IGBT junction temperature estimation method

Abstract

The invention relates to the technical field of over-temperature protection of a vehicle-mounted motor controller of a new energy automobile, in particular to an IGBT junction temperature estimation method, which comprises the following steps of: establishing an experimental platform, and placing the experimental platform in a constant-temperature box; and obtaining data such as IGBT equivalent internal resistance and a temperature coupling table according to an experiment. Calculating the total loss of the IGBT; and building an equivalent thermal resistance model, and calculating the IGBT theoretical junction temperature of the equivalent thermal resistance model according to the thermal resistance value and the total loss of the IGBT. According to the method, the current IGBT junction temperature can be accurately and effectively estimated in the operation process of the controller, the method has the advantages that the internal structure does not need to be damaged, the estimated junction temperature precision is high, modeling is simple, and other sensors or temperature acquisition circuits do not need to be added, engineers can perform protection in advance before the IGBT fails due to the too high junction temperature, the IGBT is effectively protected, and the reliability of the controller is improved. And the service life of the IGBT is greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of over-temperature protection of a motor controller on a new energy vehicle, and in particular to a method for estimating an IGBT junction temperature. Background Art

[0002] IGBT (insulated gate bipolar transistor) is widely used in energy generation, electric vehicles and other fields due to its advantages such as wide operating voltage range and large current processing capability. However, the junction temperature of IGBT (the temperature of the PN junction inside the IGBT chip, the PN junction is composed of an N-type doped region and a P-type doped region in close contact) is easily affected by changes in operating conditions and the heat dissipation environment in which it is located. Accurate calculation of the junction temperature of IGBT (insulated gate bipolar transistor) is the premise and key to active thermal management and life prediction of power devices. Industrial surveys show that the power module is also the most vulnerable component in the motor controller. More than 30% of motor controller failures are caused by power modules, of which 60% of power module failures are caused by overheating. Therefore, it is very necessary to detect the IGBT junction temperature. Only when the junction temperature of the IGBT is lower than the maximum temperature allowed by the IGBT transistor can the power tube work normally. For this reason, when selecting IGBT power tube devices, the safety of the device is usually fully considered, and a large redundant IGBT is selected to leave a larger temperature margin. However, the larger the IGBT power, the higher the device cost, resulting in a waste of device resources. Therefore, accurately estimating the IGBT junction temperature and ensuring that the device works within the allowable temperature range is not only conducive to the stable operation of the system, but also has great significance in the rational allocation of resources.

[0003] At present, the main methods for detecting IGBT junction temperature on the market are: physical contact measurement method, optical non-contact measurement method, thermistor electrical parameter extraction method, and finite element calculation method. However, the physical contact measurement method is to place temperature measuring elements such as thermistors or thermocouples inside the power device to be measured, and obtain the temperature information inside the power device according to the changes in the parameters of various temperature measuring elements themselves. It is highly invasive and has low accuracy. The optical non-contact measurement method mainly uses the characterization parameters of the light-temperature coupling effect to measure the junction temperature of the IGBT module with the help of instruments such as infrared thermal imagers. However, this method requires the destruction of the package of the device to be measured, and requires a high sampling rate for the infrared thermal imager. Thermistor electrical parameter extraction method is a method for estimating the junction temperature by online extraction of the external electrical characteristic parameters of the IGBT module. The principle is to extract the corresponding relationship between the external electrical characteristic parameters of the power device and the internal junction temperature of the device. However, in the process of obtaining the mapping relationship, due to the influence of the load current, there are different degrees of self-heating phenomena, which causes the extracted mapping relationship to produce estimation errors. The finite element calculation method can analyze the temperature distribution of each chip inside the module and the influence of thermal coupling. The calculation results are relatively accurate, but the finite element calculation requires an accurate geometric model and the modeling is complex.

[0004] In view of this, the applicant conducted an in-depth study on the above-mentioned issues, which led to the present case. Summary of the invention

