Square IGBT current distribution evaluation method and system based on surface-mounted magnetic flux coil

Abstract

The invention provides a square IGBT current distribution evaluation method and system based on a surface-mounted magnetic flux coil. The method comprises the steps that a plurality of surface-mounted magnetic flux coils are tightly attached to the surface of a shell of a square IGBT device, so that a coupling alternating magnetic field is generated between the surface-mounted magnetic flux coils and the square IGBT device, and the surface-mounted magnetic flux coils output induced voltage; measuring the induced voltage of each surface-mounted magnetic flux coil, and calculating a real-time mutual inductance value between each surface-mounted magnetic flux coil and the internal current of the square IGBT according to the induced voltage; based on the variable quantity of the real-time mutual inductance value, offset vectors corresponding to the surface-mounted magnetic flux coils are calculated, and the offset vectors are used for representing the spatial position change of the current concentration point relative to the normal direction of the surface-mounted magnetic flux coils; and superposing the offset vectors corresponding to the surface-mounted magnetic flux coils to obtain a composite vector, and evaluating the current distribution state in the square IGBT according to the composite vector.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric data measurement, in particular to a square IGBT current distribution evaluation method and system based on surface-mounted magnetic flux coils. BACKGROUND

[0002] With the rapid development of high-voltage direct current transmission technology, the press-pack IGBT device has become the core component of the converter valve due to its easy series connection, high power density and double-sided heat dissipation characteristics. Compared with the traditional soldered IGBT module, the press-pack IGBT uses mechanical pressure to realize the parallel connection of internal multi-chip, avoids the problem of bond wire aging, and has a failure short circuit mode, which significantly improves the system reliability. However, the current imbalance problem of the internal multi-chip parallel structure caused by unbalanced pressure, stray inductance parameter change, chip aging and other reasons will cause local thermal stress concentration, leading to device aging or even failure. In order to ensure the operation reliability of power electronic equipment, it is necessary to monitor the internal current distribution of the press-pack IGBT.

[0003] At present, the monitoring method of the internal current distribution of the press-pack IGBT is mainly the invasive monitoring method. However, the invasive monitoring method needs to damage the device package, which has the problems of damaging the device airtightness and accelerating the device aging.

[0004] Therefore, the present application provides a square IGBT current distribution evaluation method and system based on surface-mounted magnetic flux coils to solve one of the above technical problems. SUMMARY

[0005] The purpose of the present application is to provide a square IGBT current distribution evaluation method and system based on surface-mounted magnetic flux coils, which can solve at least one of the above technical problems. The specific scheme is as follows: According to the specific embodiment of the present application, in a first aspect, the present application provides a square IGBT current distribution evaluation method based on surface-mounted magnetic flux coils, comprising: The surface-mounted magnetic flux coils are installed close to the surface of the square IGBT device shell to generate a coupled alternating magnetic field between the surface-mounted magnetic flux coils and the square IGBT device, and the surface-mounted magnetic flux coils output an induced voltage; the induced voltage of each surface-mounted magnetic flux coil is measured, and the real-time mutual inductance value between each surface-mounted magnetic flux coil and the internal current of the square IGBT is calculated according to the induced voltage; based on the change amount of the real-time mutual inductance value, the offset vector corresponding to each surface-mounted magnetic flux coil is calculated, and the offset vector is used to represent the spatial position change of the current concentration point relative to the normal direction of the surface-mounted magnetic flux coil; the offset vectors corresponding to each surface-mounted magnetic flux coil are superimposed to obtain a resultant vector, and the current distribution state inside the square IGBT is evaluated according to the resultant vector.

[0006] In one embodiment, calculating the offset vector corresponding to each of the surface-mounted flux coils based on the change in the real-time mutual inductance value includes: obtaining the corresponding center mutual inductance value from the mutual inductance characteristic matrix according to the current current distribution state; comparing the center mutual inductance value with the real-time mutual inductance value to determine the offset vector corresponding to each of the surface-mounted flux coils.

[0007] In one embodiment, the mutual inductance characteristic matrix is ​​obtained as follows: based on the multi-turn parallel winding coaxial series structure of the surface-mount flux coil, the magnetic field generated by the equivalent current-carrying conductor of the square IGBT device in the single-turn coil region is calculated according to the Biot-Savart law; the magnetic field in the single-turn coil region is integrated to obtain the magnetic flux of the single-turn coil; the magnetic flux of all turns is summed to obtain the total magnetic flux of the surface-mount flux coil; and the mutual inductance characteristic matrix of the surface-mount flux coil is calculated according to the relationship between the total magnetic flux and the current.

