A cooling water pump control method and system based on junction temperature estimation

Abstract

The application provides a cooling water pump control method and system based on junction temperature estimation, and the cooling water pump control method comprises the following steps: a microcontroller acquires a torque control instruction and calculates an estimated current value at a next sampling time; the microcontroller acquires a current junction temperature value of an IGBT, and calculates at least one junction temperature estimation value of the IGBT at the next sampling time when the rotating speed of the cooling water pump is increased or decreased by n revolutions per minute and multiples thereof; the microcontroller calculates the difference between each junction temperature estimation value and the current junction temperature value to form at least one junction temperature fluctuation value, and compares each junction temperature fluctuation value with a preset fluctuation threshold value; the microcontroller selects the minimum value of n revolutions per minute and multiples thereof as a rotating speed change amount when the junction temperature fluctuation value is less than or equal to the fluctuation threshold value, and controls the rotating speed of the cooling water pump based on the rotating speed change amount to reduce the junction temperature fluctuation of the IGBT, thereby increasing the service life of the IGBT and the service life of the power assembly of the new energy vehicle.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicles, and in particular to a cooling water pump control method and system based on junction temperature prediction. Background Technology

[0002] Power devices are the core of power electronic devices. Their reliability and safety determine the efficient operation of the entire power electronic system and also affect the operation of electric vehicles equipped with such systems. Compared to other power devices, insulated-gate bipolar transistors (IGBTs) have high input impedance, high conduction current, and high voltage withstand capability, playing a crucial role in power electronic systems.

[0003] With the development of power electronics technology, while IGBT modules are increasing in power rating and switching frequency, their reliability is increasingly affected by junction temperature, and the electromagnetic interference they generate also impacts other electronic systems. Fluctuations in power loss during IGBT operation cause fluctuations in the device's junction temperature, and large junction temperature fluctuations accelerate the aging of the IGBT chip. Mismatches in the coefficients of thermal expansion between the layers of materials within the IGBT power module lead to thermal and mechanical stresses, accelerating the aging process, causing solder layer fatigue, bond wire cracks, and even detachment, ultimately resulting in IGBT module failure. Therefore, significant junction temperature fluctuations are a major factor in reducing the lifespan of IGBT / SiC; in IGBT lifespan assessment, the number of times the junction temperature fluctuates by more than 10°C will significantly affect its lifespan.

[0004] The IGBT temperature of a motor controller is mainly related to the current, which is usually proportional to the torque, and has little correlation with the motor speed. In typical engineering implementations, the cooling water pump of the motor controller usually maintains a constant speed or operates at a low speed (low flow rate) when the junction temperature is low, and at a high speed (high flow rate) when the junction temperature is high, based on the estimated junction temperature. This cannot suppress the junction temperature fluctuation of the IGBT, thus affecting its service life.

[0005] Therefore, a new method for controlling cooling water pumps is needed to suppress junction temperature fluctuations in IGBTs. Summary of the Invention

[0006] To overcome the above-mentioned technical defects, the purpose of this invention is to provide a cooling water pump control method and system based on junction temperature prediction, thereby reducing IGBT junction temperature fluctuations.

[0007] This invention discloses a cooling water pump control method based on junction temperature prediction, applicable to electric vehicles with a motor controller. The cooling water pump control method includes the following steps:

[0008] The microcontroller obtains a torque control command from the motor controller and calculates the expected current value at the next sampling time based on the torque control command;

[0009] The microcontroller obtains the current junction temperature value of the IGBT from the motor controller, and calculates at least one estimated junction temperature value of the IGBT at the next sampling moment when the speed of the cooling water pump increases or decreases by n revolutions per minute or its multiple, based on the current junction temperature value and the expected current value, where each estimated junction temperature value corresponds to a selection of n or its multiple.

[0010] The microcontroller calculates the difference between each estimated junction temperature and the current junction temperature, forming at least one junction temperature fluctuation value;

[0011] The microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change, and controls the speed of the cooling water pump based on the speed change.

[0012] Preferably, the step of the microcontroller selecting the smallest value among n revolutions per minute and its multiples below the fluctuation threshold, where the junction temperature fluctuation value is less than or equal to the fluctuation threshold, and controlling the speed of the cooling water pump based on the speed change includes:

[0013] The microcontroller compares each junction temperature fluctuation value with a preset fluctuation threshold.

[0014] When at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold, the microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change, and controls the speed of the cooling water pump based on the speed change.