[0005] The object of the present invention is to provide a method for estimating the junction temperature of an IGBT which does not require destruction of the internal structure, has high estimation accuracy, is simple to model, and does not require the addition of other sensors or temperature acquisition circuits.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A method for estimating the junction temperature of an IGBT comprises the following steps: S1: Establish an experimental platform and place it in a constant temperature box. Before the experiment, set the initial junction temperature of the IGBT to 25-35°C, and pre-set the width T1 of the first positive pulse width, the width T2 of the first negative pulse width, and the width T3 of the second positive pulse width of the double pulse; S2: Perform a double pulse experiment on the IGBT to obtain the IGBT turn-on time , IGBT turn-off time , bus voltage difference when IGBT is turned on and off , Current flowing through the IGBT , freewheeling diode turn-on time , freewheeling diode turn-off time , bus voltage when the freewheeling diode is turned on and off , the current flowing through the freewheeling diode , IGBT on-state voltage drop 、IGBT on-state current , IGBT duty cycle , the on-state voltage drop of the freewheeling diode when it is turned on , the on-state current of the freewheeling diode ; S3: setting the temperature of the thermostat according to an arithmetic progression, repeating step 2 at multiple temperatures of the thermostat, obtaining the on-state voltage drop and on-state current of the IGBT and the freewheeling diode at the corresponding temperature of the double pulse experiment, and calculating the relationship between the IGBT internal resistance, the freewheeling diode internal resistance and the IGBT temperature coupling according to the on-state voltage drop and the on-state current; S4: Calculate the turn-on loss of the IGBT in a single cycle , calculate the turn-off loss of the IGBT in a single cycle , the specific calculation formula is: (1); (2); S5: Calculate the turn-on loss of the freewheeling diode in a single cycle , calculate the turn-off loss of the freewheeling diode in a single cycle , the specific calculation formula is: (3); (4); S6: The turn-on loss in a single cycle of the IGBT obtained according to step S3 and the turn-off loss , calculate the synthetic switching loss of the IGBT , the specific calculation formula is: (5); S7: Obtain the turn-on loss of the freewheeling diode in a single cycle according to step S4. and the turn-off loss Calculating the resultant switching losses of the freewheeling diode , the specific calculation formula is: (6); S8: Calculate the conduction loss of IGBT , the specific calculation formula is: (7); S9: Calculate the conduction loss of the freewheeling diode , the specific calculation formula is: (8); S10: Calculate the conduction loss of the reconstructed IGBT , and its calculation formula is: (9); in, is the internal resistance of the IGBT, is the current phase current, is the duty cycle of IGBT; S11: Calculate the conduction loss of the reconstructed freewheeling diode , and its calculation formula is: (10); in, is the internal resistance of the freewheeling diode, is the current phase current; S12: Calculate the switching losses of the reconstructed IGBT , and its calculation formula is: (11); in, To actually use the bus voltage, is the current phase current, is the bus voltage during the double pulse experiment, is the phase current in the double pulse experiment; S13: Calculate the switching losses of the reconstructed freewheeling diode , and its calculation formula is: (12); in, To actually use the bus voltage, is the current phase current, is the bus voltage during the double pulse experiment, is the phase current in the double pulse experiment; S14: Build an equivalent thermal resistance model, and calculate the IGBT theoretical junction temperature of the equivalent thermal resistance model based on the thermal resistance value and the values ​​obtained in steps 10-13 , so the theoretical junction temperature of the IGBT The calculation formula is: (13); (14); (15); (16); in, is the total loss of a single tube in the IGBT, is the IGBT equivalent thermal resistance, is the equivalent thermal resistance of the freewheeling diode, is the thermal resistance of the heat sink, L is the distance from the starting point to the end point of the heat flow, is the heat conductivity of the heat sink metal, S is the cross-sectional area of ​​heat flow, is the ambient temperature.

[0007] Preferably, the IGBT has a collector C, a gate G and an emitter E, and the voltage waveform between the gate G and the emitter E of the IGBT, the voltage waveform between the electrode C and the emitter E of the IGBT, the current waveform between the electrode C and the emitter E of the IGBT, the voltage waveform of the freewheeling diode, and the current waveform of the freewheeling diode are collected by an oscilloscope during a double pulse experiment, and the data of step 2 is obtained based on the collected voltage waveform between the gate G and the emitter E of the IGBT, the voltage waveform between the electrode C and the emitter E of the IGBT, the current waveform between the electrode C and the emitter E of the IGBT, the voltage waveform of the freewheeling diode, and the current waveform of the freewheeling diode.

[0008] Preferably, there are three IGBTs, and the three IGBTs form a three-phase IGBT. The IGBT includes an upper tube and a lower tube. The theoretical junction temperature of the three-phase IGBT is The calculation formula is: (17).

