Local electric field testing method for high-voltage power modules

Abstract

A method for testing the local electric field of high-voltage power modules collects the surface potential distribution of the power module package insulation, performs central difference processing to obtain the surface electric field intensity, and then uses a second-order total variation regularization algorithm to invert the interfacial electric field distribution. This method uses a non-intrusive electrostatic probe to measure the surface potential distribution of the power module package insulation. In combination with a second-order total variation regularization inversion algorithm, it measures the electric field distribution at the interface between the ceramic plate and the potting compound, effectively detecting the local electric field distribution in complex structures.

Description

Technical Field

[0001] The present invention relates to a technology in the field of electrical engineering, in particular to a local electric field testing method for a high-voltage power module. Background Art

[0002] The complex electrode and insulation structure of high-voltage power module packaging leads to uneven electric field distribution. The most severe electric field concentration occurs at the junction of the ceramic substrate, copper cladding, and potting compound. Excessive electric field strength in a localized area can cause the material to experience increased electrothermal stress, potentially leading to localized aging, crack propagation, or material degradation, impacting the performance, reliability, and service life of the power module.

[0003] Currently, the local electric field characteristics of power modules are primarily calculated using finite element numerical simulation techniques, which analyze the electric field distribution within complex structures using mathematical models. However, numerical simulation methods inherently rely on assumptions and simplifications regarding material properties, boundary conditions, and initial values. Therefore, the validity of the results is significantly affected by the settings of these parameters. Furthermore, the results obtained from numerical simulations often reflect the electric field distribution under ideal conditions and may not necessarily reflect the electric field conditions under actual operating conditions. Therefore, experimental research methods that are closer to actual environments are needed, and these experimental methods can provide a means of verifying the effectiveness of numerical simulation methods. Existing technology can measure the electric field strength in a dielectric using electric field sensors based on technologies such as the photoelectric effect. However, this technology has limitations when applied to high-voltage power module package insulation. This is primarily due to the fact that the sensor size is comparable to the package insulation structure. Therefore, the insertion of the sensor is likely to disrupt the original electric field distribution, resulting in inaccurate test results. Summary of the Invention

[0004] In response to the problems that the existing technology is difficult to test the electric field strength at the interface between the potting compound and the ceramic substrate in the high-voltage power module, the interference of the electric field distribution caused by the intervention of the existing sensors, and the weak nonlinear optical effect of the packaging material, the present invention proposes a local electric field testing method for the high-voltage power module. The potential distribution on the surface of the power module package insulation is measured by a non-intrusive electrostatic probe, and the electric field distribution at the interface between the ceramic plate and the potting compound is measured in combination with a second-order total variation regularized inversion algorithm, thereby realizing effective detection of the local electric field distribution under complex structures.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention relates to a local electric field testing method for a high-voltage power module. The method collects the surface potential distribution of the power module package insulation, obtains the surface electric field intensity through central difference processing, and then inverts the distribution of the interface electric field by combining a second-order total variation regularization algorithm.

[0007] The acquisition is to divide the upper and lower surfaces of the potting layer, namely the surface S1 and the interface S2, into N = n × n units, and test the potential value of each unit on S1 under pressure conditions by non-invasive electrostatic probe method. i,j=1~N.

[0008] The central difference processing is to obtain the component of the electric field in the x direction according to the potential value of each unit. and the y-direction component Then the surface electric field strength on each unit is obtained Where: E i，j Construct an n×n two-dimensional matrix.

