CN116794469A - Saturation pressure drop measurement system and method, and life evaluation method and system - Google Patents

Abstract

The application provides a saturation pressure drop measuring system and method, and a service life assessment method and system, wherein the saturation pressure drop measuring system comprises: the cutting-off unit is used for cutting off the operation loop of the insulated gate bipolar transistor IGBT to be tested when the IGBT to be tested reaches a thermal balance state; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located; the maintenance measurement unit is used for maintaining the cut-off IGBT to be measured in a small current conduction state and measuring the saturation voltage drop in the cooling process of the IGBT to be measured; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

Description

Saturation pressure drop measurement system and method, and life evaluation method and system

Technical Field

The application relates to the field of electronic devices, in particular to a saturation voltage drop measurement system and method, and a service life assessment method and system.

Background

In recent years, with the increasing prominence of environmental pollution, energy crisis and other problems, the development of new energy to reduce the dependence on traditional energy has become a necessary trend. The sustainable development of energy sources is advocated for a long time in China, and the industries of wind power, photovoltaics, biomass energy power generation, electric automobiles and the like are supported in a policy mode. The high-power converter device which is used as a tie for connecting the new energy equipment with the power grid is the most critical component of the new energy equipment and is also one of the components which are most prone to failure. In the context of high reliability requirements such as aerospace, electric vehicles, offshore fans, converter stations, etc., system faults caused by high power converter failure can lead to immeasurable losses.

As a key element of the high-power converter, high reliability of an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, abbreviated as IGBT) is an important guarantee of stable operation of the system, and accurate life assessment of the IGBT is one of effective means for improving the reliability of the system. However, the service life of the IGBT is estimated at present by mostly neglecting the thermal resistance and the thermal load increasing effect caused by the fatigue of the solder layer, and the service life of the IGBT is easy to be estimated.

Disclosure of Invention

In order to solve the technical problems, the embodiment of the application provides a saturated voltage drop measuring system and method, and a service life assessment method and system, which can measure the transient thermal resistance curve of an IGBT on line, introduce the thermal resistance and thermal load increasing effect caused by the fatigue of a solder layer into a service life assessment network, and further more accurately assess the service life of the IGBT.

The embodiment of the application provides a saturation pressure drop measuring system, which comprises:

the cutting-off unit is used for cutting off the running loop of the IGBT to be tested when the IGBT to be tested reaches a thermal balance state; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located;

the maintenance measurement unit is used for maintaining the cut-off IGBT to be measured in a small current conduction state and measuring the saturation voltage drop in the cooling process of the IGBT to be measured; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

The embodiment of the application also provides a saturation pressure drop measuring method, which comprises the following steps:

when the IGBT to be tested reaches a thermal equilibrium state, cutting off an operation loop of the IGBT to be tested; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located;

maintaining the cut-off IGBT under test in a small current conduction state, and measuring the saturation voltage drop in the cooling process of the IGBT under test; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

The embodiment of the application also provides a service life assessment method, which comprises the following steps:

standard IGBT training process and measured IGBT evaluation process, wherein:

the standard IGBT training process comprises the following steps:

based on different aging states from health to failure of a standard IGBT, constructing a Cohr Caser thermal network of the standard IGBT in each of the different aging states, and identifying parameters of the corresponding Caser thermal network in each of the different aging states, wherein the standard IGBT refers to an IGBT with the same parameters as the IGBT to be tested;

based on the parameters of the Caser thermal network of the standard IGBT in different ageing states, dispersing the process from health to failure of the standard IGBT into a plurality of ageing stages;

the IGBT evaluation process comprises the following steps:

based on the junction temperature curve of the IGBT to be tested and a plurality of aging stages of the standard IGBT from health to failure, the current aging stage of the IGBT to be tested is obtained;

Based on the aging stage of the IGBT to be tested, fatigue accumulation of the aging stage of the IGBT to be tested is obtained, and a junction temperature curve of the IGBT to be tested in the next aging stage is selected;

and circulating the above IGBT evaluation process until the IGBT fails to obtain the life evaluation result of the IGBT.

The embodiment of the application also provides a service life evaluation system, which comprises:

the standard IGBT training unit is used for constructing the Caser thermal network of the standard IGBT in different aging states based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding Caser thermal network in different aging states; but also for the use of the composition,

based on the parameters of the Caser thermal network of the standard IGBT in different ageing states, dispersing the process from health to failure of the standard IGBT into a plurality of ageing stages;

the IGBT evaluation unit is used for obtaining the current aging stage of the IGBT based on the junction temperature curve of the IGBT; but also for the use of the composition,

based on the aging stage of the IGBT to be tested, fatigue accumulation of the aging stage of the IGBT to be tested is obtained, and a junction temperature curve of the IGBT to be tested in the next aging stage is selected; but also for the use of the composition,

and circulating the process until the IGBT to be tested fails, and obtaining a life evaluation result of the IGBT to be tested.

The embodiment of the application provides a saturation pressure drop measuring system and method, and a service life evaluating method and system. Wherein, saturation pressure drop measurement system includes: the cutting-off unit is used for cutting off the running loop of the IGBT to be tested when the IGBT to be tested in the loop reaches a thermal balance state; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located; the maintenance measurement unit is used for maintaining the cut-off IGBT to be measured in a small current conduction state and measuring the saturation voltage drop in the cooling process of the IGBT to be measured; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

In the embodiment of the application, the running loop of the IGBT to be tested which reaches the thermal equilibrium state can be cut off through the cutting-off unit, and then the cut-off IGBT to be tested is kept in a small current conduction state by the maintenance measuring unit, so that the IGBT to be tested is cooled, and the saturation voltage drop in the cooling process of the IGBT to be tested is measured. Therefore, the on-line measurement of the IGBT to be tested can be realized, the current transient thermal resistance curve of the IGBT to be tested is further obtained, and the service life evaluation of the IGBT to be tested is realized.

Drawings

FIG. 1 is a schematic diagram of a saturation pressure drop measurement system according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a saturation pressure drop measurement system according to an embodiment of the present application;

fig. 3a is a schematic structural diagram of a saturation voltage drop measurement system applied to a current transformer topology according to an embodiment of the present application;

fig. 3b is a schematic diagram of a current path of the IGBT under test in fig. 3a in a high current conducting state;

FIG. 3c is a schematic diagram of the current path of the IGBT in FIG. 3a in a low current conducting state;

FIG. 4 is a schematic flow chart of a saturation pressure drop measurement method according to an embodiment of the present application;

FIG. 5 is a schematic structural diagram of an on-line transient thermal resistance monitoring simulation model according to an embodiment of the present application;

FIG. 6 shows an embodiment of the application of S ₁ Schematic representation of junction temperature curves;

fig. 7 is a schematic structural diagram of an IGBT packaging system according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of a three-dimensional finite element model of a SKM50GB12T4 type IGBT according to an embodiment of the present application;

fig. 9 is a schematic diagram of the difference of the influence of the junction temperature fluctuation of the IGBT when the aging degree of each solder layer of the comparative IGBT provided in the embodiment of the application is 5% and 16%, respectively;

FIG. 10 is a flowchart of a lifetime assessment method according to an embodiment of the present application;

fig. 11 is a schematic diagram of transient thermal resistance curves corresponding to IGBTs when a chip solder layer provided by the embodiment of the present application is in different aging states;

Fig. 12 is a schematic diagram of transient thermal resistance curves corresponding to IGBTs when DBC solder layers provided by the embodiment of the present application are in different aging states;

fig. 13 is a schematic flow chart of a method for constructing a third-order Cauer thermal network of a standard IGBT in different aging states according to an embodiment of the present application;

fig. 14 is a schematic diagram of a third-order Cauer thermal network updating strategy taking into account position information of an aged solder layer according to an embodiment of the present application;

fig. 15 is a flowchart of a lifetime assessment method according to an embodiment of the present application.

Fig. 16 is a schematic diagram of an IGBT lifetime assessment method applied to a fan according to an embodiment of the present application;

FIG. 17 is a schematic diagram of the actual wind speed of a wind turbine provided by an embodiment of the present application;

FIG. 18a is a schematic diagram of a thermal load spectrum of an IGBT in a blower fan when in a healthy state;

FIG. 18b is a schematic diagram of the thermal load spectrum of an IGBT in a blower during a fourth aging stage;

fig. 19 is a schematic structural diagram of a life assessment system according to an embodiment of the present application.

Detailed Description

The following description of the technical solutions according to the embodiments of the present application will be given with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

It should be noted that, in the embodiment of the present application, the term "and/or" is merely an association relationship describing the association object, which means that three relationships may exist, for example, a and/or B may be represented: a exists alone, A and B exist together, and B exists alone. In addition, in the embodiment of the present application, the character "/", generally indicates that the front and rear association objects are in an or relationship.

In the description of the embodiments of the present application, the term "corresponding" may indicate that there is a direct correspondence or an indirect correspondence between the two, or may indicate that there is an association between the two, or may indicate a relationship between the two and the indicated, configured, etc.

In order to facilitate understanding of the technical solutions of the embodiments of the present application, the following description describes related technologies of the embodiments of the present application, and the following related technologies may be optionally combined with the technical solutions of the embodiments of the present application as alternatives, which all belong to the protection scope of the embodiments of the present application.

As a key unit of the high-power converter, high reliability of the IGBT is an important guarantee of stable operation of the system, and accurate life assessment of the IGBT is one of effective means for improving the reliability of the system. However, the current service life evaluation of the IGBT mostly ignores the thermal resistance and thermal load increasing effect caused by the fatigue of the solder layer, and the service life of the IGBT is easy to be overestimated. Several life assessment schemes are described below.

Scheme a: firstly, determining the electrical parameters of a circuit in which the IGBT is positioned according to the type and the use environment of the IGBT; then, a circuit diagram is built in simulation software according to the electrical parameters of a circuit in which the IGBT is positioned, and waveforms of junction temperature of the IGBT changing along with time are obtained through simulation according to the loss parameters and the thermal model in a data manual (Datasheet) of the IGBT; and finally, carrying out service life assessment on the IGBT by combining Bayer model parameters and the junction temperature of the IGBT. The method for determining the Bayer model parameters is to randomly select possible values of the Bayer model parameters by using a Monte Carlo analysis method so as to account service life calculation deviation of the IGBT caused by individual quality differences and improve service life prediction accuracy. The method only considers the type and the use environment of the IGBT, and does not consider the acceleration effect of the fatigue accumulation effect of the solder layer on the aging of the IGBT.

Scheme B: firstly, establishing a traction transmission system IGBT loss estimation model according to a traction level/braking level of a metro vehicle and the rotation speed of a motor; then establishing a traction transmission system IGBT junction temperature estimation model based on the Foster equivalent thermal network and IGBT loss; and finally, establishing a traction transmission system IGBT service life prediction model based on a rain flow counting method and a Miner linear fatigue accumulation theory, and predicting the service life of an IGBT module by obtaining the loss of the IGBT through a table lookup method according to the actual traction level/braking level and the motor rotating speed of the metro vehicle. The method provides a calculation mode of IGBT power loss in the working condition of the subway vehicle, and does not consider the acceleration effect of the fatigue accumulation effect of the solder layer on the aging of the IGBT.

