CN113435151B - System and method for predicting IGBT junction temperature in operation process - Google Patents

Abstract

The present invention provides a system and method for predicting IGBT junction temperature during operation, comprising the following steps: step 1, respectively calculating the module junction temperature, module housing temperature and radiator surface temperature of the IGBT to be tested; step 2, according to the step 1 Obtained module junction temperature, module shell temperature and radiator surface temperature, calculate the relationship diagram between the IGBT radiator surface temperature and module junction temperature under different ambient temperatures; step 3, linearize the relationship diagram obtained in step 2 Fitting to obtain the junction temperature prediction formula; step 4, predict the junction temperature of the IGBT to be tested according to the junction temperature prediction formula obtained in step 3; this method solves the defect that the existing IGBT junction temperature after packaging cannot be measured.

Description

System and method for predicting IGBT junction temperature during operation

technical field

The invention relates to the prediction of the junction temperature of an industrial IGBT and provides a prediction system and method for the junction temperature of the IGBT during operation.

Background technique

As the main part of the power inverter, the IGBT module is repeatedly turned on or off in daily work, and it is prone to failure or fatigue effect under the repeated action of thermal shock for a long time. Its actual state and working life will affect the entire inverter device or The normal operation of the wind energy-to-electricity energy conversion system. According to statistics, among common faults, more than 20% of them are IGBT module failures. Since IGBT faults occur on a short time scale, usually on the order of μs, replacement is generally used to eliminate faults after the fault occurs. Therefore, it is of little practical significance to study the maintenance plan after the failure; a more targeted solution is to predict the future trend of the module.

IGBT module junction temperature is a key factor causing power device failure, and the measurement method is relatively simple. It can only measure the junction temperature of unplasticized IGBT modules, and it is difficult to measure the junction temperature of plastic-encapsulated IGBT modules. Therefore, it is necessary to construct a junction temperature model using other non-invasive measurement parameters to realize IGBT junction temperature prediction.

Contents of the invention

The object of the present invention is to provide a system and method for predicting the IGBT junction temperature during operation, so as to solve the defect that the IGBT junction temperature during operation cannot be measured in the prior art.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for predicting IGBT junction temperature during operation provided by the present invention comprises the following steps:

Step 1, respectively calculate the module junction temperature, module case temperature and radiator surface temperature of the IGBT to be tested;

Step 2, according to the module junction temperature, module housing temperature and radiator surface temperature obtained in step 1, calculate the relationship between the IGBT radiator surface temperature and the module junction temperature under different ambient temperatures;

Step 3, performing linear fitting on the relationship diagram obtained in step 2 to obtain a junction temperature prediction formula;

Step 4: Predict the IGBT junction temperature to be measured according to the junction temperature prediction formula obtained in step 3.

Preferably, in step 1, respectively calculate the module junction temperature, module housing temperature and radiator surface temperature of the IGBT to be tested, the specific method is:

According to the thermal conductivity characteristics of the IGBT to be tested, the equivalent circuit of the IGBT is established;

According to the obtained equivalent circuit, the module junction temperature calculation model, the module shell temperature calculation model and the radiator surface temperature calculation model of the IGBT to be tested are respectively constructed;

According to the module junction temperature calculation model, the module shell temperature calculation model and the heat sink surface temperature calculation model, the module junction temperature, the module shell temperature and the heat sink surface temperature of the IGBT to be tested are respectively calculated.

Preferably, the expression of the module junction temperature calculation model is:

T _j =P _T ×[R _th(jc) +R _th(cf) +R _th(fa) ]+T _a ;

The module shell temperature calculation model is:

T _c =P _T ×[R _th(cf) +R _th(fa) ]+T _a ;

The calculation model of radiator surface temperature is:

T _f =P _T ×R _th(fa) +T _a ;

Among them, P _T is the loss generated by the IGBT; T _j is the module junction temperature; T _c is the module shell temperature; T _f is the surface temperature of the heat sink; T _a is the ambient temperature; R _th(jc) is the junction-case temperature Thermal resistance; R _th(cf) is the thermal resistance between the shell and the heat sink; R _th(fa) is the heat sink-external thermal resistance.