[0009] By adopting the above technical solution, the present invention has the following beneficial effects: The present invention can realize accurate and effective estimation of the current IGBT junction temperature during the operation of the controller, and has the advantages of not needing to destroy the internal structure, high junction temperature estimation accuracy, simple modeling, and no need to add other sensors or temperature acquisition circuits. Engineers can protect the IGBT in advance before it fails due to excessively high junction temperature, effectively protecting the IGBT and greatly increasing the service life of the IGBT. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The parameter setting process before calculating the junction temperature of the present invention; Figure 2 It is the circuit diagram of the double pulse experiment in the present invention; Figure 3 Schematic diagram of the pulse width of the gate-level signal Vge in the present invention; Figure 4 A process for estimating junction temperature for the present invention; Figure 5 This is the junction temperature estimation result of the present invention. DETAILED DESCRIPTION

[0011] The present invention will be further described below in conjunction with specific embodiments: like Figure 1-Figure 5 As shown, this embodiment provides a method for estimating the junction temperature of an IGBT. The junction temperature of an IGBT is determined by the power loss of the IGBT itself and the ambient temperature (the ambient temperature here refers to the coolant temperature of the IGBT). The ambient temperature (the coolant temperature of the IGBT) can be controlled manually, and the power loss includes switching loss and conduction loss. First, in an ideal switching waveform, the IGBT will not be delayed when it is turned on and off, and the voltage and current will change vertically. In this state, no excess voltage and current will be generated, so no loss will occur. In fact, due to the influence of parasitic resistance and parasitic capacity, there will be a delay, and the voltage and current waveforms will change in an inclined manner. The part where the voltage and current overlap in this inclined part is the switching loss; secondly, the conduction loss is because there will be a on-state voltage drop during the conduction of the IGBT, and the part where this voltage drop and current overlap is the conduction loss. The junction temperature of the IGBT chip is determined by the combined effects of conduction loss, switching loss and ambient temperature (coolant). Before estimating the junction temperature of the IGBT, we need to obtain the IGBT turn-on and turn-off loss, conduction loss, and turn-on and turn-off loss and conduction loss of the freewheeling diode. We also need to select the turn-on resistance and turn-off resistance of the driver board that controls the IGBT according to the requirements, including the following steps: S1: Establish an experimental platform based on the principle of double pulse testing. Specifically, use a winding inductor to short-circuit the electrode C and emitter E of the IGBT. A module includes an upper tube and a lower tube. For example, when testing the upper tube, short-circuit the electrode C and emitter E of the lower tube. When testing the lower tube, short-circuit the electrode C and emitter E of the upper tube. Connect the high-voltage isolation probe to the test end electrode C and emitter E, connect the ordinary probe to the gate G and emitter E, and cover the flexible current probe at the bus end (the current flowing through the IGBT can be tested. For example, when testing the upper tube, the flexible current probe covers the positive pole of the bus, and when testing the lower tube, the flexible current probe covers the negative pole of the bus). Cover the flexible current probe at the inductor coil end (the current flowing through the freewheeling diode can be tested). The oscilloscope and each probe are set according to the actual situation. The time of the double pulse experiment is set according to the current flowing through the IGBT. According to the formula have to , where U is the bus voltage, I is the current flowing through the IGBT, T = T1+T3 is the opening time, L is the inductance value, and the experimental platform is placed in a constant temperature box. Before the experiment, the initial junction temperature of the IGBT is set to 25-35℃, and the width T1 of the first positive pulse width of the double pulse, the width T2 of the first negative pulse width, and the width T3 of the second positive pulse width are pre-set.

[0012] S2: Perform a double pulse experiment on the IGBT, collect the voltage waveform between the gate G and emitter E of the IGBT, the voltage waveform between the electrode C and emitter E of the IGBT, the current waveform between the electrode C and emitter E of the IGBT, the voltage waveform of the freewheeling diode, and the current waveform of the freewheeling diode through an oscilloscope during the double pulse experiment, and obtain the IGBT turn-on time based on the collected voltage waveform between the gate G and emitter E of the IGBT, the voltage waveform between the electrode C and emitter E of the IGBT, the current waveform between the electrode C and emitter E of the IGBT, the voltage waveform of the freewheeling diode, and the current waveform of the freewheeling diode (When the IGBT is turned on, the time it takes for the voltage between CE to drop from 90% to 10%), IGBT turn-off time (When the IGBT is turned off, the time for the CE voltage to rise from 10% to 90%), the bus voltage difference when the IGBT is turned on and off , Current flowing through the IGBT (When the IGBT is turned on, the current flowing through the IGBT is detected), the freewheeling diode turn-on time (When the freewheeling diode is turned on, the time for the voltage between CE to drop from 90% to 10%), freewheeling diode turn-off time (The time it takes for the voltage between CE to rise from 10% to 90% when the freewheeling diode is turned off) and the bus voltage when the freewheeling diode is turned on and off , the current flowing through the freewheeling diode (The current flowing through the freewheeling diode when the freewheeling diode is turned on), the on-state voltage drop when the IGBT is turned on 、IGBT on-state current , IGBT duty cycle (turn-on time / (turn-on time + turn-off time)), on-state voltage drop when the freewheeling diode is turned on , the on-state current of the freewheeling diode .

