Method and device for evaluating damage of power device based on attenuation coefficient spectrum of electromagnetic acoustic emission signal

Abstract

The application provides a power device damage evaluation method based on an electromagnetic acoustic emission signal attenuation coefficient spectrum, which comprises the following steps: recording electromagnetic acoustic emission signals sampled at first and second monitoring points; finding minimum values of each electromagnetic acoustic emission signal, dividing the corresponding electromagnetic acoustic emission signal by taking adjacent minimum values as time windows, and performing fast Fourier transform on the windowed and divided signals to obtain an amplitude-frequency curve of each electromagnetic acoustic emission signal; matching the amplitude-frequency curve according to signal theoretical propagation time, respectively calculating attenuation coefficients of the matched amplitude-frequency curves according to time window sequences, and obtaining an attenuation coefficient time-varying curve; calculating an average value of the attenuation coefficient time-varying curve to obtain an attenuation coefficient spectrum of a single measurement, and calculating a center frequency of the attenuation coefficient spectrum; repeating the above process, and if the center frequency deviates by more than a threshold value after each repetition, it is determined that the power device is damaged. The application realizes online monitoring and evaluation of the health state of the power device by using the above scheme.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronic device health state online monitoring, and particularly relates to a power device damage evaluation method and device based on an electromagnetic acoustic emission signal attenuation coefficient spectrum. BACKGROUND

[0002] With the development of flexible DC power transmission technology, many flexible DC converter valves have been built in China. Power devices are the core devices of the converter valve control, and their reliability and service life directly affect the reliability of the converter valve system. Health state monitoring of the power device life cycle is of great significance to ensure the safe and reliable operation of the entire system.

[0003] However, the current monitoring method based on electrical parameters needs to change the original working circuit of the power device or needs to detect the device offline, which is highly invasive and costly. The detection methods based on ultrasound, X-rays and other methods are offline detection methods and cannot realize online monitoring. The monitoring method based on electromagnetic acoustic emission has the advantages of low invasiveness, high monitoring sensitivity and online monitoring. However, there is currently a lack of good damage evaluation method based on electromagnetic acoustic emission signals. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0005] To this end, the first purpose of the present application is to propose a power device damage evaluation method based on an electromagnetic acoustic emission signal attenuation coefficient spectrum, which realizes online monitoring and evaluation of the health state of the power device.

[0006] The second purpose of the present application is to propose a power device damage evaluation device based on an electromagnetic acoustic emission signal attenuation coefficient spectrum.

[0007] To achieve the above object, the first aspect of the present application proposes a power device damage evaluation method based on electromagnetic acoustic emission signal attenuation coefficient spectrum. The method realizes damage evaluation of the power device based on the sampled electromagnetic acoustic emission signal. The electromagnetic acoustic emission signal is sampled through the first monitoring point and the second monitoring point on both sides of the power device chip plane. The method comprises the following steps: step S1: recording the electromagnetic acoustic emission signal sampled at each monitoring point; step S2: finding the minimum value of each electromagnetic acoustic emission signal, dividing the corresponding electromagnetic acoustic emission signal with adjacent minimum values as time windows, and performing fast Fourier transform on the windowed and divided signal to obtain the amplitude-frequency curve of each electromagnetic acoustic emission signal; step S3: matching the amplitude-frequency curve according to the signal theoretical propagation time, respectively calculating the attenuation coefficient of the matched amplitude-frequency curve according to the time window sequence, and obtaining the time-varying curve of the attenuation coefficient; step S4: calculating the average value of the time-varying curve of the attenuation coefficient to obtain the attenuation coefficient spectrum of a single measurement, and calculating the center frequency of the attenuation coefficient spectrum; step S5: repeating steps S1-S4, taking the difference between the obtained center frequency and the center frequency of the first measurement as the center frequency offset, and judging that the power device is damaged when the center frequency offset exceeds a threshold value.

[0008] Optionally, in an embodiment of the present application, the electromagnetic acoustic emission signal is sampled at the first monitoring point, propagates through the detected area, and is sampled again at the second monitoring point.