Scheme C: firstly, an electrothermal coupling model is established to obtain real-time junction temperature data; aiming at the aging characteristic of IGBT, the method improves the Long short-term memory (LSTM) network to obtain a segmented LSTM prediction network; then, segment LSTM prediction is carried out by utilizing the monitoring value of the IGBT aging parameter, the estimated aging process is obtained, and the thresholds of different aging stages are divided in this way; comparing the threshold value with the monitoring data, judging the aging stage of the IGBT in real time, and carrying out aging correction on the parameters of the electric-thermal coupling model to ensure the accuracy of junction temperature data; finally, the temperature data is processed by using a rain flow counting method, and the real-time heat load distribution of the IGBT is calculated; and combining a fatigue damage theory and a Lesit life prediction model, and calculating the real-time accumulated damage degree and the estimated life of the IGBT. According to the method, an LSTM network is introduced to estimate the aging state of the IGBT in real time so as to correct the model, but the correction method needs a large amount of training data, the model is updated continuously during calculation, the requirement on calculation resources is high, the characteristics of an IGBT packaging system are not considered in a thermal network updating mode of an electric-thermal coupling model, and the junction temperature curve is estimated inaccurately.

Scheme D: firstly, under a long time scale, ignoring transient details of junction temperature fluctuation, and ensuring calculation efficiency; under the short time scale, the dynamic details of junction temperature fluctuation are focused to improve the calculation accuracy; and meanwhile, updating the thermal network model in a staged manner so as to account for fatigue accumulation. However, the method does not describe how to update the thermal network, if the thermal network is updated as a whole, the actual aging process of the IGBT module package is not met, and if the Foster thermal network is adopted, the junction temperature curve after aging cannot be calculated accurately.

Scheme E: firstly, working condition data are processed by using a rain flow counting algorithm, and then annual damage amount under linear fatigue accumulation damage is obtained by combining an IGBT life prediction formula. Considering that the physical parameters of the IGBT are gradually deteriorated along with the service time, the current damage amount and the service time are subjected to sectional analysis on the basis of the reliability index distribution. However, this method does not describe how to update the hot network, and the accuracy of the hot network update cannot be guaranteed.

Scheme F: firstly, constructing an MATLAB/Simulink simulation model of a photovoltaic converter with a maximum power tracking (Maximum Power Point Tracking, MPPT for short), and combining the temperature and irradiance changes of a photovoltaic system and the transient process of the heat capacity of a power module to predict the service life; and then according to the actual operation condition in one year, combining the influencing variables of the annual junction temperature curve (large load) and the minute junction temperature curve (small load), counting the number of load cycles by adopting a rain flow counting method by using a repeated iteration calculation method, and calculating the fatigue damage of the power module by using a Miner linear fatigue accumulation theory by calculating the corresponding number of times from each load cycle to the failure of the power module. However, the method does not consider the acceleration effect of the fatigue accumulation effect of the solder layer on the aging of the IGBT.

Based on the above description, the above scheme has the following drawbacks:

for scheme a: although the life calculation deviation due to individual quality difference is counted, the accuracy of life prediction is improved, but the acceleration of the aging of the IGBT by the effect of the fatigue accumulation of the solder layer is not considered.

For scheme B: although a calculation mode of IGBT power loss in the working condition of the metro vehicle is provided, acceleration of aging of the IGBT by the fatigue accumulation effect of the solder layer is not considered.

For scheme C: the thermal network is updated continuously during calculation, the requirement on calculation resources is high, the characteristics of the IGBT packaging system are not considered in the electric-thermal coupling model thermal network updating mode, and the junction temperature curve is estimated inaccurately.

For scheme D: how to update the thermal network is not described, if the thermal network is updated as a whole, the actual aging process of the IGBT module package is not met, and if the Foster thermal network is adopted, the junction temperature curve after aging cannot be calculated accurately.

For scheme E: how to update the hot network is not described, and accuracy in updating the hot network cannot be guaranteed.

For scheme F: the acceleration of IGBT aging by the effect of solder layer fatigue accumulation is not considered.

In order to solve at least part of the above-mentioned drawbacks, the following technical solutions of the embodiments of the present application are provided.

So that the manner in which the features and objects of the present application can be understood in more detail, a more particular description of the application, briefly summarized below, may be had by reference to the appended drawings, which are not necessarily limited to the embodiments described herein; the described embodiments should not be taken as limitations of the present application, and all other embodiments that would be obvious to one of ordinary skill in the art without making any inventive effort are intended to be within the scope of the present application.

Apart from sudden failures (e.g., shorts, opens, etc.), the reliability of an IGBT is typically determined by the thermal imbalance of the IGBT. The physical quantity representing heat is usually temperature, the junction temperature is an important state parameter of the IGBT, and the junction temperature level during operation is critical to the safe operation of the IGBT. Furthermore, in order to realize life assessment of the IGBT to be tested, a junction temperature curve of the IGBT to be tested needs to be obtained. A common junction temperature curve measurement method is a temperature sensitive parameter method (Temperature Sensitive Parameters, abbreviated as TSPs).

The TSPS parameter of the IGBT to be tested has saturation voltage drop V _ces Gate turn-on delay time T _don Gate threshold voltage VGE _th Maximum current change rate of collector ((dI) _c /dt) _max ) And the rate of change of the emitter voltage (dV) _ce /dt). Wherein, the gate is turned on for a delay time T _don Only a few hundred nanoseconds, the hardware requirement on the test equipment is high, and a certain difficulty exists in realizing accurate measurement. Maximum current change rate of collector ((dI) _c /dt) _max ) And the rate of change of the emitter voltage (dV) _ce And/dt) is easily interfered by circuit spurious parameters, the waveform oscillation frequency is high, and the measurement error is large.

The saturation pressure drop V _ces Refers to the voltage between the collector and emitter of the transistor in the saturation region. Based on a small current saturation voltage drop method, when the IGBT to be tested is in a small current conduction state, an extremely high linear relation exists between the saturation voltage drop and the junction temperature, and the saturation voltage drop and the junction temperature are expressed as follows by a mathematical expression:

T _j ＝kV _ces +b；

wherein k and b are constants, and can be calibrated through multiple tests, T _j Indicating the junction temperature.

Therefore, the junction temperature of the IGBT to be tested can be obtained by using a small-current saturation voltage drop method, and further the service life evaluation of the IGBT to be tested is realized.

Based on this, an embodiment of the present application provides a saturation pressure drop measurement system, and fig. 1 is a schematic structural diagram of the saturation pressure drop measurement system provided by the embodiment of the present application. As shown in fig. 1, the saturation pressure drop measurement system 100 includes:

a cutting unit 101, configured to cut off an operation loop of the IGBT to be tested when the IGBT to be tested reaches a thermal equilibrium state; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located;

The maintenance measurement unit 102 is used for maintaining the cut-off IGBT to be measured in a small current conduction state and measuring the saturation voltage drop in the cooling process of the IGBT to be measured; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

In the above scheme, the thermal balance state refers to a state that the junction temperature of the detected IGBT reaches the maximum value under the current operating condition by the large-current conduction state of the detected IGBT in the operating loop. The high-current conduction state can select rated voltage and/or rated current conduction state of the IGBT to be tested.

Further, in order to realize online measurement of saturation voltage drop of the detected IGBT without affecting an operation loop of the detected IGBT in equipment where the detected IGBT is located, when the operation loop of the detected IGBT is cut off, the same operation loop can be formed by replacing the detected IGBT with a substitute IGBT with the same parameters as the detected IGBT.

Based on this, in one embodiment, the saturation pressure drop measurement system 100 further includes:

and the substitution unit is used for substituting the IGBT to be tested for constituting the same running loop. The substitution unit adopts substitution IGBT, and parameters of the substitution IGBT are identical with parameters of the IGBT to be tested.

In the scheme, after the high-current conduction state of the IGBT to be tested is cut off, the junction temperature of the IGBT to be tested is extremely fast to drop, so that extremely high saturation voltage drop acquisition rate is required to ensure the completeness of information acquisition in the process of drop of the junction temperature of the IGBT to be tested. In order to accurately measure the saturation voltage drop in the IGBT cooling process, the switching-off unit 101 needs to perform a switching-off operation quickly, and the maintenance measurement unit 102 also starts to operate, so that the IGBT to be measured after switching-off immediately maintains a small current on state, and measures the saturation voltage drop in the IGBT cooling process. The above-described process can be realized by a driving signal featuring a fast response speed.

Based on this, in an embodiment, the cutting unit 101 includes:

the cut-off switch is used for controlling the on-off of the running loop of the IGBT to be tested;

the driving module is used for controlling the action of the disconnecting switch through a driving signal and simultaneously controlling the action of the maintenance measuring unit 102.

In the above scheme, the driving module may adopt a corresponding logic circuit module.

Further, in the above-mentioned scheme, in order to enable the cut-off switch to quickly perform the cut-off action under the control of the driving module, the cut-off switch may adopt an IGBT that can be controlled by a driving signal and that can quickly perform the cut-off action.

Based on this, in one embodiment, the cut-off switch employs a first IGBT, and, correspondingly,

the gate electrode of the first IGBT is connected with the driving signal output end of the driving module;

the first IGBT is used for controlling the on-off of an operation loop of the IGBT to be tested.

In the above scheme, the driving signal of the driving module is used for applying a forward or reverse gate voltage to the first IGBT to form or eliminate a channel, so that the first IGBT is turned on or off; the first IGBT controls the on-off of the running loop of the IGBT to be tested, namely, a current path formed by the collector and the emitter of the first IGBT is connected in series in the running loop of the IGBT to be tested, and when the first IGBT is conducted or turned off under the control of the driving module, the running loop of the IGBT to be tested is correspondingly conducted or turned off.

Further, in order to maintain the turned-off IGBT under test in a small current on state and measure the saturation voltage drop during the cooling process of the IGBT under test, in an embodiment, the maintenance measurement unit 102 includes:

the current source module is used for maintaining the cut-off IGBT to be tested in a small current conduction state;

the acquisition module is used for acquiring the saturation voltage drop of the IGBT to be tested in a small-current conduction state;

And the processing module is used for generating a saturation pressure drop curve according to the saturation pressure drop.

In the embodiment of the application, the current source module can adopt a constant current source with the output current of 100 mA; although a constant current source with an output current of 100mA generates a certain loss, the current source module can be always in an on state because its heat generation contribution is very small. Multiple tests show that the linear relation between the saturation voltage drop and the junction temperature of the IGBT to be tested is strongest in the small-current conduction state under 100mA, specifically

T _j ＝-454.9433V _{ce_100mA} +299.6334；

Wherein V is _{ce_100mA} And represents the saturation voltage drop of the detected IGBT in a small current conduction state at 100 mA.

In the embodiment of the application, the acquisition module can adopt a high-speed acquisition card of NI company, and the model of the acquisition module is USB-6351.

In the embodiment of the application, the processing module can adopt LabVIEW software.

Correspondingly, the driving module controls the action of the maintenance measurement unit 102 in such a way that the driving module controls whether the USB-6351 high-speed acquisition card acquires signals or not through driving signals.

In the embodiment of the present application, the cutting unit 101 is used to cut off the operation loop of the IGBT to be tested which reaches the thermal equilibrium state, and then the maintenance measuring unit 102 is used to maintain the cut-off IGBT to be tested in a small current conduction state, so as to cool the IGBT to be tested, and measure the saturation voltage drop in the cooling process of the IGBT to be tested. Therefore, the on-line measurement of the IGBT to be tested can be realized, and the current transient thermal resistance curve of the IGBT to be tested is further obtained, so that the service life evaluation of the IGBT to be tested is realized.

