Rapid test method for power circulation

Abstract

The invention provides a power cycle rapid test method. The method comprises the following steps: step A1, obtaining an initial estimated value of a junction temperature rising and falling control parameter according to a thermal resistance curve of a power device; a2, operating a power cycle machine based on the initial estimated value so as to debug a predetermined parameter in the junction temperature rising and falling control parameters, and obtaining a cycle test value of the junction temperature rising and falling control parameters; and step A3, setting the junction temperature rise and fall control parameter of the power cycle machine as a cycle test value, and starting to carry out the power cycle test of the power device. A traditional power cycle test method is broken through, the test efficiency is greatly improved, the service life under the actual operation condition is better simulated, the precision of a power cycle curve is improved, a test result closer to the reality is obtained, and qualitative transformation of service life evaluation from estimation to calculation is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of power device cycle testing, and in particular to a power cycle rapid testing method. Background Art

[0002] Power cycling is an important test method for evaluating the reliability of power devices under temperature fluctuations. The power cycling test simulates the periodic heating and cooling process of power devices in actual applications due to the passage of current. This process causes the internal materials of the device to generate thermomechanical stress due to different thermal expansion coefficients, thus affecting the life and reliability of the device.

[0003] In traditional power cycle testing, the IGBT module undergoes a periodic heating and cooling process, usually with a cycle of 3 to 5 seconds. During the test, if the on-state voltage drop of the device exceeds 5% of the initial value or the thermal resistance exceeds 20% of the initial value, it is judged to be a failure. This test cycle is very long, especially under conditions of low junction temperature fluctuations, because the lower the junction temperature fluctuation when the device is working, the longer the life, so the test cycle is very long. For example, for a junction temperature change of 20°C, the life of most products may be tens of millions of cycles, so the test time for a temperature point may be calculated in years.

[0004] In practical applications, such as direct-drive wind turbines, the temperature rise cycle of IGBT is much shorter than the traditional test cycle, and the temperature is much lower than the typical test conditions. This requires the impact of the actual opening time on the power cycle to be converted, and the temperature needs to be converted based on the power cycle curve. Due to the problem of test time, the power cycle curve is an estimated model curve, and the error cannot be well guaranteed, resulting in poor accuracy of life performance, which can only be used as a reference.

[0005] The equipment used in traditional power cycle testing uses electric current to heat the device to achieve a steady-state junction temperature rise, and uses water cooling to achieve a steady-state junction temperature drop. Because power devices generally have a relatively large volume and a large heat capacity, they require a long heating time and an even longer cooling time. A test cycle generally takes more than 5S, resulting in a very long overall life assessment cycle. Summary of the invention

[0006] Based on the above records, the present invention provides a power cycle rapid testing method, which aims to solve the technical problems of long test period and low efficiency of power cycle testing in the prior art.

[0007] A power cycle rapid testing method, comprising:

[0008] Step A1, obtaining an initial estimated value of a junction temperature rise and fall control parameter according to a thermal resistance curve of a power device;

[0009] Step A2, running a power cycle machine based on the initial estimated value to debug a predetermined parameter in the junction temperature rise and fall control parameter, and obtaining a cycle test value of the junction temperature rise and fall control parameter;

[0010] Step A3, setting the junction temperature rise and fall control parameters of the power cycle machine to values ​​for cycle testing, and starting the power cycle test of the power device.

[0011] Furthermore, the junction temperature rise and fall control parameters include heating current parameters and heating time parameters;

[0012] In step A1 , an initial estimated value of a heating current parameter and an initial estimated value of a heating time parameter are estimated using a zero-state response model according to a thermal resistance curve of a power device.