[0008] In one embodiment, the time-varying current of the equivalent current-carrying conductor I ( t Any point within the online turn area R =( x , y , z The generated magnetic field is expressed by the following formula: ;in, The permeability of free space, B Represents any point within the coil area R The generated magnetic field l The equivalent current-carrying conductor length; the magnetic flux through the coil in a single turn is: ;in, For the first i The magnetic flux of the coil, for the first turn i The coils form a closed region in the YZ plane with a length of [missing information]. b , width is a The inner edge distance is the equivalent current-carrying conductor distance. d .

[0009] In one embodiment, the surface-mount flux coil is arranged to satisfy the following conditions: the surface-mount flux coil is mounted close to the ceramic housing surface of the square IGBT device; the normal direction of the surface-mount flux coil is orthogonal to the current direction of the equivalent current-carrying conductor of the square IGBT device; wherein, the current direction in the equivalent current-carrying conductor is defined as the vertical direction passing through the center of the upper and lower electrodes of the square IGBT device.

[0010] In one implementation, the offset vector is calculated using the following formula: ;in, For the first i The offset vector of a surface-mounted flux coil. For the first i The unit normal vector of a surface-mounted flux coil. This is the offset coefficient. For the first i The actual mutual inductance value of a surface-mounted flux coil For the first i The center mutual inductance value of a surface-mounted flux coil when the current distribution is balanced. For the first i Normalized coefficients of a surface-mounted flux coil.

[0011] In one embodiment, the normalization coefficient This is used to map changes in mutual inductance to changes in spatial location; the mapping process uses an offset coefficient. Substitutional normalization coefficient This is indicated by the following method: when When, it indicates that the current concentration point is close to the surface-mounted flux coil; when When, it indicates that the current concentration point is far away from the surface-mounted flux coil; when When the current is evenly distributed, it indicates that the current distribution is balanced.

[0012] In one implementation, the synthesized vector is calculated using the following formula: ;in, For the synthesized vector, For the first i The offset vector of a surface-mounted flux coil.

[0013] In one embodiment, evaluating the current distribution state inside the square IGBT based on the composite vector includes: determining the azimuth angle of the current concentration point relative to the center of the square IGBT device based on the direction of the composite vector in a two-dimensional plane; calculating the magnitude of the composite vector as an index value for quantifying the degree of current distribution balance; and combining the azimuth angle and the magnitude to complete a comprehensive evaluation of the location and degree of imbalance of the current concentration point inside the square IGBT device.

[0014] According to a specific embodiment of this application, in a second aspect, this application provides a current distribution evaluation system for square IGBTs based on surface-mount flux coils, comprising: Multiple surface-mount flux coils are mounted on the surface of the housing of a square IGBT device for coupling an alternating magnetic field and outputting an induced voltage. A measurement unit, connected to the surface-mount flux coils, is used to measure the induced voltage of each surface-mount flux coil. A processing unit, connected to the measurement unit, is used to: calculate the mutual inductance value of each surface-mount flux coil based on the induced voltage; calculate an offset vector based on the change in mutual inductance value of each surface-mount flux coil; superimpose the offset vectors to obtain a composite vector; and evaluate the current distribution state inside the square IGBT based on the composite vector.

[0015] Compared with the prior art, the above-described solution of this application has at least the following beneficial effects: This application provides a method for evaluating the current distribution of a square IGBT based on a surface-mount flux coil. By mounting the surface-mount flux coil tightly against the square IGBT casing, it can directly couple the alternating magnetic field generated by the internal current and output an induced voltage, thereby achieving non-invasive monitoring of the current distribution. Furthermore, by measuring these voltages and calculating the real-time mutual inductance value, the dynamic changes in the current distribution can be captured in real time. Based on this, an offset vector is calculated based on the change in mutual inductance value, which can quantify the positional offset of the current concentration point relative to the coil normal. Finally, the offset vectors are superimposed to obtain a composite vector, thereby comprehensively evaluating the current distribution state and effectively solving the problem of the lack of measurement for the current distribution of square devices. Attached Figure Description