[0009] Optionally, in an embodiment of the present application, the electromagnetic acoustic emission signal is a stress wave signal emitted by the power device in the on-off working state, the sampling start time of the first and second monitoring points is the instant when the power device is turned on, the sampling of the monitoring points is stopped when the signal intensity is lower than a threshold value, and the threshold value is positively correlated with the initial value of the signal intensity.

[0010] Optionally, in an embodiment of the present application, when the electromagnetic acoustic emission signal is divided into time windows with adjacent minimum values, if the time window lengths are inconsistent, after fast Fourier transform, the method further comprises:

[0011] The frequency resolution of each spectrum is unified by multiple spline difference values.

[0012] Optionally, in an embodiment of the present application, the calculation formula of the theoretical propagation time of the electromagnetic acoustic emission signal is:

[0013] Δt=L / v

[0014] Wherein, L is the signal propagation distance, which is determined by the geometric size of the power device, and v is the sound speed in the medium, which is determined by the material properties of different layers of the power device.

[0015] Optionally, in an embodiment of the present application, matching the amplitude-frequency curve according to the signal theoretical propagation time comprises:

[0016] The difference between the starting time of the first monitoring point signal time window and the starting time of the second monitoring point signal time window is obtained, the two time windows with a time difference of Δt are matched, the corresponding time window starting times are arranged in sequence in the matching, and all the monitoring point amplitude-frequency curves are alternately arranged to obtain an adjacent time window amplitude-frequency curve sequence.

[0017] Optionally, in an embodiment of the present application, the attenuation coefficient solving formula at the frequency point ω0 is:

[0018]

[0019] wherein A2(t+Δt,ω0) is the amplitude at the frequency point ω0 of the second monitoring point at the time t+Δt, and A1(t,ω0) is the amplitude at the frequency point ω0 of the first monitoring point at the time t.

[0020] Optionally, in an embodiment of the present application, the center frequency solving formula of the attenuation coefficient spectrum is:

[0021]

[0022] wherein ω1 and ω2 are the minimum frequency and the maximum frequency of the attenuation coefficient spectrum, ω is the frequency of the attenuation coefficient spectrum, and H(ω) is the single measurement attenuation coefficient spectrum.

[0023] Optionally, in an embodiment of the present application, the threshold value includes a first threshold value and a second threshold value, the first threshold value is smaller than the second threshold value, and when the center frequency offset exceeds the threshold value, it is judged that the power device is damaged, including:

[0024] When the center frequency offset exceeds the first threshold value, it is judged that the power device is in an early damage state.

[0025] When the center frequency offset exceeds the second threshold value, it is judged that the power device cannot meet the scene reliability requirement.

[0026] To achieve the above purpose, a second aspect embodiment of the present application provides a power device damage evaluation device based on an electromagnetic acoustic emission signal attenuation coefficient spectrum. The device realizes damage evaluation of the power device based on the sampled electromagnetic acoustic emission signal. The electromagnetic acoustic emission signal is sampled through monitoring points on both sides of the power device chip plane. The monitoring points include a first monitoring point and a second monitoring point. The device includes:

[0027] A data acquisition module for recording the electromagnetic acoustic emission signal sampled at each monitoring point;

[0028] An amplitude-frequency curve generation module for finding the extreme minimum value of each electromagnetic acoustic emission signal, dividing the corresponding electromagnetic acoustic emission signal with adjacent extreme minimum values as time windows, and performing fast Fourier transform on the windowed and divided signal to obtain the amplitude-frequency curve of each electromagnetic acoustic emission signal.

[0029] The attenuation coefficient time-varying curve generation module is configured to match the amplitude-frequency curve according to the signal theory propagation time, to obtain the attenuation coefficient time-varying curve by respectively calculating the attenuation coefficient of the matched amplitude-frequency curve in the time window sequence.

[0030] The center frequency calculation module is configured to calculate the average value of the attenuation coefficient time-varying curve to obtain the attenuation coefficient spectrum of a single measurement, and to calculate the center frequency of the attenuation coefficient spectrum.