Preferably, the junction-case thermal resistance R _th(jc) is calculated by the following formula:

Δt=1/2f

Among them, r _n T is the resistance value of each layer in the IGBT junction-case thermal resistance Foster model; c _n T is the capacitance value of each layer in the IGBT junction-case thermal resistance Foster model, n=1, 2, 3, 4; Δt is the duration of loss; f is the operating frequency of the inverter.

Preferably, the thermal resistance R _th(cf) between the shell and the radiator is calculated by the following formula:

Δt=1/2f

Among them, r ₅ is the resistance value of the Foster model of the thermal resistance between the IGBT case and the heat sink; c ₅ is the capacitance value in the Foster model of the thermal resistance between the IGBT case and the heat sink; Δt is the loss duration; f is the operation of the inverter frequency.

Preferably, the radiator-external thermal resistance R _th(fa) is calculated by the following formula:

Δt=1/2f

Among them, r ₆ is the resistance value of the IGBT radiator-external thermal resistance Foster model; c ₆ is the capacitance value in the IGBT radiator-external thermal resistance Foster model; Δt is the loss duration; f is the operating frequency of the inverter.

Preferably, the loss _PT generated by the IGBT is calculated by the following formula:

P _T =P _sat +P _on +P _off

Among them, P _sat is the steady-state loss, P _on is the conduction loss, and P _off is the turn-off loss.

Preferably, in step 2, according to the module junction temperature, module housing temperature and radiator surface temperature obtained in step 1, calculate the relationship diagram between the IGBT radiator surface temperature and the module junction temperature under different ambient temperatures, the specific method is :

S201, set the ambient temperature T _a to 25°C, set the power factor to 0.95; set the simulated power to 0, 0.2, 0.4, 0.6, 0.8 and 1 of the rated power value;

S202, calculate and obtain the module junction temperature T _j of the IGBT, the module case temperature T _c and the radiator surface temperature T _f under the test conditions of each current value;

S203, according to the IGBT module junction temperature T _j , module case temperature T _c and heat sink surface temperature T _f under the test conditions of each current value, obtain the maximum value of the module junction temperature and the minimum value of the module junction temperature in the steady state of each cycle , the relationship between the temperature of the module shell, the surface temperature of the radiator and the ambient temperature;

S204, repeating S202 and S203 to obtain the relationship between the maximum value of the module junction temperature, the minimum value of the module junction temperature, the temperature of the module shell, the surface temperature of the radiator, and the ambient temperature under different set ambient temperature conditions;

S205, according to the relationship between the maximum value of the module junction temperature, the minimum value of the module junction temperature, the temperature of the module shell, the surface temperature of the radiator, and the ambient temperature under different ambient temperature conditions in a steady state, the construction is obtained under different ambient temperatures, Graph of heat sink surface temperature versus module junction temperature.

Preferably, in step 3, the obtained junction temperature prediction formula is as follows:

T _j =1.345×T _f -0.352×T _a

Among them, T _j is the junction temperature of the module; T _f is the surface temperature of the radiator; T _a is the ambient temperature.

A system for predicting the junction temperature of an IGBT during operation, the system capable of performing the method, comprising:

The temperature calculation module is used to separately calculate the module junction temperature, module shell temperature and radiator surface temperature of the IGBT to be tested;

The temperature comparison module is used to calculate the relationship between the surface temperature of the radiator of the IGBT and the junction temperature of the module under different ambient temperatures based on the obtained module junction temperature, module shell temperature and radiator surface temperature;

A fitting module is used to perform linear fitting on the obtained relationship diagram to obtain a junction temperature prediction formula;

The prediction module is used to predict the junction temperature of the IGBT to be tested according to the obtained junction temperature prediction formula.

Compared with prior art, the beneficial effect of the present invention is:

The invention provides a method for predicting the junction temperature of the IGBT during operation. By monitoring the external temperature of the module and the ambient temperature, the heat transfer path and heat dissipation conditions of the IGBT are mathematically modeled, and the thermal parameter network construction of thermal resistance-heat capacity is completed. According to the fitting of the relationship between the external temperature of the module, the ambient temperature and the junction temperature of the module, the predicted value of the junction temperature of the IGBT is calculated and obtained. This method solves the defect that the junction temperature of the IGBT after the packaging is completed cannot be measured in the existing method.