[0016] Figure 1 A flowchart of a method for evaluating the current distribution of a square IGBT based on a surface-mounted flux coil is shown. Figure 2 A schematic diagram of a detection apparatus for implementing the method provided in this application is shown; Figure 3 A schematic diagram of a process for performing current distribution assessment is shown; Figure 4 A flowchart of a method for obtaining mutual inductance characteristic matrix is ​​shown; Figure 5 A schematic diagram of a coil structure and the Biot-Savart law is shown. Figure 6 A schematic diagram of a mutual inductance characteristic matrix is ​​shown; Figure 7 A simulation experiment effect diagram is shown; Figure 8 A schematic diagram is shown showing how to superimpose the offset vectors corresponding to the coils in four directions; Figure 9 A flowchart of a method for evaluating the current distribution state inside a square IGBT based on a composite vector is shown. Figure 10 A schematic diagram of the experimental results is shown; Figure 11 A unit block diagram of a square IGBT current distribution evaluation system based on a surface-mount flux coil according to an embodiment of this application is shown. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0019] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0020] It should be understood that although the terms first, second, third, etc., may be used in the embodiments of this application, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, first may also be referred to as second without departing from the scope of the embodiments of this application, and similarly, second may also be referred to as first.

[0021] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0022] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0023] It should be noted that any symbols and / or numbers present in the specification that are not marked in the accompanying drawings are not reference numerals.

[0024] With the rapid development of high-voltage direct current (HVDC) transmission technology, press-fit IGBT devices have become core components of converter valves due to their ease of series connection, high power density, and bi-sided heat dissipation. Compared to traditional welded IGBT modules, press-fit IGBTs use mechanical pressure to achieve parallel connection of multiple internal chips, avoiding bond wire aging issues and possessing a failure short-circuit mode, significantly improving system reliability. However, current imbalance in the parallel structure of multiple chips within the device, caused by unbalanced pressure, stray inductance parameter variations, and chip aging, can lead to localized thermal stress concentration, resulting in device aging or even failure. Therefore, monitoring the internal current distribution of press-fit IGBTs is essential to ensure the operational reliability of power electronic equipment.

[0025] Currently, the main method for monitoring the internal current distribution of press-fit IGBTs is invasive monitoring. However, invasive monitoring requires damaging the device package, which can compromise the device's hermeticity and accelerate its aging. Therefore, related technologies have attempted to address this issue by employing invasive monitoring methods.

[0026] In the field of non-invasive current distribution monitoring, existing technologies employ segmented Rogowski coils. For example, by arranging the coils around a circular device, changes in mutual inductance are used to reflect the internal current distribution and indicate the location of the eccentric point. However, this approach has significant limitations. Its specific design for circular devices makes it unsuitable for the structural characteristics of square IGBT devices, leaving a technological gap in the measurement of current distribution for square devices. Furthermore, the installation gap between the coil and the device results in low magnetic field coupling efficiency, further affecting the sensitivity and accuracy of the measurement, making it difficult to meet the combined requirements of compact installation and high-precision monitoring in engineering applications.

[0027] In view of this, this application provides a current distribution evaluation method for square IGBT devices, which considers the use of surface-mounted coils (SMCs) to detect IGBT devices. This method is suitable for square IGBT devices and can solve the above-mentioned problems existing in the prior art.

[0028] The optional embodiments of this application are described in detail below with reference to the accompanying drawings.

[0029] The embodiments provided in this application are embodiments of a method for evaluating the current distribution of a square IGBT based on a surface-mounted flux coil.

[0030] The following is combined Figure 1 The embodiments of this application will be described in detail.

[0031] Figure 1 A flowchart illustrating a method for evaluating the current distribution of a square IGBT based on a surface-mount flux coil is shown, as follows: Figure 1 As shown, it includes the following steps.

[0032] S101. Multiple surface-mount flux coils are mounted close to the surface of the square IGBT device to generate a coupled alternating magnetic field between the surface-mount flux coils and the square IGBT device, and the surface-mount flux coils output an induced voltage.

[0033] S102. Measure the induced voltage of each surface-mounted flux coil and calculate the real-time mutual inductance between each surface-mounted flux coil and the internal current of the square IGBT based on the induced voltage.

[0034] S103. Based on the change in real-time mutual inductance value, calculate the offset vector corresponding to each surface-mounted flux coil.