[0015] When all junction temperature fluctuation values ​​are greater than the fluctuation threshold, the microcontroller controls the speed of the cooling water pump to the upper limit of the speed.

[0016] Preferably, the step of the microcontroller obtaining the current junction temperature value of the IGBT from the motor controller and calculating at least one estimated junction temperature value of the IGBT at the next sampling time when the speed of the cooling water pump increases or decreases by n rpm or its multiple based on the current junction temperature value and the expected current value includes:

[0017] The microcontroller obtains the impedance Z of the IGBT chip, diode, and thermistor within the IGBT from the motor controller. ij The power P received by the IGBT chip, diode, and thermistor in the same row. i And based on the following formula:

[0018]

[0019] Calculate the upper layer temperature T of the IGBT igbt_up The temperature T of the lower IGBT layer inside the IGBT igbt_down Diode upper layer temperature T igbt_upDiode lower layer temperature T igbt_down and thermistor temperature T ntc .

[0020] Preferably, the step of the microcontroller obtaining the current junction temperature value of the IGBT from the motor controller and calculating at least one estimated junction temperature value of the IGBT at the next sampling time when the speed of the cooling water pump increases or decreases by n rpm or its multiple based on the current junction temperature value and the expected current value further includes:

[0021] The microcontroller is based on the following formula:

[0022]

[0023] Calculate the estimated junction temperature, where T j_Switch# (t m+1 (T) is the estimated junction temperature. r (t m ) represents the current junction temperature, ΔT j_Switch#，c，i (t m )

[0024] The junction temperature change of the IGBT at c times n revolutions per minute at the current moment, -Δt m R is the change over time. th_Switch#，c，i For thermal resistance, P Switch# Power.

[0025] Preferably, the multiple is an integer multiple.

[0026] This invention also discloses a cooling water pump control system based on junction temperature prediction, applicable to electric vehicles with a motor controller. The cooling water pump control system includes a microcontroller connected to the motor controller and the cooling water pump.

[0027] The microcontroller obtains a torque control command from the motor controller and calculates the expected current value at the next sampling time based on the torque control command;

[0028] The microcontroller obtains the current junction temperature value of the IGBT from the motor controller, and calculates at least one estimated junction temperature value of the IGBT at the next sampling moment when the speed of the cooling water pump increases or decreases by n revolutions per minute or its multiple, based on the current junction temperature value and the expected current value, where each estimated junction temperature value corresponds to a selection of n or its multiple.

[0029] The microcontroller calculates the difference between each estimated junction temperature and the current junction temperature, forming at least one junction temperature fluctuation value;

[0030] The microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change, and controls the speed of the cooling water pump based on the speed change.

[0031] Preferably, the microcontroller compares each junction temperature fluctuation value with a preset fluctuation threshold; when at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold, the microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change amount, and controls the speed of the cooling water pump based on the speed change amount;

[0032] When all junction temperature fluctuation values ​​are greater than the fluctuation threshold, the microcontroller controls the speed of the cooling water pump to the upper limit of the speed.

[0033] Preferably, the microcontroller obtains the impedance Z of the IGBT chip, diode, and thermistor within the IGBT from the motor controller. ij The power P received by the IGBT chip, diode, and thermistor in the same row. i And based on the following formula:

[0034]

[0035] Calculate the upper layer temperature T of the IGBT igbt_up The temperature T of the lower IGBT layer inside the IGBT igbt_down Diode upper layer temperature T igbt_up Diode lower layer temperature T igbt_down and thermistor temperature T ntc .

[0036] Preferably, the microcontroller is based on the following formula:

[0037]

[0038] Calculate the estimated junction temperature, where T j_Switch# (t m+1 (T) is the estimated junction temperature. r (t m ) represents the current junction temperature, ΔT j_Switch#，c，i (t m )

[0039] The junction temperature change of the IGBT at c times n revolutions per minute at the current moment, -Δt m R is the change over time. th_Switch#，c，i For thermal resistance, P Switch# Power.

[0040] Preferably, the multiple is an integer multiple.

