Junction temperature estimation method and device of power semiconductor and vehicle

Abstract

The invention discloses a junction temperature estimation method and device for a power semiconductor and a vehicle, and the method comprises the steps: obtaining the loss, temperature rise data and environment temperature of the power semiconductor in an electric period, the temperature rise data comprises temperature rise values of the temperatures of the power semiconductor under different operation conditions relative to the environment temperature; determining thermal impedance according to the loss and temperature rise data; and determining the junction temperature according to the loss, the thermal impedance and the environment temperature. According to the method, the load rate of the vehicle-mounted software can be reduced, additional hardware does not need to be added, so that test resources are simple, the accuracy is high, the practicability is high, the junction temperature calculation efficiency is improved, and the calculation time is saved.

Description

Technical Field

[0001] The present invention relates to the field of vehicle technology, and in particular to a method and device for estimating the junction temperature of a power semiconductor, and a vehicle. Background Art

[0002] In the existing related technologies, there are multiple solutions for estimating the junction temperature of power semiconductors. One is to estimate by studying the temperature-sensitive parameters of the IGBT (Insulated Gate Bipolar Transistor) module and establishing its relationship with the junction temperature, but it requires additional hardware and is not applicable to low-voltage and low-power automotive IGBT modules because temperature-sensitive electrical parameters are difficult to measure. Another solution is to use a current source to heat the IGBT and record the temperature curve through an infrared thermal imager to reverse the thermal impedance and then calculate the junction temperature, but this method requires a lot of experiments and is time-consuming. Another solution is to estimate by establishing the relationship between short-circuit current and junction temperature offline, but there is a risk of IGBT overheating or even burning. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0004] To this end, an object of the present invention is to propose a method for estimating the junction temperature of a power semiconductor, which can reduce the load rate of the on-board software and does not require the addition of additional hardware, thereby making the test resources simple, accurate and practical, while also improving the efficiency of junction temperature calculation and saving calculation time.

[0005] Therefore, a second object of the present invention is to provide a junction temperature estimation device for a power semiconductor.

[0006] To this end, a third object of the present invention is to provide a vehicle.

[0007] To achieve the above-mentioned objectives, an embodiment of the first aspect of the present invention discloses a junction temperature estimation of a power semiconductor, the method comprising: obtaining the loss, temperature rise data and ambient temperature of the power semiconductor during an electrical cycle, wherein the loss includes conduction loss and switching loss, and the temperature rise data includes the temperature rise value of the power semiconductor under different operating conditions relative to the ambient temperature; determining thermal impedance based on the loss and the temperature rise data; determining the junction temperature based on the loss, the thermal impedance and the ambient temperature.

[0008] According to the junction temperature estimation method of a power semiconductor in an embodiment of the present invention, the loss, temperature rise data and ambient temperature of the power semiconductor within an electrical cycle are obtained. Since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the on-board software is greatly reduced. The thermal impedance is then determined based on the calculated loss and temperature rise data, making the calculation of the thermal impedance relatively simple and time-saving. Thereafter, the junction temperature is determined based on the calculated thermal impedance and loss in combination with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions without adding additional hardware, thereby making the test resources simple, accurate and practical, while also improving the efficiency of the junction temperature calculation and saving calculation time.

[0009] In addition, the power semiconductor junction temperature estimation method according to the above embodiment of the present invention may also have the following additional technical features: In some embodiments, when determining the junction temperature based on the loss, the thermal impedance and the ambient temperature, it includes: determining a temperature rise value based on the loss and the thermal impedance, wherein the temperature rise value includes a temperature increase value of the power semiconductor under the current operating conditions relative to the ambient temperature; and determining the junction temperature based on the temperature rise value and the ambient temperature.

[0010] In some embodiments, after determining the junction temperature based on the loss, the thermal impedance and the ambient temperature, it also includes: collecting the input voltage of the power semiconductor at the current moment, the effective value of the current of the power semiconductor under the input voltage, the switching frequency of the power semiconductor during the switching cycle and the ambient temperature, and performing temperature correction on the junction temperature based on at least one of the input voltage, the effective value of the current, the switching frequency and the ambient temperature.

[0011] In some embodiments, when the junction temperature is corrected according to at least one of the input voltage, the current effective value, the switching frequency and the ambient temperature, it includes: if at the input voltage at the current moment, the collected current effective value, the switching frequency and the ambient temperature are consistent with the data values ​​corresponding to the respective previous moments, and the duration exceeds a first preset time, then the junction temperature is set to a first preset temperature used to characterize that the temperature of the power semiconductor has reached a stable state; if at the input voltage at the current moment, the collected current effective value is less than a preset threshold, and the duration exceeds a second preset time, then the junction temperature is set to the ambient temperature, wherein the ambient temperature is less than the first preset temperature.

[0012] In some embodiments, obtaining the conduction loss of a power semiconductor within an electrical cycle includes: obtaining the conduction voltage drop and duty cycle of the power semiconductor within each switching cycle, wherein the electrical cycle includes a plurality of switching cycles; determining the conduction loss of each switching cycle based on the conduction voltage drop and the duty cycle; and summing the conduction losses of the plurality of switching cycles to obtain the conduction loss of the power semiconductor within the electrical cycle.

[0013] In some embodiments, obtaining the duty cycle of a power semiconductor within each switching cycle includes: obtaining an input voltage of the power semiconductor, a first preset action time of a first preset voltage vector, and a second preset action time of a second preset voltage vector; obtaining a third action time of a third preset voltage vector according to the first preset action time, the second preset action time, and the switching cycle, wherein the third preset voltage vector is located at the starting point of the first preset voltage vector and the second preset voltage vector; determining an average voltage generated by the power semiconductor within each switching cycle according to the input voltage, the first preset action time, the second preset action time, the third preset action time, and the switching cycle; and determining the duty cycle according to the average voltage and the input voltage.