[0013] Further, the junction temperature rise and fall control parameters include heating current parameters and heating time parameters, and the predetermined parameters include heating time parameters;

[0014] In step A2, the process of debugging the heating time parameters includes:

[0015] Step B1, the power cycle machine heats the power device according to the set heating current parameter value and heating time parameter value;

[0016] Step B2, after the heating time is over, the measured junction temperature of the power device is obtained, and it is determined whether the measured junction temperature of the power device reaches the target junction temperature:

[0017] If not, go to step B3;

[0018] If yes, go to step B4;

[0019] Step B3, adjusting the value of the heating time parameter of the power cycle machine, and returning to step B1;

[0020] Step B4, using the value of the heating time parameter currently set by the power cycle machine as the value for the cycle test of the heating time parameter.

[0021] Further, the junction temperature rise and fall control parameters include junction temperature cooling time parameters;

[0022] In step A1, an initial estimate of the junction temperature cooling time parameter is estimated using a zero-input response model based on the thermal resistance curve of the power device.

[0023] Further, the junction temperature rise and fall control parameter also includes a junction temperature cooling time parameter, and the predetermined parameter includes the junction temperature cooling time parameter;

[0024] In step A2, after debugging the heating time parameter, the junction temperature cooling time parameter is debugged. The process of debugging the junction temperature cooling time parameter includes:

[0025] Step C1, setting the warm cooling time parameter of the power cycle machine to a corresponding initial estimated value;

[0026] Step C2, the power cycler cyclically executes a preset number of heating-cooling processes, during the heating process of the heating-cooling process, the power cycler heats the power device according to the cycle test value corresponding to the heating time parameter, and during the cooling process of the heating-cooling process, the power cycler cools the power device according to the set value of the cooling time parameter and the preset water cooling temperature;

[0027] Step C3, determining whether the measured junction temperature of the power device after heating shows an upward trend during the preset number of heating-cooling processes:

[0028] If yes, go to step C4;

[0029] If not, go to step C5;

[0030] Step C4, adjusting the setting value of the junction temperature cooling time parameter of the power cycle machine upward and then continuing to step C2;

[0031] Step C5, using the setting value of the junction temperature cooling time parameter of the current power cycle machine as the cycle test value of the junction temperature cooling time parameter.

[0032] Furthermore, after step A3, the method further includes:

[0033] Step A4: stop the power cycle test when the test stop criterion is reached.

[0034] Furthermore, in step A4, one of the test stopping criteria is:

[0035] The saturation voltage drop of the power device exceeds a first preset range.

[0036] Furthermore, in step A4, one of the test stopping criteria is:

[0037] The thermal resistance of the power device exceeds a second preset range.

[0038] Furthermore, after step A4, the following steps are further included:

[0039] Step A5, counting the number of cycle tests and the junction temperature measurement results, and drawing a power cycle curve.

[0040] The beneficial technical effect of the present invention is that by estimating the test control parameters of the test machine according to the thermal resistance curve of the power device, and then fine-tuning the control parameters according to the actual situation, and finally using the control parameters in the actual cycle test, the traditional power cycle test method is broken, the test efficiency is greatly improved, the life under the actual operating conditions is better simulated, the accuracy of the power cycle curve is improved, and a test result that is closer to the actual is obtained, completing the qualitative transformation of life assessment from estimation to calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1-3 The present invention is a flowchart of the steps of a power cycle rapid testing method. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0045] See also Figure 1 The present invention provides a power cycle rapid testing method, comprising:

[0046] Step A1, obtaining an initial estimated value of a junction temperature rise and fall control parameter according to a thermal resistance curve of a power device;

[0047] Step A2, running a power cycle machine based on the initial estimated value to debug a predetermined parameter in the junction temperature rise and fall control parameter, and obtaining a cycle test value of the junction temperature rise and fall control parameter;

[0048] Step A3, setting the junction temperature rise and fall control parameters of the power cycle machine to values ​​for cycle testing, and starting the power cycle test of the power device.

[0049] Specifically, the power device is an IGBT module.

[0050] Specifically, the power cycle machine may be an existing general-purpose power cycle machine.

[0051] Specifically, the thermal resistance curve of the power device is a transient thermal resistance curve.