[0035] The offset vector represents the spatial position change of the current concentration point relative to the normal direction of the surface-mounted flux coil.

[0036] S104. The offset vectors corresponding to each surface-mounted flux coil are superimposed to obtain a composite vector. The current distribution state inside the square IGBT is evaluated based on the composite vector.

[0037] The method provided in this application, by mounting a surface-mount flux coil tightly against the casing of a square IGBT, can directly couple the alternating magnetic field generated by the internal current and output an induced voltage, thereby achieving non-invasive monitoring of the current distribution. Furthermore, by measuring these voltages and calculating the real-time mutual inductance value, the dynamic changes in the current distribution can be captured in real time. Based on this, an offset vector is calculated based on the change in mutual inductance value, which quantifies the positional offset of the current concentration point relative to the coil normal. Finally, the offset vectors are superimposed to obtain a composite vector, thereby comprehensively evaluating the current distribution state and effectively solving the problem of measurement gaps in current distribution measurements for square devices.

[0038] Figure 2 A schematic diagram of a detection apparatus for implementing the method provided in this application is shown.

[0039] in, Figure 2 a illustrates the mounting relationship between a square press-fit IGBT device (including an IGBT submodule and a ceramic housing), a busbar, and the surface-mounted coils (SMCs) proposed in this application, such as... Figure 2 b illustrates the spatial relationship corresponding to the physical object. The overall layout of the surface-mount coil consists of multiple independent coil units, each closely attached to one of the four sides of the square IGBT. The busbar includes the current input terminal ( I in ) and current output terminal ( I out Surface-mount coils can be printed circuit board (PCB) flux coils. According to Faraday's law of electromagnetic induction, the coil can couple an alternating magnetic field to output an induced voltage.

[0040] Figure 3 A schematic diagram of a process for performing current distribution assessment is shown.

[0041] For example, such as Figure 3 As shown, the mutual inductance characteristic matrix can be used to pre-establish a reference system for the expected mutual inductance values ​​of each coil under different current distribution conditions, thereby comparing the actual mutual inductance values ​​measured in real-time monitoring with the reference values ​​in the matrix.

[0042] Among them, the comparison mechanism based on pre-modeling transforms the current distribution assessment into an analysis of the degree of deviation from the benchmark. This not only effectively eliminates the influence of fixed interference factors such as busbar current, but also achieves precise positioning of current concentration points and quantitative assessment of distribution status through sensitive capture of changes, significantly improving the anti-interference capability of the measurement and the interpretability of the results.

[0043] In some embodiments, the offset vector corresponding to each surface-mounted flux coil is calculated based on the change in real-time mutual inductance value, including: obtaining the corresponding center mutual inductance value from the mutual inductance characteristic matrix according to the current current distribution state; comparing the center mutual inductance value with the real-time mutual inductance value to determine the offset vector corresponding to each surface-mounted flux coil.

[0044] The mutual inductance characteristic matrix defines the center mutual inductance value for different current distribution states, which facilitates offset evaluation after comparison with the real-time mutual inductance value.

[0045] In this embodiment, a mutual inductance characteristic matrix can be used to pre-establish a reference system for the expected mutual inductance values ​​of each coil under different current distribution conditions, thereby comparing the actual mutual inductance values ​​measured in real-time monitoring with the reference values ​​in the matrix. The comparison mechanism based on pre-modeling transforms current distribution assessment into an analysis of the degree of deviation from the reference. This not only effectively eliminates the influence of fixed interference factors such as busbar current, but also achieves precise positioning of current concentration points and quantitative assessment of distribution states through sensitive capture of changes, significantly improving the measurement's anti-interference capability and the interpretability of the results.

[0046] Figure 4 A flowchart of a method for obtaining the mutual inductance characteristic matrix is ​​shown, as follows: Figure 4 As shown, it includes the following steps.

[0047] S401. Based on the coaxial series structure of multi-turn parallel windings of surface-mount flux coils, calculate the magnetic field generated by the equivalent current-carrying conductor of a square IGBT device in the region of a single-turn coil according to the Biot-Savart law.

[0048] S402. Integrate the magnetic field of the single-turn coil region to obtain the magnetic flux of the single-turn coil.

[0049] S403. Sum the magnetic flux of all turns to obtain the total magnetic flux of the surface-mounted flux coil.

