction internal resistance;

[0035] Step S212, based on the initial conduction voltage drop, the IGBT conduction internal resistance, and the instantaneous collector current, determine the first instantaneous conduction loss of the IGBT, and multiply the first instantaneous conduction loss by the IGBT conduction duty cycle to obtain the first transient conduction loss of the IGBT at the preset junction temperature;

[0036] It should be noted that the instantaneous collector current can be the transient collector current when the IGBT is conducting. The IGBT conduction duty cycle is characterized as the proportion of the time when the IGBT is in the conducting state in a switching cycle of the switching power module. The initial conduction voltage drop is characterized as the voltage drop between the collector (C) and emitter (E) of the IGBT at the moment when the IGBT starts to conduct at the preset junction temperature. The IGBT conduction internal resistance is characterized as the equivalent resistance between the collector and emitter when the IGBT is in the conducting state and is affected by the preset junction temperature. Different preset junction temperatures may result in different corresponding initial conduction voltage drops and different IGBT conduction internal resistances. Both the initial conduction voltage drop and the IGBT conduction internal resistance are affected by temperature. The first instantaneous conduction loss is characterized as the power consumption generated at the moment when the IGBT conducts, and the first transient conduction loss is characterized as the accumulation of the instantaneous conduction losses corresponding to multiple IGBT conductions. To better understand this embodiment, the following gives an example of the derivation process for calculating the first transient conduction loss. Since there is a conduction voltage drop when the IGBT conducts forward, if there is current flowing through the device at this time, power loss will be generated, and this loss is called the conduction loss. The initial calculation formula for the conduction loss is formula 1.1:

[0037] P con_T = (V ce (T j ,I C ))I C (Equation 1.1);

[0038] Among them, P con_T represents the conduction loss, I C represents the current collector current, V ce (T j ,I C ) represents the conduction voltage drop between the collector and emitter in the IGBT. The conduction voltage drop Vce of the IGBT is related to the junction temperature and the collector current I C passing through the IGBT. As shown in Figure 2 , Figure 2 the abscissa is the conduction voltage drop Vce, the ordinate is the collector current I C , Figure 2 the Tvj shown in represents the junction temperature, Figure 2 and the curves of Vce varying with the collector current when the junction temperatures are 25 °C, 150 °C, and 175 °C respectively are shown. If the junction temperature remains constant, the relationship between Vce and I C can be approximated as an oblique straight line. When the collector current I C passing through the IGBT is 0, Vce is a constant positive value. Therefore, when the junction temperature remains constant, the relationship between Vce and the collector current I C can be expressed by a linear function, and this linear function is Equation 1.2. It can be expressed by the following formula:

[0039] V ce (T j = x, Ic) = V ce0x + r cex I c (Equation 1.2);

[0040] Among them, V ce (T j = x, Ic) is the conduction voltage drop of the IGBT affected by Ic when the junction temperature is x, V ce0x is the initial conduction voltage drop of the IGBT at the initial conduction moment when the junction temperature is x, r cex is the on-resistance of the IGBT when the junction temperature is x. When the junction temperature changes, both of these two parameters r cex and V ce0x will change significantly. Considering the influence of the junction temperature, Equation 1.2 can be rewritten as Equation 1.3:

[0041] V ce (T j , Ic) = V ce0 (Tj ) + r ce (T j )I c (Formula 1.3);

[0042] Among them, V ce0 (T j ) is the initial on - state voltage drop affected by the junction temperature, r cw (T j ) is the on - resistance of the IGBT affected by the junction temperature, V ce (T j , Ic) is characterized as the on - state voltage drop between the collector and emitter of the IGBT affected by the junction temperature and the collector current. During a switching cycle, the IGBT has both a continuously conducting state and a continuously non - conducting state. The calculation formula for the first instantaneous conduction loss is as follows

[0043] Formula 1.4:

[0044]

[0045] Among them, P a is the first instantaneous conduction loss, Swt_Stste = On indicates that the switching state of the IGBT is conducting, and Swt_Stste = Off indicates that the switching state of the IGBT is non - conducting. The formula for calculating the energy of the IGBT loss during a switching cycle is Formula 1.5:

[0046]

[0047] Among them, E is the energy lost by the IGBT during a switching cycle, T Pwm is the switching cycle, and dt is the time differential. Using Formula 1.6 for calculating the average conduction loss of the IGBT during a switching cycle, the calculation formula for the first transient conduction loss, Formula 1.7, is derived. Among them, Formula 1.6 and Formula 1.7 are as follows:

[0048]

[0049] Among them, assuming that during a switching cycle, the collector current I c and the junction temperature T j remain unchanged, combining with Formula 1.6, Formula 1.7 can be obtained:

[0050]

[0051] Among them, P con_T is the first transient conduction loss, T on is the conduction duration of the IGBT during the switching cycle. If it is defined that D is the conduction duty cycle of the IGBT. Therefore, the formula for calculating the first transient conduction loss can be Formula 1.8:

[0052] P con_T = (V ce0 (T j ) + r ce (T j )I c )I c *D (Equation 1.8);

[0053] Wherein, P con_T is the first transient conduction loss, D is the IGBT conduction duty cycle, V ce0 (T j ) is the initial conduction voltage drop when the junction temperature is the preset junction temperature T j , r ce (T j ) is the IGBT conduction internal resistance when the junction temperature is the preset junction temperature T j , D is the IGBT conduction duty cycle, I c is the instantaneous collector current. In this embodiment, the influence of the junction temperature on the loss is also considered when determining the first transient conduction loss, thereby improving the accuracy of determining the first transient conduction loss. When estimating the junction temperature of the motor in this embodiment, a closed-loop feedback method is also adopted for estimation, thereby facilitating the improvement of the accuracy of the motor junction temperature estimation.

[0054] Step S213, obtain the diode current and the diode conduction duty cycle when the diode conducts, and determine the diode conduction voltage and the diode conduction internal resistance at the preset junction temperature;

[0055] Step S214, determine the second transient conduction loss of the diode according to the diode conduction voltage, the diode conduction internal resistance and the diode current, and multiply the second transient conduction loss by the diode conduction duty cycle to obtain the second transient conduction loss of the diode at the preset junction temperature.

[0056] It should be noted that the diode current is the instantaneous current flowing through the diode when the diode conducts, and the diode conduction internal resistance refers to the equivalent resistance value of the diode in the conducting state. The diode conduction voltage refers to the voltage drop between the anode and the cathode of the diode when it conducts forward. The instantaneous conduction power consumption of the diode refers to the power consumed when the diode conducts at a certain moment. The transient conduction loss of the diode is the loss generated during the low-speed operation of the motor. Exemplarily, the formula for calculating the second transient conduction loss of the diode can be Equation 1.9, and the derivation process of the formula for calculating the second transient conduction loss is the same as that of the formula for calculating the first transient conduction loss of the IGBT, which will not be elaborated in this embodiment.

[0057] P con_D = (V F0 (T j ) + rF0 (T j )I a )I a *(1 - D) (Equation 1.9);

[0058] Wherein, P con_D is the second transient turn - on loss, V F0 (T j ) is the diode turn - on voltage, r F0 (T j ) is the diode on - resistance, I a is the diode current, (1 - D) is the diode conduction duty cycle, (V F0 (T j ) + r F0 (T j )I a )I a_D is the second instantaneous turn - on loss. In this embodiment, the influence of the junction temperature on the loss is also considered when determining the second transient turn - on loss, thereby improving the accuracy of determining the second transient turn - on loss.

[0059] Step S22, determine the transient turn - on loss and the transient turn - off loss of the IGBT, and accumulate the transient turn - on loss and the transient turn - off loss to obtain the first transient switching loss of the IGBT;

[0060] It should be noted that the transient turn - on loss is the total loss generated at the moment of turn - on during the low - speed operation of the motor by the IGBT, and the transient turn - off loss is the total loss generated at the moment of turn - off during the low - speed operation of the motor by the IGBT. The first transient switching loss is the sum of the transient turn - on loss and the transient turn - off loss. Exemplarily, for each turn - on power module, the transient turn - on loss and the transient turn - off loss of the IGBT are determined at a preset junction temperature, and the first transient switching loss can be obtained by accumulating the transient turn - on loss and the transient turn - off loss.

[0061] In a feasible embodiment, step S22 further includes steps S221 to S224:

[0062] Step S221, based on the obtained junction - temperature turn - on - loss energy relationship data, construct a turn - on - loss energy relationship formula, wherein the turn - on - loss energy relationship formula represents: the mapping relationship between the turn - on - loss energy of the IGBT at different junction temperatures and the square value and the linear value of the collector current. The turn - on - loss energy relationship formula also includes a first square - term coefficient, a first linear - term coefficient, and a first constant term related to the junction temperature;

[0063] It should be noted that the data on the relationship between the turn-on loss energy and the junction temperature can include the curve of the turn-on loss energy of the IGBT varying with the collector current and the junction temperature. Thus, through the data on the relationship between the turn-on loss energy and the junction temperature, the turn-on loss energy formula can be obtained by fitting. There is a corresponding mapping relationship between the turn-on loss energy of the IGBT and the square value and the linear value of the collector current. The first square term coefficient, the first linear term coefficient, and the first constant term included in the relationship between the turn-on loss energy will all change with the change of the junction temperature. The first square term coefficient is the coefficient of the square value of the collector current, and the first linear term coefficient is the coefficient before the linear value of the collector current. At the moment of turn-on of the IGBT, due to the rapid change of the voltage and the current, the product of the two is not zero, so power loss will be generated at the moment of turn-on. To better understand this embodiment, the process of deriving the turn-on loss energy formula is briefly described below. For example, the data on the relationship between the turn-on loss energy and the junction temperature can be referred to Figure 3 in which E on refers to the curve, where Tvj in the figure represents the junction temperature, Figure 3 shows two E on curves. One is the E on curve with Tvj being 150 °C, and the other is the E on curve with Tvj being 175 °C. Figure 3 The abscissa in is the collector current, with the unit of ampere (A), and the ordinate is the energy E, with the unit of millijoule (mJ). Referring to the Eon curve in the figure, it can be seen that when the junction temperature is x, the turn-on loss energy E on of the IGBT increases with the increase of the collector current I c , so it can be approximately regarded as a quadratic function relationship. The turn-on loss energy E on can be expressed by Equation 2.0:

[0064]

[0065] where E on (T j =x, Ic) represents the turn-on loss energy of the IGBT when the junction temperature T j is constant at x, a onx is the first square term coefficient when the junction temperature is constant at x, b onx is the first linear term coefficient when the junction temperature is constant at x, and c onx is the first constant term when the junction temperature is constant at x. is the square value of the collector current, I C is the linear value of the collector current. Considering the influence of the junction temperature on the turn-on loss energy, Equation 2.0 can be rewritten as Equation 2.1, and Equation 2.1 is the turn-on loss energy formula:

[0066]

[0067] Among them, E on (T j , Ic) is the turn-on loss energy of the IGBT, a on (T j ) is the first quadratic term coefficient varying with the junction temperature, b on (T j ) is the first linear term coefficient varying with the junction temperature, c on (T j ) is the first constant term varying with the junction temperature. is the square value of the collector current, I C is expressed as the linear value of the collector current.