It should be noted that: in the saturation pressure drop measurement system 100 according to the embodiment of the present application, only the division of each program unit is used for illustration, and in practical application, the process allocation may be performed by different program units according to needs, i.e. the internal structure of the system is divided into different program units to complete all or part of the processes described above.

The saturation pressure drop measurement system according to the embodiments of the present application is further described below with reference to application examples:

fig. 2 is a schematic structural diagram of a saturation pressure drop measurement system according to an embodiment of the present application. The saturation pressure drop measurement system 200 includes:

a cutting unit 201, configured to cut off an operation loop of the IGBT to be tested when the IGBT to be tested reaches a thermal equilibrium state; wherein, the liquid crystal display device comprises a liquid crystal display device,

the cut-off unit 301 includes a cut-off switch and a driving module; wherein, the liquid crystal display device comprises a liquid crystal display device,

the cut-off switch is used for controlling the on-off of the running loop of the IGBT to be tested;

the driving module is used for controlling the action of the disconnecting switch through a driving signal and simultaneously controlling the action of the maintenance measuring unit;

a substitution unit 202 for substituting the IGBT to be tested with a substitution IGBT to constitute the same operation loop;

A maintenance measurement unit 203, configured to maintain the cut-off IGBT to be measured in a small current on state, and measure a saturation voltage drop in the cooling process of the IGBT to be measured; wherein, the liquid crystal display device comprises a liquid crystal display device,

the maintenance measurement unit 303 comprises a current source module, an acquisition module and a processing module; wherein, the liquid crystal display device comprises a liquid crystal display device,

the current source module is used for enabling the cut-off IGBT to be tested to maintain a small current conduction state;

the acquisition module is used for acquiring the saturation voltage drop of the IGBT to be tested in a small-current conduction state;

the processing module is used for generating a saturation pressure drop curve according to the saturation pressure drop.

The saturation voltage drop measurement system 200 provided in the application embodiment of the present application is further described below by taking an example that the saturation voltage drop measurement system 200 is applied to a converter topology.

Fig. 3a is a schematic structural diagram of a saturation voltage drop measurement system applied to a converter topology according to an embodiment of the present application. The converter topology adopts a single-phase full-bridge inverter circuit and comprises a direct current power supply DC, a capacitor C, a resistor R, an inductor L and four IGBTs forming a full bridge, wherein the first IGBT to the fourth IGBT are respectively represented by a symbol S ₁ To S ₄ Representation, S ₁ To S ₄ Flywheel diodes are respectively arranged. Wherein S is ₁ And S is equal to ₄ A pair of bridge arms S ₂ And S is equal to ₃ And the other pair of bridge arms is formed, the pair of bridge arms are simultaneously conducted, and the two pairs of bridge arms are alternately conducted for 180 degrees. In FIG. 3a, at S ₁ Described as an example of the IGBT under test, wherein S _aux1 Represents the substitute IGBT, S _aux2 Representing the cut-off switch, i _s Representing the current source module; the driving module, the acquisition module and the processing module are omitted in fig. 3a in order to ensure the integrity and clarity of the converter topology.

S is measured by using the saturation pressure drop measuring system 200 provided by the application embodiment of the application ₁ At saturation pressure drop of S ₁ Before reaching the state of thermal equilibrium S _aux1 Turn off, S _aux2 On, the current path is shown in fig. 3b, and fig. 3b is a schematic diagram of the current path when the IGBT under test in fig. 3a is in a large current on state. Wherein the thick solid line in fig. 3b represents the current path; when in a large current conduction state, S ₁ In heating mode, S ₁ The junction temperature of (C) increases until S ₁ Reaching a thermal equilibrium state.

At this time, the driving module controls S by a driving signal _aux2 Turn off by S _aux1 Substitute S ₁ In operation, the current path is shown in fig. 3c, and fig. 3c is a schematic diagram of the current path when the IGBT under test in fig. 3a is in a small current conducting state. Wherein the thick solid line in fig. 3c represents the current path; s is in a small current conduction state ₁ In a cooling mode, S ₁ The junction temperature of (C) is lowered by using the acquisition moduleThe block and the processing module can measure S ₁ And obtaining a saturation pressure drop curve.

Based on the saturation pressure drop measuring system disclosed by the embodiment of the application, the embodiment of the application also provides a saturation pressure drop measuring method. Fig. 4 is a schematic flow chart of a saturation pressure drop measurement method according to an embodiment of the present application. As shown in fig. 4, the saturation pressure drop measurement method includes:

step 401: when the IGBT to be tested reaches a thermal equilibrium state, cutting off an operation loop of the IGBT to be tested; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located;

step 402: maintaining the cut-off IGBT under test in a small current conduction state, and measuring the saturation voltage drop in the cooling process of the IGBT under test; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

Further, in order to realize online measurement of saturation voltage drop of the detected IGBT without affecting an operation loop of the detected IGBT in equipment where the detected IGBT is located, when the operation loop of the detected IGBT is cut off, the same operation loop can be formed by replacing the detected IGBT with a substitute IGBT with the same parameters as the detected IGBT.

Based on this, in an embodiment, the saturation pressure drop measurement method further includes:

And replacing the tested IGBT by using the replacing IGBT to form the same operation loop.

In order to verify the feasibility of the saturation pressure drop measuring method provided by the embodiment of the application, a transient thermal resistance online monitoring simulation model is built in a Simulink. As shown in fig. 5, fig. 5 is a schematic structural diagram of an on-line transient thermal resistance monitoring simulation model according to an embodiment of the present application. To measure S in FIG. 3 ₁ For example, based on the linear relationship T between saturation pressure drop and junction temperature _j ＝kV _{ce_100mA} +b, through simulation finding, can successfully obtain S ₁ Junction temperature profile of (c). As shown in FIG. 6, FIG. 6 shows S provided by an embodiment of the present application ₁ A schematic representation of the junction temperature profile of (a).

Further, in the life evaluation of the IGBT under test using the above-described schemes a to F, the solder layer fatigue accumulation is not generally consideredThe effect is to accelerate the aging of the IGBT. However, as shown in fig. 7, fig. 7 is a schematic structural diagram of an IGBT packaging system according to an embodiment of the present application. In fig. 7, 71 denotes a Diode (Diode) chip, 72 denotes a chip solder layer, 73 denotes an upper copper layer, 74 denotes a ceramic layer, 75 denotes a lower copper layer, 76 denotes a copper-clad ceramic substrate (Direct Bonding Copper, abbreviated as DBC) solder layer, 77 denotes a copper substrate layer, 78 denotes a collector, 79 denotes a gate, and 70 denotes an emitter. In the IGBT packaging system, diode chip 71, chip solder layer 72, DBC layer, DBC solder layer 76, and copper substrate layer 77 are included in this order from Diode chip 71 to copper substrate 77. The DBC layer sequentially comprises an upper copper layer 73, a ceramic layer 74 and a lower copper layer 75 from top to bottom, wherein a collector 78 and an emitter 70 of the IGBT are welded on the upper copper layer 73, and a gate 79 of the IGBT is welded on the diode chip 71. The solder layer (including the chip solder layer 72 and the DBC solder layer 76) is used as a main heat dissipation channel, and in a complex thermal cycle during the operation of the IGBT, cracking or/and falling off are easy to occur due to thermal stress, so that the thermal resistance of the IGBT increases. Therefore, thermal resistance is also often used as a characterizing parameter for solder layer failure. The increase of thermal resistance tends to cause the rise of junction temperature, accelerating the life consumption of the IGBT. According to theory of heat transfer, heat transfer process of heat flow inside IGBT The mathematical expression can be expressed as:

wherein lambda is the heat conductivity coefficient of the packaging material, rho is the density of the packaging material, c is the specific heat coefficient of the packaging material, H is the heating power of the chip, and T is the internal temperature distribution of the IGBT. As can be taken from the above formula, the heat transfer process is related to the encapsulation material corresponding to the physical structure of the encapsulation system of the IGBT. From the physical structure point of view, since the physical positions of the chip solder layer 72 and the DBC solder layer 76 are different, the chip solder layer 72 is closer to a heat source (die chip), and when cracking or/and falling-off occurs in the chip solder layer 72 and the DBC solder layer 76, respectively, damage to the physical structure of the IGBT is also different. Therefore, when different solder layers age due to damage, the junction temperature change inside the IGBT is inevitably different. Namely, when the life of the IGBT to be tested is evaluated, the physical position corresponding to the aged solder layer of the IGBT to be tested must be considered.

A three-dimensional finite element (Finite Element Method, FEM for short) model is built by taking SKM50GB12T4 IGBT of SEMIKRON company as a research object. As shown in fig. 8, fig. 8 is a schematic structural diagram of a three-dimensional FEM model of a SKM50GB12T4 type IGBT according to an embodiment of the present application, where 81 represents a Diode chip and 82 represents an IGBT chip. And performing electro-thermal simulation analysis on the IGBT by using a three-dimensional FEM model, and analyzing the difference of the influence of each solder layer on the junction temperature change of the IGBT under the same failure degree. For convenience of analysis, the aging state F of the IGBT is defined in terms of steady-state thermal resistance increment, expressed as: Wherein DeltaR _th R is the steady-state thermal resistance increment of IGBT in the current aging state _th(cs) Is the thermal resistance of the IGBT in health. Under different working frequencies, each solder layer is set to be in an aging state of 5%, as shown in table 1, and table 1 is a junction temperature change table of the IGBT under different working frequencies. In Table 1, deltaT _j Indicating junction temperature fluctuation, T _jm The average junction temperature is shown, and it is seen that different operating frequencies have an effect on the junction temperature variation of the IGBT.

TABLE 1 junction temperature Change Meter for IGBTs at different operating frequencies

In order to more obviously compare differences of influences of different ageing degrees of the solder layers on junction temperature changes of the IGBT, the solder layers are set to be in an ageing state of 16%, the differences of the junction temperature changes of the IGBT are shown in fig. 9, and fig. 9 is a schematic diagram of differences of influences on junction temperature fluctuation of the IGBT when the ageing degrees of the solder layers of the comparison IGBT provided by the embodiment of the application are respectively 5% and 16%. Wherein, deltaT (DeltaT) _j ) Representation IThe individual solder layers of the GBT age by 5% and 16% respectively, with differences in the impact on temperature fluctuations.

As shown in table 1 and fig. 9, the comprehensive analysis of IGBT in the operating frequency range of 0.1Hz to 50Hz, when the aging degree of each solder layer of IGBT is 5% and 16% respectively, the junction temperature fluctuation of IGBT also changes due to the different aging degree of each solder layer. Namely, the aging degree of each solder layer has influence on junction temperature fluctuation of the IGBT to be tested, and the influence is larger, and the aging acceleration effect of the IGBT to be tested is more remarkable. It is therefore expected that the life consumption rate of the IGBT under test will increase progressively with the increase in the degree of ageing of the solder layers. When the service life of the IGBT is estimated, if the influence of the fatigue accumulation effect on the thermal resistance is ignored, the amplitude of junction temperature fluctuation is underestimated, the service life of the IGBT is overestimated, and unnecessary loss is caused. Therefore, when the life of the IGBT to be tested is evaluated, the acceleration of the aging of the IGBT to be tested due to the fatigue accumulation effect corresponding to different aging states before each solder layer of the IGBT to be tested fails must be considered.