[0050] S404. Based on the relationship between total magnetic flux and current, the mutual inductance characteristic matrix of the surface-mounted magnetic flux coil is calculated.

[0051] In this embodiment, a mutual inductance characteristic matrix can be used to pre-establish a reference system for the expected mutual inductance values ​​of each coil under different current distribution conditions, thereby comparing the actual mutual inductance values ​​measured in real-time monitoring with the reference values ​​in the matrix. This pre-modeling-based comparison mechanism transforms current distribution assessment into an analysis of the degree of deviation from the reference, effectively eliminating the influence of fixed interference factors such as busbar current, and achieving precise positioning of current concentration points and quantitative assessment of distribution status through sensitive capture of changes, significantly improving the anti-interference capability of the measurement and the interpretability of the results.

[0052] In the above embodiments, the surface-mount flux coil takes the PCB flux coil as an example. The PCB flux coil is based on Faraday's law of electromagnetic induction and the rate of change of current (…). dI / dt The sensing device works by detecting the induced electromotive force generated when an alternating magnetic field penetrates the coil windings, thus characterizing the time-varying current characteristics of a conductor. When current flows around the coil, based on the mutual inductance effect, the coil captures the alternating magnetic flux generated by the time-varying current through magnetic coupling, and outputs an induced voltage according to Faraday's law of electromagnetic induction. ; in, Indicates the induced voltage. M The mutual inductance coefficient between the time-varying current loop and the PCB flux coil is characterized by the coil geometry and the spatial distribution of the magnetic circuit.

[0053] Figure 5 A schematic diagram of a coil structure and Biot-Saffar's law is shown.

[0054] For example, such as Figure 5 As shown, the coil internally employs a multi-turn parallel winding coaxial series structure, such as... Figure 2 A magnified view of a portion of the image. At a length of... l The current-carrying conductor carries time-varying current along the Z-axis direction. I ( t ). No. i The coils form a closed region in the YZ plane (length is shown in the enlarged image). b , width is a The distance between the inner edge and the current-carrying conductor is d The red area satisfies the spatial orthogonality constraint.

[0055] Based on this, the time-varying current of the equivalent current-carrying conductor I ( t Any point within the online turn area R = ( x , y , z The generated magnetic field is expressed by the following formula: ; in, The permeability of free space, B Represents any point within the coil area R The generated magnetic field l This is the equivalent current-carrying conductor length.

[0056] Furthermore, the magnetic flux through a single turn of the coil is expressed by the following formula: ; in, For the first i The magnetic flux of the coil, for the first turn i The coils form a closed region in the YZ plane with a length of [missing information]. b , width is a The inner edge distance is the equivalent current-carrying conductor distance. d .

[0057] In some specific embodiments, the mutual inductance characteristic matrix of the device is calculated according to the above formula, as follows: Figure 6 As shown.

[0058] In this embodiment of the application, in order to enable the detection device to be installed inside the compact converter valve and at the same time improve the efficiency of the coil coupling magnetic field, the application proposes a surface-mount coil layout, that is, the PCB coil is installed close to the IGBT ceramic housing.

[0059] In conjunction with the above embodiments, according to the formula Analysis shows that the magnitude of the magnetic field is inversely proportional to the square of the distance; therefore, minimizing the distance between the coil and the current is an effective way to improve the coil's ability to capture magnetic fields. To verify the superiority of surface-mount layout in capturing magnetic field information, a design was developed as follows... Figure 7 The simulation experiment is shown. Among them, as shown... Figure 7 As shown in (a), assuming the device current... I The flow occurs along the Z-axis. A moving observation point is established in the YOZ plane, and the spatial magnetic field distribution is measured along both the Y and Z axes using coordinate scanning. B X Component field strength distribution as follows Figure 7 As shown in (b) and 7(c).

[0060] Based on the above embodiments, the layout of the surface-mount flux coil satisfies the following conditions: the surface-mount flux coil is mounted close to the ceramic housing surface of the square IGBT device; the normal direction of the surface-mount flux coil is orthogonal to the current direction of the equivalent current-carrying conductor of the square IGBT device. The current direction in the equivalent current-carrying conductor is defined as the perpendicular direction passing through the centers of the upper and lower electrodes of the square IGBT device.