[0041] Compared with existing technologies, the above technical solution has the following advantages:

[0042] 1. Significantly reduces junction temperature fluctuations in power devices, thus improving device lifespan;

[0043] 2. Based on the torque feedforward mechanism, the cooling water pump can be adjusted without changing the current. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the cooling water pump control method in a preferred embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram showing the arrangement of IGBTs and diodes in a preferred embodiment of the present invention. Detailed Implementation

[0046] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0047] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0048] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0049] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0050] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0051] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0052] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0053] See Figure 1 The diagram shows a flowchart of a cooling water pump control method according to a preferred embodiment of the present invention. In this embodiment, to control the junction temperature fluctuation of the IGBT, the cooling water pump control method includes the following steps:

[0054] S100: The microcontroller obtains a torque control command from the motor controller and calculates the expected current value at the next sampling time based on the torque control command;

[0055] The motor controller has the ability to adjust the three-phase current according to torque control commands. Therefore, it also stores torque control commands for subsequent torque adjustments. It can be understood that when a torque control command is issued, at the next sampling time or command execution time, the current in each phase of the three-phase circuit will be adjusted to achieve the value of the torque control command (which also means that at the current moment, the current in each phase of the three-phase circuit has not yet changed). Thus, the electric vehicle's microcontroller will calculate the expected current value for the upcoming change at the next sampling time based on the acquired torque control command.

[0056] S200: The microcontroller obtains the current junction temperature value of the IGBT from the motor controller, and calculates at least one junction temperature estimate of the IGBT at the next sampling time when the speed of the cooling water pump increases or decreases by n revolutions per minute or its multiple, based on the current junction temperature value and the expected current value, wherein each junction temperature estimate corresponds to a selection of n and its multiple.

[0057] Each chip within an IGBT is equipped with a temperature sensor (which is indirectly measured based on the current from each circuit) that can display or calculate the current junction temperature of the IGBT in real time. It's understandable that the junction temperature, being the highest temperature of the actual semiconductor chip (wafer, die) in the electronic device, is typically higher than the case temperature and the device surface temperature. The temperature displayed or measured by the temperature sensor may not reflect the true junction temperature. Therefore, the microcontroller obtains the current flowing through the IGBT from the motor controller to further calculate the current junction temperature. Based on the current junction temperature and the expected change in the IGBT's current, it calculates the estimated junction temperature after the change in the speed of the cooling water pump used for IGBT cooling. In particular, the adjustment of the cooling water pump speed in the above embodiments will be based on n revolutions per minute. For example, at the current speed of the cooling water pump, n revolutions per minute can be increased, n revolutions per minute can be decreased, or n*m revolutions per minute can be increased or n*m revolutions per minute can be decreased (m can preferably be a natural number). With the selection of m, multiple adjusted expected speeds of the cooling water pump will be obtained. At each expected speed, the estimated junction temperature of the IGBT after the junction temperature change at the next sampling time is calculated.

[0058] S300: The microcontroller calculates the difference between each estimated junction temperature and the current junction temperature, forming at least one junction temperature fluctuation value;

[0059] Furthermore, the microcontroller calculates the difference between the estimated junction temperature and the current junction temperature at each expected rotational speed. Each difference represents the impact of adjusting the cooling water pump speed on junction temperature fluctuations. A relatively large difference indicates significant junction temperature fluctuations, while a relatively small difference indicates less fluctuations. Each difference generates at least one junction temperature fluctuation value, and optionally, each fluctuation value is compared to a preset fluctuation threshold in the microcontroller (or the junction temperature value with each fluctuation value is compared to the junction temperature threshold). This fluctuation threshold represents the allowable value for junction temperature fluctuations.

[0060] S400: The microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change, and controls the speed of the cooling water pump based on the speed change.

[0061] Based on the comparison, the microcontroller will select one from all predicted speeds. The selection criteria are: firstly, the difference between the predicted junction temperature at the predicted speed and the current junction temperature should be less than or equal to a fluctuation threshold (this criterion is optional) to control junction temperature fluctuations; secondly, the predicted speed adjustment should be minimized to reduce the amount of cooling water pump speed adjustment. Therefore, the microcontroller selects the smallest value among n rpm and its multiples where the junction temperature fluctuation is less than or equal to the fluctuation threshold, and ultimately controls the cooling water pump speed based on this speed change.

[0062] Based on the above configuration, the junction temperature fluctuation is ultimately controllable, and the adjustment of the cooling water pump is minimized, so as to control the junction temperature of the IGBT in the shortest possible time.

[0063] In a preferred embodiment, step S400 includes:

[0064] S410: The microcontroller compares each of the junction temperature fluctuation values ​​with a preset fluctuation threshold;

[0065] S420: When at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold, the microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change amount, and controls the speed of the cooling water pump based on the speed change amount;

[0066] The microcontroller will select the smallest value among n revolutions per minute and its multiples as the speed change, and control the speed of the cooling water pump based on the speed change, if and only if at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold.