[0068] Step S222: According to the values of the first quadratic term coefficient, the first linear term coefficient, and the first constant term corresponding to the preset junction temperature obtained from the preset turn-on junction temperature coefficient mapping relationship, update the turn-on loss energy relationship to obtain the turn-on loss energy relationship at the preset junction temperature;

[0069] It should be noted that the turn-on junction temperature coefficient mapping relationship can be determined in advance based on experimental data, and this embodiment does not make specific limitations. The values of the first quadratic term coefficient, the first linear term coefficient, and the first constant term corresponding to the preset junction temperature can be found from the turn-on junction temperature coefficient mapping relationship. Furthermore, the value of the first quadratic term coefficient corresponding to the preset junction temperature can be substituted into the first quadratic term coefficient in the turn-on loss energy relationship, and the value of the first linear term coefficient corresponding to the preset junction temperature can be substituted into the first linear term coefficient in the turn-on loss energy relationship, and the value of the first constant term corresponding to the preset junction temperature can be substituted into the first constant term in the turn-on loss energy relationship to obtain the turn-on loss energy relationship at the junction temperature.

[0070] Step S223: According to the instantaneous collector current when the IGBT is turned on and the turn-on loss energy relationship at the junction temperature, determine the instantaneous turn-on loss at the preset junction temperature, and adjust the instantaneous turn-on loss by the ratio of the current bus voltage of the motor to the rated voltage of the motor to obtain the corrected instantaneous turn-on loss;

[0071] Step S224: Calculate the product of the corrected instantaneous turn-on loss and the switching frequency of the IGBT to obtain the transient turn-on loss.

[0072] It should be noted that the current bus voltage is the bus voltage corresponding to the detected motor, and the rated voltage is the rated bus voltage corresponding to the motor. The instantaneous collector current is the collector current at the moment when the IGBT is turned on. Substituting the instantaneous collector current into the energy relationship of the turn-on loss at the junction temperature, the instantaneous turn-on loss at the preset junction temperature can be obtained. However, since the loss of the IGBT turn-on is also affected by the voltage, it is necessary to use the ratio of the current bus voltage to the rated voltage to correct the instantaneous turn-on loss, and then obtain the corrected instantaneous turn-on loss. The switching frequency of the IGBT is the number of switching times of the IGBT. Exemplarily, the formula for calculating the transient turn-on loss of the IGBT is Formula 2.2:

[0073] P Igbt_on =f sw *E on_Z (Formula 2.2);

[0074]

[0075] Among them, P Igbt_on is the transient turn-on loss, E on_Z is the corrected instantaneous turn-on loss, U dc is the current bus voltage, U dcNorm is the rated voltage, a on (T w ) is the value of the first quadratic term coefficient when the junction temperature is the preset junction temperature T w , b on (T w ) is the value of the first linear term coefficient when the junction temperature is the preset junction temperature T w , c on (T w ) is the value of the first constant term when the junction temperature is the preset junction temperature T w . is the square value of the instantaneous collector current when the IGBT is turned on, I C1 is the linear value of the instantaneous collector current when the IGBT is turned on, f sw is the switching frequency. Among them, Formula 2.3 is the calculation formula for calculating the corrected instantaneous turn-on loss. In this embodiment, by constructing the energy relationship of the turn-on loss, the influence of parameters such as the junction temperature and the collector current on the turn-on loss energy can be considered simultaneously, and then the accuracy of determining the transient turn-on loss can be improved, which is convenient for accurately estimating the junction temperature subsequently.

[0076] In a feasible embodiment, step S22 further includes steps S225 to S228:

[0077] Step S225: Based on the obtained turn-off loss energy relationship data of the junction temperature, a turn-off loss energy relationship formula is constructed. The turn-off loss energy relationship formula represents the mapping relationship between the turn-off loss energy of the IGBT at different junction temperatures and the square value and linear value of the collector current. The turn-off loss energy relationship formula includes a second square term coefficient, a second linear term coefficient, and a second constant term related to the junction temperature.

[0078] It should be noted that the turn-off loss energy relationship data of the junction temperature may include the curve of the turn-off loss energy of the IGBT varying with the collector current and the junction temperature. Thus, the turn-off loss energy relationship formula can be obtained by fitting the turn-off loss energy relationship data. There is a corresponding mapping relationship between the turn-off loss energy of the IGBT and the square value and linear value of the collector current. The second square term coefficient, the second linear term coefficient, and the second constant term included in the turn-off loss energy relationship will all change with the change of the junction temperature. The second square term coefficient is the coefficient of the square value of the collector current, and the second linear term coefficient is the coefficient before the linear value of the collector current. At the moment of turn-off of the IGBT, due to the rapid change of voltage and current, the product of the two is not zero, so power loss will be generated at the moment of turn-off. To better understand this embodiment, the process of deriving the turn-off loss energy relationship formula is briefly described below. For example, the turn-off loss energy relationship data of the junction temperature can be referred to Figure 3 , Figure 3 where the curve referred to by E off is concerned. Among them, Figure 3 Tvj in Figure 3 represents the junction temperature, and Figure 3 shows two curves of E off . One is the E off curve with Tvj being 150 °C, and the other is the E off curve with Tvj being 175 °C. It can be seen from that when the junction temperature is fixed at x, the turn-off loss energy E off of the IGBT increases with the increase of the collector current I c . Therefore, it can be approximately regarded as a quadratic function relationship. The turn-off loss energy E off can be expressed by Formula 2.4:

[0079]

[0080] off (T j = x, Ic,) represents the turn-off loss energy of the IGBT when the junction temperature T j is constant at x. a offx is the second square term coefficient when the junction temperature is constant at x, b offx is the second linear term coefficient when the junction temperature is constant at x, and c offx is the second constant term when the junction temperature is constant at x. is the square value of the collector current, I C is the linear value of the collector current. Considering the influence of the junction temperature on the turn-off loss energy and referring to Figure 3 it can be known that when the junction temperature changes, the curve of the turn-on loss energy of the IGBT will not coincide with the curve of the turn-off loss energy. Therefore, it is necessary to separately construct the turn-on loss energy relationship formula and the turn-off loss energy relationship formula of the IGBT. Therefore, Formula 2.4 can be rewritten as Formula 2.5, and Formula 2.5 is the turn-off loss energy relationship formula:

[0081]

[0082] where, E off (T j , Ic) is the turn-off loss energy of the IGBT, a off (T j ) is the second quadratic term coefficient varying with the junction temperature, b off (T j ) is the second linear term coefficient varying with the junction temperature, c off (T j ) is the second constant term varying with the junction temperature. is the square value of the collector current, I C is expressed as the linear value of the collector current.

[0083] Step S226, according to the values of the second quadratic term coefficient, the second linear term coefficient and the second constant term corresponding to the preset junction temperature obtained from the preset turn-off junction temperature coefficient mapping relationship, update the turn-off loss energy relationship formula to obtain the junction temperature turn-off loss energy relationship formula at the preset junction temperature;

[0084] It should be noted that the turn-off junction temperature coefficient mapping relationship can be determined in advance based on experimental data, and this embodiment does not make specific limitations on this. The values of the second quadratic term coefficient, the second linear term coefficient and the second constant term corresponding to the preset junction temperature can be found from the turn-off junction temperature coefficient mapping relationship. Furthermore, the value of the second quadratic term coefficient corresponding to the preset junction temperature can be substituted into the second quadratic term coefficient in the turn-off loss energy relationship formula, and then the value of the second linear term coefficient corresponding to the preset junction temperature can be substituted into the second linear term coefficient in the turn-off loss energy relationship formula, and then the value of the second constant term corresponding to the preset junction temperature can be substituted into the second constant term in the turn-off loss energy relationship formula to obtain the junction temperature turn-off loss energy relationship formula.

[0085] Step S227, according to the instantaneous collector current at the turn-off of the IGBT and the junction temperature turn-off loss energy relationship formula, determine the instantaneous turn-off loss at the preset junction temperature, and adjust the instantaneous turn-off loss through the ratio of the current bus voltage of the motor to the rated voltage of the motor to obtain the corrected instantaneous turn-off loss;

[0086] Step S228: Calculate the product of the corrected instantaneous turn-off loss and the switching frequency of the IGBT to obtain the transient turn-off loss.

[0087] It should be noted that the current bus voltage is the bus voltage corresponding to the detected motor, and the rated voltage is the rated bus voltage corresponding to the motor. The instantaneous collector current during IGBT turn-off is the collector current at the moment of IGBT turn-off. Substituting the instantaneous collector current at the moment of IGBT turn-off into the turn-off loss energy relationship of the junction temperature, the instantaneous turn-off loss at the preset junction temperature can be obtained. However, since the loss during IGBT turn-off is also affected by the voltage, it is necessary to correct the instantaneous turn-off loss using the ratio of the current bus voltage to the rated voltage, and then obtain the corrected instantaneous turn-off loss. Exemplarily, the formula for calculating the transient turn-off loss of the IGBT is Formula 2.6:

[0088] P Igbt_off =f sw *E off_Z (Formula 2.6);

[0089]

[0090] Where, P Igbt_off is the transient turn-off loss, E off_Z is the corrected instantaneous turn-off loss, U dc is the current bus voltage, U dcNorm is the rated voltage, a off (T w ) is the value of the second squared coefficient when the junction temperature is the preset junction temperature T w , b off (T w ) is the value of the second linear coefficient when the junction temperature is the preset junction temperature T w , C off (T w ) is the value of the second constant term when the junction temperature is the preset junction temperature T w , is the squared value of the instantaneous collector current when the IGBT turns off, I C2 is the linear value of the instantaneous collector current when the IGBT turns off, f sw is the switching frequency. Among them, Formula 2.7 is the calculation formula for calculating the corrected instantaneous turn-off loss. In this embodiment, by constructing the turn-off loss energy relationship, the influence of parameters such as the junction temperature and the collector current on the turn-off loss energy can be considered simultaneously, thereby improving the accuracy of determining the transient turn-off loss and facilitating the subsequent accurate estimation of the junction temperature.