[0014] In some embodiments, obtaining the first preset action time and the second preset action time includes: synthesizing the first preset voltage vector and the second preset voltage vector to obtain a target voltage vector; determining a target angle based on the target voltage vector, wherein the target angle is the angle between the target voltage vector and the first preset voltage vector; determining the first preset action time and the second preset action time based on the input voltage, the target voltage vector and the target angle.

[0015] In some embodiments, when obtaining the switching loss of the power semiconductor within the electrical cycle, it includes: obtaining the switching frequency of the power semiconductor within the switching cycle, the input voltage of the power semiconductor, the maximum current value of the power semiconductor within the switching cycle, the reference switching loss energy, the preset reference bus voltage and the preset reference current, wherein the reference switching loss energy is determined based on the preset reference bus voltage and the preset reference current, and the switching frequency is determined based on the switching cycle of the power semiconductor; the switching loss is determined according to the switching frequency, the input voltage, the maximum current value, the reference switching loss energy, the preset reference voltage and the preset reference current.

[0016] To achieve the above-mentioned purpose, an embodiment of the second aspect of the present invention discloses a junction temperature estimation device for a power semiconductor, which includes: an acquisition module, used to obtain the loss, temperature rise data and ambient temperature of the power semiconductor during an electrical cycle, wherein the loss includes conduction loss and switching loss, and the temperature rise data includes the temperature rise value of the power semiconductor under different operating conditions relative to the ambient temperature; a first determination module, used to determine the thermal impedance based on the loss and the temperature rise data; and a second determination module, used to determine the junction temperature based on the loss, the thermal impedance and the ambient temperature.

[0017] According to the junction temperature estimation device of the power semiconductor of the embodiment of the present invention, the loss, temperature rise data and ambient temperature of the power semiconductor within the electrical cycle are acquired through the acquisition module. Since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the vehicle-mounted software is greatly reduced. The first determination module then determines the thermal impedance based on the calculated loss and temperature rise data, so that the calculation of the thermal impedance is relatively simple and time-saving. After that, the second determination module determines the junction temperature based on the calculated thermal impedance and loss and combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions without adding additional hardware, so that the test resources are simple, accurate and practical, and the efficiency of the junction temperature calculation is improved, saving calculation time.

[0018] To achieve the above-mentioned purpose, an embodiment of the third aspect of the present invention discloses a vehicle, comprising: a power semiconductor; and a junction temperature estimation device for a power semiconductor as described in the embodiment of the second aspect of the present invention; or, a processor, a memory, and a junction temperature estimation program for a power semiconductor stored in the memory and executable on the processor, wherein the junction temperature estimation program for a power semiconductor, when executed by the processor, implements a junction temperature estimation method for a power semiconductor as described in any one of the embodiments of the first aspect of the present invention.

[0019] According to the vehicle of the embodiment of the present invention, by obtaining the loss, temperature rise data and ambient temperature of the power semiconductor within an electrical cycle, since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the on-board software is greatly reduced, and the thermal impedance is determined based on the calculated loss and temperature rise data, so that the calculation of the thermal impedance is relatively simple and time-saving. Thereafter, the junction temperature is determined based on the calculated thermal impedance and loss and combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions without adding additional hardware, so that the test resources are simple, accurate and practical, and the efficiency of the junction temperature calculation is improved, saving calculation time.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 is a flow chart of a method for estimating junction temperature of a power semiconductor according to an embodiment of the present invention; Figure 2 is a schematic diagram of a thermal network model according to an embodiment of the present invention; Figure 3 is a structural block diagram of a junction temperature estimation device for a power semiconductor according to an embodiment of the present invention; Figure 4 is a structural block diagram of a vehicle according to an embodiment of the present invention; Figure 5 is a structural block diagram of a vehicle according to another embodiment of the present invention. DETAILED DESCRIPTION

[0022] Embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. Embodiments of the present invention are described in detail below.

[0023] Reference below Figure 1 A method for estimating the junction temperature of a power semiconductor according to an embodiment of the present invention is described.

[0024] Figure 1 FIG. 1 is a flow chart of a method for estimating the junction temperature of a power semiconductor according to an embodiment of the present invention. Figure 1 As shown, the control method at least includes steps S1 to S3.

[0025] Step S1, obtaining the loss, temperature rise data and ambient temperature of the power semiconductor during an electrical cycle, wherein the loss includes conduction loss and switching loss, and the temperature rise data includes the temperature rise value of the power semiconductor under different operating conditions relative to the ambient temperature.

[0026] In an embodiment, the conduction loss and switching loss of the power semiconductor in an electrical cycle can be calculated, and the loss of the power semiconductor can be obtained based on the calculated conduction loss and switching loss, wherein the power semiconductor includes, for example, IGBT and FWD (Free Wheeling Diode, freewheeling diode chip); the ambient temperature can be obtained through a temperature sensor, such as an NTC sensor (Negative Temperature Coefficient Sensor, negative temperature coefficient sensor). The electrical cycle is much longer than the switching cycle, so the number of loss calculations performed in one electrical cycle is relatively small, which greatly reduces the load rate of the vehicle software.

[0027] For example, bench tests can be used to simulate the operation of the motor under different working conditions to obtain temperature rise data. Specifically, the motor speed step is set to 1000rpm and the torque step is set to 10Nm. In this way, the motor can be tested in a wide range of working conditions. At each working point, the motor will run stably for a period of time so that the thermocouple can accurately record the temperature rise data of the power semiconductor.