[0031] The judgment module is configured to repeatedly call the data acquisition module, the amplitude-frequency curve generation module, the attenuation coefficient time-varying curve generation module and the center frequency calculation module, to obtain the center frequency offset by taking the difference between the obtained center frequency and the center frequency of the first measurement after each repetition, and to judge that the power device is damaged when the center frequency offset exceeds a threshold value.

[0032] The additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be known by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 A flowchart of a power device damage evaluation method based on an electromagnetic acoustic emission signal attenuation coefficient spectrum provided by an embodiment of the present application;

[0035] Figure 2 A flowchart of another power device damage evaluation method based on an electromagnetic acoustic emission signal attenuation coefficient spectrum provided by an embodiment of the present application;

[0036] Figure 3 A structural diagram of a power device damage evaluation device based on an electromagnetic acoustic emission signal attenuation coefficient spectrum provided by an embodiment of the present application;

[0037] Figure 4 A first and second monitoring point position diagram of an embodiment of the present application;

[0038] Figure 5 An electromagnetic acoustic emission signal waveform diagram collected by a first monitoring point of an embodiment of the present application;

[0039] Figure 6 A structural diagram of another power device damage evaluation device based on an electromagnetic acoustic emission signal attenuation coefficient spectrum provided by an embodiment of the present application. DETAILED DESCRIPTION

[0040] Embodiments of the present application are described below in detail with reference to the accompanying drawings, wherein the same or similar components are denoted by the same or similar reference numerals throughout the drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0041] The method and device for evaluating damage of a power device based on an attenuation coefficient spectrum of an electromagnetic acoustic emission signal of an embodiment of the present application are described below with reference to the accompanying drawings.

[0042] Figure 1 A flowchart of the method for evaluating damage of a power device based on an attenuation coefficient spectrum of an electromagnetic acoustic emission signal of Embodiment One of the present application is provided.

[0043] The method evaluates damage of a power device based on a sampled electromagnetic acoustic emission signal, which is sampled through a first monitoring point and a second monitoring point on both sides of a chip plane of the power device.

[0044] As shown in Figure 1 The method for evaluating damage of a power device based on an attenuation coefficient spectrum of an electromagnetic acoustic emission signal of the power device includes the following steps:

[0045] Step 101: Record the electromagnetic acoustic emission signals sampled at each monitoring point.

[0046] Step 102: Find the minimum value of each electromagnetic acoustic emission signal, divide the corresponding electromagnetic acoustic emission signal with adjacent minimum values as time windows, and perform fast Fourier transform on the windowed and divided signals to obtain the amplitude-frequency curve of each electromagnetic acoustic emission signal.

[0047] Step 103: Match the amplitude-frequency curve according to the signal theoretical propagation time, respectively calculate the attenuation coefficient of the matched amplitude-frequency curve in the order of time windows, and obtain the time-varying curve of the attenuation coefficient.

[0048] Step 104: Calculate the average value of the time-varying curve of the attenuation coefficient to obtain the attenuation coefficient spectrum of a single measurement, and calculate the center frequency of the attenuation coefficient spectrum.

[0049] Step 105: Repeat steps 101-104, and after each repetition, take the difference between the obtained center frequency and the center frequency of the first measurement as the center frequency offset. When the center frequency offset exceeds a threshold value, it is determined that the power device is damaged.

[0050] Optionally, in an embodiment of the present application, the electromagnetic acoustic emission signal is sampled at the first monitoring point, propagates through the detected region, and is resampled at the second monitoring point.

[0051] Optionally, in one embodiment of the present application, the electromagnetic acoustic emission signal is a stress wave signal emitted by the power device in the on-off working state, the sampling start time of the first and second monitoring points is the instant when the power device is turned on, and the sampling of the monitoring points is stopped when the signal intensity is lower than the threshold value, and the threshold value is positively correlated with the initial value of the signal intensity.

[0052] Optionally, in one embodiment of the present application, when the electromagnetic acoustic emission signal is divided into time windows with adjacent minima as the time windows, if the lengths of the time windows are inconsistent, after fast Fourier transform is performed, the method further comprises:

[0053] The frequency resolution of each frequency spectrum is unified through multiple spline difference values.