Based on the service life evaluation method, the embodiment of the application also provides a service life evaluation method. Fig. 10 is a flowchart of a lifetime assessment method according to an embodiment of the present application, as shown in fig. 10. The life evaluation method comprises the following steps:

standard IGBT training process and measured IGBT evaluation process, wherein:

the standard IGBT training process comprises the following steps:

step 1001: based on different aging states from health to failure of the standard IGBT, constructing a Coulter heat network of the standard IGBT in each of the different aging states, and identifying parameters of the corresponding Casuer heat network in each of the different aging states;

step 1002: based on the parameters of the Caser thermal network of the standard IGBT in different ageing states, dispersing the process from health to failure of the standard IGBT into a plurality of ageing stages;

the IGBT evaluation process comprises the following steps:

step 1003: based on the junction temperature curve of the IGBT to be tested and a plurality of aging stages of the standard IGBT from health to failure, the current aging stage of the IGBT to be tested is obtained;

step 1004: based on the aging stage of the IGBT to be tested, fatigue accumulation of the aging stage of the IGBT to be tested is obtained, and a junction temperature curve of the IGBT to be tested in the next aging stage is selected;

Step 1005: and circulating the above IGBT evaluation process until the IGBT fails to obtain the life evaluation result of the IGBT.

In the scheme, the standard IGBT is the IGBT with the same parameters as the IGBT to be tested.

Further, in the above scheme, the fatigue accumulation of the aging stage where the IGBT under test is currently located refers to the fatigue accumulation of damage generated by the IGBT under test due to the increase of the cycle number under the alternating load when the IGBT under test performs power cycle under a certain working condition. In the embodiment of the application, the damage generated by the IGBT to be tested is the damage generated by the thermal stress of the solder layer of the IGBT to be tested.

Furthermore, in the scheme, according to the electric-thermal equivalent comparison principle, establishing a Foster thermal network or a Cauer thermal network with centralized parameters is one of main methods for analyzing the junction temperature change of the IGBT to be tested. The junction temperature change process of the IGBT to be tested in the life evaluation is used for analyzing the junction temperature curve of the IGBT to be tested. Of these, the Foster thermal network is simply a mathematical fit to the transient thermal resistance obtained from the junction temperature curve. Unlike Foster thermal networks, the Cauer thermal network has characteristics corresponding to the physical structure of the IGBT packaging system. Specifically, the thermal resistance value and the thermal capacitance value of each step in the Cauer thermal network correspond to the actual physical layer in the physical structure of the IGBT packaging system, and the parameters of each step of the Cauer thermal network can be calculated through the thermal parameters of the packaging materials corresponding to the actual physical layer. The parameters of each stage of the Caser thermal network are expressed as mathematical expressions:

Wherein ρ is _i 、c _i 、λ _i 、d _i 、A _eff Respectively represent the density, specific heat coefficient and heat conduction system of the i-th layer packaging material of the actual physical layerNumber, thickness and effective heat dissipation area, R _thi Represents the thermal resistance value of the i-th layer packaging material, C _thi The heat capacity value of the i-th layer encapsulation material is shown. When the solder layer of the IGBT is aged, phenomena such as cracking or/and falling of the solder layer can cause the heat conduction performance of the packaging material to be reduced, and the effective heat dissipation area is reduced. According to the mathematical expression of the parameters of each step of the Cauer thermal network, the R of the ith step in the Cauer thermal network can be known _thi 、 C _thi The temperature of the IGBT to be tested is correspondingly changed, so that the Cauer thermal network can utilize the characteristics to represent the influence of different solder layers on the junction temperature change of the IGBT to be tested due to different physical positions and ageing stages. Considering that the IGBT physical layers are more and the thermal resistance corresponding to each layer is smaller, the parameters of the Caser thermal network are difficult to obtain, so that the Caser thermal network corresponding to each physical layer one by one does not need to be established.

Based on this, in an embodiment, the constructing the Cauer thermal network of the standard IGBT in each different aging state based on the different aging states from healthy to invalid of the standard IGBT, and identifying the parameters of the corresponding Cauer thermal network in each different aging state includes:

And constructing a third-order Caser thermal network of the standard IGBT in each different aging state based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding third-order Caser thermal network in each different aging state.

In the above scheme, in order to construct a third-order Cauer thermal network of the standard IGBT in different aging states, a transient thermal resistance curve of the standard IGBT in different aging states must be obtained according to conditions of the construction of the Cauer thermal network.

Based on this, in an embodiment, the constructing the third-order cause thermal network of the standard IGBT in each different aging state based on the different aging states from healthy to dead of the standard IGBT, and identifying the parameters of the corresponding third-order cause thermal network in each different aging state includes:

carrying out power circulation on the standard IGBT, and collecting transient thermal resistance curves of the standard IGBT in each power circulation;

and constructing a third-order Caser thermal network of the standard IGBT in different aging states by using a transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order Caser thermal network in different aging states.

In the scheme, the transient thermal resistance curve represents the response process of the IGBT junction temperature under the unit loss power, and is analogous to the step response of a circuit. According to JESD51-14 standard formulated by solid state technology Association, the transient thermal resistance of the IGBT can be calculated according to a junction temperature reduction curve in the IGBT cooling process, and is expressed as follows by mathematical expression:

Wherein T is _j (0) To the junction temperature of IGBT at the beginning of the cooling process, T _j And (t) is the junction temperature of the IGBT at the moment t in the cooling process, and P is the loss power of the IGBT. The transient thermal resistance curve reflects the dynamic transfer process of heat flow from the Diode chip to the copper substrate in the IGBT, and reflects the heat radiation performance of the IGBT packaging system.

Based on this, in an embodiment, the constructing a third-order cause thermal network of the standard IGBT in each different aging state by using the transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order cause thermal network in each different aging state includes:

measuring the saturated voltage drop in the cooling process of the standard IGBT in each power cycle to obtain a saturated voltage drop curve in the cooling process of the standard IGBT in each power cycle;

based on a saturated voltage drop curve in the cooling process of the standard IGBT in each power cycle, obtaining a junction temperature curve of the standard IGBT in each power cycle by utilizing a fitting relation of the junction temperature and the saturated voltage drop;

based on a junction temperature curve of the standard IGBT in each power cycle, obtaining a transient thermal resistance curve of the standard IGBT in each power cycle;

and constructing a third-order Caser thermal network of the standard IGBT in different aging states by using a transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order Caser thermal network in different aging states.

In the above scheme, the fitting relation between the junction temperature and the saturation pressure drop can be obtained by the saturation pressure drop V _ces And junction temperature T _j Wherein the saturation pressure drop V is expressed by a mathematical expression of the linear relation of _ces And junction temperature T _j The mathematical expression of the linear relation of (2) is expressed as:

T _j ＝kV _ces +b；

furthermore, in the above scheme, the method for measuring the saturation voltage drop in the cooling process of the standard IGBT during each power cycle may use the method for measuring the saturation voltage drop provided by the embodiment of the present application.

Further, in the above-mentioned scheme, as shown in fig. 11, fig. 11 is a schematic diagram of a transient thermal resistance curve corresponding to an IGBT when a chip solder layer provided in an embodiment of the present application is in different aging states. The transient thermal resistance curves corresponding to the IGBTs when the chip solder layers are in different ageing states can be obtained by performing simulation analysis on the ageing process of the IGBTs by using a three-dimensional FEM model shown in fig. 8. When the three-dimensional FEM model is utilized to simulate and analyze the transient thermal resistance curves of the IGBT in different ageing states, the thermal conductivity coefficient, the effective area or the thickness of the packaging material can be adjusted, so that the ageing effect of the solder layer of the IGBT can be effectively simulated, and the transient thermal resistance curves of the IGBT when the solder layer of the chip is in different ageing states can be obtained. As can be seen from fig. 11, as the aging degree of the solder layer of the chip increases, the transient thermal resistance curve corresponding to the IGBT gradually shifts upward, and the transient thermal resistance curve corresponding to the IGBT is separated very early. This is because the burn-in of the chip solder layer changes the heat flow transfer process inside the IGBT and the physical distance of the chip solder layer from the heat source (die chip) is short, so that the time required for the heat flow to be transferred from the die chip to the chip solder layer is very small when the chip solder layer is burned-in. From this, it is known that the longer the path of heat flow to the DBC solder layer, the longer the time required, and when the DBC solder layer ages, the later the separation point of the transient thermal resistance curve corresponding to the IGBT should be. As shown in fig. 12, fig. 12 is a schematic diagram of a transient thermal resistance curve corresponding to an IGBT when a DBC solder layer provided by the embodiment of the present application is in different aging states. Therefore, the separation points of the transient thermal resistance curves corresponding to the IGBTs when different solder layers are in different ageing states are analyzed, and whether the aged solder layers are chip solder layers or DBC solder layers can be effectively judged.

However, in the above description, when the chip solder layer and the DBC solder layer of the IGBT are aged simultaneously, the point of separation of the transient thermal resistance curve is earlier as when only the chip solder layer is aged. In order to distinguish the two conditions, quantitative evaluation of the contribution of aging of different solder layers to the overall aging of the IGBT is realized, a transient thermal resistance curve is required to be further analyzed, a structural function of the IGBT is extracted, and a third-order Caser thermal network of the IGBT in different aging states is constructed.

Based on this, in an embodiment, as shown in fig. 13, fig. 13 is a schematic flow chart of a method for constructing a third-order Cauer thermal network of a standard IGBT in different aging states according to an embodiment of the present application. The method for constructing the third-order cause thermal network of the standard IGBT in different aging states by utilizing the transient thermal resistance curve of the standard IGBT in each power cycle and identifying the parameters of the corresponding third-order cause thermal network in different aging states comprises the following steps:

step 1301: based on the transient thermal resistance curve of the standard IGBT in each power cycle, carrying out logarithmic processing on the time axis of the transient thermal resistance curve and differentiating to obtain a thermal time constant spectrum of the standard IGBT in each power cycle;

step 1302: based on a thermal time constant spectrum of the standard IGBT in each power cycle, constructing a Foster thermal network of the standard IGBT in different aging states;

Step 1303: based on Foster thermal networks of the standard IGBT in different aging states, obtaining a third-order Caser thermal network of the standard IGBT in different aging states through Foster-Caser network transformation;

step 1304: and identifying parameters of the third-order Cauer thermal network of the standard IGBT in different aging states.

In step 1304, parameters of the third-order Cauer thermal network of the standard IGBT in different aging states are also identified. The existing parameter identification method of the Cauer thermal network mainly comprises the following steps:

scheme a: the power loss, junction temperature and shell temperature of the IGBT at a certain moment are measured to obtain a junction temperature response curve of a time domain, and then the junction temperature response curve is fitted and converted correspondingly, so that the Caser thermal network parameters are obtained. The method needs to apply constant loss to the IGBT module, and in an actual power conversion device, the loss is difficult to accurately measure due to the influence of various factors, and a loss model is difficult to accurately establish, so that the method has a certain difficulty.

Scheme b: and according to the physical parameters and the sizes of the packaging materials of each layer in the IGBT, directly calculating or performing FEM model simulation analysis to obtain the Cauer thermal network parameters. According to the method, the calculation is carried out according to the initial thermal parameters of the packaging materials of each layer in the IGBT, and the thermal parameters of the packaging materials of each layer of the IGBT are not changed due to the fatigue accumulation effect in actual work, so that the method is not suitable for the parameter identification of the Cauer thermal network of the IGBT in the aging process.