[0028] For example, during the test, the motor speed is set to 1000rpm, and the torque starts from 10Nm and gradually increases by 10Nm each time until the maximum torque at that speed is reached. At each torque point, the motor is allowed to run stably for a period of time, and a thermocouple is used to record the junction temperature change of the IGBT (or FWD), thereby obtaining a series of junction temperature curves. After completing the test of all torque points at 1000rpm, the speed is increased to 2000rpm, and the above process is repeated, that is, starting from 10Nm torque, gradually increasing to the maximum torque, and recording the junction temperature curve at each torque point. Then, the speed is continued to be increased to 3000rpm and 4000rpm until the maximum speed of the motor is reached. A complete test from minimum torque to maximum torque is performed at each speed. In this way, the power semiconductor junction temperature curve of the motor at different speed and torque combinations can be obtained, thereby obtaining temperature rise data and reducing the difficulty of calculation.

[0029] Step S2, determining thermal impedance according to the loss and temperature rise data.

[0030] In the embodiment, the thermal impedance of the power semiconductor under the current working condition can be obtained by calculating the calculated loss and the temperature rise data obtained through the bench test using the definition formula of thermal impedance. For example, the loss is recorded as , the temperature rise data is recorded as , thermal impedance is , we can get That is, the thermal impedance is equal to the ratio of the temperature rise data to the loss. The thermal impedance here can be understood as the transient thermal impedance in the offline mode. The thermal impedance constructed in this way can reduce the amount of calculation and improve the calculation efficiency in the subsequent junction temperature calculation.

[0031] Step S3, determining the junction temperature according to the loss, thermal impedance and ambient temperature.

[0032] In an embodiment, Figure 2 As shown, the thermal impedance formula can be obtained based on the thermal network model, namely: (1) (2) In formula (1) and formula (2), is the thermal resistance, is the thermal time constant, is the heat capacity, and = , while the thermal resistance and thermal time constant It can be obtained through bench test, so the thermal resistance and thermal time constant If the heat capacity is known, .

[0033] The thermal impedance formula, loss and ambient temperature are integrated into the on-board software. In the on-board software, the operating status of the motor and the loss of the power semiconductor are collected in real time, and the junction temperature of the power semiconductor is calculated online using the integrated thermal impedance formula and ambient temperature. Therefore, by adopting the above-mentioned experimental resources and testing methods, there is no need to add additional hardware, making the experimental resources simple, accurate and practical.

[0034] Therefore, the above-mentioned method for estimating the junction temperature of the power semiconductor obtains the loss, temperature rise data and ambient temperature of the power semiconductor within an electrical cycle. Since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the on-board software is greatly reduced. The thermal impedance is then determined based on the calculated loss and temperature rise data, making the calculation of the thermal impedance relatively simple and time-saving. Thereafter, the junction temperature is determined based on the calculated thermal impedance and loss, combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions, and there is no need to add additional hardware, which makes the test resources simple, accurate and practical, while also improving the efficiency of the junction temperature calculation and saving calculation time.

[0035] In one embodiment of the present invention, when determining the junction temperature based on the loss, thermal impedance and ambient temperature, it includes: determining the temperature rise value based on the loss and thermal impedance, wherein the temperature rise value includes the temperature increase value of the power semiconductor under the current operating conditions relative to the ambient temperature; determining the junction temperature based on the temperature rise value and the ambient temperature.

[0036] In the embodiment, based on the loss generated by the power semiconductor during operation and the thermal impedance measured by experimental means, the loss and thermal impedance are applied to the vehicle software, and the temperature rise value of the power semiconductor under the current operating condition can be calculated. For example, the temperature rise value is recorded as , according to the temperature rise value is equal to the product of loss and thermal impedance, the temperature rise value can be obtained, that is, .

[0037] The ambient temperature is obtained through the NTC sensor, and the temperature rise value is summed with the ambient temperature. For example, the junction temperature is recorded as , the ambient temperature is recorded as ,but , so that the junction temperature of the power semiconductor under the current working conditions can be accurately calculated , increasing the junction temperature The accuracy of the calculation also provides important data support for the thermal management of power semiconductors, thereby ensuring that they operate within a safe operating temperature range.

[0038] In one embodiment of the present invention, after determining the junction temperature based on the loss, thermal impedance and ambient temperature, it also includes: collecting the input voltage of the power semiconductor at the current moment, the effective value of the current of the power semiconductor under the input voltage, the switching frequency of the power semiconductor during the switching cycle and the ambient temperature, and performing temperature correction on the junction temperature based on at least one of the input voltage, the effective value of the current, the switching frequency and the ambient temperature.

[0039] In an embodiment, for example, the input voltage of the power semiconductor at the current moment is collected by a voltage sensor, and the effective value of the current of the power semiconductor under the input voltage and the switching frequency of the power semiconductor in the switching cycle are obtained, wherein the switching frequency can be determined according to the switching cycle, for example, the switching cycle is recorded as , the switching frequency is recorded as , due to the switching frequency With switching cycle The product of is 1, then .

[0040] Subsequently, the previously calculated junction temperature is corrected based on at least one of these parameters, such as changes in input voltage, the magnitude of the effective value of current, the switching frequency, and fluctuations in ambient temperature, which may all affect the junction temperature of the power semiconductor. Therefore, correcting the junction temperature can more accurately reflect the junction temperature of the power semiconductor under actual working conditions, thereby improving the accuracy of junction temperature measurement and avoiding the risk of overheating of the power semiconductor, which may cause the power semiconductor to burn out.