Description of drawings

Fig. 1 is a flowchart of the invention;

Figure 2 is an IGBT module diagram and an equivalent circuit diagram;

Figure 3 is the equivalent circuit of the thermal resistance of the IGBT module;

Figure 4 is a Foster model circuit diagram of the thermal resistance between the IGBT junction and the case;

Fig. 5 is the thermal resistance Foster model circuit diagram of shell-radiator;

Fig. 6 is the radiator-external thermal resistance Foster model circuit diagram;

Figure 7 The relationship between junction temperature, case temperature, external temperature, and ambient temperature under different power conditions (ambient temperature 25°C);

Figure 8 shows the relationship between the maximum junction temperature, external temperature and ambient temperature under different power conditions;

Figure 9 shows the relationship between the maximum junction temperature and the module temperature under different environments.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

A prediction model of IGBT junction temperature during operation provided by the present invention selects Fuji (Fuji) company 2MBI600XHA120-50 model IGBT as the research modeling object, and its block diagram and equivalent circuit diagram are shown in FIG. 2 .

Flow chart of the present invention as shown in Figure 1, specifically comprises the following steps:

Step 1, refer to the device manual, and combine the heat conduction characteristics of the semiconductor to establish the equivalent circuit of the IGBT thermal resistance, as shown in Figure 3, where P _T is the loss generated by the IGBT; T _j is the module junction temperature; T _c is the module shell body temperature; T _f is the surface temperature of the radiator; T _a is the ambient temperature; R _th(jc) is the thermal resistance between the junction and the case; R _th(cf) is the thermal resistance between the case and the heat sink; R _{th(fa )} is the heat sink-external thermal resistance.

Through the above equivalent circuit, the module junction temperature calculation model, the module shell temperature calculation model and the heat sink surface temperature calculation model are constructed respectively, where the module junction temperature calculation model is:

T _j =P _T ×[R _th(jc) +R _th(cf) +R _th(fa) ]+T _a

The module shell temperature calculation model is:

T _c =P _T ×[R _th(cf) +R _th(fa) ]+T _a ;

The calculation model of radiator surface temperature is:

T _f =P _T ×R _th(fa) +T _a ;

Step 2, establish the thermal resistance Foster model between the IGBT junction and case shown in Figure 4, and calculate it according to the following formula:

Δt=1/2f

Among them, r _n T is the resistance value of each layer in the IGBT junction-case thermal resistance Foster model; c _n T is the capacitance value of each layer in the IGBT junction-case thermal resistance Foster model, n=1, 2, 3, 4; Δt is the duration of loss; f is the operating frequency of the inverter.

Establish the Foster model of the thermal resistance between the IGBT and the heat sink as shown in Figure 5, and calculate it according to the following formula:

Among them, r ₅ is the resistance value of the Foster model of the thermal resistance between the IGBT shells and the heat sink; c ₅ is the capacitance value in the Foster model of the thermal resistance between the IGBT shells and the heat sink.

Establish the heat sink-external thermal resistance Foster model of the IGBT as shown in Figure 6, and calculate it according to the following formula:

Among them, r ₆ is the resistance value of the IGBT radiator-external thermal resistance Foster model; c ₆ is the capacitance value in the IGBT radiator-external thermal resistance Foster model.

Step 3, establish the IGBT loss calculation model; where the IGBT loss algorithm is as follows:

P _T =P _sat +P _on +P _off

Among them, P _sat is the steady-state loss, P _on is the conduction loss, P _off is the turn-off loss, and P _T is the total loss of the IGBT; the calculation methods of P _sat , P _on and P _off refer to the device manual;

Step 4, calculated according to step 2, R _th(cf) is 0.0125°C/W; R _th(fa) is 0.02°C/W; set the simulation conditions, that is, set the ambient temperature T _a to 25°C, and set the power factor to 0.95; set the simulation power to 0, 0.2, 0.4, 0.6, 0.8 and 1 of the rated power value;

The module junction temperature T _j , the module case temperature T _c and the heat sink surface temperature T _f of the IGBT are obtained by calculation under the test conditions of each current value.