[0091] In other embodiments, the first transient switching loss of the IGBT can also be calculated by Formula 2.8:

[0092] P IgbtSwtLoss =fsw *(E on_Z +E off_Z ) (Formula 2.8)

[0093] Wherein, P IgbtswtLoss is the first transient switching loss, f sw is the switching frequency, E off_Z is the corrected instantaneous turn-off loss, and E on_Z is the corrected instantaneous turn-on loss.

[0094] Step S23, determine the second transient switching loss of the diode;

[0095] Step S24, accumulate the first transient conduction loss and the first transient switching loss to obtain the IGBT transient loss, and accumulate the second transient conduction loss and the second transient switching loss to obtain the diode transient loss.

[0096] It should be noted that the second transient switching loss of the diode is the reverse recovery energy loss of the diode. For example, for each switching power module, the second transient switching loss of the diode can be calculated at a preset junction temperature. For each switching power module, the first transient conduction loss and the first transient switching loss are used as the IGBT transient loss of the IGBT, and the second transient conduction loss and the second transient switching loss are used as the diode transient loss of the diode. In this embodiment, by calculating the IGBT transient loss and the diode transient loss at a preset junction temperature, the influence of the actual junction temperature on the loss is considered, thereby improving the accuracy of the loss calculation. It is convenient to improve the accuracy of the junction temperature estimation.

[0097] In a feasible embodiment, step S23 further includes steps S231 to S234:

[0098] Step S231, based on the obtained junction temperature diode energy relationship data, construct a reverse recovery energy relationship formula for the diode. Among them, the reverse recovery energy relationship formula represents: the mapping relationship between the reverse recovery energy of the diode at different junction temperatures and the cubic value, square value, and linear value of the diode current. The reverse recovery energy relationship formula includes a cubic term coefficient, a third square term coefficient, a third linear term coefficient, and a third constant term related to the junction temperature;

[0099] It should be noted that the junction temperature diode energy relationship data includes the curve of the reverse recovery loss energy of the diode changing with the diode current and the junction temperature. For example, it can be referred to Figure 4 , Figure 4 which shows the curve corresponding to the reverse recovery loss energy of the diode, Figure 4 where the abscissa IF in Figure 4The Tvj shown in [reference] can refer to the junction temperature. Figure 4 It shows the curve of the reverse recovery loss energy Erec when Tvj is 150 °C, and also shows the curve of the reverse recovery loss energy Erec when Tvj is 175 °C. In this embodiment, the reverse recovery energy relationship formula can be obtained by fitting the junction temperature diode energy relationship data. The reverse recovery energy of the diode has corresponding mapping relationships with the cubic value, square value, and linear value of the diode current. The values of the cubic term coefficient, the third square term coefficient, the third linear term coefficient, and the third constant term will change with the change of the junction temperature. The cubic term coefficient is the coefficient of the cubic term of the diode current, the third square term coefficient is the coefficient of the square term of the diode current, and the third linear term coefficient is the coefficient of the linear term of the diode current. For example, the following briefly describes the process of deriving the reverse recovery energy relationship formula: Since the turn-on time of the diode is very short compared to the switching period, the switching loss is extremely small and can be ignored. Due to the reverse recovery characteristics of the diode, there is a loss during the reverse recovery when the diode turns off.

[0100] From Figure 4 it can be seen that when the junction temperature is fixed at x, the reverse recovery loss energy E rec of the diode increases with the increase of the diode current, but the increasing trend slows down as the current increases. The deviation of fitting with a quadratic function is relatively large, so a cubic function is used for fitting. The formula for the reverse recovery loss energy when the junction temperature is fixed at x is obtained:

[0101]

[0102] where, E rec (T j = x, I r ) is the reverse recovery loss energy related to the diode current when the junction temperature is x, I r is the diode current, a recx is the value of the cubic term coefficient when the junction temperature is x, b recx is the value of the third square coefficient when the junction temperature is x, c recx is the value of the third linear coefficient term when the junction temperature is x, d recx is the value of the third constant term when the junction temperature is x. I r is the linear value of the diode current, is the square value of the diode current, is the cubic value of the diode current. Considering the influence of the junction temperature on the reverse recovery loss energy, formula 2.9 is rewritten as formula 3.0, and formula 3.0 is the reverse recovery energy relationship formula:

[0103]

[0104] where, a recx(T j ) is the coefficient of the cubic term, b recx (T j ) is the coefficient of the third quadratic term, c recx (T j ) is the coefficient of the third linear term, d recx (T j ) is the third constant term, E rec (T j , I r ) is the amount of reverse recovery energy loss affected by the junction temperature and diode current.

[0105] Step S232: According to the obtained values of the coefficient of the cubic term, the coefficient of the third quadratic term, the coefficient of the third linear term, and the third constant term corresponding to the preset junction temperature from the preset diode junction temperature coefficient mapping relationship, update the reverse recovery energy relationship formula to obtain the junction temperature reverse recovery energy relationship formula at the preset junction temperature;

[0106] It should be noted that the diode junction temperature coefficient mapping relationship can be determined in advance based on experimental data, and this embodiment does not make specific limitations on this. The diode junction temperature coefficient mapping relationship includes the obtained values of the coefficient of the cubic term, the coefficient of the third quadratic term, the coefficient of the third linear term, and the third constant term corresponding to different junction temperatures respectively. The obtained values of the coefficient of the cubic term, the coefficient of the third quadratic term, the coefficient of the third linear term, and the third constant term corresponding to the preset junction temperature can be found from the diode junction temperature coefficient mapping relationship. Furthermore, the obtained value of the coefficient of the cubic term corresponding to the preset junction temperature can be substituted into the coefficient of the cubic term in the reverse recovery energy relationship formula, the obtained value of the coefficient of the third quadratic term corresponding to the preset junction temperature can be substituted into the coefficient of the third quadratic term in the reverse recovery energy relationship formula, and then the obtained value of the coefficient of the third linear term corresponding to the preset junction temperature can be substituted into the coefficient of the third linear term in the reverse recovery energy relationship formula, and then the obtained value of the first constant term corresponding to the preset junction temperature can be substituted into the third constant term in the reverse recovery energy relationship formula to obtain the junction temperature reverse recovery energy relationship formula.

[0107] Step S233: According to the diode current and the junction temperature reverse recovery energy relationship formula when the diode is turned off, determine the reverse recovery loss energy at the preset junction temperature, and adjust the reverse recovery loss energy through the ratio of the current bus voltage of the motor to the rated voltage of the motor to obtain the corrected reverse recovery loss energy;

[0108] Step S234: Calculate the product of the corrected reverse recovery loss energy and the switching frequency of the diode to obtain the second transient switching loss of the diode.

[0109] It should be noted that since the loss of diode turn-off is also affected by voltage, it is necessary to use the ratio of the current bus voltage to the rated voltage to correct the reverse recovery loss energy, so as to obtain the corrected reverse recovery loss energy. The reverse recovery loss energy is the loss energy of the diode without considering the influence of voltage. Exemplarily, the formula for calculating the second transient switching loss of the diode is Formula 3.1

[0110] P EwdswtLoss =f sw *E rec _f (Formula 3.1);

[0111]

[0112] Wherein, P EwdSwtLoss is the second transient switching loss, f sw is the switching frequency, E rec _f is the corrected reverse recovery loss energy, a rec (T w ) is the value of the cubic term when the preset junction temperature is T w , b rec (T w ) is the value of the coefficient of the third square term when the preset junction temperature is T w , c rec (T w ) is the value of the coefficient of the third linear term when the preset junction temperature is T w , d rec (T w ) is the value of the coefficient of the third constant term when the preset junction temperature is T w . is the cubic value of the diode current when the diode is turned off, is the square value of the diode current when the diode is turned off, I r _ f is the linear value of the diode current when the diode is turned off. In this embodiment, when calculating the second transient switching loss of the diode, the influence of the junction temperature is also considered, thereby improving the accuracy of calculating the second transient switching loss.

[0113] Step S30, if the rotational speed is greater than or equal to the preset speed threshold, determine the respective average losses of each switching power module, and use the average losses together as the power loss of the motor during operation;

[0114] It should be noted that when the rotational speed is greater than the preset speed threshold, the motor runs at a high speed. When the motor runs at a high speed, the number of switchings is small. Therefore, the average loss calculation method can be used to calculate the losses of each switching power module in the motor. When the motor runs at a high speed, the average losses can be used together as the power loss of the motor during operation, which is convenient for estimating the junction temperature of the motor in the subsequent high-speed operation state of the motor. The average losses include the IGBT average loss and the diode average loss. Exemplarily, if the rotational speed is greater than or equal to the preset speed threshold, the average losses of each switching power module are calculated, and the average losses are used together as the power loss of the motor during operation. The average loss can be the average loss of the motor when it is running at a high speed and at a preset junction temperature. The average loss is calculated by the average calculation method. It can be understood that when the motor runs at a high speed, it is considered that the losses generated by each switching of the switching power module are almost the same. Therefore, the loss of a certain switching can be calculated, and the loss of this switching can be used as the loss generated by each switching of the switching power module when the motor runs at a high speed, and the losses of each switching are accumulated, so that the average loss of the motor when it runs at a high speed can be obtained.

[0115] In a feasible embodiment, the average losses include the IGBT average loss and the diode average loss; step S30 further includes steps S31 to S33:

[0116] Step S31, for each switching power module, determine the first average conduction loss of the IGBT in the switching power module and the second average conduction loss of the diode in the switching power module;

[0117] It should be noted that when the motor runs at a high speed, each IGBT in each phase of the motor in each switching power module has its corresponding first average conduction power consumption, and each diode in each switching power module has its corresponding second average conduction power consumption. The first average conduction power consumption is the conduction loss generated by the IGBT when the motor runs at a high speed, and the second average conduction power consumption is the conduction loss generated by the diode when the motor runs at a high speed. Exemplarily, when the motor runs at a high speed, for each switching power module, calculate the first average conduction loss of the IGBT in the switching power module and the second average conduction loss of the diode.