[0013] S3: The temperature of the thermostat is set according to an arithmetic progression. In this embodiment, the temperature of the thermostat is set so that the IGBT junction temperature is at 50-60°C, 75-85°C, 100-110°C, 125-135°C, and 150-160°C. Specifically, an infrared thermometer can be used to detect whether the IGBT junction temperature reaches the target temperature. Step 2 is repeated at multiple temperatures of the thermostat, and the relationship between the IGBT internal resistance, the freewheeling diode internal resistance and the IGBT temperature coupling is calculated based on the on-state voltage drop and the on-state current. At this time, the relationship between the IGBT on-state voltage drop and the on-state current and the IGBT temperature coupling at the corresponding temperature of the double pulse experiment can be obtained. , the coupling relationship between the IGBT internal resistance and the IGBT junction temperature can be established; the coupling relationship between the IGBT junction temperature and the freewheeling diode internal resistance can be established.

[0014] S4: Calculate the turn-on loss of the IGBT in a single cycle , calculate the turn-off loss of the IGBT in a single cycle , the specific calculation formula is: (1); (2); S5: Calculate the turn-on loss of the freewheeling diode in a single cycle , calculate the turn-off loss of the freewheeling diode in a single cycle , the specific calculation formula is: (3); (4); S6: The turn-on loss in a single cycle of the IGBT obtained according to step S3 and the turn-off loss , calculate the synthetic switching loss of the IGBT , the specific calculation formula is: (5); S7: Obtain the turn-on loss of the freewheeling diode in a single cycle according to step S4. and the turn-off loss Calculating the resultant switching losses of the freewheeling diode , the specific calculation formula is: (6); S8: Calculate the conduction loss of IGBT , the specific calculation formula is: (7); S9: Calculate the conduction loss of the freewheeling diode , the specific calculation formula is: (8); S10: Calculate the conduction loss of the reconstructed IGBT , and its calculation formula is: (9); in, is the internal resistance of the IGBT, is the current phase current, is the duty cycle of IGBT; S11: Calculate the conduction loss of the reconstructed freewheeling diode , and its calculation formula is: (10); in, is the internal resistance of the freewheeling diode, is the current phase current; S12: Calculate the switching losses of the reconstructed IGBT , and its calculation formula is: (11); in, To actually use the bus voltage, is the current phase current, is the bus voltage during the double pulse experiment, is the phase current in the double pulse experiment; S13: Calculate the switching losses of the reconstructed freewheeling diode , and its calculation formula is: (12); in, To actually use the bus voltage, is the current phase current, is the bus voltage during the double pulse experiment, is the phase current in the double pulse experiment; S14: Build an equivalent thermal resistance model, and calculate the IGBT theoretical junction temperature of the equivalent thermal resistance model based on the thermal resistance value and the values ​​obtained in steps 10-13 , so the theoretical junction temperature of the IGBT The calculation formula is: (13); (14); (15); (16); in, is the total loss of a single tube in the IGBT, is the IGBT equivalent thermal resistance, is the equivalent thermal resistance of the freewheeling diode, is the thermal resistance of the heat sink, L is the distance from the starting point to the end point of the heat flow, is the heat conductivity of the heat sink metal, S is the cross-sectional area of ​​heat flow, is the ambient temperature.

[0015] There are three IGBTs, and the three IGBTs form a three-phase IGBT. The IGBT includes an upper tube and a lower tube, so the theoretical junction temperature of the three-phase IGBT is The calculation formula is: (17).

[0016] In summary, the present invention can achieve accurate and effective estimation of the current IGBT junction temperature during the operation of the controller, and has the advantages of no need to destroy the internal structure, high estimated junction temperature accuracy, simple modeling, and no need to add other sensors or temperature acquisition circuits. Engineers can protect the IGBT in advance before it fails due to excessively high junction temperature, effectively protecting the IGBT and greatly increasing the service life of the IGBT.

[0017] The present invention is described in detail above with reference to the accompanying drawings, but the embodiments of the present invention are not limited to the above embodiments. Those skilled in the art can make various modifications to the present invention based on the prior art, which all belong to the protection scope of the present invention.