[0067] S420': When all junction temperature fluctuation values ​​are greater than the fluctuation threshold, the microcontroller controls the speed of the cooling water pump to the upper limit of the speed.

[0068] If the comparison result is that all junction temperature fluctuation values ​​are greater than the fluctuation threshold, it means that no matter how the speed of the cooling water pump is adjusted, the junction temperature fluctuation cannot be controlled within the allowable range. In this case, the microcontroller will control the speed of the cooling water pump to the upper limit of the speed to reduce the junction temperature value as much as possible and slow down the wear and tear on electronic devices under hardware conditions.

[0069] In a preferred embodiment, step S200 includes:

[0070] S210: The microcontroller obtains the impedance Z of the IGBT chip, diode, and thermistor within the IGBT from the motor controller. ij The power P received by the IGBT chip, diode, and thermistor in the same row. i And based on the following formula:

[0071]

[0072] Calculate the upper layer temperature T of the IGBT igbt_up The temperature T of the lower IGBT layer inside the IGBT igbt_down Diode upper layer temperature T igbt_up Diode lower layer temperature T igbt_down and thermistor temperature T ntc .

[0073] See Figure 2The upper and lower layers of an IGBT have different temperatures. Simultaneously, the diodes, IGBT chips, and thermistors (NTC, reflecting the IGBT's ambient temperature) within the IGBT also have different temperatures. Each layer of diodes, IGBT chips, and thermistors has its own impedance Z. ij (Z ij In actual parameter extraction, a multi-order Foster model is used, and the upper IGBT chip, lower IGBT chip, upper diode, and lower diode in the same column are treated as devices in the same column, receiving a unified input power P. i Thus, the aforementioned thermal resistance matrix is ​​established.

[0074] Furthermore, step S200 also includes:

[0075] S220: The microcontroller is based on the following formula:

[0076]

[0077] Calculate the estimated junction temperature, where T j_Switch#，c，i (t m+1 (T) is the estimated junction temperature. r (t m ) represents the current junction temperature, ΔT j_Switch#，c，i (t m ) represents the junction temperature change of the IGBT at c times n revolutions per minute at the current time, -Δt m R is the change over time. th_Swith#，c，i For thermal resistance, P Switch# Power.

[0078] This invention also discloses a cooling water pump control system based on junction temperature prediction, applied to electric vehicles with a motor controller. The cooling water pump control system includes a microcontroller connected to the motor controller and the cooling water pump. The microcontroller obtains a torque control command from the motor controller and calculates the expected current value at the next sampling time based on the torque control command. The microcontroller obtains the current junction temperature value of the IGBT from the motor controller and calculates at least one junction temperature prediction value of the IGBT at the next sampling time when the speed of the cooling water pump increases or decreases by n revolutions per minute or a multiple thereof, based on the current junction temperature value and the expected current value. Each junction temperature prediction value corresponds to a selection of n or a multiple thereof. The microcontroller calculates the difference between each junction temperature prediction value and the current junction temperature value to form at least one junction temperature fluctuation value. The microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change and controls the speed of the cooling water pump based on the speed change.

[0079] Preferably, the microcontroller compares each junction temperature fluctuation value with a preset fluctuation threshold; when at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold, the microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change amount, and controls the speed of the cooling water pump based on the speed change amount; when all junction temperature fluctuation values ​​are greater than the fluctuation threshold, the microcontroller controls the speed of the cooling water pump to the upper speed limit value.

[0080] Preferably, the microcontroller obtains the impedance Z of the IGBT chip, diode, and thermistor within the IGBT from the motor controller. ij The power P received by the IGBT chip, diode, and thermistor in the same row. i And based on the following formula:

[0081]

[0082] Calculate the upper layer temperature T of the IGBT igbt_up The temperature T of the lower IGBT layer inside the IGBT igbt_down Diode upper layer temperature T igbt_up Diode lower layer temperature T igbt_down and thermistor temperature T ntc .

[0083] Preferably, the microcontroller is based on the following formula:

[0084]

[0085] Calculate the estimated junction temperature, where T j_Swithch# (t m+1 (T) is the estimated junction temperature. r (t m ) represents the current junction temperature, ΔT j_Switch#，c，i (t m ) represents the junction temperature change of the IGBT at c times n revolutions per minute at the current time, -Δt m R is the change over time. th_Switch，c，i For thermal resistance, P Switch# Power.

[0086] Preferably, the multiple is an integer multiple.