Scheme c: according to the method for identifying the parameters of the Caser thermal network based on the zero input response, the parameters are identified according to the zero input response of the measurable nodes in the Caser thermal network, a specific excitation signal is not needed, the test condition is relaxed, and the parameters of the Caser thermal network of the IGBT in the aging process can be accurately identified.

Based on this, in an embodiment, the identifying parameters of the third-order Cauer thermal network of the standard IGBT in each different aging state includes:

based on the third-order Caser thermal network of the standard IGBT in different aging states, identifying parameters of the third-order Caser thermal network of the standard IGBT in different aging states through a Caser thermal network parameter identification method based on zero input response.

In the above scheme, since the third-order cause thermal network of the standard IGBT in each different aging state corresponds to the actual physical layer of the standard IGBT, simulation analysis of the aging process of the standard IGBT using the three-dimensional FEM model shown in fig. 8 shows that the step points of the third-order cause thermal network of the standard IGBT in each different aging state are on the ceramic layer. The chip solder layer and the DBC solder layer are classified into a first order and a third order of a third order Cauer thermal network, respectively. Therefore, in the third-order cause thermal network of the standard IGBT in each different aging state, the chip solder layer is classified into the first order of the third-order cause thermal network, and the DBC solder layer is classified into the third order of the third-order cause thermal network. When the chip solder layer is aged, the first-order thermal resistance value and the heat capacity value are equivalently updated, and when the DBC solder layer is aged, the third-order thermal resistance value and the heat capacity value are correspondingly updated. In the updating process, the influence on the heat capacity parameter is small when the solder layer is subjected to aging phenomena such as cracking or/and falling off, and the change trend and the size of the heat capacity along with the aging of the solder layer are difficult to determine. Therefore, in the embodiment of the application, the change of the heat capacity parameter is not considered when the third-order Cauer heat network of the standard IGBT in different aging states is updated.

Furthermore, in practical application, the difficulty of updating parameters of the third-order Cauer thermal network of the standard IGBT in real time under different aging states is high, and the service life consumption of the IGBT by single power cycle is also very small. On the other hand, the specific aging process of each solder layer is unknown, and the existing research results can not fully support the real-time update of the refined third-order Cauer thermal network. But because the physical location of the chip solder layer is closer to the heat source, it is more prone to burn-in due to thermal stress. Therefore, in the embodiment of the application, the aging process from health to failure of the standard IGBT is discretized into a plurality of stages by adopting a mode of periodically updating the third-order Cauer thermal network of the IGBT in different aging states. In the aging stage, the parameters of the third-order cause thermal network of the standard IGBT are assumed to be unchanged, and in the aging stage, when the third-order cause thermal network of the standard IGBT is updated, the influence of fatigue accumulation is counted under the most serious condition, namely, the failure of only the chip solder layer is assumed.

Based on this, in an embodiment, the process of dispersing the standard IGBT from health to failure into a plurality of aging stages based on the parameters of the third-order Cauer thermal network in different aging states of the standard IGBT includes:

Obtaining a first-order thermal resistance value of the third-order cause thermal network under the standard IGBT health state based on the parameters of the third-order cause thermal network under the standard IGBT health state;

based on the update coefficient of the third-order Caser heat network, the process from health to failure of the standard IGBT is discretized into a plurality of aging stages, wherein the update coefficient refers to that in two adjacent aging stages, the first-order thermal resistance value of the third-order Caser heat network of the next aging stage is increased by a preset value compared with the first-order thermal resistance value of the third-order Caser heat network of the previous aging stage.

In the above scheme, the aging process of the standard IGBT is considered as the most serious condition to be influenced by fatigue accumulation, namely, the update strategy of the corresponding third-order Cauer thermal network is shown in fig. 14 on the assumption that only the chip solder layer fails. Fig. 14 is a schematic diagram of a third-order Cauer thermal network updating strategy taking into account position information of an aged solder layer according to an embodiment of the present application. In FIG. 14, P _IGBT Represents the power loss of IGBT, T _jI Represents the junction temperature of IGBT, T _c Represents the shell temperature of IGBT, R _{jc_I1} 、ΔR _{jc_I1} Respectively representing the first-order thermal resistance value and the thermal resistance change value of the third-order Cauer thermal network, R _{jc_I2} Representing the thermal resistance value of the second order of a third-order Cauer thermal network, R _{jc_I3} 、ΔR _{jc_I3} Respectively representing the third-order thermal resistance value and the thermal resistance change value of the third-order Cauer thermal network, C _{jc_I1} 、ΔC _{jc_I1} Respectively representing the first-order heat capacity value and the heat capacity change value of the third-order Cauer heat network, C _{jc_I2} Representing the second-order heat capacity value, C, of a third-order Cauer heat network _{jc_I3} 、ΔC _{jc_I3} The third-order heat capacity value and the third-order heat capacity change value of the third-order cause heat network are respectively represented. P (P) _Diode Representing the power loss of the diode chip, T _jD Represents the junction temperature, T, of the IGBT in consideration of the position information of the aged solder layer _c Shell temperature of IGBT representing position information considering ageing solder layer, R _{jc_D1} 、ΔR _{jc_D1} Respectively representing a first-order thermal resistance value and a thermal resistance change value of a third-order cause thermal network considering position information of an aged solder layer, R _{jc_D2} Representing a second order thermal resistance value of a third order Cauer thermal network considering position information of an aged solder layer, R _{jc_D3} 、ΔR _{jc_D3} Respectively representing a thermal resistance value and a thermal resistance change value of a third order of a third-order Cauer thermal network considering position information of an aged solder layer, C _{jc_D1} 、ΔC _{jc_D1} Respectively representing position information considering aged solder layersThe first-order heat capacity value and the heat capacity change value of the third-order Cauer heat network, C _{jc_D2} Representing the second-order heat capacity value of a third-order cause thermal network considering the positional information of the aged solder layer, C _{jc_D3} 、ΔC _{jc_D3} The third-order heat capacity value and the third-order heat capacity variation value of the third-order Cauer heat network considering the position information of the aged solder layer are respectively represented. R is R _sa 、R _cs Representing the thermal resistance of the radiator's thermal network, C _sa 、C _cs Representing the heat capacity value, T, of a radiator heat network _a Indicating the ambient temperature.

To verify the effectiveness of the above-described third-order Cauer thermal network update strategy considering the position information of the aged solder layer, a comparison analysis may be performed with the result of performing a simulation analysis on the aging process of the standard IGBT using the three-dimensional FEM model as shown in fig. 8. And establishing an equivalent third-order Foster thermal network and a third-order Caser thermal network according to the result of simulation analysis of the aging process of the standard IGBT by the three-dimensional FEM model shown in fig. 8. The chip solder layer and the DBC solder layer are arranged in the same aging state, so that the overall thermal resistance of the standard IGBT is increased by 16%. Only the thermal resistance value of the corresponding order is updated in the third-order guer thermal network. And the third-order Foster thermal network adopts a mode of updating the thermal resistance of each order in equal proportion. The operating frequency of the standard IGBT is set to be 10Hz, and simulation results of the three-dimensional FEM model, the third-order Foster thermal network and the third-order Caser thermal network are shown in Table 2. When the chip solder layer fails, the junction temperature change of the third-order Caser thermal network updating strategy based on the position information of the aging solder layer is high in coincidence with the simulation result of the three-dimensional FEM model, the junction temperature fluctuation difference is only 1.294 ℃, and the error rate is 3.4%, which is caused by the fact that the thermal capacity parameter is not updated by the third-order Caser thermal network updating strategy. And the update strategy based on the third-order Cauer thermal network can underestimate junction temperature fluctuation, and compared with a three-dimensional FEM model, the update strategy is 6.346 ℃. When the DBC solder layer of the standard IGBT fails, the update strategy based on the third-order Caser thermal network is very accurate in predicting the junction temperature change, and the update strategy based on the third-order Foster thermal network overestimates the junction temperature fluctuation.

Table 2 thermal parameter comparison table for different update strategies

Based on this, in an embodiment, the process of discretizing the standard IGBT from healthy to dead into a plurality of aging stages based on the preset third-order guer thermal network update coefficient includes:

the failure multiple is preset, wherein the failure multiple is the preset failure multiple of which the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in a failure state is the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in a health state;

based on a preset updating coefficient and a preset failure multiple, the process from health to failure of the standard IGBT is discretized into a plurality of aging stages.

In the above scheme, in order to realize life assessment of the IGBT to be tested, the aging stage of the IGBT to be tested at present needs to be obtained, and the aging stage of the IGBT to be tested at present can be determined by the parameter value of the current third-order Cauer thermal network.

Based on this, in an embodiment, the obtaining the aging stage of the IGBT under test at the present time based on the junction temperature curve of the IGBT under test and the aging stages of the standard IGBT from healthy to dead process includes:

based on the junction temperature curve of the IGBT to be tested, obtaining a transient thermal resistance curve of the IGBT to be tested;

Constructing a third-order Cauer thermal network of the IGBT to be tested based on a transient thermal resistance curve of the IGBT to be tested;

identifying parameters of a third-order Caser thermal network of the IGBT to be tested, and obtaining a first-order thermal resistance value of the third-order Caser thermal network of the IGBT to be tested;

and obtaining the aging stage of the IGBT to be tested at present based on the first-order thermal resistance value of the third-order Caser thermal network of the IGBT to be tested and a plurality of aging stages of the standard IGBT from health to failure.

In the scheme, the linear relation T of the saturation pressure drop and the junction temperature is based _j ＝kV _{ce_100mA} +b, the junction temperature curve of the IGBT to be measured can be obtained by using the saturation voltage drop measuring method provided by the embodiment of the application, and the junction temperature curve is the most optimalThe first-order thermal resistance value of the third-order cause thermal network of the IGBT to be tested is finally obtained,

based on this, in an embodiment, the method for measuring the junction temperature curve of the IGBT to be measured is as follows:

the saturation voltage drop measuring method provided by the embodiment of the application is used for measuring the saturation voltage drop in the IGBT cooling process to obtain a saturation voltage drop curve in the IGBT cooling process;

and obtaining a junction temperature curve of the IGBT to be tested by utilizing a fitting relation between the junction temperature and the saturation voltage drop based on the saturation voltage drop curve in the IGBT to be tested cooling process.

In the above scheme, in order to account for the acceleration effect of the fatigue accumulation effect of the aging stage of the IGBT under test on the aging of the IGBT under test, the fatigue accumulation of the aging stage of the IGBT under test can be obtained by the fatigue accumulation theory. From the results of simulation analysis of the aging process of the standard IGBT by the three-dimensional FEM model shown in fig. 8, it can be considered that the fatigue accumulation of the IGBT under test is linearly accumulated in each aging stage.

Based on this, in an embodiment, the obtaining the fatigue accumulation of the aging stage in which the IGBT under test is currently located based on the aging stage in which the IGBT under test is currently located includes:

and obtaining fatigue accumulation of the aging stage of the IGBT to be tested at present based on the aging stage of the IGBT to be tested at present through the Miner linear fatigue accumulation theory.

In the scheme, the Miner linear fatigue accumulation theory is expressed as a mathematical expression:

wherein D represents fatigue accumulation at the ith aging stage where the IGBT under certain load is positioned, N _f The failure cycle times of the IGBT to be tested under a certain load and at a certain aging stage are represented, and the standard IGBT aging process can be calibrated according to the simulation analysis result of the three-dimensional FEM model shown in figure 8, N _i Represents the total cycle number of the IGBT to be tested in the life cycle of the IGBT under a certain load, and n representsAnd the ith aging stage of the IGBT to be tested is currently located.