[0054] Please refer to Figure 2 , Figure 2 A flowchart of a power device damage evaluation method based on an electromagnetic acoustic emission signal attenuation coefficient spectrum provided by an embodiment of the present application is shown. The method is executed by an electronic device.

[0055] Specifically, the method comprises:

[0056] S1: record the electromagnetic acoustic emission signals of the first monitoring point and the second monitoring point as W1 and W2 respectively.

[0057] S2: calculate the positions of the minima of the first and second electromagnetic acoustic emission signals as t 11 -t 1n , t 21 -t 2n .

[0058] S3: divide the signal into time windows with adjacent minima as the time windows, perform fast Fourier transform on the windowed signal, and obtain an amplitude-frequency curve.

[0059] S4: calculate the theoretical propagation time according to the power device parameters and the propagation speed, match the electromagnetic acoustic emission signal amplitude-frequency curve according to the theoretical propagation time, and obtain a series of amplitude-frequency curves arranged in the order of time windows.

[0060] S5: calculate the attenuation coefficient a of the sequence of adjacent time window amplitude-frequency curves, and obtain the time-varying curve a(t, ω) of the attenuation coefficient under a single frequency.

[0061] S6: calculate the mean value of the time-varying curve, obtain the single-measurement attenuation coefficient spectrum H(ω), and calculate the center frequency ω m of the attenuation coefficient spectrum.

[0062] S7: record the electromagnetic acoustic emission signal multiple times according to a certain monitoring frequency, calculate the center frequency of the attenuation coefficient spectrum, and obtain the time-varying sequence ω m (t) of the center frequency.

[0063] S8: judging whether the center frequency offset exceeds the first threshold value, if yes, judging that the power device has slight damage.

[0064] S9: further judging whether the center frequency exceeds the second threshold value, if yes, judging that the power device has greater damage, and issuing a device replacement warning.

[0065] In some embodiments, the first and second monitoring points are respectively located on both sides of the power device chip plane, so as to ensure that the electromagnetic acoustic emission signal is first sampled at the first monitoring point, then propagates through the detected area, and finally is sampled at the second monitoring point.

[0066] In some embodiments, the electromagnetic acoustic emission signal is a stress wave signal emitted by the power device in the on-off working state, and the sampling start time of the first and second monitoring points is the instant when the power device is turned on, and the sampling is stopped when the signal strength is lower than 5% of the initial value.

[0067] In some embodiments, the time window length may be inconsistent, when the time window length is inconsistent, Fourier transform is first performed, then the frequency resolution of each spectrum is unified through cubic spline interpolation, and finally the resolution is unified to 1 kHz and the maximum frequency is 10 MHz.

[0068] In some embodiments, the theoretical propagation time calculation formula is Δt=L / v, wherein L is the signal propagation distance 2mm, v is the acoustic velocity in the medium 3500m / s, and the time interval is 0.57us.

[0069] In some embodiments, the amplitude-frequency curve matching method of the electromagnetic acoustic emission signal is: the difference between the start time of the time window of the first monitoring point and the time window of the second monitoring point is calculated, the two time windows with a time difference of Δt are matched, and the amplitude-frequency curve sequence of adjacent time windows is arranged alternately according to the amplitude-frequency curves of the two monitoring points, and arranged in the order of the start time of the corresponding time window.

[0070] In some embodiments, the attenuation coefficient solving formula at the frequency point ω0 is:

[0071]

[0072] Wherein, A2(t+Δt,ω0) is the amplitude at the frequency point ω0 of the second monitoring point at t+Δt, and A1(t,ω0) is the amplitude at the frequency point ω0 of the first monitoring point at t.

[0073] In some embodiments, the attenuation coefficient spectrum center frequency solving formula is:

[0074]

[0075] Wherein, ω1 and ω2 are respectively the minimum frequency and the maximum frequency of the attenuation coefficient spectrum.

[0076] Further, in one embodiment of the present application, the first threshold is set to 95% of the central frequency of the healthy power device, for the evaluation of the early damage state, and the second threshold is determined according to the application scenario of the power device and is set to 70%.