[0118] In a feasible embodiment, step S31 further includes steps S311 to S313:

[0119] Step S311, obtain the peak current, modulation coefficient and power factor angle of the motor, and determine the initial conduction voltage drop and IGBT conduction internal resistance of the IGBT at the preset junction temperature;

[0120] Step S312, determining a first average conduction loss of the IGBT according to the peak current, the modulation factor, the power factor angle, the initial conduction voltage drop, and the conduction internal resistance;

[0121] It should be noted that the peak current of the motor is characterized as the peak current when the motor is running at high speed. The peak current can be determined based on the d-axis current and q-axis current of the motor, and the modulation coefficient can also be determined based on the d-axis voltage, q-axis voltage and bus voltage of the motor. The power factor angle is the phase difference between the voltage and current in the motor. The initial on-state voltage drop is the voltage drop when the junction temperature of the IGBT is the preset junction temperature, and the on-state internal resistance of the IGBT is the on-state internal resistance when the junction temperature is the preset junction temperature. The initial on-state voltage drop and the on-state internal resistance of the IGBT are different for different junction temperatures. The initial on-state voltage drop and the on-state internal resistance of the IGBT corresponding to the preset junction temperature can be found in the preset junction temperature voltage drop internal resistance mapping relationship. The preset junction temperature voltage drop internal resistance mapping relationship is determined in advance based on experimental data. This embodiment does not make specific limitations on this. The preset junction temperature voltage drop internal resistance mapping relationship includes the initial on-state voltage drop and the on-state internal resistance of the IGBT corresponding to different junction temperatures. Exemplarily, the formula for calculating the first average conduction loss of the IGBT is formula 3.3, and formula 3.3 can be derived from formula 3.4;

[0122]

[0123]

[0124]

[0125]

[0126] Among them, P IgbtCondLossAvg is the first average conduction loss, φ is the power factor angle, V ceo (T w ) is the junction temperature of the IGBT, T w The initial on-state voltage drop, r ce (T w ) is the junction temperature of the IGBT, T w The IGBT on-resistance, I m is the peak current, m is the modulation factor, the peak current calculation formula can refer to formula 3.31, Id is the d-axis current of the motor, Iq is the q-axis current of the motor, the modulation factor calculation formula can refer to formula 3.32, Ud is the d-axis voltage of the motor, Uq is the q-axis voltage of the motor, Udc is the bus voltage of the motor, sqrt(3) is the square root of 3. Formula 3.3 can be derived from formula 3.4, where T0 is the fundamental period corresponding to the motor, V ce(t) is the voltage between the collector and emitter of the IGBT within the fundamental wave period, i(t) is the current corresponding to the IGBT within the fundamental wave period, τ′(t) is the conduction duration of the IGBT within the fundamental wave period, and dt is the differential of time. In this embodiment, the first average conduction loss of the IGBT can be calculated by Formula 3.3.

[0127] Step S313: Determine the diode conduction voltage and diode conduction internal resistance of the diode at the preset junction temperature, and determine the second conduction loss of the diode based on the peak current, modulation coefficient, power factor angle, diode conduction voltage, and diode conduction internal resistance.

[0128] It should be noted that the diode conduction voltage and diode conduction internal resistance corresponding to different junction temperatures of the diode are different. The diode conduction voltage and diode conduction internal resistance corresponding to the preset junction temperature can be found in the preset diode junction temperature mapping relationship, which includes the diode conduction voltage and diode conduction internal resistance corresponding to different junction temperatures respectively.

[0129] Exemplarily, the process of deriving the formula for the second conduction loss of the diode is similar to the process of deriving the formula for the first conduction loss of the IGBT, which will not be elaborated in this embodiment. The formula for calculating the second conduction loss can be Formula 3.5:

[0130]

[0131] Among them, P con-FWD-Avg is the second conduction loss, φ is the power factor angle, V FO (T w ) is the diode conduction voltage when the junction temperature of the switching power module is T w , R F (T w ) is the diode conduction internal resistance when the junction temperature of the switching power module is T w , I m is the peak current, and m is the modulation factor.

[0132] Step S32: Determine the first average switching loss of the IGBT and the second average switching loss of the diode;

[0133] Step S33: Accumulate the first average conduction loss and the first average switching loss to obtain the IGBT average loss, and accumulate the second average conduction loss and the second average switching loss to obtain the diode average loss.

[0134] It should be noted that when the motor is running at high speed, each IGBT in each switching power module in each phase of the motor has its corresponding first average switching power consumption, and each diode in each switching power module has its corresponding second average switching power consumption. The first average switching power consumption is the turn-on and turn-off losses generated by the IGBT when the motor is running at high speed, and the second average conduction power consumption is the reverse recovery loss generated by the diode when the motor is running at high speed. Exemplarily, when the motor is running at high speed, for each switching power module, calculate the first average switching loss of the IGBT in the switching power module and calculate the second average switching loss of the diode. The sum of the first average conduction loss and the first average switching loss is used as the IGBT average loss, and the second average conduction loss and the second average switching loss are used as the diode average loss.

[0135] In a feasible embodiment, step S32 further includes steps S321 to S325:

[0136] Step S321, obtain the junction temperature turn-on loss energy relationship and the junction temperature turn-off loss energy relationship of the IGBT at a preset junction temperature, and determine the target turn-on loss energy of the IGBT according to the obtained peak current of the motor and the junction temperature turn-on loss energy relationship, and determine the target turn-off loss energy of the IGBT according to the peak current and the junction temperature turn-off loss energy relationship;

[0137] It should be noted that when the motor is in a high-speed running state, the peak current can be the peak current when the motor is running at high speed. The peak current can be substituted into the junction temperature turn-on loss energy relationship, and then the target turn-on loss energy of the IGBT can be determined. The peak current can be substituted into the junction temperature turn-off loss energy relationship, and then the target turn-off loss energy of the IGBT can be determined. The target turn-on loss energy can reflect the energy lost during the turn-on of the IGBT as the collector current waveform changes when the motor is running at high speed. The target turn-off energy can reflect the energy lost during the turn-off of the IGBT as the collector current waveform changes when the motor is running at high speed.

[0138] Step S322, within the half fundamental wave period corresponding to the motor, integrate the product of the target turn-on loss energy, the switching frequency, and the voltage ratio to obtain the turn-on integration result, and integrate the product of the target turn-off loss energy, the switching frequency, and the voltage ratio to obtain the turn-off integration result, where the voltage ratio is the ratio of the current bus voltage of the motor to the rated voltage;

[0139] Step S323, accumulate the turn-on integration result and the turn-off integration result to obtain the switching integration result, and use the ratio of the switching integration result to the fundamental wave period corresponding to the motor as the first average switching loss of the IGBT;

[0140] It should be noted that the half fundamental wave period is half of the fundamental wave period. During the fundamental wave period, the IGBT conducts and turns off. The result of the turn-on integration is the turn-on loss generated by the IGBT within the half fundamental wave period, and the result of the turn-off integration is the turn-off loss generated by the IGBT within the half fundamental wave period. Exemplarily, the formula for calculating the first average switching loss can be Formula 3.6:

[0141]

[0142]

[0143] Among them, Formula 3.6 can be derived from Formula 3.06. P sw_igbt is the first average switching loss, f sw is the switching frequency, is the voltage ratio, T0 is the fundamental wave period, is the half fundamental wave period, E on (T w , Ic, t) is the relationship formula of the turn-on energy loss of the junction temperature related to time t, E off (T w , Ic, t) is the relationship formula of the turn-off energy loss of the junction temperature related to time t. a on (T w ) is the value of the first quadratic term coefficient when the junction temperature is the preset junction temperature T w , b on (T w ) is the value of the first linear term coefficient when the junction temperature is the preset junction temperature T w , c on (T w ) is the value of the first constant term when the junction temperature is the preset junction temperature T w . It means that within the half fundamental wave period, the product of the target turn-on loss energy, the switching frequency, and the voltage ratio is integrated to obtain the turn-on integration result. Since T0 exists in the numerator of the turn-on integration result, during the derivation from Formula 3.06 to Formula 3.6, the 1 / T0 multiplied by the turn-on integration result and the T0 in the numerator of the turn-on integration result are reduced. Similarly, for the turn-off integration result, T0 also exists in the numerator, so T0 does not exist in Formula 3.6.

[0144] Step S324, obtain the relationship formula of the reverse recovery energy of the junction temperature of the diode at the preset junction temperature, and determine the reverse recovery energy of the current junction temperature based on the peak current and the relationship formula of the reverse recovery energy of the junction temperature;

[0145] Step S325: Integrate the product of the reverse recovery energy of the current junction temperature, the switching frequency, and the voltage ratio within the half fundamental wave period corresponding to the motor to obtain the integration result of the reverse recovery loss, and use the ratio of the integration result of the reverse recovery loss to the fundamental wave period corresponding to the motor as the second average switching loss of the diode.

[0146] It should be noted that the reverse recovery energy of the current junction temperature can reflect the reverse recovery loss energy generated by the diode under the influence of the peak current and the junction temperature when the motor is running at high speed. The integration result of the reverse recovery loss characterizes the reverse recovery loss energy generated by the diode within the half fundamental wave period. Exemplarily, the formula for calculating the second average switching loss can be Formula 3.7:

[0147]

[0148]

[0149] Among them, Formula 3.07 can be derived from Formula 3.7; for example, by calculating the integral in Formula 3.07, Formula 3.7 can be obtained, and this embodiment will not elaborate too much on this. P FwdRec-Avg is the second average switching loss, T0 is the fundamental wave period, is the half fundamental wave period, is the voltage ratio, f sw is the switching frequency, E rec (T w ,I r ,t) is the relationship formula of the reverse recovery energy of the junction temperature related to time t. a rec (T w ) is the value of the cubic term when the preset junction temperature is T w , b rec (T w ) is the value of the coefficient of the third square term when the preset junction temperature is T w , c rec (T w ) is the value of the coefficient of the third linear term when the preset junction temperature is T w , d rec (T w ) is the value of the coefficient of the third constant term when the preset junction temperature is T w The second average switching loss of the diode can be calculated through Formula 3.7. In this embodiment, by calculating the average loss of the IGBT and the average loss of the diode when the motor is running at high speed, the efficiency of loss calculation is improved while ensuring the accuracy of loss calculation, and there is no need to calculate each loss separately.

[0150] Step S40: Estimate the target junction temperature of the motor based on the power loss and the preset junction temperature conduction model.

[0151] It should be noted that the preset junction temperature conduction model is pre-constructed, and different switching power modules correspond to different preset junction temperature conduction models. The target junction temperature of the motor is the highest junction temperature among the three phases of the motor. The junction temperature of each phase in the motor is determined based on the junction temperature of the switching power module provided in that phase.

[0152] Exemplarily, when the rotational speed is greater than the preset speed threshold, the power loss is each transient loss. At this time, based on each transient loss and the preset junction temperature conduction model, the target junction temperature of the motor is estimated. When the rotational speed is greater than the preset speed threshold, the power loss is each average loss. In this case, based on each average loss, the target junction temperature of the motor is estimated. By obtaining the rotational speed of the motor in the embodiments of the present application, different loss calculation methods can be dynamically selected according to the operating state (low speed or high speed) of the motor, thereby improving the accuracy of power loss calculation. Specifically, when the rotational speed is less than the preset speed threshold, it indicates that the motor is in a low-speed operating state. At this time, the number of switchings within the electrical cycle of the motor is relatively large, and each switching operation will generate switching losses. The switching losses will increase as the number of switchings increases. Therefore, in the embodiments of the present application, when in the low-speed operating state, the respective transient losses corresponding to each switching power module are determined, so as to realize the cumulative calculation of the transient losses of the switching power modules, improve the accuracy of the losses, and avoid the situation of underestimating the losses of the switching power modules due to determining the losses in the low-speed operating state in the manner of average losses. Furthermore, each transient loss can be jointly used as the power loss during the operation of the motor, and the target junction temperature of the motor is estimated based on the power loss and the preset junction temperature conduction model, improving the accuracy of junction temperature estimation in the low-speed operating state of the motor.