Furthermore, in the scheme, according to the Miner linear fatigue accumulation theory, the fatigue accumulation of the aging stage of the IGBT to be tested at present can be obtained.

Based on this, in an embodiment, the obtaining, based on the aging stage in which the IGBT under test is currently located by using the Miner linear fatigue accumulation theory, the fatigue accumulation of the aging stage in which the IGBT under test is currently located includes:

Obtaining fatigue accumulation of the standard IGBT in different aging stages according to a Miner linear fatigue accumulation theory;

and based on the aging stage of the IGBT to be tested, obtaining the fatigue accumulation of the aging stage of the IGBT to be tested.

In the above scheme, according to the mathematical expression of the Miner linear fatigue accumulation theory, when fatigue accumulation of the aging stage where the tested IGBT is currently located is obtained, the failure cycle times corresponding to each aging stage of the standard IGBT are required to be obtained. A common method of calculating the number of failure cycles is a method of calculating using a life prediction network.

Based on this, in an embodiment, the fatigue accumulation of the standard IGBT in different aging stages is obtained by the Miner linear fatigue accumulation theory, including:

based on different aging stages of the standard IGBT, measuring a junction temperature curve of each aging stage of the standard IGBT;

based on a junction temperature curve corresponding to each aging stage of the standard IGBT, obtaining junction temperature fluctuation and a junction temperature average value corresponding to each aging stage of the standard IGBT;

obtaining failure circulation times corresponding to each aging stage of the standard IGBT through a life prediction network based on junction temperature fluctuation and junction temperature average value corresponding to each aging stage of the standard IGBT;

And obtaining fatigue accumulation corresponding to the standard IGBT in different aging stages through a Miner linear fatigue accumulation theory based on the failure cycle times corresponding to each aging stage of the standard IGBT.

In the above scheme, in order to obtain fatigue accumulation from the current aging stage of the IGBT to all the aging stages experienced when the IGBT fails, a junction temperature curve of the IGBT to be tested in the next aging stage is selected based on the current aging stage of the IGBT to be tested; in the scheme, the junction temperature curve of each aging stage of the standard IGBT is obtained, so that the junction temperature curve of the next aging stage of the IGBT to be tested can be selected according to the junction temperature curve of each aging stage of the standard IGBT.

Based on this, in an embodiment, the selecting the junction temperature curve of the next aging stage of the IGBT under test includes:

based on the current aging stage of the IGBT to be tested, the junction temperature curve of the IGBT to be tested in the next aging stage is selected according to the junction temperature curves of the standard IGBT in different aging states.

In the above scheme, in order to obtain the life evaluation result of the IGBT under test, it is also necessary to obtain the number of failure cycles from the current aging stage of the IGBT under test to all the aging stages that the IGBT under test experiences when it fails.

Based on this, in an embodiment, the circulating the foregoing IGBT evaluation process until the IGBT fails, to obtain a lifetime evaluation result of the IGBT, includes:

based on the aging stage of the IGBT to be tested, obtaining the failure cycle times of the aging stage of the IGBT to be tested according to the junction temperature curve of the aging stage of the IGBT to be tested;

obtaining failure cycle times of the next aging stage of the IGBT to be tested based on a junction temperature curve of the next aging stage of the IGBT to be tested;

and (5) circulating the process until the IGBT to be tested fails, and obtaining a life evaluation result of the IGBT to be tested.

In the above scheme, when the life of the power device is evaluated, a Coffin-Mason-Arrhenius life prediction network is generally adopted, because the Coffin-Mason-Arrhenius life prediction network has a tight relationship with the junction temperature curve of the power device.

Based on this, in an embodiment, the obtaining, based on the aging stage in which the IGBT under test is currently located, the number of failure cycles of the aging stage in which the IGBT under test is currently located through the life prediction network according to the junction temperature curve of the aging stage in which the IGBT under test is currently located includes:

and obtaining junction temperature fluctuation and junction temperature average value of the aging stage of the IGBT to be tested according to the junction temperature curve of the aging stage of the IGBT to be tested, and obtaining the failure cycle times of the aging stage of the IGBT to be tested through the Coffin-Mason-Arrhenius life prediction network.

In the scheme, the Coffin-Mason-Arrhenius life prediction network is expressed as a mathematical expression:

wherein N is _f Because the aging process of the standard IGBT is dispersed into a plurality of stages in the embodiment of the application, N is the number of failure cycles of the module under a certain thermal load _f The failure cycle times of the IGBT to be tested at a certain aging stage under a certain heat load are specifically shown; e (E) _a Represents activation energy, and the value is 9.89 multiplied by 10-20J; k (k) _B Represents the Boltzmann constant, the value of which is 1.38X10-23 J.K-1; a and α are network parameters and have no actual physical meaning. In order to ensure the effectiveness of the Coffin-Mason-Arrhenius life prediction network, the interference of external factors is eliminated, network parameters obtained on the basis of a large number of tests are taken as references, specifically, A= 97.2231 and alpha= -3.1292.

Based on this, in an embodiment, the circulating the above process until the IGBT to be tested fails, to obtain the life evaluation result of the IGBT to be tested, includes:

the fatigue accumulation linear accumulation of each aging stage from the current aging stage of the IGBT to be tested to the aging stage in the failure process of the IGBT to be tested is carried out, and whether the IGBT to be tested fails or not is judged based on the result of the fatigue accumulation linear accumulation;

when the IGBT to be tested fails, the number of failure cycles from the aging stage where the IGBT to be tested is currently located to each aging stage in the failure process of the IGBT to be tested is linearly accumulated, and the total number of failure cycles from the aging stage where the IGBT to be tested is currently located to the failure process of the IGBT to be tested is obtained;

And obtaining a life evaluation result of the IGBT to be tested based on the total failure cycle times from the current aging stage of the IGBT to be tested to the failure process of the IGBT to be tested.

In the scheme, if and only if the fatigue accumulation linear accumulation result is 1, the IGBT to be tested is judged to be invalid. At this time, the circulation is stopped, and the failure circulation times of each aging stage in the circulation process are linearly accumulated, so that the total failure circulation times from the current aging stage of the IGBT to be tested to the failure process of the IGBT to be tested, namely the circulation times of the current residual life of the IGBT to be tested, can be obtained; in practical applications, the ratio of the number of cycles of the remaining life to the total number of cycles in the life cycle is generally used as the life evaluation result of the IGBT under test.

The lifetime assessment method according to the embodiment of the present application will be further described below with reference to application examples:

fig. 15 is a schematic flow chart of a lifetime assessment method according to an embodiment of the present application. According to the life assessment method provided by the embodiment of the application, according to the simulation analysis result of the three-dimensional FEM model of the SKM50GB12T4 type IGBT shown in fig. 8, the thermal resistance is increased by 50% as the criterion of IGBT failure, namely, the preset failure multiple is set to be 1.5 times, namely, the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in the failure state is 1.5 times that of the third-order cause thermal network of the standard IGBT in the healthy state. The method comprises the steps that a third-order cause thermal network updating coefficient is preset, and in two adjacent aging stages, the first-order thermal resistance value of the third-order cause thermal network of the next aging stage is increased by 10% compared with the first-order thermal resistance value of the third-order cause thermal network of the previous aging stage; the method comprises the steps that a process from healthy to invalid of a standard IGBT is dispersed into 5 ageing stages, a first-order thermal resistance value of a third-order Caser thermal network of the first ageing stage of the standard IGBT is 1.1 times of a first-order thermal resistance value of the third-order Caser thermal network of the standard IGBT in a healthy state, a first-order thermal resistance value of the third-order Caser thermal network of the second ageing stage of the standard IGBT is 1.2 times of a first-order thermal resistance value of the third-order Caser thermal network of the standard IGBT in a healthy state, a first-order thermal resistance value of the third-order Caser thermal network of the third ageing stage of the standard IGBT is 1.3 times of a first-order thermal resistance value of the third-order Caser thermal network of the standard IGBT in a healthy state, and a first-order thermal resistance value of the third-order Caser thermal network of the fifth ageing stage (invalid state) of the standard IGBT is 1.3 times of a first-order thermal resistance value of the third-order Caser thermal network of the standard IGBT in a healthy state.

Based on the above, the lifetime assessment method provided by the application embodiment of the application comprises the following steps:

step 1501: dispersing the aging process of the standard IGBT into five stages, and constructing a third-order Cauer thermal network corresponding to the five aging stages of the standard IGBT;

step 1502: obtaining junction temperature curves of each aging stage of the standard IGBT based on five stages of the aging process of the standard IGBT;

step 1503: based on five stages of the aging process of the standard IGBT, fatigue accumulation in each aging stage of the standard IGBT is obtained;

step 1504: and selecting a junction temperature curve of the IGBT to be tested in the next aging stage according to the current aging stage and fatigue accumulation of the IGBT to be tested, and circulating until the IGBT to be tested fails, so as to obtain a life evaluation result of the IGBT to be tested.

In step 1503, since the aging process of the standard IGBT is dispersed into five stages and the fatigue accumulation of each aging stage is considered to be linearly accumulated, the fatigue accumulation of the next aging stage is increased by 0.2 from the previous aging stage in two adjacent aging stages of the standard IGBT. Namely, the fatigue accumulation of the standard IGBT is 0.2 at the end of the first aging period, 0.4 at the end of the second aging period, 0.6 at the end of the third aging period, 0.8 at the end of the fourth aging period, and 1 at the end of the fifth aging period.

In order to facilitate a person skilled in the art to further understand the lifetime assessment method provided by the application embodiment of the present application, the lifetime assessment method provided by the application embodiment of the present application is further described below by taking an IGBT lifetime assessment of the lifetime assessment method applied to a fan as an example.

As shown in fig. 16, fig. 16 is a schematic diagram of an IGBT lifetime assessment method applied to a fan according to an embodiment of the present application. Wherein, IGBT life-span evaluation in the fan includes following steps:

step 1601: based on the actual running condition of the fan, measuring the environmental air temperature data and the actual running wind speed of the fan;

step 1602: based on the environmental air temperature data and the actual running wind speed of the fan, a three-dimensional FEM model of a standard IGBT in the fan is established based on a three-dimensional FEM model of the SKM50GB12T4 IGBT shown in fig. 8;

step 1603: dispersing the aging process of the standard IGBT in the fan into five stages, and constructing a third-order Cauer thermal network corresponding to the five aging stages of the standard IGBT in the fan;

specifically, the first-order thermal resistance value of the third-order cause thermal network of the first aging stage of the standard IGBT in the fan is 1.1 times of the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in the healthy state, the first-order thermal resistance value of the third-order cause thermal network of the second aging stage of the standard IGBT is 1.2 times of the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in the healthy state, the first-order thermal resistance value of the third-order cause thermal network of the third aging stage of the standard IGBT is 1.3 times of the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in the healthy state, the first-order thermal resistance value of the third-order cause thermal network of the fourth aging stage of the standard IGBT is 1.4 times of the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in the healthy state, and the first-order thermal resistance value of the third-order cause thermal network of the fifth aging stage of the standard IGBT is 1.5 times of the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in the healthy state; judging that the standard IGBT fails when the fifth aging stage of the standard IGBT is finished;

Step 1604: obtaining a junction temperature curve of each aging stage of the standard IGBT in the fan based on five stages of the aging process of the standard IGBT in the fan;

step 1605: based on five stages of the aging process of the standard IGBT in the fan, fatigue accumulation in each aging stage of the standard IGBT in the fan is obtained;

specifically, the first aging stage of the standard IGBT in the blower fan has a fatigue accumulation of 0.2, the second aging stage has a fatigue accumulation of 0.4, the third aging stage has a fatigue accumulation of 0.6, the fourth aging stage has a fatigue accumulation of 0.8, and the fifth aging stage has a fatigue accumulation of 1;

step 1606: according to the current aging stage and fatigue accumulation of the IGBT to be tested in the fan, selecting a junction temperature curve of the IGBT to be tested in the next aging stage;

step 1607: and circulating until the IGBT to be tested fails, and obtaining a life evaluation result of the IGBT to be tested.