[0077] The application also provides a power device damage evaluation device based on an electromagnetic acoustic emission signal attenuation coefficient spectrum.

[0078] The nodes in the topological graph include cable load terminals, cable line branch points, and frequency response curve test nodes, wherein the node type of the cable load terminal is marked as 1, the node type of the cable line branch point is marked as 2, and the node type of the frequency response curve test node is marked as 3, and the generated original topological characterization matrix T0 is an adjacency matrix of the cable topology.

[0079] The following focuses on a power device damage monitoring device based on a power device electromagnetic acoustic emission signal attenuation coefficient spectrum, which includes an electromagnetic acoustic emission acquisition module and a control module, as shown in Figure 3

[0080] The electromagnetic acoustic emission acquisition module includes an acoustic emission sensor, a preamplifier, a power taking unit, and a communication antenna, and is used for acquiring the electromagnetic acoustic emission signal of the power device.

[0081] The control module includes a signal receiving antenna, a central processing unit, and a data storage and display unit, and is used for processing the acquired electromagnetic acoustic emission signal and then evaluating the damage state of the power device.

[0082] Specifically, in the embodiment of the present application, a first and second monitoring point position schematic diagram of the acoustic emission sensor arrangement is shown in Figure 4

[0083] Wherein 1 represents the copper layer of the power device, 2 represents the solder layer of the power device, 3 represents the chip layer of the power device, 4 and 5 respectively represent the first monitoring point and the second monitoring point, and the acoustic emission signal is emitted from the chip layer and then passes through the first monitoring point and the second monitoring point in turn after reflection.

[0084] Specifically, in the embodiment of the present application, a waveform diagram of the electromagnetic acoustic emission signal collected by the first monitoring point is shown in Figure 5

[0085] The power device damage evaluation method and device based on the power device electromagnetic acoustic emission signal attenuation coefficient spectrum according to the embodiments of the present application can better find the early defects of the power device, can give a warning before the power device fails, and has the advantages of online monitoring, low invasiveness, high monitoring sensitivity, etc.

[0086] ​​​In order to realize the above-mentioned embodiments, the application further provides a power device damage evaluation device based on an attenuation coefficient spectrum of an electromagnetic acoustic emission signal.

[0087] Figure 6 A structural schematic diagram of a power device damage evaluation device based on an attenuation coefficient spectrum of an electromagnetic acoustic emission signal provided for the embodiments of the application.

[0088] The device realizes damage evaluation of the power device based on the sampled electromagnetic acoustic emission signal, and the electromagnetic acoustic emission signal is sampled through monitoring points on both sides of the power device chip plane, and the monitoring points include a first monitoring point and a second monitoring point.

[0089] As Figure 6 shown, the power device damage evaluation device based on the attenuation coefficient spectrum of the electromagnetic acoustic emission signal of the power device includes:

[0090] A data acquisition module, configured to record the electromagnetic acoustic emission signal sampled at each monitoring point;

[0091] An amplitude-frequency curve generation module, configured to find a minimum value of each electromagnetic acoustic emission signal, divide the corresponding electromagnetic acoustic emission signal with adjacent minimum values as time windows, and perform fast Fourier transform on the windowed and divided signal to obtain an amplitude-frequency curve of each electromagnetic acoustic emission signal;

[0092] An attenuation coefficient time-varying curve generation module, configured to match the amplitude-frequency curve according to a signal theoretical propagation time, respectively calculate attenuation coefficients of the matched amplitude-frequency curves in time window order, and obtain an attenuation coefficient time-varying curve;

[0093] A center frequency calculation module, configured to calculate an average value of the attenuation coefficient time-varying curve, obtain an attenuation coefficient spectrum of a single measurement, and calculate a center frequency of the attenuation coefficient spectrum;

[0094] A judgment module, configured to repeatedly call the data acquisition module, the amplitude-frequency curve generation module, the attenuation coefficient time-varying curve generation module and the center frequency calculation module, take a difference between the obtained center frequency and the center frequency of the first measurement as a center frequency offset after each repetition, and judge that the power device is damaged when the center frequency offset exceeds a threshold.