[0153] Furthermore, when the rotational speed is less than the preset speed threshold, it indicates that the motor is in a high-speed operating state. At this time, the number of switchings is relatively small, and the switching losses are relatively small. Therefore, the average losses of each switching power module in the motor can be determined by the method of average losses to improve the accuracy of the losses. Furthermore, each average loss can be jointly used as the power loss during the operation of the motor, and the target junction temperature of the motor is estimated based on the power loss and the preset junction temperature conduction model, improving the accuracy of junction temperature estimation in the high-speed operating state of the motor. Therefore, the embodiments of the present application can solve the technical problem of low accuracy of junction temperature estimation.

[0154] For a better understanding of this embodiment, please refer to Figure 5, a brief description of the process in this embodiment is as follows. Step Y10: Determine whether the rotational speed of the motor is less than a preset speed threshold. If the rotational speed is less than the preset speed threshold, then determine Step Y20a: Low speed, indicating that the motor is in a low-speed operation state, and execute Step Y30a: Determine the transient loss, and execute Step Y40a: Estimate the target junction temperature of the motor based on the transient loss. For example, the transient loss can be determined based on data such as the bus voltage, q-axis current, d-axis current, switching frequency, power factor angle, etc. of the motor obtained. If the rotational speed is less than the preset speed threshold, then determine Step Y20b: High speed, indicating that the motor is in a high-speed operation state, and execute Step Y30b: Determine the average loss, and execute Step Y40b: Estimate the target junction temperature of the motor based on the average loss. For example, the average loss can be determined based on data such as the bus voltage, q-axis current, d-axis current, switching frequency, power factor angle, etc. of the motor obtained.

[0155] In a feasible embodiment, the motor includes three phases, each phase of the motor includes an upper bridge arm and a lower bridge arm, and switching power modules are provided on both the upper bridge arm and the lower bridge arm. The preset junction temperature conduction model includes a preset upper bridge arm junction temperature model and a preset lower bridge arm junction temperature model; Step S40 further includes Steps S41 to S43:

[0156] Step S41, for each upper bridge arm in the motor, calculate the upper bridge arm junction temperature of the upper bridge arm based on the module loss of the switching power module in the upper bridge arm obtained from the power loss and the preset upper bridge arm junction temperature model of the upper bridge arm, and calculate the first junction temperature difference between the upper bridge arm junction temperature and the preset junction temperature. If the first junction temperature difference is greater than the preset convergence threshold, then update the preset junction temperature, and calculate the module loss of the switching power module with the first junction temperature difference greater than the preset convergence threshold based on the updated preset junction temperature until the first junction temperature difference is less than or equal to the preset convergence threshold, and take the upper bridge arm junction temperature as the upper module junction temperature of the switching power module in the upper bridge arm;

[0157] It should be noted that the motor includes three phases, namely U, V, and W. Each phase includes an upper bridge arm and a lower bridge arm. A switching power module is provided in both the upper bridge arm and the lower bridge arm. The corresponding preset junction temperature conduction models are different for different bridge arms where the switching power modules are located. The accuracy of the constructed preset junction temperature conduction model also affects the accuracy of junction temperature estimation. In this embodiment, the preset junction temperature conduction models corresponding to the upper bridge arm and the lower bridge arm are different. The upper bridge arm corresponds to a preset upper bridge arm junction temperature model, and the lower bridge arm corresponds to a preset lower bridge arm junction temperature model. Since an NTC (Negative Temperature Coefficient, thermistor) is provided on the upper bridge arm, when estimating the junction temperature of the upper bridge arm, the temperature detected by the NTC can be combined for estimation. Also, because the NTC is provided on the upper bridge arm, if the NTC is still used to estimate the junction temperature of the lower bridge arm, there will be a large error. Specifically, when the chip on the upper bridge arm generates heat, the thermal coupling received by the NTC is stronger than that received by the lower bridge arm. And since the lower bridge arm is provided with a coolant, the junction temperature of the lower bridge arm needs to be predicted in combination with the coolant.

[0158] Therefore, in this embodiment, the preset junction temperature conduction models corresponding to the upper and lower bridge arms are different. The preset upper bridge arm junction temperature models corresponding to different upper bridge arms may also be different, but the principles for constructing the preset upper bridge arm junction temperature models corresponding to different upper bridge arms are the same, which is to construct the preset upper bridge arm junction temperature model by combining the temperature detected by the NTC. The preset lower bridge arm junction temperature models corresponding to different lower bridge arms may also be different, but the principles for constructing the preset lower bridge arm junction temperature models corresponding to different lower bridge arms are the same, which is to construct the preset lower bridge arm junction temperature model by combining the temperature of the coolant in the lower bridge arm. The preset upper bridge arm junction temperature model can estimate the junction temperature of the upper bridge arm using the module loss of the upper bridge arm. When the rotational speed is less than the preset rotational speed threshold, the module loss of the switching power module is transient loss. When the rotational speed is greater than or equal to the preset rotational speed threshold, the loss of the switching power module is average loss. The upper bridge arm junction temperature is the junction temperature estimated using the preset upper bridge arm junction temperature model.

[0159] The first junction temperature difference is the absolute value of the difference between the junction temperature of the upper bridge arm and the preset junction temperature. The preset convergence threshold can be set based on the actual situation, and this embodiment does not make specific limitations on this. Each upper bridge arm in the motor has its corresponding preset upper bridge arm junction temperature model, and the preset upper bridge arm junction temperature models corresponding to different upper bridge arms are different. This is because the preset upper bridge arm junction temperature model is also related to parameters such as the self-heat resistance of the IGBT and diode in the switching power module set on the upper bridge arm. For example, for each upper bridge arm in the motor, substitute the module loss corresponding to the switching power module in the upper bridge arm into the preset upper bridge arm junction temperature model corresponding to the upper bridge arm to estimate the junction temperature of the upper bridge arm, and calculate the first junction temperature difference between the junction temperature of the upper bridge arm and the preset junction temperature. When the first junction temperature difference is greater than the preset convergence threshold, it indicates that the preset junction temperature or the calculated junction temperature of the upper bridge arm is not the true junction temperature of the upper bridge arm. Therefore, it is necessary to update the preset junction temperature, and based on the updated preset junction temperature, recalculate the module loss corresponding to the switching power module. For example, when the motor is in a high-speed operation state, recalculate the average loss of the switching power module based on the updated preset junction temperature. When the motor is in a low-speed operation state, recalculate the transient loss of the switching power module based on the updated preset junction temperature. When the first junction temperature difference is less than or equal to the preset convergence threshold, the last calculated junction temperature of the upper bridge arm or the last updated preset junction temperature can be used as the true junction temperature of the upper bridge arm, that is, the upper module junction temperature, and the upper module junction temperature is the true junction temperature corresponding to the upper bridge arm.

[0160] This embodiment estimates the junction temperature of the upper bridge arm by using a closed-loop feedback method, that is, first give a preset junction temperature, calculate the loss using this preset junction temperature, then calculate a new junction temperature using the calculated loss, and compare the gap between the preset junction temperature and the new junction temperature. If the gap is less than or equal to the preset convergence threshold, it indicates that the given preset junction temperature may be the true junction temperature. If the gap is greater than the preset convergence threshold, continue to update the preset junction temperature until the gap is less than or equal to the preset convergence threshold. Initially, the preset junction temperature can be 0, and the preset junction temperature can be iterated from 0 until the true junction temperature corresponding to the switching power module can be determined. This embodiment estimates the true junction temperature through a closed-loop feedback method, improving the accuracy of junction temperature estimation. The possible situations in this embodiment include: the true junction temperature corresponding to the upper bridge arm A has been estimated, but the true junction temperature of the upper bridge arm B has not been estimated yet. Therefore, the preset junction temperature will be updated, and the module loss corresponding to the upper bridge arm B will be recalculated based on the updated preset junction temperature, and continue to estimate the junction temperature of the upper bridge arm B. For the upper bridge arm A, it is not necessary to continue estimating the junction temperature of the upper bridge arm A, and the last calculated junction temperature of the upper bridge arm A corresponding to the upper bridge arm can be directly used as the upper module junction temperature of the upper bridge arm.

[0161] Step S42: For each lower arm in the motor, based on the module loss of the switching power module in the lower arm obtained from the power loss and the preset lower-arm junction temperature model of the lower arm, calculate the lower-arm junction temperature of the lower arm, and calculate the second junction temperature difference between the lower-arm junction temperature and the preset junction temperature. If the second junction temperature difference is greater than the preset convergence threshold, update the preset junction temperature, and based on the updated preset junction temperature, calculate the module loss of the switching power module for which the second junction temperature difference is greater than the preset convergence threshold until the second junction temperature difference is less than or equal to the preset convergence threshold. Then, take the lower-arm junction temperature as the lower-module junction temperature of the switching power module of the lower arm.

[0162] It should be noted that the preset lower-arm junction temperature model can estimate the junction temperature of the lower arm using the module loss of the lower arm. When the rotational speed is less than the preset rotational speed threshold, the module loss of the switching power module is the transient loss. When the rotational speed is greater than or equal to the preset rotational speed threshold, the loss of the switching power module is the average loss. The lower-arm junction temperature is the junction temperature estimated using the preset lower-arm junction temperature model.

[0163] The second junction temperature difference is the absolute value of the difference between the lower-arm junction temperature and the preset junction temperature. The preset convergence threshold can be set based on the actual situation, and this embodiment does not make specific limitations on it. Each lower arm in the motor has its own corresponding preset lower-arm junction temperature model, and the preset lower-arm junction temperature models corresponding to different lower arms are different because the preset lower-arm junction temperature model is also related to parameters such as the self-heat resistance of the IGBT and diode in the switching power module set in the lower arm.

[0164] For example, for each lower arm in the motor, substitute the module loss corresponding to the switching power module in the lower arm into the preset lower-arm junction temperature model corresponding to the lower arm to estimate the lower-arm junction temperature, and calculate the second junction temperature difference between the lower-arm junction temperature and the preset junction temperature. When the second junction temperature difference is greater than the preset convergence threshold, it indicates that the preset junction temperature or the calculated lower-arm junction temperature is not the true junction temperature of the lower arm. Therefore, it is necessary to update the preset junction temperature and, based on the updated preset junction temperature, recalculate the module loss corresponding to the switching power module. For example, when the motor is in a high-speed operation state, recalculate the average loss of the switching power module based on the updated preset junction temperature. When the motor is in a low-speed operation state, recalculate the transient loss of the switching power module based on the updated preset junction temperature.