[0052] By estimating the test control parameters of the test machine based on the thermal resistance curve of the power device, fine-tuning the control parameters according to the actual situation, and finally using the control parameters in the actual cycle test, the traditional power cycle test method has been broken, the test efficiency has been greatly improved, the life under actual operating conditions has been better simulated, the accuracy of the power cycle curve has been improved, and test results that are closer to reality have been obtained, completing the qualitative transformation of life assessment from estimation to calculation.

[0053] Furthermore, the junction temperature rise and fall control parameters include heating current parameters and heating time parameters;

[0054] In step A1 , an initial estimated value of a heating current parameter and an initial estimated value of a heating time parameter are estimated using a zero-state response model according to a thermal resistance curve of a power device.

[0055] The zero-state response model is the response of the circuit caused by external excitation in the zero initial state (the initial energy storage of the dynamic element is zero). The thermal resistance of a power device is a parameter that measures the ability of the heat generated inside the device to be transferred from a heat source (such as a semiconductor junction) to an external heat dissipation environment (such as a heat sink or air). The thermal resistance curve is used to estimate the initial value of a heating time and heating temperature, and then debugging is performed to achieve a transient junction temperature rise with a large current in a short time. Compared with the steady-state junction temperature rise of the prior art, the heating time is shortened. The shortening of the heating time shortens the cycle period of the cycle test and improves the efficiency of the cycle test.

[0056] Estimation of heating current and heating time, setting target junction temperature and initial junction temperature. The initial junction temperature can be set according to the ambient temperature or the temperature of the cooling medium. The target junction temperature is the junction temperature that the power device is expected to reach after heating. The thermal energy required from the initial junction temperature to the target junction temperature is calculated. A heating current value is set. Based on the heating current value and the thermal resistance curve, it is estimated how long it will take to reach the set target junction temperature. The heating current can be adjusted to shorten the heating time as much as possible, thereby making an estimate.

[0057] See also Figure 2 ,Furthermore, the junction temperature rise and fall control parameters include heating current parameters and heating time parameters, and the predetermined parameters include heating time parameters;

[0058] In step A2, the process of debugging the heating time parameters includes:

[0059] Step B1, the power cycle machine heats the power device according to the set heating current parameter value and heating time parameter value;

[0060] Step B2, after the heating time is over, the measured junction temperature of the power device is obtained, and it is determined whether the measured junction temperature of the power device reaches the target junction temperature:

[0061] If not, go to step B3;

[0062] If yes, go to step B4;

[0063] Step B3, adjusting the value of the heating time parameter of the power cycle machine, and returning to step B1;

[0064] Step B4, using the value of the heating time parameter currently set by the power cycle machine as the value for the cycle test of the heating time parameter.

[0065] During the debugging of the heating time parameters, first set the heating time of the power cycle machine to the corresponding initial estimated value, and set the heating current to the corresponding initial estimated value, then use the set heating time and heating current to heat the power device, and when the heating time is over, measure the junction temperature. If it is lower than the target junction temperature, the heating time may need to be extended. If the measured junction temperature is higher than the target junction temperature, the heating time may need to be shortened. Generally, the estimated heating time is shorter and the measured junction temperature is lower than the target junction temperature. Therefore, the heating time is gradually extended in most cases.

[0066] In step B3, the power device is cooled by a given water cooling temperature and then the process continues to step B1.

[0067] Further, the junction temperature rise and fall control parameters include junction temperature cooling time parameters;

[0068] In step A1, an initial estimate of the junction temperature cooling time parameter is estimated using a zero-input response model based on the thermal resistance curve of the power device.

[0069] The zero input response model describes the response of the system caused only by the initial conditions when the external input to the system is zero. In other words, the zero input response refers to the natural response of the system due to its internal state or the existence of energy storage elements (such as charge in capacitors and magnetic flux in inductors) in the absence of any external excitation. When estimating the cooling time, the heat loss is determined based on the starting junction temperature of the power device to the junction temperature after cooling, and the cooling time is calculated based on the heat loss and thermal resistance curve.