[0009] The second-order total variation regularization algorithm specifically includes:

[0010] Step 1) According to the electrostatic field theory, for any point p on the surface S1 and its corresponding point q on the interface S2, i.e., the point perpendicular to the point in the direction of the interface normal vector, establish the surface electric field and interface electric field model. Among them: (i, j) is the two-dimensional coordinate of the plane where point p and point q are located. and The interface electric field and surface electric field The electric field modulus at point (i, j) corresponds to the surface electric field and interface electric field d is the insulation thickness between the surface S1 and the interface S2, ε is the dielectric constant of the material, q k is the volume charge density of the kth unit in the insulation, m is the total number of charge units in the insulation, R k q k The distance from point p, θ k q k The angle between the line connecting the point and point p and the tangent vector of the plane is, is the unit vector pointing from qk to point (i, j),

[0011] Step 2) Convert the two-dimensional surface electric field and interface electric field model into one-dimensional: According to the surface electric field intensity distribution, the position of the maximum electric field intensity i = a, j = b is obtained. Further, a one-dimensional array E containing the maximum electric field intensity is obtained. s1 [n], n is the length of the one-dimensional array.

[0012] Step 3) Use second-order total variation regularization to solve the ill-posed problem from surface electric field to interface electric field: construct the objective function min(||E S1 (x)-∫M(x,x')E S2 (x')dx'‖ 2 +λTV (2)(E S2 (x))), where: M(x,x') is the kernel function describing the transfer relationship between the surface electric field and the interface electric field, x is the surface electric field coordinate, x' is the interface electric field coordinate, λ is the regularization parameter, TV (2) (E S2 (x)) is the second-order total variation regularization term. The problem is converted to the frequency domain and discretized to obtain Where: E s1 [k] and E S2 [k] is the discretized one-dimensional surface electric field and interface electric field distribution, M[k] is the discretized one-dimensional kernel function or discretized transfer array, and then the gradient descent method is used to optimize the objective function. The parameter update is: E S2 [k] (t+1) =E S2 [k] (t) +α t d t , where: E S2 [k] (t+1) is the estimated value of the interface electric field at the t+1th iteration, E S2 [k] (t) is the estimated value of the interface electric field at the tth iteration, α t is the iteration step length, d t For the objective function E S2 The gradient of [k].

[0013] Step 4) Iterative optimization obtains the interface electric field E in the frequency domain S2 After [k], the interface electric field distribution is finally obtained by inverse Fourier transform to the time domain.

[0014] The present invention relates to a system for implementing the above-mentioned method, comprising: a surface potential testing unit, a data acquisition unit, an electric field calculation unit and an interface electric field inversion unit, wherein: the surface potential testing unit obtains two-dimensional potential distribution data of the upper surface of the power module potting layer according to a non-intrusive electrostatic probe testing method; the data acquisition unit receives the potential data obtained from the electrostatic probe test and performs preprocessing to eliminate environmental noise interference during the measurement process; the electric field calculation unit performs central difference processing on the preprocessed potential data to obtain a two-dimensional surface electric field distribution; the interface electric field inversion unit converts the two-dimensional electric field distribution into a one-dimensional electric field distribution according to the two-dimensional surface electric field distribution and the position of the maximum electric field intensity, and according to the surface electric field and interface electric field models, adopts second-order total variation regularization and gradient descent method to iteratively optimize to obtain the interface electric field, and then obtains the one-dimensional interface electric field distribution in the time domain through inverse Fourier transform.

[0015] Technical Effects

[0016] This method uses a non-intrusive electrostatic probe to measure the surface potential, combined with a second-order total variation regularized inversion algorithm, to reconstruct the local electric field distribution at the interface between the ceramic substrate and the potting compound. This method avoids the problem of sensor interference in traditional testing methods, which can lead to interference with the electric field distribution. It also fills the gap in existing experimental research on the local electric field of power modules, providing an effective tool for studying local electric field distribution in complex structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Flowchart of the present invention;

[0018] Figure 2 (a) is a power module sample in the embodiment;

[0019] Figure 2 (b) Schematic diagram of the probe scanning measurement area in the non-intrusive surface potential test;

[0020] In the figure: electrostatic voltage probe 1, power module sample 2, potting glue layer 3, L-shaped copper cladding 4, square copper cladding 5, ceramic substrate 6, electrostatic voltage probe scanning area 7 in the embodiment, high-voltage power supply 8;

[0021] Figure 3 Schematic diagram of surface and interface partitioning method;