In step 1606, if the blower operates at different frequencies in different time periods, i.e. the thermal load of the blower is different, a rain flow counting method may be adopted, and the fatigue accumulation of the IGBT to be tested in the blower may be calculated by using the thermal load spectrum of the IGBT in the blower.

In the process, in order to verify the accuracy of the life assessment method provided by the embodiment of the application, the life of the IGBT to be tested in the fan under the actual wind speed is compared and analyzed with the existing life prediction network. The existing life prediction network adopts a segmented life prediction network provided on the basis of a large number of ageing tests, and the segmented life prediction network divides the ageing process of the IGBT into a linear stage and a nonlinear stage. The fatigue accumulation of the IGBT to be tested in the linear stage is calculated by adopting Miner linear fatigue accumulation theory, and the mathematical expression of the thermal resistance accumulation growth rate of the IGBT to be tested under the current load in the nonlinear stage is shown as follows:

Wherein b ₁ 、b ₂ 、b ₃ 、b ₄ 、b ₅ 、b ₆ Is constant. The parameter values are 706.1824, -4656.0962, 2.7835, 3.7811, -3.4773 and-1.1005 respectively based on a large number of ageing tests. R is the IGBT to be tested under the current load of the nonlinear stageIs the rate of thermal resistance build-up, R _th And updating the IGBT with each cycle period as a unit, wherein the updating is represented as the thermal resistance of the IGBT to be tested under the current load. The piecewise life prediction network considers the nonlinear law of accelerated aging rate in the later period of the IGBT aging stage, shows that the aging rate is related to the current aging state and the heat load degree of the IGBT, and reflects the memory effect of heat stress after acting on a solder layer.

Taking the service life evaluation of the IGBT in the fan described in the application embodiment of the application as an example, a doubly-fed fan simulation model is built in MATIA/Simulink, and the capacity is 1.5MW and the rated voltage is 690V. The specification of IGBT adopted by the practical fan is higher than 1200V/50A, and the capacity requirement of the fan can be met by a mode that a plurality of IGBTs are connected in parallel. The switching frequency of the IGBT is 2kHz, and the ambient temperature T _a =20℃. Parameters of the third-order Cauer thermal network of the IGBT in the fan were extracted according to the technical manual, as shown in table 3. Table 3 is a table of parameters for the third-order Caser thermal network of SKM50GB12T 4.

Table 3 parameter Table of third order Cauer thermal network of SKM50GB12T4

As shown in fig. 17, fig. 17 is a schematic diagram of an actual wind speed of a wind turbine according to an embodiment of the present application. The thermal load spectrum of each aging stage of the IGBT is analyzed according to the actual wind speed of the wind turbine, as shown in fig. 18a and 18b, fig. 18a is a schematic diagram of the thermal load spectrum when the IGBT in the wind turbine is in a healthy state, and fig. 18b is a schematic diagram of the thermal load spectrum when the IGBT in the wind turbine is in a fourth aging stage. When the IGBT is in a healthy state, the junction temperature thereof fluctuates by delta T _j All less than 45 c, most of the junction temperature fluctuations of the thermal load are concentrated in the (0, 10 c) region. When the IGBT is in the fourth aging stage, the heat load is obviously increased, and the junction temperature fluctuates delta T _j The maximum temperature reaches 55 ℃. Wherein, the life evaluation result of the sectional model is 21.0098 years. The life evaluation result of the life evaluation method provided by the embodiment of the application is 17.7050 years, and the evaluation result is more conservative, because only a chip is considered when the third-order Cauer thermal network is updatedThe cause of solder layer failure. If the influence of the fatigue accumulation effect is not considered, the evaluation result of the traditional Coffin-Mason-Arrhenius life prediction network is 35.0245 years, and the life of the IGBT is seriously overestimated.

In order to realize the life assessment method provided by the embodiment of the application, the embodiment of the application also provides a life assessment system. Fig. 19 is a schematic structural diagram of a lifetime assessment system according to an embodiment of the present application, as shown in fig. 19, the lifetime assessment system 1900 includes:

the standard IGBT training unit 1901 is used for constructing a Caser thermal network of the standard IGBT in different aging states based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding Caser thermal network in the different aging states, wherein the standard IGBT refers to an IGBT with the same parameters as the IGBT to be tested; but also for the use of the composition,

based on the parameters of the Caser thermal network of the standard IGBT in different ageing states, dispersing the process from health to failure of the standard IGBT into a plurality of ageing stages;

the measured IGBT evaluation unit 1902 is used for obtaining the current aging stage of the measured IGBT based on the junction temperature curve of the measured IGBT; but also for the use of the composition,

based on the aging stage of the IGBT to be tested, fatigue accumulation of the aging stage of the IGBT to be tested is obtained, and a junction temperature curve of the IGBT to be tested in the next aging stage is selected; but also for the use of the composition,

and circulating the process until the IGBT to be tested fails, and obtaining a life evaluation result of the IGBT to be tested.

In an embodiment, the standard IGBT training unit 1901 comprises:

the Cauer thermal network construction module is used for constructing the Cauer thermal network of the standard IGBT in different aging states based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding Cauer thermal network in different aging states;

the failure process discrete module is used for dispersing the process from health to failure of the standard IGBT into a plurality of aging stages based on the parameters of the Cauer thermal network under different aging states of the standard IGBT.

In an embodiment, the IGBT under test evaluation unit 1902 includes:

the aging stage acquisition module is used for acquiring the current aging stage of the IGBT to be tested based on the junction temperature curve of the IGBT to be tested;

the fatigue accumulation acquisition module is used for acquiring fatigue accumulation of the aging stage of the IGBT to be tested at present based on the aging stage of the IGBT to be tested at present;

the junction temperature curve acquisition module is used for selecting a junction temperature curve of the IGBT to be tested in the next aging stage based on the current aging stage of the IGBT to be tested;

and the service life evaluation module is used for obtaining the service life evaluation result of the IGBT to be tested.

It should be noted that: in the lifetime assessment system 1900 according to the embodiment of the present application, only the division of each program unit is used for illustration, and in practical application, the process allocation may be performed by different program units according to needs, i.e. the internal structure of the system is divided into different program units to complete all or part of the processes described above. In addition, the lifetime assessment system 1900 provided in the above embodiment and the lifetime assessment method embodiment belong to the same concept, and detailed implementation processes of the lifetime assessment system are shown in the method embodiment, which is not repeated here.

Those skilled in the art will appreciate that the implementation functions of the units in the lifetime assessment system 1900 shown in fig. 19 can be understood with reference to the foregoing description of the lifetime assessment method. The functions of the units in the lifetime assessment system 1900 shown in fig. 19 may be implemented by a program running on a processor or by a specific logic device.

The technical schemes described in the embodiments of the present application may be arbitrarily combined without any collision.

In the several embodiments provided in the present application, it should be understood that the disclosed method may be implemented in other manners. The above described device embodiments are only illustrative, e.g. the division of the units is only one logical function division, and there may be other divisions in practice, such as: multiple units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed. In addition, the various components shown or discussed may be coupled or directly coupled or communicatively coupled to each other via some interface, whether indirectly coupled or communicatively coupled to devices or units, whether electrically, mechanically, or otherwise.

The units described as separate units may or may not be physically separate, and units displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units; some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated in one second processing unit, or each unit may be separately used as one unit, or two or more units may be integrated in one unit; the integrated units may be implemented in hardware or in hardware plus software functional units.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present application.

Claims (29)

1. A saturation pressure drop measurement system, comprising:

the cutting-off unit is used for cutting off the operation loop of the insulated gate bipolar transistor IGBT to be tested when the IGBT to be tested reaches a thermal balance state; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located;

The maintenance measurement unit is used for maintaining the cut-off IGBT to be measured in a small current conduction state and measuring the saturation voltage drop in the cooling process of the IGBT to be measured; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

2. The system of claim 1, further comprising:

and the substitution unit is used for substituting the IGBT to be tested for constituting the same running loop.

3. The system of claim 2, wherein the shut-off unit comprises:

the cut-off switch is used for controlling the on-off of the running loop of the IGBT to be tested;

and the driving module is used for controlling the action of the disconnecting switch through a driving signal and simultaneously controlling the action of the maintenance measuring unit.

4. The system of claim 3, wherein the cut-off switch employs a first IGBT, and wherein, in response,

the gate electrode of the first IGBT is connected with the driving signal output end of the driving module;

the first IGBT is used for controlling the on-off of an operation loop of the IGBT to be tested.

5. The system of claim 2, wherein the replacement unit employs a replacement IGBT that has the same electrical parameters as the IGBT under test.

6. The system of any one of claims 1-5, wherein the maintenance measurement unit comprises:

the current source module is used for maintaining the cut-off IGBT to be tested in a small current conduction state;

the acquisition module is used for acquiring the saturation voltage drop of the IGBT to be tested in a small-current conduction state;

and the processing module is used for generating a saturation pressure drop curve according to the saturation pressure drop.

7. A saturation pressure drop measurement method, comprising:

when the IGBT to be tested reaches a thermal equilibrium state, cutting off an operation loop of the IGBT to be tested; the operation loop refers to an operation loop of the IGBT to be tested in equipment where the IGBT to be tested is located;

maintaining the cut-off IGBT under test in a small current conduction state, and measuring the saturation voltage drop in the cooling process of the IGBT under test; the cooling process refers to a falling process of the junction temperature of the IGBT to be measured.

8. The method as recited in claim 7, further comprising:

and replacing the tested IGBT by using the replacing IGBT to form the same operation loop.

9. The life evaluation method is characterized by comprising a standard IGBT training process and a tested IGBT evaluation process, wherein:

the standard IGBT training process comprises the following steps:

based on different aging states from health to failure of the standard IGBT, constructing a Coulter heat network of the standard IGBT in each of the different aging states, and identifying parameters of the corresponding Casuer heat network in each of the different aging states;

Based on the parameters of the Caser thermal network of the standard IGBT in different ageing states, dispersing the process from health to failure of the standard IGBT into a plurality of ageing stages;

the IGBT evaluation process comprises the following steps:

based on the junction temperature curve of the IGBT to be tested and a plurality of aging stages of the standard IGBT from health to failure, the current aging stage of the IGBT to be tested is obtained;

based on the aging stage of the IGBT to be tested, fatigue accumulation of the aging stage of the IGBT to be tested is obtained, and a junction temperature curve of the IGBT to be tested in the next aging stage is selected;

and circulating the above IGBT evaluation process until the IGBT fails to obtain the life evaluation result of the IGBT.