[0070] The initial value of a junction temperature cooling time parameter is estimated through the thermal resistance curve, and then debugged to achieve a short-term junction temperature drop. Compared with the steady-state junction temperature drop in the prior art, the cooling time is shortened. The shortened cooling time shortens the cycle period of the cycle test and improves the efficiency of the cycle test.

[0071] The heating time and cooling time are shortened because of the estimation of thermal resistance curve and actual debugging, which greatly shortens the cycle of the cycle test and greatly improves the test efficiency. Moreover, the time of one cycle is greatly shortened, and more cycles can be tested in the same time. By increasing the number of test cycles, the test can be completed from the beginning of the power device to the end of the power device failure, improving the accuracy of the power cycle curve and obtaining test results closer to reality.

[0072] See also Figure 3 ,Furthermore, the junction temperature rise and fall control parameter also includes a junction temperature cooling time parameter, and the predetermined parameter includes the junction temperature cooling time parameter;

[0073] In step A2, after debugging the heating time parameter, the junction temperature cooling time parameter is debugged. The process of debugging the junction temperature cooling time parameter includes:

[0074] Step C1, setting the warm cooling time parameter of the power cycle machine to a corresponding initial estimated value;

[0075] Step C2, the power cycler cyclically executes a preset number of heating-cooling processes, during the heating process of the heating-cooling process, the power cycler heats the power device according to the cycle test value corresponding to the heating time parameter, and during the cooling process of the heating-cooling process, the power cycler cools the power device according to the set value of the cooling time parameter and the preset water cooling temperature;

[0076] Step C3, determining whether the measured junction temperature of the power device after heating shows an upward trend during the preset number of heating-cooling processes:

[0077] If yes, go to step C4;

[0078] If not, go to step C5;

[0079] Step C4, adjusting the setting value of the junction temperature cooling time parameter of the power cycle machine upward and then continuing to step C2;

[0080] Step C5, using the setting value of the junction temperature cooling time parameter of the current power cycle machine as the cycle test value of the junction temperature cooling time parameter.

[0081] In step C2, the preset number of times can be less than 10 times, for example, there can be 3 times. If the 3 tests show that the measured junction temperature rises after heating, it means that the cooling time is not long enough, and the power device is heated again before cooling to the basic temperature (such as water cooling temperature), resulting in an upward trend. Therefore, it is necessary to increase the value of the junction temperature cooling time parameter and adjust it gradually to achieve the best cooling effect with the shortest cooling time and shorten a cycle test period.

[0082] In step C4, step C2 is performed only once to find that the measured junction temperature does not show an upward trend. It is also possible to consider appropriately shortening the value of the junction temperature cooling time parameter to further execute step C2 again to see the trend of the measured junction temperature. By debugging the value of the junction temperature cooling time parameter, it is ensured that sufficient cooling can be obtained in a shorter time, thereby shortening the test cycle once.

[0083] Furthermore, after step A3, the method further includes:

[0084] Step A4: stop the power cycle test when the test stop criterion is reached.

[0085] Furthermore, in step A4, one of the test stopping criteria is:

[0086] The saturation voltage drop of the power device exceeds a first preset range.

[0087] Furthermore, in step A4, one of the test stopping criteria is:

[0088] The thermal resistance of the power device exceeds a second preset range.

[0089] The test stop criterion may be a criterion for failure of the power device, for example, stopping when the saturation voltage drop Vcesat of the power device exceeds 5% of the initial saturation voltage drop of the power device, or stopping when the thermal resistance of the power device exceeds 20% of the initial thermal resistance of the power device.

[0090] Furthermore, after step A4, the following steps are further included:

[0091] Step A5, counting the number of cycle tests and the junction temperature measurement results, and drawing a power cycle curve.

[0092] The present invention utilizes the large thermal capacity of power devices, uses large current for short-time heating, and estimates the junction temperature drop parameters in combination with the cooling characteristics of the device itself, thereby greatly shortening the test time of one cycle of the device. One test cycle is reduced from 5s to 100ms, which greatly speeds up the test and can achieve more cycle tests. At the same time, this heating and cooling method is closer to actual operation.