[0041] In one embodiment of the present invention, when the junction temperature is corrected according to at least one of the input voltage, the effective current value, the switching frequency and the ambient temperature, it includes: if at the input voltage at the current moment, the collected effective current value, the switching frequency and the ambient temperature are consistent with the data values ​​corresponding to the previous moment, and the duration exceeds the first preset time, then the junction temperature is set to the first preset temperature used to characterize that the temperature of the power semiconductor has reached a stable state; if at the input voltage at the current moment, the collected effective current value is less than the preset threshold value, and the duration exceeds the second preset time, then the junction temperature is set to the ambient temperature, wherein the ambient temperature is less than the first preset temperature.

[0042] In an embodiment, when it is detected that under the input voltage condition at the current moment, the three parameters of the current effective value, the switching frequency and the ambient temperature are consistent with the data values ​​at the previous moment, and the duration of this stable state exceeds the set first preset time, such as t1, it is considered that the working state of the power semiconductor has reached stability. In this stable state, the junction temperature of the power semiconductor is set to the first preset temperature, and the execution of the relevant temperature calculation code is suspended, which can reduce the calculation load of the vehicle software and avoid unnecessary resource consumption, thereby effectively improving the operating efficiency and response speed of the vehicle software while ensuring the accuracy of junction temperature monitoring.

[0043] On the other hand, if under the current input voltage, the collected current effective value is lower than the preset threshold, and this low current state lasts for longer than a set second preset time, such as t2, it is considered that the power semiconductor is not currently in a working state, and the junction temperature is set to the ambient temperature. This allows the temperature data to be managed in a simple and effective manner, while avoiding unnecessary temperature calculations for power semiconductors in a non-working state, thereby reducing resource consumption.

[0044] In one embodiment of the present invention, when obtaining the conduction loss of a power semiconductor within an electrical cycle, it includes: obtaining the conduction voltage drop and duty cycle of the power semiconductor within each switching cycle, wherein the electrical cycle includes multiple switching cycles; determining the conduction loss of each switching cycle based on the conduction voltage drop and the duty cycle; and summing the conduction losses of multiple switching cycles to obtain the conduction loss of the power semiconductor within the electrical cycle.

[0045] Among them, the on-state voltage drop is the reduction value of the voltage across the power semiconductor in the on state; the duty cycle is the proportion of time that the power semiconductor is in the on state during the switching cycle.

[0046] In an embodiment, in order to accurately calculate the conduction loss of a power semiconductor in a complete electrical cycle, it is necessary to obtain the conduction voltage drop and duty cycle of the power semiconductor in each switching cycle, wherein the electrical cycle includes a time period of multiple consecutive switching cycles. Then, the conduction loss of the switching cycle is determined by a specific calculation formula using the conduction voltage drop and duty cycle in each switching cycle. Finally, the conduction losses of all switching cycles are accumulated to obtain the total conduction loss of the power semiconductor in the entire electrical cycle.

[0047] Specifically, the switching period of PWM (Pulse Width Modulation) is set to , the electrical cycle is , there are multiple switching cycles in one electrical cycle, for example, there are N switching cycles, where N is a positive integer greater than 0.

[0048] For example, to calculate the conduction loss of an IGBT in one electrical cycle, the formula for the discrete conduction loss of an IGBT in N switching cycles in one electrical cycle can be expressed as:

[0049] In formula (3), [ ] is the on-state voltage drop of IGBT, is the tube voltage drop of the IGBT when the current is infinitely close to 0, is the resistance between the collector and emitter of the IGBT, is the current flowing through the IGBT, is the duty cycle.

[0050] The PWM switching cycle is generally much shorter than the electrical cycle. Therefore, the conduction loss of the IGBT in the electrical cycle is calculated. , the calculation frequency can be reduced by accumulating multiple switching cycles, thereby reducing the load rate of low-in-vehicle software.

[0051] The above formula (3) can be converted into the continuous conduction loss formula of the IGBT for N switching cycles in one electrical cycle, namely:

[0052] in, is the duty cycle, and according to formula (4), the conduction loss of IGBT during the electrical cycle can be calculated .

[0053] Similarly, the calculation method of the conduction loss of FWD in an electrical cycle is the same as that of IGBT, that is, the formula for the discrete conduction loss of FWD in N switching cycles in one electrical cycle can be expressed as:

[0054] In formula (5), [ ] is the on-state voltage drop of FWD, is the tube voltage drop of FWD when the current is infinitely close to 0, is the resistance of FWD, is the current flowing through FWD, is the duty cycle.

[0055] The above formula (5) can be converted into the continuous conduction loss formula of FWD for N switching cycles in one electrical cycle, that is:

[0056] in, is the duty cycle, and according to formula (6), the conduction loss of FWD during the electrical cycle can be calculated .

[0057] Therefore, combining formula (4) and formula (6), the total conduction loss of the power semiconductor during the electrical cycle can be obtained: ,Right now .

[0058] In one embodiment of the present invention, the duty cycle of a power semiconductor in each switching cycle is obtained, including: obtaining an input voltage of the power semiconductor, a first preset action time of a first preset voltage vector and a second preset action time of a second preset voltage vector; obtaining a third action time of a third preset voltage vector according to the first preset action time, the second preset action time and the switching cycle, wherein the third preset voltage vector is located at the starting point of the first preset voltage vector and the second preset voltage vector; determining an average voltage generated by the power semiconductor in each switching cycle according to the input voltage, the first preset action time, the second preset action time, the third preset action time and the switching cycle; and determining the duty cycle according to the average voltage and the input voltage.