10. The method of claim 9, wherein constructing the Cauer thermal network of the standard IGBT in each of the different aging states based on the different aging states of the standard IGBT from healthy to dead, and identifying parameters of the corresponding Cauer thermal network in each of the different aging states, comprises:

and constructing a third-order Caser thermal network of the standard IGBT in each different aging state based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding third-order Caser thermal network in each different aging state.

11. The method of claim 10, wherein the constructing the third-order guer thermal network of the standard IGBT in each of the different aging states based on the different aging states from healthy to dead of the standard IGBT, and identifying parameters of the corresponding third-order guer thermal network in each of the different aging states, comprises:

carrying out power circulation on the standard IGBT, and collecting transient thermal resistance curves of the standard IGBT in each power circulation;

and constructing a third-order Caser thermal network of the standard IGBT in different aging states by using a transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order Caser thermal network in different aging states.

12. The method of claim 11, wherein constructing the third-order guer thermal network of the standard IGBT in each different aging state using the transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order guer thermal network in each different aging state, comprises:

measuring the saturated voltage drop in the cooling process of the standard IGBT in each power cycle to obtain a saturated voltage drop curve in the cooling process of the standard IGBT in each power cycle;

based on a saturated voltage drop curve in the cooling process of the standard IGBT in each power cycle, obtaining a junction temperature curve of the standard IGBT in each power cycle by utilizing a fitting relation of the junction temperature and the saturated voltage drop;

Based on a junction temperature curve of the standard IGBT in each power cycle, obtaining a transient thermal resistance curve of the standard IGBT in each power cycle;

and constructing a third-order Caser thermal network of the standard IGBT in different aging states by using a transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order Caser thermal network in different aging states.

13. The method according to claim 12, characterized in that the method of measuring the saturation voltage drop during cooling of a standard IGBT per power cycle uses the saturation voltage drop measuring method according to claim 7 or 8.

14. The method according to any one of claims 10-13, wherein constructing the third-order guer thermal network of the standard IGBT in each different aging state using the transient thermal resistance curve of the standard IGBT in each power cycle, and identifying parameters of the corresponding third-order guer thermal network in each different aging state, comprises:

based on the transient thermal resistance curve of the standard IGBT in each power cycle, carrying out logarithmic processing on the time axis of the transient thermal resistance curve and differentiating to obtain a thermal time constant spectrum of the standard IGBT in each power cycle;

based on a thermal time constant spectrum of the standard IGBT in each power cycle, constructing a Foster thermal network of the standard IGBT in different aging states;

Based on Foster thermal networks of the standard IGBT in different aging states, obtaining a third-order Caser thermal network of the standard IGBT in different aging states through Foster-Caser network transformation;

and identifying parameters of the third-order Cauer thermal network of the standard IGBT in different aging states.

15. The method of claim 14, wherein identifying parameters of the third-order Cauer thermal network of the standard IGBT in each different aging state comprises:

based on the third-order Caser thermal network of the standard IGBT in different aging states, identifying parameters of the third-order Caser thermal network of the standard IGBT in different aging states through a Caser thermal network parameter identification method based on zero input response.

16. The method of claim 10, wherein the discretizing the health-to-failure process of the standard IGBT into a plurality of aging stages based on parameters of the third-order Cauer thermal network for each different aging state of the standard IGBT comprises:

obtaining a first-order thermal resistance value of the third-order cause thermal network under the standard IGBT health state based on the parameters of the third-order cause thermal network under the standard IGBT health state;

based on the update coefficient of the third-order Caser heat network, the process from health to failure of the standard IGBT is discretized into a plurality of aging stages, wherein the update coefficient refers to that in two adjacent aging stages, the first-order thermal resistance value of the third-order Caser heat network of the next aging stage is increased by a preset value compared with the first-order thermal resistance value of the third-order Caser heat network of the previous aging stage.

17. The method of claim 16, wherein the discretizing the health-to-failure process of the standard IGBT into a plurality of aging stages based on the preset third-order guer thermal network update coefficients comprises:

the failure multiple is preset, wherein the failure multiple is the preset failure multiple of which the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in a failure state is the first-order thermal resistance value of the third-order cause thermal network of the standard IGBT in a health state;

based on a preset updating coefficient and a preset failure multiple, the process from health to failure of the standard IGBT is discretized into a plurality of aging stages.

18. The method of claim 10, wherein the obtaining the aging stage in which the IGBT under test is currently located based on the junction temperature curve of the IGBT under test and a plurality of aging stages of the standard IGBT from healthy to dead comprises:

based on the junction temperature curve of the IGBT to be tested, obtaining a transient thermal resistance curve of the IGBT to be tested;

constructing a third-order Cauer thermal network of the IGBT to be tested based on a transient thermal resistance curve of the IGBT to be tested;

identifying parameters of a third-order Caser thermal network of the IGBT to be tested, and obtaining a first-order thermal resistance value of the third-order Caser thermal network of the IGBT to be tested;

and obtaining the aging stage of the IGBT to be tested at present based on the first-order thermal resistance value of the third-order Caser thermal network of the IGBT to be tested and a plurality of aging stages of the standard IGBT from health to failure.

19. The method of claim 18, wherein the method for measuring the junction temperature profile of the IGBT under test is:

measuring the saturation voltage drop in the IGBT cooling process by using the saturation voltage drop measuring method of claim 7 or 8 to obtain a saturation voltage drop curve in the IGBT cooling process;

and obtaining a junction temperature curve of the IGBT to be tested by utilizing a fitting relation between the junction temperature and the saturation voltage drop based on the saturation voltage drop curve in the IGBT to be tested cooling process.

20. The method of claim 10, wherein the deriving fatigue accumulation for the aging phase in which the IGBT under test is currently located based on the aging phase in which the IGBT under test is currently located comprises:

and obtaining fatigue accumulation of the aging stage of the IGBT to be tested at present based on the aging stage of the IGBT to be tested at present through the Miner linear fatigue accumulation theory.

21. The method of claim 20, wherein the deriving the fatigue accumulation of the aging phase in which the IGBT under test is currently located based on the aging phase in which the IGBT under test is currently located by Miner's linear fatigue accumulation theory comprises:

obtaining fatigue accumulation of the standard IGBT in different aging stages according to a Miner linear fatigue accumulation theory;

And based on the aging stage of the IGBT to be tested, obtaining the fatigue accumulation of the aging stage of the IGBT to be tested.

22. The method of claim 21, wherein said deriving fatigue accumulation for standard IGBTs at different aging stages by Miner's linear fatigue accumulation theory comprises:

based on different aging stages of the standard IGBT, measuring a junction temperature curve of each aging stage of the standard IGBT;

based on a junction temperature curve corresponding to each aging stage of the standard IGBT, obtaining junction temperature fluctuation and a junction temperature average value corresponding to each aging stage of the standard IGBT;

obtaining failure circulation times corresponding to each aging stage of the standard IGBT through a life prediction network based on junction temperature fluctuation and junction temperature average value corresponding to each aging stage of the standard IGBT;

and obtaining fatigue accumulation corresponding to the standard IGBT in different aging stages through a Miner linear fatigue accumulation theory based on the failure cycle times corresponding to each aging stage of the standard IGBT.

23. The method of claim 22, wherein selecting the junction temperature profile of the next aging stage of the IGBT under test comprises:

based on the current aging stage of the IGBT to be tested, the junction temperature curve of the IGBT to be tested in the next aging stage is selected according to the junction temperature curves of the standard IGBT in different aging states.

24. The method of claim 10, wherein the cycling the above-mentioned IGBT evaluation process until the IGBT fails, to obtain a lifetime evaluation result of the IGBT, includes:

based on the aging stage of the IGBT to be tested, obtaining the failure cycle times of the aging stage of the IGBT to be tested according to the junction temperature curve of the aging stage of the IGBT to be tested;

obtaining failure cycle times of the next aging stage of the IGBT to be tested based on a junction temperature curve of the next aging stage of the IGBT to be tested;

and (5) circulating the process until the IGBT to be tested fails, and obtaining a life evaluation result of the IGBT to be tested.

25. The method of claim 24, wherein the obtaining, based on the aging phase in which the IGBT under test is currently located, the number of failure cycles of the aging phase in which the IGBT under test is currently located through the lifetime prediction network according to the junction temperature curve of the aging phase in which the IGBT under test is currently located, comprises:

and obtaining junction temperature fluctuation and junction temperature average value of the aging stage of the IGBT to be tested according to the junction temperature curve of the aging stage of the IGBT to be tested, and obtaining the failure cycle times of the aging stage of the IGBT to be tested through the Coffin-Mason-Arrhenius life prediction network.

26. The method of claim 25, wherein the cycling the above process until the IGBT to be tested fails, to obtain a lifetime assessment result of the IGBT to be tested, comprises:

the fatigue accumulation linear accumulation of each aging stage from the current aging stage of the IGBT to be tested to the aging stage in the failure process of the IGBT to be tested is carried out, and whether the IGBT to be tested fails or not is judged based on the result of the fatigue accumulation linear accumulation;

when the IGBT to be tested fails, the number of failure cycles from the aging stage where the IGBT to be tested is currently located to each aging stage in the failure process of the IGBT to be tested is linearly accumulated, and the total number of failure cycles from the aging stage where the IGBT to be tested is currently located to the failure process of the IGBT to be tested is obtained;

and obtaining a life evaluation result of the IGBT to be tested based on the total failure cycle times from the current aging stage of the IGBT to be tested to the failure process of the IGBT to be tested.

27. A life assessment system, comprising:

the standard IGBT training unit is used for constructing the Caser thermal network of the standard IGBT in different aging states based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding Caser thermal network in different aging states; but also for the use of the composition,

Based on the parameters of the Caser thermal network of the standard IGBT in different ageing states, dispersing the process from health to failure of the standard IGBT into a plurality of ageing stages;

the IGBT evaluation unit is used for obtaining the current aging stage of the IGBT based on the junction temperature curve of the IGBT; but also for the use of the composition,

based on the aging stage of the IGBT to be tested, fatigue accumulation of the aging stage of the IGBT to be tested is obtained, and a junction temperature curve of the IGBT to be tested in the next aging stage is selected; but also for the use of the composition,

and circulating the process until the IGBT to be tested fails, and obtaining a life evaluation result of the IGBT to be tested.

28. The system of claim 27, wherein the standard IGBT training unit comprises:

the Cauer thermal network construction module is used for constructing the Cauer thermal network of the standard IGBT in different aging states based on different aging states from health to failure of the standard IGBT, and identifying parameters of the corresponding Cauer thermal network in different aging states;

the failure process discrete module is used for dispersing the process from health to failure of the standard IGBT into a plurality of aging stages based on the parameters of the Cauer thermal network under different aging states of the standard IGBT.

29. The system of claim 27, wherein the IGBT evaluation unit under test comprises:

The aging stage acquisition module is used for acquiring the current aging stage of the IGBT to be tested based on the junction temperature curve of the IGBT to be tested;

the fatigue accumulation acquisition module is used for acquiring fatigue accumulation of the aging stage of the IGBT to be tested at present based on the aging stage of the IGBT to be tested at present;

the junction temperature curve acquisition module is used for selecting a junction temperature curve of the IGBT to be tested in the next aging stage based on the current aging stage of the IGBT to be tested;

and the service life evaluation module is used for obtaining the service life evaluation result of the IGBT to be tested.