[0022] Figure 4 Schematic diagram of the two-dimensional distribution of surface potential obtained from the test;

[0023] Figure 5 Schematic diagram of the two-dimensional distribution of the surface electric field obtained by central difference processing;

[0024] Figure 6 Schematic diagram of one-dimensional distribution of surface electric field;

[0025] Figure 7 Schematic diagram of the inversion transfer function in the frequency domain;

[0026] Figure 8 Schematic diagram of the one-dimensional distribution of the interface electric field in the time domain. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, this embodiment involves a local electric field testing method for a high-voltage power module. After collecting the surface potential distribution of the power module package insulation through a non-intrusive electrostatic probe, the surface electric field strength is obtained through central difference processing, and then the distribution of the interface electric field is inverted by combining the second-order total variation regularization algorithm.

[0028] like Figure 2As shown in (a), the power module comprises: a ceramic substrate 6, an L-shaped copper cladding 4 and a square copper cladding 5 arranged thereon, and a potting glue layer 3 that is entirely coated on the outside.

[0029] The thickness of the potting glue layer is d=1mm, the dielectric constant is 2.8, the thickness of the ceramic substrate 6 is 0.635mm, the distance between the L-shaped copper cladding 4 and the square copper cladding 5 is 5mm, the corner radius is 0.3mm, and the thickness of the copper cladding is 0.3mm. During the surface potential test, the high-voltage power supply in the surface potential test unit of the non-intrusive electrostatic probe 1 has a stable output voltage of 5kV, which is connected to the L-shaped copper cladding lead-out terminal of the power module, and the square copper cladding is grounded. The non-intrusive electrostatic probe is 2mm from the upper surface of the potting layer, the probe test sensitivity is 10mV, the probe movement rate is 4mm / s, and the sampling rate is 100s. -1 , the moving range is a square area with a side length of 16mm, such as Figure 2 (b) shown.

[0030] like Figure 3 The potential value of each unit on S1 under pressure is tested by non-invasive electrostatic probe method. i, j = 1 to N. In this embodiment, n is set to 400.

[0031] like Figure 4 As shown in FIG, the two-dimensional distribution of the surface potential of the power module encapsulation layer obtained through the above measurement; according to the two-dimensional distribution data of the surface potential, the central difference processing is used to obtain the two-dimensional distribution data of the surface electric field, as shown in FIG. Figure 5 As shown in Figure 1, the interface electric field distribution of ceramic and potting compound is obtained by combining surface electric field data with inversion algorithm; according to the two-dimensional distribution data of surface potential, the one-dimensional distribution data of electric field at the intersection of the maximum electric field intensity position (i=a=75) is obtained, as shown in Figure 1. Figure 6 As shown in the figure, it is the surface electric field distribution at the intersection along the y direction; according to the surface electric field and interface electric field model, the discretized transfer array M[k] in the frequency domain is obtained, as shown in the figure: Figure 7 As shown, it is M[k] in the frequency domain; according to the one-dimensional distribution data of the surface electric field obtained by the test and the transfer array, the interface electric field is obtained by iterative optimization using the second-order total variation regularization and gradient descent method. The number of iterations is 100, and then the one-dimensional distribution of the interface electric field in the time domain is obtained by inverse Fourier transform, as shown in Figure 8 As shown, the interface electric field distribution at the interface at i=a=75 and along the y direction.

[0032] Compared with traditional sensor-based direct intervention electric field measurement, the present invention uses a non-intrusive electrostatic probe to collect the surface potential distribution of the power module package insulation, avoiding the interference of the sensor on the electric field distribution and ensuring the accuracy and reliability of the test results. By introducing a second-order total variation regularization algorithm and a gradient descent method, the interface electric field is inverted and optimized. Compared with the existing technology, the present invention improves the reconstruction accuracy of the electric field distribution and solves the edge problem of possible mutations in the electric field at the interface. It fills the gap in experimental research on local electric fields under complex structures.