[0059] In the embodiments, reference Figure 3 As shown, the first preset voltage vector is, for example, U100, the second preset voltage vector is U110, and the angle between the first preset voltage vector U100 and the second preset voltage vector U110 is In other words, the first preset voltage vector U100 and the second preset voltage vector U110 are two adjacent basic vectors in a sector, and the first action time of the first preset voltage vector U100 is, for example, , the second action time of the second preset voltage vector U110 is, for example, , the third preset voltage vector is a zero vector, such as Figure 3 The zero vectors U000 and U111 shown are located at the starting points of the first preset voltage vector U100 and the second preset voltage vector U110. The third preset action time is the total action time of the zero vector U000 and the zero vector U111, and the action time of each zero vector accounts for half of the third preset action time.

[0060] Specifically, after obtaining the first preset action time and the second preset action time After that, according to the known switching cycle , the third preset action time can be calculated, for example, as , that is, according to , then the third preset action time is obtained .

[0061] In this way, according to the calculated first preset action time , Second preset action time and the third preset action time , and the switching cycle and input voltage (e.g. ), the average voltage generated by the power semiconductor in each switching cycle can be calculated, for example, the average voltage is recorded as , then the average voltage The formula can be expressed as:

[0062] in, is the duty cycle in a switching cycle, and the duty cycle value is between 0 and 1. In a PWM switching cycle, the duty cycle Determines the voltage at a high level ( / 2) and low level ( / 2) of the time ratio. When the duty cycle is When the voltage is / 2; and when the duty cycle is [ ], the voltage is / 2. By taking a weighted average of these two voltage values ​​according to their respective time ratios, the average voltage within the switching cycle can be obtained. .

[0063] like Figure 3 As shown, the average voltage in a sector The calculation formula of the product of the action time can be expressed as:

[0064] The duty cycle in a sector is , based on the first preset action time obtained above , Second preset action time and the third preset action time , and the switching cycle and input voltage , the average voltage in the sector It is expressed as:

[0065] The average voltage can be further obtained The expression is:

[0066] This gives the average voltage .in, is the modulation ratio, and is a known quantity.

[0067] In addition, the average voltage of other sectors can also be obtained The expression is:

[0068] Therefore, combined with formula (7), the duty cycle of each sector can be obtained, namely:

[0069] In a specific embodiment, it is assumed that the phase angle of the phase current of the power semiconductor is , the phase current can be expressed by formula (13): .

[0070]

[0071] in, is the peak value of the phase current, is the phase angle of the phase current.

[0072] Due to the existence of the motor resistive inductive load, there is a phase difference between the phase voltage vector and the phase current vector. represents the power factor angle, then the conduction loss of IGBT can be expressed as:

[0073] Similarly, the conduction loss of FWD can be expressed as:

[0074] In one embodiment of the present invention, obtaining the first preset action time and the second preset action time includes: synthesizing the first preset voltage vector and the second preset voltage vector to obtain a target voltage vector; determining a target angle according to the target voltage vector, wherein the target angle is the angle between the target voltage vector and the first preset voltage vector; determining the first preset action time and the second preset action time according to the input voltage, the target voltage vector and the target angle.

[0075] In an embodiment, Figure 3 As shown, the first preset voltage vector U100 and the second preset voltage vector U110 are synthesized to obtain a target voltage vector, for example, , specifically, refer to Figure 2 As shown, for example, the voltage magnitude of the first preset voltage vector U100 is V4, which acts for a period of time in the entire synthesis cycle, that is, the first preset action time At the same time, the voltage magnitude of the second preset voltage vector U110 is V6, and it also acts for another period of time in the entire synthesis cycle, that is, the second preset action time According to the respective action time of the two voltage vectors, the voltage values ​​of the two voltage vectors are weighted averaged to obtain an equivalent synthetic voltage vector, namely the target voltage vector .

[0076] According to the target voltage vector Target angle can be determined , where the target angle is the target voltage vector The angle between the first preset voltage vector U100 and the first preset voltage vector U100 is as follows: and target angle , and combined with the input voltage , based on the volt-second balance principle:

[0077] By calculating the above formula (16), the first preset action time can be calculated: and the second preset action time ,Right now:

[0078]

[0079] Since the duty cycle contains the parameter target angle , then the duty cycle expressed as a time function can be Expressed as duty cycle as a function of angle .

[0080] The duty cycle If it meets the Dirichlet criterion, it can be represented by the Fourier series, through the function To express it as:

[0081] According to the Fourier series expansion theorem, we can get the function ,Right now:

[0082] In the above formula (20), the coefficients can be expressed as:

[0083] Further coefficient Analysis shows:

[0084] Taking the fundamental wave and the third harmonic components, we can get:

[0085] Further get:

[0086] This gives the duty cycle .

[0087] Therefore, combined with the duty cycle calculated by the above formula (22), the conduction loss of the IGBT can be further obtained as:

[0088] Therefore, the conduction loss of the IGBT based on the electrical cycle is calculated by the above formula (23):

[0089] Similarly, the conduction loss of FWD based on the electrical cycle can be calculated as:

[0090] The conduction loss of the power semiconductor is obtained as follows: .

[0091] In one embodiment of the present invention, when obtaining the switching loss of a power semiconductor within an electrical cycle, it includes: obtaining the switching frequency of the power semiconductor within the switching cycle, the input voltage of the power semiconductor, the maximum current value of the power semiconductor within the switching cycle, the reference switching loss energy, the preset reference bus voltage and the preset reference current, wherein the reference switching loss energy is determined based on the preset reference bus voltage and the preset reference current, and the switching frequency is determined based on the switching cycle of the power semiconductor; the switching loss is determined according to the switching frequency, the input voltage, the maximum current value, the reference switching loss energy, the preset reference voltage and the preset reference current.