[0165] When the second junction temperature difference is less than or equal to the preset convergence threshold, the finally calculated lower-arm junction temperature or the finally updated preset junction temperature can be taken as the true junction temperature of the lower arm, that is, the lower-module junction temperature. The lower-module junction temperature is the true junction temperature corresponding to the lower arm.

[0166] In this embodiment, a closed-loop feedback method is used to estimate the junction temperature of the lower bridge arm. That is, a preset junction temperature is first given, and the losses are calculated using this preset junction temperature. Then, the new junction temperature is calculated using the calculated losses. The difference between the preset junction temperature and the new junction temperature is compared. If the difference is less than or equal to the preset convergence threshold, it means that the given preset junction temperature can be the true junction temperature. If the difference is greater than the preset convergence threshold, the preset junction temperature is continuously updated until the difference is less than or equal to the preset convergence threshold. Initially, the preset junction temperature can be 0, and the preset junction temperature can be iterated from 0 until the true junction temperature corresponding to the switching power module can be determined. In this embodiment, the true junction temperature is estimated by means of closed-loop feedback, improving the accuracy of junction temperature estimation.

[0167] Step S43: Determine the junction temperature with the maximum value among the junction temperatures of each upper module and each lower module as the target junction temperature of the motor.

[0168] Among them, when the rotational speed is less than the preset rotational speed threshold, the module loss of the switching power module is the transient loss. When the rotational speed is greater than or equal to the preset rotational speed threshold, the loss of the switching power module is the average loss. It should be noted that the target junction temperature of the motor is the junction temperature with the maximum value among the three phases of the motor. The junction temperature of each phase is determined based on the junction temperatures corresponding to the upper bridge arm and the lower bridge arm of that phase. For each phase, the junction temperature of that phase is the junction temperature with the maximum value among the upper bridge arm and the lower bridge arm. Therefore, in this embodiment, the junction temperature with the maximum value can be directly determined among the junction temperatures of each upper module and each lower module as the target junction temperature of the motor. In other embodiments, it can also be to first determine the junction temperature of each phase, and then determine the junction temperature with the maximum value among the phases as the target junction temperature. The steps for determining the junction temperature of each phase include: for the upper bridge arm and the lower bridge arm belonging to the same phase, compare the upper module junction temperature corresponding to the upper bridge arm and the lower module junction temperature corresponding to the lower bridge arm, and determine the junction temperature with the maximum value among the upper module junction temperature and the lower module junction temperature as the junction temperature of that phase. In this embodiment, the target junction temperature is determined by means of closed-loop feedback, thereby improving the accuracy of junction temperature estimation. Moreover, the junction temperature of the upper bridge arm is estimated in combination with the temperature detected by the NTC, and the junction temperature of the lower bridge arm is estimated in combination with the coolant, further improving the accuracy of junction temperature estimation.

[0169] In a feasible embodiment, the junction temperature estimation method further includes steps X10 to X20:

[0170] Step X10: For each upper bridge arm in the motor, obtain the first self-heat resistance of the IGBT in the upper bridge arm, the second self-heat resistance of the diode, the first mutual heat resistance from the IGBT to the diode, and the second mutual heat resistance from the diode to the IGBT, and obtain the first temperature detected by the thermistor provided on the upper bridge arm, and construct a preset upper bridge arm junction temperature model.

[0171] It should be noted that the IGBT and diode in the upper bridge arm each have their corresponding self-thermal resistances, and the mutual thermal resistance is the thermal resistance of the mutual influence between the IGBT and the diode. The first self-thermal resistance characterizes the thermal resistance encountered when the heat generated by the IGBT in the upper bridge arm is transferred inside the IGBT, and the second self-thermal resistance characterizes the thermal resistance encountered when the heat generated by the diode in the upper bridge arm is transferred inside the diode. The first mutual thermal resistance represents the thermal resistance encountered when the heat generated by the IGBT in the upper bridge arm is transferred to the diode in the upper bridge arm; the second mutual thermal resistance represents the thermal resistance encountered when the heat generated by the diode in the upper bridge arm is transferred to the IGBT in the upper bridge arm. The thermistor is an NTC and is set in the upper bridge arm. The first self-thermal resistance, the second self-thermal resistance, the first mutual thermal resistance, and the second mutual thermal resistance of the upper bridge arm can be directly obtained. For example, the corresponding self-thermal resistance and mutual thermal resistance can be directly obtained from the product specification of the device. In other embodiments, data related to thermal characteristics can also be obtained from the device's data sheet (datasheet), and then these data are used for fitting to obtain the self-thermal resistance, etc. The present embodiment does not specifically limit the method of obtaining the self-thermal resistance and mutual thermal resistance. Different IGBTs may have different self-thermal resistances, and different diodes may have different self-thermal resistances, and the corresponding mutual thermal resistances may also be different. The preset upper bridge arm junction temperature model is used to map the module loss of the switching power module in the upper bridge arm to the upper bridge arm junction temperature corresponding to the upper bridge arm. The first temperature is the temperature detected by the thermistor set in the upper bridge arm. The preset upper bridge arm junction temperature model can be used to map the module loss of the switching power module in the upper bridge arm to the upper bridge arm junction temperature corresponding to the upper bridge arm.

[0172] Exemplarily, the preset upper bridge arm junction temperature model can be expressed as Equation 3.8:

[0173]

[0174] Where, T HT is the junction temperature corresponding to the IGBT in the upper bridge arm, T HD is the junction temperature corresponding to the IGBT in the upper bridge arm, Z 11 is the first self-thermal resistance, Z 22 is the second self-thermal resistance, Z 12 is the first mutual thermal resistance, Z 21 is the second mutual thermal resistance, T NTC is the first temperature, P HT is the loss of the IGBT in the upper bridge arm, P HD is the loss of the diode in the upper bridge arm. When the rotational speed is greater than or equal to the preset speed threshold, P HT is the average loss of the IGBT in the upper bridge arm, P HD is the average loss of the diode in the upper bridge arm; when the rotational speed is less than the preset speed threshold, P HTis the IGBT transient loss in the upper bridge arm, P HD is the diode transient loss in the upper bridge arm. The upper bridge arm junction temperature can be T HT and T HD with the maximum junction temperature value. The module losses in the upper bridge arm can be substituted into Equation 3.8, so that the upper bridge arm junction temperature corresponding to the module losses can be determined. For example, the losses of the IGBT and the diode in the module losses can be respectively substituted into Equation 3.8, and then the upper bridge arm junction temperature can be estimated. The type of the preset upper bridge arm junction temperature model can be the Foster model (local network model). For example, reference can be made to Figure 6 , Figure 6 shows a schematic diagram of the upper and lower bridge arms. Among them, the NTC is set on the left side of the upper bridge arm, and the specific connection relationship of the NTC is not shown in Figure 6 . Figure 6 shows the upper and lower bridge arms corresponding to each of the three phases in the motor. Among them, TH1~TH3 are the IGBTs of the upper bridge arms corresponding to the three phases respectively, DH1~DH3 are the diodes of the lower bridge arms corresponding to the three phases respectively, TL1~TL3 are the IGBTs of the lower bridge arms corresponding to the three phases respectively, and DL1~DL3 are the diodes of the lower bridge arms corresponding to the three phases respectively.

[0175] Step X20: For each lower bridge arm in the motor, obtain the third self-thermal resistance of the IGBT, the fourth self-thermal resistance of the diode, the third mutual-thermal resistance from the IGBT to the diode, and the fourth mutual-thermal resistance from the diode to the IGBT in the lower bridge arm, and obtain the coolant temperature corresponding to the lower bridge arm, and construct a preset lower bridge arm junction temperature model for the lower bridge arm.

[0176] It should be noted that the IGBT and diode in the lower arm each have their own corresponding self-thermal resistance, and the mutual thermal resistance is the thermal resistance of the mutual influence between the IGBT and the diode. The third self-thermal resistance is characterized by the thermal resistance encountered when the heat generated by the IGBT in the lower arm is transferred inside the IGBT, and the fourth self-thermal resistance is characterized by the thermal resistance encountered when the heat generated by the diode in the lower arm is transferred inside the diode. The third mutual thermal resistance represents the thermal resistance encountered when the heat generated by the IGBT in the lower arm is transferred to the diode in the lower arm; the fourth mutual thermal resistance represents the thermal resistance encountered when the heat generated by the diode in the lower arm is transferred to the IGBT in the lower arm. The coolant temperature is the detected temperature of the coolant. The third self-thermal resistance, the fourth self-thermal resistance, the third mutual thermal resistance, and the fourth mutual thermal resistance of the lower arm can be directly obtained. For example, the corresponding self-thermal resistance and mutual thermal resistance can be directly obtained from the product specification of the device. In other embodiments, data related to thermal characteristics can also be obtained from the device's data sheet (datasheet), and then these data can be used for fitting to obtain the self-thermal resistance, etc. The present embodiment does not specifically limit the method for obtaining the self-thermal resistance and the mutual thermal resistance. Different IGBTs may have different self-thermal resistances, and different diodes may have different self-thermal resistances, and the corresponding mutual thermal resistances may also be different. The preset lower arm junction temperature model can be used to map the module loss of the switching power module in the lower arm to the corresponding lower arm junction temperature.