[0033] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A local electric field testing method for a high-voltage power module, characterized in that: After collecting the surface potential distribution of the power module package insulation, the surface electric field intensity is obtained through central difference processing, and then the distribution of the interface electric field is inverted by combining the second-order total variation regularization algorithm; The second-order total variation regularization algorithm specifically includes: Step 1) According to the electrostatic field theory, the surface electric field and interface electric field models are established for any point p on the surface S1 and its corresponding point q on the interface S2. , where: (i, j) is the two-dimensional coordinates of point p and point q. and The interface electric field and surface electric field The electric field modulus at point (i, j) corresponds to the surface electric field and interface electric field , d is the insulation thickness between the surface S1 and the interface S2, ε is the dielectric constant of the material, q k is the volume charge density of the kth unit in the insulation, m is the total number of charge units in the insulation, R k q k The distance between the point and point p, θ k q k The angle between the line connecting the point and point p and the tangent vector of the plane is, For q k The unit vector of the point pointing to point (i, j); Step 2) Convert the two-dimensional surface electric field and interface electric field model into one-dimensional: According to the surface electric field intensity distribution, the position of the maximum electric field intensity i=a, j=b is obtained, and further a one-dimensional array E containing the maximum electric field intensity is obtained. s1 [n], n is the length of the one-dimensional array; Step 3) Construct the objective function , where: M(x,x') is the kernel function describing the transfer relationship between the surface electric field and the interface electric field, x is the surface electric field coordinate, x' is the interface electric field coordinate, λ is the regularization parameter, TV (2) (E S2 (x)) is the second-order total variation regularization term. The problem is converted to the frequency domain and discretized to obtain , where: E s1 [k] and E S2 [k] is the discretized one-dimensional surface electric field and interface electric field distribution, M[k] is the discretized one-dimensional kernel function or discretized transfer array, and the gradient descent method is used to optimize the objective function. The parameter update is: ,in: is the estimated value of the interface electric field at the t+1th iteration, is the estimated value of the interface electric field at the tth iteration, α t is the iteration step length, d t For the objective function E S2 The gradient of [k]; Step 4) Iterative optimization obtains the interface electric field E in the frequency domain S2 After [k], the interface electric field distribution is finally obtained by inverse Fourier transform to the time domain.

2. The local electric field testing method for a high-voltage power module according to claim 1, wherein: The acquisition is as follows: the upper and lower surfaces of the potting layer, namely the surface S1 and the interface S2, are divided into N=n×n units respectively, and the potential value φ of each unit on S1 under pressure is tested by a non-invasive electrostatic probe method. i,j , i, j=1~N.

3. The local electric field testing method for a high-voltage power module according to claim 2, wherein: The central difference processing is to obtain the component of the electric field in the x direction according to the potential value of each unit. and the y-direction component , and then the surface electric field intensity on each unit is obtained , where: E i，j Construct an n×n two-dimensional matrix.

4. A local electric field testing system for a high-voltage power module implementing the method according to any one of claims 1 to 3, characterized in that: include: A surface potential testing unit, a data acquisition unit, an electric field calculation unit, and an interface electric field inversion unit, wherein: the surface potential testing unit obtains two-dimensional potential distribution data on the upper surface of the power module potting layer according to a non-invasive electrostatic probe testing method; the data acquisition unit receives the potential data obtained from the electrostatic probe test and preprocesses it to eliminate environmental noise interference during the measurement process; the electric field calculation unit performs central difference processing on the preprocessed potential data to obtain a two-dimensional distribution of the surface electric field; the interface electric field inversion unit converts the two-dimensional electric field distribution into a one-dimensional electric field distribution according to the two-dimensional surface electric field distribution and the position of the maximum electric field intensity, and according to the surface electric field and interface electric field model, adopts second-order total variation regularization and gradient descent method to iteratively optimize the interface electric field, and then obtains the one-dimensional distribution of the interface electric field in the time domain through inverse Fourier transform.

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