[0092] In an embodiment, the switching frequency, input voltage, and maximum current value of the power semiconductor within a switching cycle are determined, and a reference switching loss energy determined based on a preset reference bus voltage and a preset reference current is introduced as a benchmark; subsequently, a comprehensive calculation is performed in combination with the switching frequency, input voltage, maximum current value, reference switching loss energy, preset reference voltage, and current to accurately derive the switching loss of the power semiconductor within an electrical cycle.

[0093] Specifically, the calculation formula for IGBT switching loss based on the electrical cycle is:

[0094] in, and Respectively represent in one switching cycle The switching loss energy of the power semiconductor when it is turned on and the switching loss energy when it is turned off are obtained by double pulse test. When considering an electrical cycle, it contains N such switching cycles. The switching loss energy during each switching cycle can be accumulated, that is, the switching loss energy during N turns on. The switching loss energy when N is turned off The sum of N switching cycles is obtained The total energy loss during the time period is To get the average power loss during this electrical cycle, divide the total energy loss by the duration of the electrical cycle. . Due to the switching frequency With switching cycle The product of is equal to 1 (i.e. =1), indicating that the product of the number of switches per second and the time required for each switch is a constant value. Ultimately, through this series of calculations, the switching loss of the power semiconductor in one electrical cycle can be obtained.

[0095] According to the calculation method of switching loss of the switching cycle, the switching loss of IGBT can be obtained as follows:

[0096] Among them, the switching loss energy at turn-on and the switching loss energy during turn-off is further broken down into the turn-on delay time , Turn-off delay time , Input voltage and the current flowing through the IGBT In other words, the switching loss energy during turn-on Not only the turn-on delay time of IGBT The input voltage at this moment is also affected and the current flowing through the IGBT Similarly, the switching loss energy during turn-off Also with the turn-off delay time , Input voltage and the current flowing through the IGBT when it is turned off This enables a more accurate understanding and calculation of the energy loss during IGBT switching.

[0097] The switching loss formula of the IGBT in (27) can be further simplified through the PWM switching cycle as follows:

[0098] Since the input voltage in one electrical cycle If it remains unchanged, the above formula (28) can be further expressed as:

[0099] When the motor is running, it is a sinusoidal current, and the current of half an electrical cycle will flow through the IGBT. The above formula can be expressed as:

[0100] Solving the above equation, the IGBT switching loss can be expressed as:

[0101] Similarly, the FWD reverse recovery loss based on the electrical cycle can be obtained:

[0102] The switching loss of the power semiconductor is obtained as follows: .

[0103] Therefore, the power semiconductor losses are: .

[0104] In summary, according to the junction temperature estimation method of the power semiconductor according to the embodiment of the present invention, by obtaining the loss, temperature rise data and ambient temperature of the power semiconductor within an electrical cycle, since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the on-board software is greatly reduced, and the thermal impedance is determined based on the calculated loss and temperature rise data, so that the calculation of the thermal impedance is relatively simple and time-saving. Thereafter, the junction temperature is determined based on the calculated thermal impedance and loss, combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions, and there is no need to add additional hardware, which makes the test resources simple, accurate and practical, and also improves the efficiency of the junction temperature calculation and saves calculation time.

[0105] The present invention further provides a junction temperature estimation device for a power semiconductor in an embodiment.

[0106] Figure 3 FIG. 1 is a block diagram of a device for estimating junction temperature of a power semiconductor according to an embodiment of the present invention. Figure 3 As shown, the power semiconductor junction temperature estimation device 100 includes: an acquisition module 110 , a first determination module 120 and a second determination module 130 .

[0107] Among them, the acquisition module 110 is used to obtain the loss, temperature rise data and ambient temperature of the power semiconductor during the electrical cycle, wherein the loss includes conduction loss and switching loss, and the temperature rise data includes the temperature rise value of the power semiconductor under different operating conditions relative to the ambient temperature; the first determination module 120 is used to determine the thermal impedance based on the loss and temperature rise data; the second determination module 130 is used to determine the junction temperature based on the loss, thermal impedance and ambient temperature.

[0108] According to the junction temperature estimation device 100 of the power semiconductor according to the embodiment of the present invention, the loss, temperature rise data and ambient temperature of the power semiconductor in an electrical cycle are obtained through the acquisition module 110. Since the number of loss calculations performed in one electrical cycle is relatively small, the load rate of the vehicle-mounted software is greatly reduced. The first determination module 120 then determines the thermal impedance based on the calculated loss and temperature rise data, so that the calculation of the thermal impedance is relatively simple and time-saving. After that, the second determination module 120 determines the junction temperature based on the calculated thermal impedance and loss and combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions without adding additional hardware, so that the test resources are simple, accurate and practical, and the efficiency of the junction temperature calculation is improved, saving calculation time.

[0109] In one embodiment of the present invention, when the second determination module 130 determines the junction temperature based on the loss, thermal impedance and ambient temperature, it includes: determining the temperature rise value based on the loss and thermal impedance, wherein the temperature rise value includes the temperature increase value of the power semiconductor under the current operating conditions relative to the ambient temperature; determining the junction temperature based on the temperature rise value and the ambient temperature.

[0110] In one embodiment of the present invention, after determining the junction temperature based on the loss, thermal impedance and ambient temperature, the second determination module 130 further includes: collecting the input voltage of the power semiconductor at the current moment, the effective value of the current of the power semiconductor under the input voltage, the switching frequency of the power semiconductor during the switching cycle and the ambient temperature, and performing temperature correction on the junction temperature based on at least one of the input voltage, the effective value of the current, the switching frequency and the ambient temperature.