[0177] Exemplarily, the preset lower arm junction temperature model can be expressed as Equation 3.9:

[0178]

[0179] Where, T LT is the junction temperature corresponding to the IGBT in the lower arm, T LD is the junction temperature corresponding to the IGBT in the lower arm, Z 33 is the third self-thermal resistance, Z 34 is the fourth self-thermal resistance, Z 43 is the third mutual thermal resistance, Z 44 is the fourth mutual thermal resistance, T coolant is the third temperature, P LT is the loss of the IGBT in the lower arm, P LD is the loss of the diode in the lower arm. When the rotational speed is greater than or equal to the preset speed threshold, P LT is the average loss of the IGBT in the lower arm, P LD is the average loss of the diode in the lower arm; when the rotational speed is less than the preset speed threshold, P LT is the transient loss of the IGBT in the lower arm, P LD is the transient loss of the diode in the lower arm. The lower arm junction temperature can be T LT and TLD The one with the maximum junction temperature. The module losses in the lower arm can be substituted into Equation 3.9, so that the junction temperature of the lower arm corresponding to the module losses can be determined. For example, the losses of the IGBT and the diode in the module losses can be respectively substituted into Equation 3.9, and then the junction temperature of the lower arm can be estimated. The type of the preset lower arm junction temperature model can be the Foster model. In this embodiment, the preset upper arm junction temperature model is constructed by the self-thermal resistance and the corresponding mutual thermal resistance of the power devices (IGBT and diode) in the upper arm and the temperature detected by the NTC, so as to facilitate improving the accuracy of estimating the junction temperature corresponding to the upper arm. The preset lower arm junction temperature model is constructed by the self-thermal resistance and the corresponding mutual thermal resistance of the power devices (IGBT and diode) in the lower arm and the coolant temperature, so as to facilitate improving the accuracy of estimating the junction temperature corresponding to the lower arm. In addition, to better understand Equation 3.8 and Equation 3.9, the principle of deriving Equation 3.8 is briefly described below. The estimation formula of the junction temperature in the thermal network can refer to Equation 4.0,

[0180] T g =P loss *R thjc +T c (Equation 4.0);

[0181] P loss =P tot(T) +P tot(D) (Equation 4.1);

[0182] Wherein, T g is the estimated junction temperature, R thjc is the thermal resistance, T c is the temperature of the heat dissipation end. For example, it can be the temperature detected by the NCT or the coolant temperature, P loss is the loss, P tot(T) is the loss of the IGBT, P tot(D) is the loss of the diode. Among them, the thermal resistance R thjc can be equivalent to an RC (Resistor-Capacitor Network) network. The thermal resistance R thjc can be set between the position where T g is located and the position where T c is located. In this embodiment, the IGBT and the diode can be equivalent to an RC network, and Equation 4.0 can be converted into Equation 3.8 or Equation 3.9 in this embodiment. In this embodiment, the IGBT and the diode can be equivalent to a fourth-order RC network, and the heat dissipation end can be equivalent to a first-order RC network. For example, reference can be made to Figure 7 , Figure 7 which shows the fourth-order RC network of the IGBT and the diode and the first-order RC network of the heat dissipation end. Wherein, TgIGBT1 is the estimated temperature T corresponding to the IGBT g , T gFWD1 is the estimated temperature T corresponding to the diode g , R thT1 ~R thT4 and C thT1 ~C thT4 is the fourth-order RC network corresponding to the IGBT, R thD1 ~R thD4 and C thD1 ~C thD4 is the fourth-order RC network corresponding to the diode, P IGBT1 is the loss corresponding to the IGBT, P FWD1 is the loss corresponding to the diode, is the temperature of the heat dissipation end, R th(c-h) , R th(h-a) and C th(h-a) is the first-order RC network corresponding to the heat dissipation end.

[0183] The embodiment of the present application also provides a junction temperature estimation device. Please refer to Figure 8 , the device includes: an acquisition module 10, configured to acquire the rotation speed of the motor during operation; a transient determination module 20, configured to determine the respective transient losses of each switching power module in the motor if the rotation speed is less than a preset speed threshold, and use the respective transient losses together as the power loss of the motor during operation; an average determination module 30, configured to determine the respective average losses of each switching power module if the rotation speed is greater than or equal to the preset speed threshold, and use the respective average losses together as the power loss of the motor during operation; a junction temperature estimation module 40, configured to estimate the target junction temperature of the motor according to the power loss and a preset junction temperature conduction model.

[0184] The junction temperature estimation device provided by the embodiment of the present application adopts the junction temperature estimation method in the above embodiment, aiming at the technical problem of low accuracy of junction temperature estimation. Compared with the prior art, the beneficial effects of the junction temperature estimation method provided by the embodiment of the present application are the same as those of the junction temperature estimation method provided by the above embodiment, and other technical features in the junction temperature estimation device are the same as those disclosed in the method of the above embodiment, and will not be elaborated here. The present application provides an electronic device, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the junction temperature estimation method in the first embodiment above. Next, refer to Figure 9, which shows a schematic structural diagram of an electronic device suitable for implementing the embodiments of the present application. The electronic devices in the embodiments of the present application may include, but are not limited to, mobile terminals such as mobile phones, laptop computers, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions: tablet computers), PMPs (Portable Media Players), in-vehicle terminals (such as in-vehicle navigation terminals), etc., and fixed terminals such as digital TVs, desktop computers, etc. Figure 9 The electronic device shown is merely an example and should not impose any limitation on the functions and scope of use of the embodiments of the present application. As Figure 9 shown, the electronic device may include a processing device 1001 (such as a central processing unit, a graphics processing unit, etc.), which may perform various appropriate actions and processes according to the program stored in the read-only memory 1002 or the program loaded from the storage device 1003 into the random access memory 1004. In the random access memory 1004, various programs and data required for the operation of the electronic device are also stored. The processing device 1001, the read-only memory 1002, and the random access memory 1004 are connected to each other through a bus 1005. The input / output interface 1006 is also connected to the bus. Generally, the following systems may be connected to the input / output interface 1006: an input device 1007 including, for example, a touch screen, a touchpad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; an output device 1008 including, for example, a liquid crystal display (LCD: Liquid Crystal Display), a speaker, a vibrator, etc.; a storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 may allow the electronic device to communicate with other devices wirelessly or wiredly to exchange data. Although the figure shows an electronic device with various systems, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems may be implemented or had alternatively. In particular, according to the embodiments disclosed in the present application, the processes described above with reference to the flowcharts may be implemented as computer software programs. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes program codes for performing the methods shown in the flowcharts. In such an embodiment, the computer program may be downloaded and installed from the network through the communication device, or installed from the storage device 1003, or installed from the read-only memory 1002. When the computer program is executed by the processing device 1001, the above functions defined in the methods of the embodiments disclosed in the present application are executed.

[0185] The electronic device provided by this application adopts the junction temperature estimation method in the above-mentioned embodiments, and can solve the technical problem of low accuracy of junction temperature estimation. It should be understood that each part disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in a suitable manner in any one or more embodiments or examples. The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

[0186] This embodiment provides a computer-readable storage medium having computer-readable program instructions stored thereon for performing the junction temperature estimation method in the first embodiment above. The computer-readable storage medium provided by the embodiments of the present application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor devices, apparatuses, or components, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable EPROM (Electrical Programmable Read Only Memory), or flash memory, optical fibers, portable compact disc CD-ROM (compact disc read-only memory), optical storage devices, magnetic storage devices, or any suitable combination of the above. In this embodiment, the computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution device, apparatus, or component. The program code contained on the computer-readable storage medium can be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination of the above. The above computer-readable storage medium may be included in an electronic device; or may exist separately without being assembled into the electronic device. The above computer-readable storage medium carries one or more programs, and when the one or more programs are executed by an electronic device, the electronic device: obtains the rotational speed of the motor during operation; if the rotational speed is less than a preset speed threshold, determines the respective transient losses of each switching power module in the motor, and takes the sum of the transient losses as the power loss of the motor during operation; if the rotational speed is greater than or equal to the preset speed threshold, determines the respective average losses of each switching power module, and takes the sum of the average losses as the power loss of the motor during operation; estimates the target junction temperature of the motor based on the power loss and a preset junction temperature conduction model. The computer program code for performing the operations of the present disclosure can be written in one or more programming languages or combinations thereof. The above programming languages include object-oriented programming languages - such as Java, Smalltalk, C++; and also include conventional procedural programming languages - such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed as an independent software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server.In the case of a remote computer, the remote computer can be connected to the user computer through any type of network - including a LAN (local area network) or a WAN (Wide Area Network) - or, alternatively, can be connected to an external computer (e.g., by using an Internet service provider to connect through the Internet). The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of devices, methods, and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagram can represent a module, a segment of a program, or a part of code that contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based device that performs the specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions. The modules described in the embodiments of the present disclosure can be implemented in software or in hardware. In some cases, the name of the module does not constitute a limitation on the unit itself.

[0187] The computer-readable storage medium provided by the embodiments of the present application stores computer-readable program instructions for executing the above-mentioned junction temperature estimation method, aiming at the technical problem of low accuracy of junction temperature estimation. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided by the embodiments of the present application are the same as those of the junction temperature estimation method provided by the above embodiments, and will not be elaborated here. The embodiments of the present application also provide a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the steps of the junction temperature estimation method as described above. The computer program product provided by the embodiments of the present application aims at the technical problem of low accuracy of junction temperature estimation. Compared with the prior art, the beneficial effects of the computer program product provided by the embodiments of the present application are the same as those of the junction temperature estimation method provided by the above embodiments, and will not be elaborated here. The above are only the preferred embodiments of the embodiments of the present application, and do not limit the patent scope of the embodiments of the present application. Any equivalent structural or equivalent process transformation made by using the specification and drawings of the embodiments of the present application, or directly or indirectly applied to other related technical fields, are equally included in the patent scope of the embodiments of the present application.

Claims

1. A junction temperature estimation method, characterized in that: The method includes: Get the speed of the motor during operation; If the rotation speed is less than a preset speed threshold, determining the transient loss of each switching power module in the motor, and taking the transient losses together as the power loss of the motor during the operation; If the rotation speed is greater than or equal to the preset speed threshold, determining the average loss of each of the switch power modules, and using the average losses as the power loss of the motor during the operation; The target junction temperature of the motor is estimated based on the power loss and a preset junction temperature conduction model.

2. The junction temperature estimation method according to claim 1, characterized in that: The switching power module includes an IGBT and a diode, and the transient loss includes an IGBT transient loss and a diode transient loss; The step of determining the transient loss of each switching power module comprises: For each switching power module, determining a first transient conduction loss of an IGBT in the switching power module and a second transient conduction loss of a diode in the switching power module; Determine a transient turn-on loss and a transient turn-off loss of the IGBT, and accumulate the transient turn-on loss and the transient turn-off loss to obtain a first transient switching loss of the IGBT; determining a second transient switching loss of the diode; The first transient conduction loss and the first transient switching loss are accumulated to obtain the IGBT transient loss, and the second transient conduction loss and the second transient switching loss are accumulated to obtain the diode transient loss.

3. The junction temperature estimation method according to claim 2, characterized in that: The step of determining a first transient conduction loss of an IGBT in the switching power module and a second transient conduction loss of a diode in the switching power module comprises: Obtaining the instantaneous collector current and the IGBT on-duty ratio when the IGBT is turned on, and determining the initial on-voltage drop and the IGBT on-resistance at a preset junction temperature; Determine a first instantaneous conduction loss of the IGBT according to the initial conduction voltage drop, the IGBT conduction internal resistance and the instantaneous collector current, and obtain a first instantaneous conduction loss of the IGBT at a preset junction temperature by multiplying the first instantaneous conduction loss by the IGBT conduction duty cycle; Obtaining a diode current and a diode conduction duty cycle when the diode is turned on, and determining a diode conduction voltage and a diode conduction internal resistance of the diode at a preset junction temperature; The second instantaneous conduction loss of the diode is determined according to the diode conduction voltage, the diode conduction internal resistance and the diode current, and the second instantaneous conduction loss of the diode at a preset junction temperature is obtained by multiplying the second instantaneous conduction loss by the diode conduction duty cycle.