[0061] In this embodiment, the busbar is essential in the actual use of IGBT devices, thus the PCB coil faces the problem of busbar current coupling. From the perspective of signal magnitude, this results in a low signal-to-noise ratio. Therefore, this invention proposes a current concentration point location method based on the change in mutual inductance.

[0062] For a rectangular PCB flux coil, the rate of change of current in its normal direction is quite sensitive. By extracting the changes in the normal direction of each coil and linearly superimposing them, the current distribution variation of the device can be determined. Therefore, this application proposes an offset vector... This can be achieved through the following formula: ; in, For the first i The offset vector of a surface-mounted flux coil. For the first i The unit normal vector of a surface-mounted flux coil. This is the offset coefficient. For the first i The actual mutual inductance value of a surface-mounted flux coil For the first i The center mutual inductance value of a surface-mounted flux coil when the current distribution is balanced. For the first i Normalized coefficients of a surface-mounted flux coil.

[0063] In this embodiment, the normalization coefficient can map changes in mutual inductance values ​​to changes in spatial location. Therefore, as a feasible implementation, the normalization coefficient... This is used to map changes in mutual inductance to changes in spatial location; the mapping process uses an offset coefficient. Substitutional normalization coefficient This is indicated in the following manner: when When the actual mutual inductance of the coils is greater than the center mutual inductance, it means that the current concentration point is close to the surface-mounted flux coil. when When the actual mutual inductance of the coils is less than the center mutual inductance, it means that the current concentration point is far away from the surface-mounted flux coil. when When the actual mutual inductance of the coils is equal to the central mutual inductance, it indicates that the current distribution is balanced.

[0064] Therefore, in Figure 7 (b) shows the mutual inductance characteristic diagram. The starting point is the center point of the mutual inductance characteristic, which is (0mm, 0mm), and the ending point is the center of the mutual inductance characteristic. The intersection of the equipotential lines and the coil normal. In this embodiment of the application, the change in mutual inductance signal of the coil can be converted into a spatial offset signal.

[0065] Figure 8 A schematic diagram is shown showing how to superimpose the offset vectors corresponding to the coils in the four directions.

[0066] For example, such as Figure 8 As shown, the offset vectors corresponding to the coils in the four directions can be superimposed to obtain a composite vector used to indicate the current concentration point. The calculation formula is as follows: ; in, For the synthesized vector, For the first i The offset vector of a surface-mounted flux coil.

[0067] Figure 9 A flowchart illustrating a method for evaluating the current distribution state inside a square IGBT based on a synthesized vector is shown, as follows: Figure 9 As shown, it includes the following steps.

[0068] S901. Determine the azimuth angle of the current concentration point relative to the center of the square IGBT device based on the direction of the composite vector in the two-dimensional plane.

[0069] S902. Calculate the magnitude of the composite vector as an index value used to quantify the degree of balance in current distribution.

[0070] S903. Combining azimuth and module length, a comprehensive evaluation of the location and degree of imbalance of the internal current concentration point of the square IGBT device is completed.

[0071] In some embodiments, after the synthetic vector calculation is completed, a vector analysis algorithm is used to parse it, including direction determination and magnitude calculation, and finally outputs a comprehensive assessment report containing location and severity.

[0072] As a feasible implementation, the azimuth angle is determined by calculating the angle between the synthesized vector and a preset reference axis. Specifically, a two-dimensional coordinate system is established with the center of the IGBT device as the origin, and the coordinate values ​​of the synthesized vector are input into the arctangent function to calculate its azimuth angle. For example, when the coordinates of the synthesized vector are (0.15, 0.25), the calculated azimuth angle is approximately 59 degrees, indicating that the current concentration point is located in the upper right region of the device center. To ensure the accuracy of the angle, a quadrant correction mechanism can also be introduced in this process to automatically correct the physical meaning of the calculation results.

[0073] As a specific implementation, the modulus can be calculated, for example, using the Euclidean norm formula. After receiving the coordinate components of the composite vector, the accurate modulus value is obtained through square root operations. For example, three typical threshold ranges are set: a modulus less than 0.1 is considered balanced, between 0.1 and 0.3 is considered slightly unbalanced, and greater than 0.3 is considered severely unbalanced. This modulus parameter is normalized to ensure comparability between devices of different sizes.