[0095] It should be noted that the foregoing explanation and description of the power device damage evaluation method based on the attenuation coefficient spectrum of the electromagnetic acoustic emission signal also apply to the power device damage evaluation device based on the attenuation coefficient spectrum of the electromagnetic acoustic emission signal of the embodiments, which will not be described here again.

[0096] In the description of the application, reference to "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. The illustrative appearances of the above- described terms in various places in the specification are not intended to exclude that the terms can be combined with one another in other embodiments or examples of the application, nor are they intended to exclude that terms described in one embodiment or example can be combined with terms described in another embodiment or example. Although the application has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the application. Any further variations to the specific aspects of the application described herein will be apparent to those skilled in the art and are considered to fall within the scope of the application as defined by the appended claims.

[0097] In addition, the terms "first", "second", etc. are used herein only to describe various steps in a method, process, or algorithm. Thus, the terms "first", "second", etc. are not intended to, and should not be construed to, refer to a ranking or order of importance of or relative importance of, or superiority or inferiority of, the various steps in the method, process, or algorithm, but instead are used merely to distinguish one step from another. In addition, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated items, including items that are the same as or different from each other.

[0098] Any process or method described in a flowchart or otherwise described herein can be understood as representing code modules, segments, or portions of code that include one or more executable instructions for implementing specific logic functions (or steps) of the process, and alternate implementations are possible. In some embodiments, the processes or methods described in this application can be tailored or varied by those skilled in the art to include more or less steps than those expressly described, and to use alternative arrangements, structures, or variations of the steps described herein without departing from the scope of the present application.

[0099] The logic and / or steps represented in the flowcharts and / or described herein, for example, can be considered as a sequence of instructions to implement logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, apparatus, or device, such as a computer-based system, processor- based system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For purposes of this specification, a "computer-readable medium" can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be a computer- readable storage medium or a computer-readable signal medium. The computer- readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium include the following: an electrical connection having one or more wires (electrical connections), a portable computer diskette (a magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium can even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, for example, via optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.

[0100] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the above embodiments, various steps or methods can be implemented in software or firmware that is stored in memory and executed by a suitable instruction execution system. As such, in some embodiments, specifically configured hardware can be used to implement at least some of the functionality described herein. For example, if implemented in hardware, the hardware can include any or a combination of the following: a discrete logic circuit having logic gates for implementing logic functions upon data signals, an application specific integrated circuit having appropriate combinational logic gates, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0101] Those of skill in the art would understand that information and signals can be represented using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0102] In addition, each of the functional units in the various embodiments of the present application can be integrated in one processing module, or each of the units can be physically present separately, or two or more units can be integrated in one module. The integrated module can be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer readable storage medium.

[0103] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for assessing damage to power devices based on the attenuation coefficient spectrum of electromagnetic acoustic emission signals, characterized in that, The method assesses damage to power devices based on sampled electromagnetic acoustic emission signals, which are obtained by sampling at first and second monitoring points on both sides of the power device chip plane. The method includes: Step S1: Record the electromagnetic acoustic emission signal sampled at each monitoring point; Step S2: Find the minimum value of each electromagnetic acoustic emission signal, divide the corresponding electromagnetic acoustic emission signal into time windows with adjacent minimum values, and perform a fast Fourier transform on the windowed signal to obtain the amplitude-frequency curve of each electromagnetic acoustic emission signal. Step S3: Based on the signal propagation time matching amplitude-frequency curve according to the signal theory, calculate the attenuation coefficient of the matching amplitude-frequency curve in the order of the time window to obtain the time-varying curve of the attenuation coefficient; Step S4: Calculate the average value of the time-varying curve of the attenuation coefficient to obtain the attenuation coefficient spectrum of a single measurement, and calculate the center frequency of the attenuation coefficient spectrum; Step S5: Repeat steps S1-S4. After each repetition, use the difference between the obtained center frequency and the first measured center frequency as the center frequency offset. If the center frequency offset exceeds the threshold, it is determined that the power device is damaged.

2. The method as described in claim 1, characterized in that, The electromagnetic acoustic emission signal is sampled at the first monitoring point, propagates through the detected area, and is sampled again at the second monitoring point.