[0093] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A power cycle rapid testing method, characterized in that: include: Step A1, obtaining an initial estimated value of a junction temperature rise and fall control parameter according to a thermal resistance curve of a power device; Step A2, running a power cycle machine based on the initial estimated value to debug a predetermined parameter in the junction temperature rise and fall control parameter to obtain a cycle test value of the junction temperature rise and fall control parameter; Step A3, setting the junction temperature rise and fall control parameters of the power cycle machine to the cycle test values, and starting the power cycle test of the power device.

2. A power cycle rapid testing method as claimed in claim 1, characterized in that: The junction temperature rise and fall control parameters include heating current parameters and heating time parameters; In the step A1, an initial estimated value of the heating current parameter and an initial estimated value of the heating time parameter are estimated based on a thermal resistance curve of the power device using a zero-state response model.

3. A power cycle rapid testing method as claimed in claim 1, characterized in that: The junction temperature rise and fall control parameters include a heating current parameter and a heating time parameter, and the predetermined parameters include the heating time parameter; In step A2, the process of debugging the heating time parameter includes: Step B1, the power cycle machine heats the power device according to the set value of the heating current parameter and the set value of the heating time parameter; Step B2, after the heating time is over, obtaining the measured junction temperature of the power device, and determining whether the measured junction temperature of the power device reaches the target junction temperature: If not, go to step B3; If yes, go to step B4; Step B3, adjusting the value of the heating time parameter of the power cycle machine, and returning to step B1; Step B4, using the value of the heating time parameter currently set for the power cycle machine as the value for the cycle test of the heating time parameter.

4. A power cycle rapid testing method as claimed in claim 1, characterized in that: The junction temperature rise and fall control parameters include junction temperature cooling time parameters; In the step A1, an initial estimated value of the junction temperature cooling time parameter is estimated using a zero input response model according to a thermal resistance curve of the power device.

5. A power cycle rapid testing method as claimed in claim 3, characterized in that: The junction temperature rise and fall control parameter also includes a junction temperature cooling time parameter, and the predetermined parameter includes the junction temperature cooling time parameter; In the step A2, after debugging the heating time parameter, the junction temperature cooling time parameter is debugged, and the process of debugging the junction temperature cooling time parameter includes: Step C1, setting the warm cooling time parameter of the power cycle machine to a corresponding initial estimated value; Step C2, the power cycler cyclically performs a preset number of heating-cooling processes, during the heating process of the heating-cooling process, the power cycler heats the power device according to the cycle test value corresponding to the heating time parameter, and during the cooling process of the heating-cooling process, the power cycler cools the power device according to the set value of the cooling time parameter and a preset water cooling temperature; Step C3, determining whether the measured junction temperature of the power device after heating in the heating-cooling process of the preset number of times shows an upward trend: If yes, go to step C4; If not, go to step C5; Step C4, adjusting the setting value of the junction temperature cooling time parameter of the power cycle machine upward and then continuing with step C2; Step C5, using the current setting value of the junction temperature cooling time parameter of the power cycle machine as the cycle test value of the junction temperature cooling time parameter.

6. A power cycle rapid testing method as claimed in claim 1, characterized in that: After step A3, the method further includes: Step A4: stopping the power cycle test when the test stop criterion is reached.

7. A power cycle rapid testing method as claimed in claim 6, characterized in that: In step A4, one of the test stopping criteria is: The saturation voltage drop of the power device exceeds a first preset range.

8. A power cycle rapid testing method as claimed in claim 6, characterized in that: In step A4, one of the test stopping criteria is: The thermal resistance of the power device exceeds a second preset range.

9. A power cycle rapid testing method as claimed in claim 6, characterized in that: After step A4, the following steps are also included: Step A5, counting the number of cycle tests and the junction temperature measurement results, and drawing a power cycle curve.

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