Step 5. According to the conditions set in step 4 and the formula in the previous step, the maximum value of the module junction temperature, the minimum value of the module junction temperature, the temperature of the module shell, and the surface temperature of the heat sink are respectively compared with the ambient temperature in the steady state of each cycle. The relationship between (25°C) is shown in Figure 7.

Step 6, repeat steps 4 and 5 to obtain the relationship between the maximum value of the module junction temperature, the minimum value of the module junction temperature, the temperature of the module shell, the surface temperature of the heat sink, and the ambient temperature under different set ambient temperature conditions in a steady state, Figure 8 shows.

In step 7, according to the results obtained in step 6, construct a relationship diagram between the surface temperature of the radiator and the junction temperature of the module under different ambient temperatures, as shown in FIG. 9 .

Step 8, linearly fit the relationship diagram obtained in step 7 to obtain the junction temperature prediction formula:

T _j =1.345×T _f -0.352×T _a

Step 9: Predict the junction temperature of the IGBT to be measured according to the prediction formula obtained in step 8.

Principle of work of the present invention:

IGBT is the most critical power device in the inverter system, and its thermal stability becomes the key to evaluate the performance of the system. It is necessary to conduct in-depth research on the process and influence of heat transfer under different working conditions. However, the temperature sensor cannot be installed inside the repackaged IGBT, so that the temperature of the IGBT junction temperature cannot be directly measured. At present, for the monitoring of IGBT junction temperature, the industry basically agrees to predict it by establishing a "thermal model". The prediction method provided by this program can be used in engineering. By monitoring the external temperature of the module and the ambient temperature, the heat transfer path and heat dissipation conditions of the IGBT are mathematically modeled, and the thermal resistance-heat capacity thermal parameter network is completed. According to the external temperature of the module , The relationship between the ambient temperature and the module junction temperature is fitted, and the predicted value of the IGBT junction temperature is obtained by calculation.

Claims (8)

1. The method for predicting the junction temperature of the IGBT in the operation process is characterized by comprising the following steps of:

step 1, respectively calculating the module junction temperature, the module shell temperature and the radiator surface temperature of the IGBT to be tested;

step 2, calculating a relation diagram of the surface temperature of the radiator of the IGBT and the junction temperature of the module under different environmental temperatures according to the junction temperature of the module, the temperature of the shell of the module and the surface temperature of the radiator obtained in the step 1;

step 3, performing linear fitting on the relation diagram obtained in the step 2 to obtain a junction temperature prediction formula;

step 4, predicting the junction temperature of the IGBT to be detected according to the junction temperature prediction formula obtained in the step 3;

in step 2, according to the module junction temperature, the module shell temperature and the radiator surface temperature obtained in step 1, calculating to obtain a relation diagram of the radiator surface temperature and the module junction temperature of the IGBT under different environment temperatures, wherein the specific method comprises the following steps:

s201, setting an ambient temperature T _a Setting the power factor to be 0.95 at 25 ℃; setting the simulation power as 0, 0.2, 0.4, 0.6, 0.8 and 1 of rated power values respectively;

s202, calculating and obtaining the module junction temperature T of the IGBT under the test condition of each current value _j Module case temperature T _c And radiator surface temperature T _f ；

S203, according to the module junction temperature T of the IGBT under each current value test condition _j Module case temperature T _c And radiator surface temperature T _f Obtaining the relations among the maximum module junction temperature value, the minimum module junction temperature value, the module shell temperature, the radiator surface temperature and the environment temperature respectively under each cycle period steady state;

s204, repeating S202 and S203 to obtain the relationship among the maximum module junction temperature, the minimum module junction temperature, the module shell temperature, the radiator surface temperature and the environment temperature under the different set environment temperature conditions;

s205, constructing and obtaining a relation diagram between the surface temperature of the radiator and the junction temperature of the module under different environment temperatures according to the relation among the maximum value of the junction temperature of the module, the minimum value of the junction temperature of the module, the temperature of the shell of the module, the surface temperature of the radiator and the environment temperature under different set environment temperature conditions;

in step 3, the obtained junction temperature prediction formula is as follows:

T _j ＝1.345×T _f -0.352×T _a

wherein T is _j For the module junction temperature T _f Is the radiator surface temperature; t (T) _a Is ambient temperature.