[0111] In one embodiment of the present invention, when the second determination module 130 performs temperature correction on the junction temperature according to at least one of the input voltage, the effective current value, the switching frequency and the ambient temperature, it includes: if at the input voltage at the current moment, the collected effective current value, the switching frequency and the ambient temperature are consistent with the data values ​​corresponding to the previous moment, and the duration exceeds the first preset time, the junction temperature is set to the first preset temperature used to characterize that the temperature of the power semiconductor has reached a stable state; if at the input voltage at the current moment, the collected effective current value is less than the preset threshold, and the duration exceeds the second preset time, the junction temperature is set to the ambient temperature, wherein the ambient temperature is less than the first preset temperature.

[0112] In one embodiment of the present invention, when the acquisition module 110 acquires the conduction loss of the power semiconductor within an electrical cycle, it includes: acquiring the conduction voltage drop and duty cycle of the power semiconductor within each switching cycle, wherein the electrical cycle includes multiple switching cycles; determining the conduction loss of each switching cycle according to the conduction voltage drop and the duty cycle; and summing the conduction losses of multiple switching cycles to obtain the conduction loss of the power semiconductor within the electrical cycle.

[0113] In one embodiment of the present invention, the acquisition module 110 acquires the duty cycle of the power semiconductor in each switching cycle, including: acquiring the input voltage of the power semiconductor, the first preset action time of the first preset voltage vector and the second preset action time of the second preset voltage vector; obtaining the third action time of the third preset voltage vector according to the first preset action time, the second preset action time and the switching cycle, wherein the third preset voltage vector is located at the starting point of the first preset voltage vector and the second preset voltage vector; determining the average voltage generated by the power semiconductor in each switching cycle according to the input voltage, the first preset action time, the second preset action time, the third preset action time and the switching cycle; determining the duty cycle according to the average voltage and the input voltage.

[0114] In one embodiment of the present invention, the acquisition module 110 acquires the first preset action time and the second preset action time, including: synthesizing the first preset voltage vector and the second preset voltage vector to obtain a target voltage vector; determining a target angle according to the target voltage vector, wherein the target angle is the angle between the target voltage vector and the first preset voltage vector; determining the first preset action time and the second preset action time according to the input voltage, the target voltage vector and the target angle.

[0115] In one embodiment of the present invention, when the acquisition module 110 acquires the switching loss of the power semiconductor within an electrical cycle, it includes: acquiring the switching frequency of the power semiconductor within the switching cycle, the input voltage of the power semiconductor, the maximum current value of the power semiconductor within the switching cycle, the reference switching loss energy, the preset reference bus voltage and the preset reference current, wherein the reference switching loss energy is determined based on the preset reference bus voltage and the preset reference current, and the switching frequency is determined based on the switching cycle of the power semiconductor; the switching loss is determined according to the switching frequency, the input voltage, the maximum current value, the reference switching loss energy, the preset reference voltage and the preset reference current.

[0116] It should be noted that when estimating the junction temperature of a power semiconductor, the specific implementation method of the junction temperature estimation device of the power semiconductor is similar to the specific implementation method of the junction temperature estimation method of the power semiconductor described in the above-mentioned first aspect embodiment of the present invention. Therefore, for a detailed exemplary description of the junction temperature estimation device of the power semiconductor, please refer to the aforementioned description of the junction temperature estimation method of the power semiconductor. In order to reduce redundancy, it will not be repeated here.

[0117] According to the junction temperature estimation device of the power semiconductor of the embodiment of the present invention, the loss, temperature rise data and ambient temperature of the power semiconductor within the electrical cycle are obtained through the acquisition module 110. Since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the vehicle-mounted software is greatly reduced. The first determination module 120 then determines the thermal impedance based on the calculated loss and temperature rise data, so that the calculation of the thermal impedance is relatively simple and time-saving. After that, the second determination module 120 determines the junction temperature based on the calculated thermal impedance and loss and combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions without adding additional hardware, so that the test resources are simple, accurate and practical, and the efficiency of the junction temperature calculation is improved, saving calculation time.

[0118] A further embodiment of the present invention provides a vehicle 200 comprising power semiconductors.

[0119] And, in some embodiments, as Figure 4 As shown, a vehicle 200 according to an embodiment of the present invention includes the junction temperature estimation device 100 of a power semiconductor as described in the above embodiment of the present invention.

[0120] In other embodiments, Figure 5 As shown, the vehicle 200 includes: a processor 201, a memory 202, and a power semiconductor junction temperature estimation control program stored in the memory 202 and executable on the processor 201. When the power semiconductor junction temperature estimation program is executed by the processor 201, a power semiconductor junction temperature estimation method as described in any one of the above-mentioned embodiments of the present invention is implemented.

[0121] It should be noted that when the vehicle estimates the junction temperature of the power semiconductor, its specific implementation method is similar to the specific implementation method of the junction temperature estimation device or method of the power semiconductor in any of the above-mentioned embodiments of the present invention. Therefore, for a detailed exemplary description of the junction temperature estimation of the power semiconductor, please refer to the relevant description part of the aforementioned junction temperature estimation device or method of the power semiconductor. In order to reduce redundancy, it will not be repeated here.

[0122] According to the vehicle 200 of the embodiment of the present invention, by obtaining the loss, temperature rise data and ambient temperature of the power semiconductor within an electrical cycle, since the number of loss calculations performed within an electrical cycle is relatively small, the load rate of the on-board software is greatly reduced, and the thermal impedance is determined based on the calculated loss and temperature rise data, so that the calculation of the thermal impedance is relatively simple and time-saving. Thereafter, the junction temperature is determined based on the calculated thermal impedance and loss and combined with the ambient temperature. In this way, the junction temperature of the power semiconductor can be determined according to the actual operating conditions without adding additional hardware, so that the test resources are simple, accurate and practical, and the efficiency of the junction temperature calculation is improved, saving calculation time.