3. The method as described in claim 1, characterized in that, The electromagnetic acoustic emission signal is a stress wave signal emitted by the power device in the on / off working state. The sampling start time of the first and second monitoring points is the instant when the power device is turned on. Sampling of the monitoring points is stopped when the signal strength is lower than the threshold value. The threshold value is positively correlated with the initial value of the signal strength.

4. The method as described in claim 1, characterized in that, When dividing the electromagnetic acoustic emission signal into time windows using adjacent minimum values, if the time window lengths are inconsistent, after performing a fast Fourier transform, the following steps are also included: The frequency resolution of each spectrum is unified by multiple spline interpolation.

5. The method as described in claim 1, characterized in that, The formula for calculating the theoretical propagation time of electromagnetic acoustic signals is: Δt=L / v Where L is the signal propagation distance, which is determined by the geometric dimensions of the power device, and v is the sound velocity in the medium, which is determined by the material properties of different layers of the power device.

6. The method as described in claim 5, characterized in that, The step of matching the amplitude-frequency curve according to the signal propagation time theory includes: Calculate the difference in the starting time of the signal time windows of the first monitoring point and the second monitoring point. Match the two time windows with a time difference of Δt. Arrange them in the order of the starting time of the corresponding time windows during matching. Alternately arrange the amplitude-frequency curves of all monitoring points to obtain the amplitude-frequency curve sequence of adjacent time windows.

7. The method as described in claim 1, characterized in that, The formula for calculating the attenuation coefficient at frequency ω0 is: Where A2(t+Δt,ω0) is the amplitude at the ω0 frequency point at the second monitoring point at time t+Δt, and A1(t,ω0) is the amplitude at the ω0 frequency point at the first monitoring point at time t.

8. The method as described in claim 1, characterized in that, The formula for determining the center frequency of the attenuation coefficient spectrum is: Where ω1 and ω2 are the minimum and maximum frequencies of the attenuation coefficient spectrum, ω is the frequency of the attenuation coefficient spectrum, and H(ω) is the attenuation coefficient spectrum measured in a single measurement.

9. The method according to claim 1, characterized in that, The threshold includes a first threshold and a second threshold, wherein the first threshold is less than the second threshold. The step of determining that the power device is damaged when the center frequency offset exceeds the threshold includes: When the center frequency deviation exceeds the first threshold, the power device is determined to be in an early damage state. When the center frequency offset exceeds the second threshold, it is determined that the power device cannot meet the scenario reliability requirements.

10. A power device damage assessment device based on the attenuation coefficient spectrum of electromagnetic acoustic emission signals, characterized in that, The device assesses damage to power devices based on sampled electromagnetic acoustic emission signals. These signals are obtained by sampling at monitoring points on both sides of the power device chip plane. The monitoring points include a first monitoring point and a second monitoring point. The device comprises: The data acquisition module is used to record the electromagnetic acoustic emission signals sampled at each monitoring point; The amplitude-frequency curve generation module is used to find the minimum value of each electromagnetic acoustic emission signal, divide the corresponding electromagnetic acoustic emission signal into time windows with adjacent minimum values, and perform a fast Fourier transform on the windowed signal to obtain the amplitude-frequency curve of each electromagnetic acoustic emission signal. The attenuation coefficient time-varying curve generation module is used to match the amplitude-frequency curve according to the theoretical propagation time of the signal, and to obtain the attenuation coefficient of the matched amplitude-frequency curve in the order of the time window, so as to obtain the attenuation coefficient time-varying curve. The center frequency calculation module is used to calculate the average value of the time-varying curve of the attenuation coefficient, obtain the attenuation coefficient spectrum of a single measurement, and calculate the center frequency of the attenuation coefficient spectrum. The judgment module is used to repeatedly call the data acquisition module, the amplitude-frequency curve generation module, the attenuation coefficient time-varying curve generation module, and the center frequency calculation module. After each repetition, the difference between the obtained center frequency and the center frequency measured for the first time is used as the center frequency offset. When the center frequency offset exceeds a threshold, it is judged that the power device is damaged.

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