A method for online monitoring of IGBT junction temperature of controller

Abstract

The present invention discloses a method for online monitoring of the junction temperature of an IGBT of a controller, and belongs to the field of electric drive of new energy vehicles. Through the Duhamel integral principle, a Duhamel integral equation is constructed to show the relationship between the temperature of an NTC thermistor and the junction temperature of an IGBT and the heat dissipation capacity of a cooling water channel; the Duhamel integral equation is solved by the Laplace transform method to obtain an explicit equation for predicting the junction temperature of an IGBT with the temperature of an NTC thermistor, thereby directly realizing online monitoring of the junction temperature of an IGBT. The advantages of the present invention are in two aspects: first, the actual operating conditions and power loss of the controller do not need to be considered, and the junction temperature of the IGBT can be predicted in real time only based on the temperature of the NTC thermistor; second, it is easy to implement, and there is no need to change the original NTC temperature acquisition module of the controller, and only the program code for implementing the method needs to be added to the control program.

Description

Technical Field

[0001] The present invention belongs to the field of electric drive of new energy vehicles, and in particular relates to an online monitoring method for the junction temperature of an IGBT of a controller. Background Art

[0002] The technology of the electric vehicle industry is developing rapidly. As a key component of the electric drive system, the power density and switching frequency of the controller are constantly increasing, which leads to the problem of high heat loss density. On the one hand, the excessively high junction temperature of the controller IGBT (Insulate-Gate Bipolar Transistor) will increase the power loss of the device and reduce the efficiency; on the other hand, the high temperature rise will cause thermal aging of semiconductor devices, and thermal stress shock will also cause fatigue fracture of the device material interface. Therefore, it is necessary to perform thermal management on the electric vehicle controller to ensure its efficient and reliable operation.

[0003] Real-time and accurate monitoring of the junction temperature of the running controller IGBT is a key link in implementing the active control of the online temperature rise of the controller IGBT. At present, NTC thermistors are mainly used to monitor the temperature of the controller. The temperature collected is not the IGBT junction temperature, but the DBC (Direct Bonded Copper) temperature where the chip is located. The device that generates heat loss has a very small thermal capacity and therefore has an extremely fast transient temperature response characteristic, resulting in a serious lag in amplitude and phase between the NTC reading and the transient IGBT junction temperature change.

[0004] In summary, in the prior art, it is impossible to directly measure the junction temperature of the controller IGBT through conventional temperature sensors, and the temperature given by the NTC thermistor has a large deviation relative to the IGBT junction temperature and cannot reflect the real-time changes in the junction temperature of the controller chip IGBT. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a controller IGBT junction temperature online monitoring method. Different from the traditional real-time junction temperature calculation method that directly uses a thermal model and takes power loss as input, the real-time junction temperature prediction value in the present invention is obtained by dynamic compensation based on NTC temperature. First, through the Duhamel integral principle, the Duhamel integral equation of the relationship between NTC temperature and IGBT junction temperature and the heat dissipation capacity of the cooling water channel is constructed, and then through Laplace transformation, the explicit equation for predicting the IGBT junction temperature with NTC temperature is obtained.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for online monitoring of IGBT junction temperature of a controller, the method comprising the following steps:

[0008] Step 1: Based on the Duhamel integral principle, construct the Duhamel integral equation that describes the relationship between the NTC thermistor temperature, the IGBT junction temperature, and the heat dissipation capacity of the cooling water channel:

[0009] The NTC thermistor temperature Expressed as the junction temperature of the IGBT The heating process and the response to the heat dissipation process determined by its own temperature can be expressed as follows according to the Duhamel integration principle:

[0010]

[0011] In the formula, is the time variable, is the integral variable with respect to time, ; Indicates the temperature of NTC thermistor The response function to the IGBT junction temperature, Indicates the temperature of NTC thermistor Response function to cooling water channel;

[0012] Step 2: Solve the Duhamel integral equation by Laplace transform method to obtain an explicit equation for predicting the IGBT junction temperature by using the NTC thermistor temperature.

[0013] The beneficial effects of the present invention are in two aspects:

[0014] The present invention does not need to consider the actual operating conditions and power loss of the controller, and can predict the IGBT junction temperature in real time only according to the NTC thermistor temperature; it is easy to implement, and does not need to change the original NTC temperature acquisition module of the controller, and only needs to add the program code for implementing the method into the control program. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of IGBT power module;

[0016] Figure 2 The junction temperature prediction result under constant power loss;

[0017] Figure 3 This is the junction temperature prediction result under rectangular pulse power loss. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] The present invention proposes an online monitoring method for the IGBT junction temperature of a controller, and obtains the real-time IGBT junction temperature of the controller by compensating the real-time reading of NTC.