[0087] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A cooling water pump control method based on junction temperature prediction, applied to electric vehicles with motor controllers, characterized in that, The cooling water pump control method includes the following steps: The microcontroller obtains a torque control command from the motor controller and calculates the expected current value at the next sampling time based on the torque control command; The microcontroller obtains the current junction temperature value of the IGBT from the motor controller, and calculates at least one estimated junction temperature value of the IGBT at the next sampling moment when the speed of the cooling water pump increases or decreases by n revolutions per minute or its multiple, based on the current junction temperature value and the expected current value, wherein each estimated junction temperature value corresponds to the selection of n revolutions per minute or its multiple. The microcontroller calculates the difference between each estimated junction temperature and the current junction temperature to form at least one junction temperature fluctuation value; The microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change, and controls the speed of the cooling water pump based on the speed change. The step of controlling the speed of the cooling water pump based on the smallest value among n revolutions per minute and its multiples includes: The microcontroller compares each junction temperature fluctuation value with a preset fluctuation threshold. When at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold, the microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change amount, and controls the speed of the cooling water pump based on the speed change amount; When all junction temperature fluctuation values ​​are greater than the fluctuation threshold, the microcontroller controls the speed of the cooling water pump to the upper speed limit. The step of the microcontroller obtaining the current junction temperature value of the IGBT from the motor controller and calculating at least one estimated junction temperature value of the IGBT at the next sampling moment based on the current junction temperature value and the expected current value, when the speed of the cooling water pump increases or decreases by n rpm or its multiple, includes: The microcontroller obtains the impedance Z of the IGBT chip, diode, and thermistor within the IGBT from the motor controller. ij The power P received by the IGBT chip, diode, and thermistor in the same row. i And based on the following formula: Calculate the upper layer temperature of the IGBT IGBT lower layer temperature Diode top layer temperature Diode lower layer temperature and thermistor temperature ; The step of the microcontroller obtaining the current junction temperature value of the IGBT from the motor controller and calculating at least one estimated junction temperature value of the IGBT at the next sampling moment based on the current junction temperature value and the expected current value, when the speed of the cooling water pump increases or decreases by n rpm or its multiple, further includes: The microcontroller is based on the following formula: Calculate the estimated junction temperature, where For the estimated junction temperature, This is the current junction temperature value. This represents the junction temperature change of the IGBT at c times n revolutions per minute at the current time. For the time-varying quantity, For thermal resistance, Power.

2. The cooling water pump control method as described in claim 1, characterized in that, The multiple is an integer multiple.

3. A cooling water pump control system based on junction temperature prediction, applied to electric vehicles with motor controllers, characterized in that, The cooling water pump control system includes a microcontroller, which is connected to the motor controller and the cooling water pump. The microcontroller obtains a torque control command from the motor controller and calculates the expected current value at the next sampling time based on the torque control command; The microcontroller obtains the current junction temperature value of the IGBT from the motor controller, and calculates at least one estimated junction temperature value of the IGBT at the next sampling moment when the speed of the cooling water pump increases or decreases by n revolutions per minute or its multiple, based on the current junction temperature value and the expected current value, wherein each estimated junction temperature value corresponds to the selection of n revolutions per minute or its multiple. The microcontroller calculates the difference between each estimated junction temperature and the current junction temperature to form at least one junction temperature fluctuation value; The microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change, and controls the speed of the cooling water pump based on the speed change. The microcontroller compares each junction temperature fluctuation value with a preset fluctuation threshold. When at least one junction temperature fluctuation value is less than or equal to the fluctuation threshold, the microcontroller selects the smallest value among n revolutions per minute and its multiples as the speed change amount, and controls the speed of the cooling water pump based on the speed change amount; When all junction temperature fluctuation values ​​are greater than the fluctuation threshold, the microcontroller controls the speed of the cooling water pump to the upper speed limit. The microcontroller obtains the impedance Z of the IGBT chip, diode, and thermistor within the IGBT from the motor controller. ij The power P received by the IGBT chip, diode, and thermistor in the same row. i And based on the following formula: Calculate the upper layer temperature of the IGBT IGBT lower layer temperature Diode top layer temperature Diode lower layer temperature and thermistor temperature ; The microcontroller is based on the following formula: Calculate the estimated junction temperature, where For the estimated junction temperature, This is the current junction temperature value. This represents the junction temperature change of the IGBT at c times n revolutions per minute at the current time. For the time-varying quantity, For thermal resistance, Power.

4. The cooling water pump control system as described in claim 3, characterized in that, The multiple is an integer multiple.

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