2. The method for predicting the junction temperature of the IGBT in the operation process according to claim 1, wherein step 1, respectively calculating the module junction temperature, the module case temperature and the radiator surface temperature of the IGBT to be measured, comprises the following specific steps:

establishing an equivalent circuit of the IGBT according to the heat conduction characteristic of the IGBT to be tested;

respectively constructing a module junction temperature calculation model, a module shell temperature calculation model and a radiator surface temperature calculation model of the IGBT to be tested according to the obtained equivalent circuit;

and respectively calculating the module junction temperature, the module shell temperature and the radiator surface temperature of the IGBT to be measured according to the module junction temperature calculation model, the module shell temperature calculation model and the radiator surface temperature calculation model.

3. The method for predicting the junction temperature of an IGBT in an operation according to claim 2, wherein the expression of the module junction temperature calculation model is:

T _j ＝P _T ×[R _th(j-c) +R _th(c-f) +R _th(f-a) ]+T _a ；

the module shell temperature calculation model is as follows:

T _c ＝P _T ×[R _th(c-f) +R _th(f-a) ]+T _a ；

the radiator surface temperature calculation model is as follows:

T _f ＝P _T ×R _th(f-a) +T _a ；

wherein P is _T Losses generated for IGBTs; t (T) _j The junction temperature of the module is; t (T) _c The module housing temperature; t (T) _f Is the radiator surface temperature; t (T) _a Is ambient temperature; r is R _th(j-c) Is the thermal resistance between the junction and the shell; r is R _th(c-f) Is the thermal resistance between the housing and the heat sink; r is R _th(f-a) Is the heat sink-external thermal resistance.

4. A method for predicting the junction temperature of an IGBT during operation as claimed in claim 3, wherein the junction-to-housing thermal resistance R _th(j-c) Calculated by the following formula:

Δt＝1/2f

wherein r is _n T is the resistance value of each layer in the thermal resistance Foster model between the IGBT junction and the shell; c _n T is the capacitance value of each layer in the IGBT junction-housing thermal resistance Foster model, n=1, 2,3,4; Δt is the duration of the loss; f is the frequency of operation of the frequency converter.

5. A method for predicting IGBT junction temperature during operation as claimed in claim 3, wherein the thermal resistance R between the housing and the heat sink _th(c-f) Calculated by the following formula:

Δt＝1/2f

wherein r is ₅ The resistance value of the thermal resistance Foster model of the IGBT shell-radiator is obtained; c ₅ The capacitance value in a thermal resistance Foster model of the IGBT shell-radiator; Δt is the duration of the loss; f is the frequency of operation of the frequency converter.

6. A method for predicting IGBT junction temperature during operation as claimed in claim 3, wherein the heat sink-external thermal resistance R _th(f-a) Calculated by the following formula:

Δt＝1/2f

wherein r is ₆ The resistance value of the Foster model is the external thermal resistance of the IGBT radiator; c ₆ The capacitance value in the thermal resistance Foster model outside the IGBT radiator; Δt is the duration of the loss; f is the frequency of operation of the frequency converter.

7. A method for predicting the junction temperature of an IGBT during operation as claimed in claim 3, wherein the IGBT generates a loss P _T Calculated by the following formula:

P _T ＝P _sat +P _on +P _off

wherein P is _sat Is steady state loss, P _on P is the conduction loss _off Is the turn-off loss.

8. A system for predicting IGBT junction temperature during operation, the system being capable of operating the method of any one of claims 1 to 7, comprising:

the temperature calculation module is used for calculating the module junction temperature, the module shell temperature and the radiator surface temperature of the IGBT to be measured respectively;

the temperature comparison module is used for calculating and obtaining a relation diagram of the surface temperature of the radiator and the junction temperature of the module under different environment temperatures according to the obtained junction temperature of the module, the temperature of the shell of the module and the surface temperature of the radiator;

the fitting module is used for carrying out linear fitting on the obtained relation diagram to obtain a junction temperature prediction formula;

and the prediction module is used for predicting the junction temperature of the IGBT to be detected according to the obtained junction temperature prediction formula.

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