[0020] like Figure 1 As shown in the figure, it is a schematic diagram of the IGBT power module. The controller NTC thermistor is mainly heated by the heat loss of the device and the heat dissipation of the cooling water channel. Among them, the efficiency of heating depends on the IGBT junction temperature level, while the efficiency of heat dissipation through the cooling water channel is related to its own temperature. According to the Duhamel integral principle, the temperature of the NTC thermistor and IGBT junction temperature The relationship can be expressed as follows, where the temperature of the cooling water channel is :

[0021]

[0022] In the formula, is the time variable, Is the integral variable over time. During thermal relaxation, the response function of NTC temperature to IGBT junction temperature is and the response function to the cooling water channel Can be expressed as:

[0023]

[0024]

[0025] In the response function, , and are the first, second and third thermal relaxation time constants, is a dimensionless constant, and e represents an exponential function. These constants can be obtained by fitting the measured junction temperature of the IGBT and the temperature data of the NTC thermistor, or by numerical simulation by establishing a computational fluid dynamics (CFD) temperature field model when the detailed packaging structure of the IGBT is known.

[0026] Substituting equation (2a)-(2b) into equation (1) and integrating by parts, we obtain the following equation containing convolution:

[0027]

[0028] By performing Laplace transform on equation (3), we can obtain the IGBT junction temperature in the Laplace domain: and NTC thermistor temperature The algebraic equation for , s represents the state variable in the Laplace domain:

[0029]

[0030] Furthermore, the explicit equation for the IGBT junction temperature can be obtained from equation (4) and written as follows:

[0031]

[0032] In the formula, the intermediate parameter .

[0033] Finally, perform an inverse Laplace transform on equation (5) to obtain the explicit IGBT junction temperature equation in the time domain:

[0034]

[0035] Therefore, based on equation (6), the real-time temperature reading from the NTC thermistor is The instantaneous value of the IGBT junction temperature can be predicted .

[0036] In order to implement the calculation, Equation (6) is discretized in time. Assume that the time step used is , then the time The discrete expression of IGBT junction temperature is:

[0037]

[0038] In the formula, is the discrete time step corresponding to the current moment, are the discrete time steps from the initial moment to the current moment.

[0039] For an inverter IGBT module, combined with experimental data, a CFD simulation model of its temperature field is established, and the values ​​of each time constant and dimensionless constant α in the temperature response function are calculated as shown in Table 1 below:

[0040] Table 1

[0041]

[0042] Among them, due to the existence of the initial irregular stage, the cooling curve of the NTC thermistor temperature of the IGBT module under the action of cooling water is not a strict exponential curve, so the time constant Actually equivalent value.

[0043] Substituting the above parameters into discrete equation (7), the prediction result of IGBT junction temperature curve under NTC thermistor temperature curve can be obtained, as Figure 2 and Figure 3 As shown. Among them, Figure 2 Comparison between the temperature curve of the NTC thermistor under a certain constant power condition, the IGBT junction temperature curve obtained by NTC temperature compensation, and the measured junction temperature curve; Figure 3The figure is a comparison between the temperature curve of the NTC thermistor under the excitation of a square wave pulse heat source, the junction temperature curve of the IGBT obtained by NTC temperature compensation, and the measured junction temperature curve. It can be seen that the value predicted by the method of the present invention has a high reliability.

[0044] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A controller IGBT junction temperature online monitoring method, characterized in that: The method comprises the following steps: Step 1: Based on the Duhamel integral principle, construct the Duhamel integral equation that describes the relationship between the NTC thermistor temperature, the IGBT junction temperature, and the heat dissipation capacity of the cooling water channel: The NTC thermistor temperature Expressed as the junction temperature of the IGBT The heating process and the response to the heat dissipation process determined by its own temperature can be expressed as follows according to the Duhamel integration principle: In the formula, is the time variable, is the integral variable with respect to time, ; Indicates the temperature of NTC thermistor The response function to the IGBT junction temperature, Indicates the temperature of NTC thermistor Response function to cooling water channel; Step 2, solving the Duhamel integral equation by Laplace transform method to obtain an explicit equation for predicting the IGBT junction temperature by using the NTC thermistor temperature; Wherein, the step 1 comprises: The NTC thermistor temperature Response function to IGBT junction temperature Represented as having first and second time constants , The unit step temperature rise response function is: In the formula, is a dimensionless constant, e represents an exponential function; The NTC thermistor temperature Response function to cooling water channel Expressed as having a third time constant The unit step temperature rise response function is: (2b)。 2. A controller IGBT junction temperature online monitoring method according to claim 1, characterized in that: The step 2 comprises: Substituting equation (2a)-(2b) into equation (1) and integrating by parts, we obtain the following equation containing convolution: Perform Laplace transform on equation (3) to obtain the IGBT junction temperature in the Laplace domain: and NTC thermistor temperature The algebraic equation for , s represents the state variable in the Laplace domain: Based on equation (4), the explicit equation for the IGBT junction temperature is obtained: In the formula, the intermediate parameter ; Performing an inverse Laplace transform on equation (5) yields the explicit IGBT junction temperature equation in the time domain: Indicates the instantaneous value of the IGBT junction temperature.

Images