Claims

1. A method for estimating IGBT junction temperature, characterized in that: The steps include: S1: Establish an experimental platform and place it in a constant temperature box. Before the experiment, set the initial junction temperature of the IGBT to 25-35°C, and pre-set the width T1 of the first positive pulse width, the width T2 of the first negative pulse width, and the width T3 of the second positive pulse width of the double pulse; S2: Perform a double pulse experiment on the IGBT to obtain the IGBT turn-on time , IGBT turn-off time , bus voltage difference when IGBT is turned on and off , Current flowing through the IGBT , freewheeling diode turn-on time , freewheeling diode turn-off time , bus voltage when the freewheeling diode is turned on and off , the current flowing through the freewheeling diode , IGBT on-state voltage drop 、IGBT on-state current , IGBT duty cycle , the on-state voltage drop of the freewheeling diode when it is turned on , the on-state current of the freewheeling diode ; S3: setting the temperature of the thermostat according to an arithmetic progression, repeating step 2 at multiple temperatures of the thermostat, obtaining the on-state voltage drop and on-state current of the IGBT and the freewheeling diode at the corresponding temperature of the double pulse experiment, and calculating the relationship between the IGBT internal resistance, the freewheeling diode internal resistance and the IGBT temperature coupling according to the on-state voltage drop and the on-state current; S4: Calculate the turn-on loss of the IGBT in a single cycle , calculate the turn-off loss of the IGBT in a single cycle , the specific calculation formula is: （1）； （2）； S5: Calculate the turn-on loss of the freewheeling diode in a single cycle , calculate the turn-off loss of the freewheeling diode in a single cycle , the specific calculation formula is: （3）； （4）； S6: The turn-on loss in a single cycle of the IGBT obtained according to step S3 and the turn-off loss , calculate the synthetic switching loss of the IGBT , the specific calculation formula is: （5）； S7: Obtain the turn-on loss of the freewheeling diode in a single cycle according to step S4. and the turn-off loss Calculating the resultant switching losses of the freewheeling diode , the specific calculation formula is: （6）； S8: Calculate the conduction loss of IGBT , the specific calculation formula is: （7）； S9: Calculate the conduction loss of the freewheeling diode , the specific calculation formula is: （8）； S10: Calculate the conduction loss of the reconstructed IGBT , and its calculation formula is: （9）； in, is the internal resistance of the IGBT, is the current phase current, is the duty cycle of IGBT; S11: Calculate the conduction loss of the reconstructed freewheeling diode , and its calculation formula is: （10）； in, is the internal resistance of the freewheeling diode, is the current phase current; S12: Calculate the switching losses of the reconstructed IGBT , and its calculation formula is: （11）； in, To actually use the bus voltage, is the current phase current, is the bus voltage during the double pulse experiment, is the phase current in the double pulse experiment; S13: Calculate the switching losses of the reconstructed freewheeling diode , and its calculation formula is: （12）； in, To actually use the bus voltage, is the current phase current, is the bus voltage during the double pulse experiment, is the phase current in the double pulse experiment; S14: Build an equivalent thermal resistance model, and calculate the theoretical junction temperature of the IGBT of the equivalent thermal resistance model based on the thermal resistance value and the values ​​obtained in steps 10-13 , so the theoretical junction temperature of the IGBT The calculation formula is: （13）； （14）； （15）； （16）； in, is the total loss of a single tube in the IGBT, is the IGBT equivalent thermal resistance, is the equivalent thermal resistance of the freewheeling diode, is the thermal resistance of the heat sink, L is the distance from the starting point to the end point of the heat flow, is the heat conductivity of the heat sink metal, S is the cross-sectional area of ​​heat flow, is the ambient temperature.

2. The method for estimating the junction temperature of an IGBT according to claim 1, characterized in that: The IGBT has a collector C, a gate G and an emitter E. The voltage waveform between the gate G and the emitter E of the IGBT, the voltage waveform between the electrode C and the emitter E of the IGBT, the current waveform between the electrode C and the emitter E of the IGBT, the voltage waveform of the freewheeling diode and the current waveform of the freewheeling diode are collected by an oscilloscope during a double pulse experiment. The data of step 2 is obtained based on the collected voltage waveform between the gate G and the emitter E of the IGBT, the voltage waveform between the electrode C and the emitter E of the IGBT, the current waveform between the electrode C and the emitter E of the IGBT, the voltage waveform of the freewheeling diode and the current waveform of the freewheeling diode.

3. The method for estimating the junction temperature of an IGBT according to claim 1, characterized in that: There are three IGBTs, and the three IGBTs form a three-phase IGBT. The IGBT includes an upper tube and a lower tube. The theoretical junction temperature of the three-phase IGBT The calculation formula is: （17）。

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