[0123] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0124] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for estimating the junction temperature of a power semiconductor, characterized in that: include: Acquire the loss, temperature rise data and ambient temperature of the power semiconductor during an electrical cycle, wherein the loss includes conduction loss and switching loss, and the temperature rise data includes the temperature rise value of the power semiconductor under different operating conditions relative to the ambient temperature; Determining thermal impedance based on the loss and the temperature rise data; A junction temperature is determined based on the losses, the thermal impedance, and the ambient temperature.

2. The method for estimating the junction temperature of a power semiconductor according to claim 1, characterized in that: When the junction temperature is determined according to the loss, the thermal impedance and the ambient temperature, it includes: Determining a temperature rise value according to the loss and the thermal impedance, wherein the temperature rise value includes a temperature rise value of the power semiconductor under the current operating condition relative to the ambient temperature; The junction temperature is determined according to the temperature rise value and the ambient temperature.

3. The method for estimating the junction temperature of a power semiconductor according to claim 1, characterized in that: After determining the junction temperature according to the loss, the thermal impedance and the ambient temperature, the method further includes: The input voltage of the power semiconductor at the current moment, the effective value of the current of the power semiconductor under the input voltage, the switching frequency of the power semiconductor in a switching cycle and the ambient temperature are collected, and the junction temperature is temperature corrected according to at least one of the input voltage, the effective value of the current, the switching frequency and the ambient temperature.

4. The method for estimating the junction temperature of a power semiconductor according to claim 3, characterized in that: When the junction temperature is corrected according to at least one of the input voltage, the effective value of the current, the switching frequency and the ambient temperature, the method comprises: If, under the input voltage at the current moment, the collected current effective value, the switching frequency and the ambient temperature are consistent with the data values ​​corresponding to the previous moment, and the duration exceeds a first preset time, the junction temperature is set to a first preset temperature for indicating that the temperature of the power semiconductor has reached a stable state; If, under the input voltage at the current moment, the collected current effective value is less than a preset threshold value and lasts for more than a second preset time, the junction temperature is set to the ambient temperature, wherein the ambient temperature is less than the first preset temperature.

5. The method for estimating the junction temperature of a power semiconductor according to claim 1, characterized in that: When obtaining the conduction losses of power semiconductors during an electrical cycle, it includes: Acquire the conduction voltage drop and duty cycle of the power semiconductor in each switching cycle, wherein the electrical cycle includes a plurality of the switching cycles; Determine the conduction loss of each switching cycle according to the conduction voltage drop and the duty cycle; The conduction losses of the multiple switching cycles are summed to obtain the conduction losses of the power semiconductor in the electrical cycle.

6. The method for estimating the junction temperature of a power semiconductor according to claim 5, characterized in that: Obtain the duty cycle of the power semiconductor in each switching cycle, including: Acquire an input voltage of the power semiconductor, a first preset action time of a first preset voltage vector, and a second preset action time of a second preset voltage vector; Obtaining a third action time of a third preset voltage vector according to the first preset action time, the second preset action time and the switching period, wherein the third preset voltage vector is located at a starting point of the first preset voltage vector and the second preset voltage vector; Determine an average voltage generated by the power semiconductor in each switching cycle according to the input voltage, the first preset action time, the second preset action time, the third preset action time and the switching cycle; The duty cycle is determined according to the average voltage and the input voltage.

7. The method for estimating the junction temperature of a power semiconductor according to claim 6, characterized in that: Acquiring the first preset action time and the second preset action time includes: synthesizing the first preset voltage vector and the second preset voltage vector to obtain a target voltage vector; determining a target angle according to the target voltage vector, wherein the target angle is an angle between the target voltage vector and the second preset voltage vector; The first preset action time and the second preset action time are determined according to the input voltage, the target voltage vector and the target angle.

8. The method for estimating the junction temperature of a power semiconductor according to claim 1, characterized in that: When obtaining the switching loss of the power semiconductor in the electrical cycle, it includes: Acquire a switching frequency of the power semiconductor in a switching cycle, an input voltage of the power semiconductor, a maximum current value of the power semiconductor in a switching cycle, a reference switch loss energy, a preset reference bus voltage, and a preset reference current, wherein the reference switch loss energy is determined based on the preset reference bus voltage and the preset reference current, and the switching frequency is determined based on the switching cycle of the power semiconductor; The switching loss is determined according to the switching frequency, the input voltage, the maximum current value, the reference switching loss energy, the preset reference voltage, and the preset reference current.

9. A junction temperature estimation device for a power semiconductor, characterized in that: include: An acquisition module, used to acquire the loss, temperature rise data and ambient temperature of the power semiconductor during an electrical cycle, wherein the loss includes conduction loss and switching loss, and the temperature rise data includes the temperature rise value of the power semiconductor under different operating conditions relative to the ambient temperature; A first determination module, used to determine thermal impedance according to the loss and the temperature rise data; The second determination module is used to determine the junction temperature according to the loss, the thermal impedance and the ambient temperature.

10. A vehicle, characterized in that: include: Power semiconductors; as well as, The junction temperature estimation device of a power semiconductor as claimed in claim 9; or, A processor, a memory, and a power semiconductor junction temperature estimation program stored in the memory and executable on the processor, wherein the power semiconductor junction temperature estimation program, when executed by the processor, implements the power semiconductor junction temperature estimation method as described in any one of claims 1 to 8.

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