4. The junction temperature estimation method according to claim 2, characterized in that: The step of determining the transient turn-on loss of the IGBT comprises: According to the acquired junction temperature turn-on loss energy relationship data, a turn-on loss energy relationship formula is constructed, wherein the turn-on loss energy relationship formula represents: a mapping relationship between the turn-on loss energy of the IGBT and the square value and the linear value of the collector current at different junction temperatures, and the turn-on loss energy relationship formula also includes a first square term coefficient, a first linear term coefficient and a first constant term related to the junction temperature; According to the values ​​of the first square term coefficient, the first linear term coefficient and the first constant term corresponding to the preset junction temperature obtained from the preset turn-on junction temperature coefficient mapping relationship, the turn-on loss energy relationship formula is updated to obtain the turn-on loss energy relationship formula of the junction temperature at the preset junction temperature; Determine the instantaneous turn-on loss at the preset junction temperature according to the instantaneous collector current when the IGBT is turned on and the junction temperature turn-on loss energy relationship, and adjust the instantaneous turn-on loss by the ratio of the current bus voltage of the motor to the rated voltage of the motor to obtain the corrected instantaneous turn-on loss; The product of the corrected instantaneous turn-on loss and the switching frequency of the IGBT is calculated to obtain the transient turn-on loss.

5. The junction temperature estimation method according to claim 2, characterized in that: The step of determining the transient turn-off loss of the IGBT comprises: According to the acquired junction temperature turn-off loss energy relationship data, a turn-off loss energy relationship formula is constructed, wherein the turn-off loss energy relationship formula represents: a mapping relationship between the turn-off loss energy of the IGBT and the square value and the linear value of the collector current at different junction temperatures, and the turn-off loss energy relationship formula includes a second square term coefficient, a second linear term coefficient, and a second constant term related to the junction temperature; According to the values ​​of the second square term coefficient, the second linear term coefficient and the second constant term corresponding to the preset junction temperature obtained from the preset shutdown junction temperature coefficient mapping relationship, the shutdown loss energy relationship formula is updated to obtain the junction temperature shutdown loss energy relationship formula under the preset junction temperature; According to the relationship between the instantaneous collector current when the IGBT is turned off and the junction temperature turn-off loss energy, the instantaneous turn-off loss at the preset junction temperature is determined, and the instantaneous turn-off loss is adjusted by the ratio of the current bus voltage of the motor to the rated voltage of the motor to obtain the corrected instantaneous turn-off loss; The product of the corrected instantaneous turn-off loss and the switching frequency of the IGBT is calculated to obtain the transient turn-off loss.

6. The junction temperature estimation method according to claim 2, characterized in that: The step of determining a second transient switching loss of the diode comprises: According to the obtained junction temperature diode energy relationship data, a reverse recovery energy relationship formula of the diode is constructed, wherein the reverse recovery energy relationship formula represents: a mapping relationship between the reverse recovery energy of the diode and the cube value, square value and linear value of the diode current at different junction temperatures, and the reverse recovery energy relationship formula includes a cubic term coefficient, a third square term coefficient, a third linear term coefficient and a third constant term related to the junction temperature; According to the values ​​of the cubic term coefficient, the third square term coefficient, the third linear term coefficient and the third constant term corresponding to the preset junction temperature obtained from the preset diode junction temperature coefficient mapping relationship, the reverse recovery energy relationship formula is updated to obtain the junction temperature reverse recovery energy relationship formula under the preset junction temperature; Determine the reverse recovery loss energy at the preset junction temperature according to the diode current when the diode is turned off and the junction temperature reverse recovery energy relationship, and adjust the reverse recovery loss energy by the ratio of the current bus voltage of the motor to the rated voltage of the motor to obtain the corrected reverse recovery loss energy; The product of the corrected reverse recovery loss energy and the switching frequency of the diode is calculated to obtain a second transient switching loss of the diode.

7. The junction temperature estimation method according to claim 1, characterized in that: The average loss includes the average IGBT loss and the average diode loss; The step of determining the average loss of each of the switching power modules comprises: For each of the switching power modules, determining a first average conduction loss of an IGBT in the switching power module and a second average conduction loss of a diode in the switching power module; Determining a first average switching loss of the IGBT, and a second average switching loss of the diode; The first average conduction loss and the first average switching loss are accumulated to obtain the IGBT average loss, and the second average conduction loss and the second average switching loss are accumulated to obtain the diode average loss.

8. The junction temperature estimation method according to claim 7, characterized in that: The step of determining a first average conduction loss of an IGBT in the switching power module and a second average conduction loss of a diode in the switching power module comprises: Obtaining the peak current, modulation factor and power factor angle of the motor, and determining the initial on-state voltage drop of the IGBT and the on-state internal resistance of the IGBT at a preset junction temperature; Determining a first average conduction loss of the IGBT according to the peak current, the modulation coefficient, the power factor angle, the initial conduction voltage drop, and the conduction internal resistance; Determine the diode conduction voltage and the diode conduction internal resistance of the diode at a preset junction temperature, and determine the second conduction loss of the diode based on the peak current, the modulation factor, the power factor angle, the diode conduction voltage and the diode conduction internal resistance.

9. The junction temperature estimation method according to claim 7, characterized in that: The step of determining a first average switching loss of the IGBT and a second average switching loss of the diode comprises: Obtaining a junction temperature turn-on loss energy relationship formula and a junction temperature turn-off loss energy relationship formula of the IGBT at a preset junction temperature, and determining a target turn-on loss energy of the IGBT according to the obtained peak current of the motor and the junction temperature turn-on loss energy relationship formula, and determining a target turn-off loss energy of the IGBT according to the peak current and the junction temperature turn-off loss energy relationship formula; In the half fundamental wave period corresponding to the motor, the product of the target turn-on loss energy, the switching frequency and the voltage ratio is integrated to obtain a turn-on integral result, and the product of the target turn-off loss energy, the switching frequency and the voltage ratio is integrated to obtain a turn-off integral result, wherein the voltage ratio is the ratio of the current bus voltage of the motor to the rated voltage; Accumulating the turn-on integral result and the turn-off integral result to obtain a switch integral result, and taking the ratio of the switch integral result to the fundamental wave period corresponding to the motor as the first average switching loss of the IGBT; Obtaining a junction temperature reverse recovery energy relationship formula of the diode at a preset junction temperature, and determining the current junction temperature reverse recovery energy according to the peak current and the junction temperature reverse recovery energy relationship formula; Within the half fundamental period corresponding to the motor, the product of the current junction temperature reverse recovery energy, the switching frequency and the voltage ratio is integrated to obtain a reverse recovery loss integral result, and the ratio of the reverse recovery loss integral result to the fundamental period corresponding to the motor is used as the second average switching loss of the diode.

10. The junction temperature estimation method according to claim 1, characterized in that: The motor comprises three phases, each phase of the motor comprises an upper bridge arm and a lower bridge arm, the upper bridge arm and the lower bridge arm are both provided with a switch power module, and the preset junction temperature conduction model comprises a preset upper bridge arm junction temperature model and a preset lower bridge arm junction temperature model; The step of estimating the target junction temperature of the motor according to the power loss and the preset junction temperature conduction model comprises: For each of the upper bridge arms in the motor, based on the module loss of the switching power module in the upper bridge arm obtained from the power loss and the preset upper bridge arm junction temperature model of the upper bridge arm, the upper bridge arm junction temperature of the upper bridge arm is calculated, and a first junction temperature difference between the upper bridge arm junction temperature and the preset junction temperature is calculated; if the first junction temperature difference is greater than a preset convergence threshold, the preset junction temperature is updated, and based on the updated preset junction temperature, the module loss of the switching power module whose first junction temperature difference is greater than the preset convergence threshold is calculated, until the first junction temperature difference is less than or equal to the preset convergence threshold, and the upper bridge arm junction temperature is used as the upper module junction temperature of the switching power module in the upper bridge arm; For each of the lower bridge arms in the motor, based on the module loss of the switching power module in the lower bridge arm obtained from the power loss and the preset lower bridge arm junction temperature model of the lower bridge arm, the lower bridge arm junction temperature of the lower bridge arm is calculated, and a second junction temperature difference between the lower bridge arm junction temperature and the preset junction temperature is calculated; if the second junction temperature difference is greater than a preset convergence threshold, the preset junction temperature is updated, and based on the updated preset junction temperature, the module loss of the switching power module whose second junction temperature difference is greater than the preset convergence threshold is calculated, until the second junction temperature difference is less than or equal to the preset convergence threshold, and the lower bridge arm junction temperature is used as the lower module junction temperature of the switching power module of the lower bridge arm; Determining the largest junction temperature value among the upper module junction temperatures and the lower module junction temperatures as the target junction temperature of the motor; When the rotation speed is less than a preset rotation speed threshold, the module loss of the switching power module is a transient loss, and when the rotation speed is greater than or equal to the preset rotation speed threshold, the loss of the switching power module is an average loss.

11. The junction temperature estimation method according to any one of claims 1 to 10, characterized in that: The junction temperature estimation method further includes: For each upper bridge arm in the motor, obtain a first self-thermal resistance of the IGBT, a second self-thermal group of the diode, a first mutual thermal resistance from the IGBT to the diode, and a second mutual thermal resistance from the diode to the IGBT in the upper bridge arm, and obtain a first temperature detected by a thermistor set in the upper bridge arm, and construct a preset upper bridge arm junction temperature model of the upper bridge arm; For each lower bridge arm in the motor, the third self-thermal resistance of the IGBT, the fourth self-thermal group of the diode, the third mutual thermal resistance from the IGBT to the diode, and the fourth mutual thermal resistance from the diode to the IGBT in the lower bridge arm are obtained, and the coolant temperature corresponding to the lower bridge arm is obtained to construct a preset lower bridge arm junction temperature model of the lower bridge arm.

12. An electronic device, characterized in that: The electronic device comprises: at least one processor; and a memory communicatively coupled to the at least one processor; The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can perform the steps of the junction temperature estimation method described in any one of claims 1 to 11.

13. A storage medium, characterized in that: The storage medium is a computer-readable storage medium, on which is stored a program for implementing the junction temperature estimation method, and the program for implementing the junction temperature estimation method is executed by a processor to implement the steps of the junction temperature estimation method as described in any one of claims 1 to 11.

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