[0074] Based on this, the final output includes a polar coordinate description of the current concentration point and a balance level assessment. For example, it can output quantitative conclusions such as "current concentration point azimuth angle 125 degrees, unbalance level 2". This result can be directly used for early warning judgment of equipment condition monitoring systems or to guide maintenance personnel to carry out targeted maintenance on specific areas.

[0075] Figure 10 A schematic diagram of the experimental results is shown.

[0076] like Figure 10 As shown, tests were conducted on a dual-pulse experimental platform. A single submodule was manually controlled to conduct, the coil's output voltage was measured, and the mutual inductance value was calculated. The offset vector was calculated and superimposed according to the steps described above in this application to obtain a result containing... Figure 10 (a) Figure 10 (b) and Figure 10 (c) and other experimental results.

[0077] This application also provides system embodiments that follow the above embodiments, for implementing the method steps described in the above embodiments. The interpretation of the same names is the same as that in the above embodiments, and they have the same technical effects as those in the above embodiments, so they will not be repeated here.

[0078] like Figure 11 As shown, this application provides a square IGBT current distribution evaluation system 1100 based on a surface-mount flux coil, comprising: Multiple surface-mount flux coils 1101 are mounted on the surface of the housing of a square IGBT device to couple an alternating magnetic field and output an induced voltage.

[0079] The measuring unit 1102 is connected to the surface-mounted magnetic flux coil and is used to measure the induced voltage of each surface-mounted magnetic flux coil.

[0080] The processing unit 1103, connected to the measurement unit, is used to: calculate the mutual inductance value of each surface-mounted flux coil based on the induced voltage; calculate an offset vector based on the change in mutual inductance value of each surface-mounted flux coil; superimpose the offset vectors to obtain a composite vector; and evaluate the current distribution state inside the square IGBT based on the composite vector.

[0081] Regarding the system in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0082] Although the operations are described in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all of the operations shown to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0083] The methods and systems of this application can be implemented using standard programming techniques, utilizing rule-based logic or other logic to implement various method steps. It should also be noted that the terms "system" and "module" as used herein and in the claims are intended to include implementations using one or more lines of software code and / or hardware implementations and / or devices for receiving input.

[0084] Any step, operation, or procedure described herein may be performed or implemented using one or more hardware or software modules, either alone or in combination with other devices. In one embodiment, the software module is implemented using a computer program product comprising a computer-readable medium containing computer program code, which is executable by a computer processor to perform any or all of the described steps, operations, or procedures.

[0085] The foregoing description of implementations of this application has been provided for illustrative and descriptive purposes. The foregoing description is not exhaustive and is not intended to limit this application to the exact forms disclosed. Various modifications and variations may exist in accordance with the foregoing teachings, or may arise from practice of this application. These embodiments were chosen and described to illustrate the principles of this application and its practical application, enabling those skilled in the art to utilize this application in various implementations and modifications to suit the specific purpose of the concept.

[0086] Regarding the system in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0087] It can be further understood that, unless otherwise specified, "connection" includes both direct connections where no other components exist between the two parties and indirect connections where other components exist between them.

[0088] It is further understood that although the operations are described in a specific order in the accompanying drawings in the embodiments of this application, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all the operations shown to be performed to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0089] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the field of this application that are not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0090] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0091] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for evaluating the current distribution of a square IGBT based on a surface-mount flux coil, characterized in that, Includes the following steps: Multiple surface-mount flux coils are mounted close to the housing surface of a square IGBT device to generate a coupled alternating magnetic field between the surface-mount flux coils and the square IGBT device, and the surface-mount flux coils output an induced voltage. Measure the induced voltage of each of the surface-mounted flux coils, and calculate the real-time mutual inductance value between each of the surface-mounted flux coils and the internal current of the square IGBT based on the induced voltage; Based on the change in the real-time mutual inductance value, the offset vector corresponding to each of the surface-mounted magnetic flux coils is calculated. The offset vector is used to represent the spatial position change of the current concentration point relative to the normal direction of the surface-mounted magnetic flux coil. The offset vectors corresponding to each of the surface-mounted flux coils are superimposed to obtain a composite vector, and the current distribution state inside the square IGBT is evaluated based on the composite vector.

2. The method according to claim 1, characterized in that, The calculation of the offset vector corresponding to each of the surface-mounted flux coils based on the change in the real-time mutual inductance value includes: According to the current current distribution state, obtain the corresponding center mutual inductance value from the mutual inductance characteristic matrix; The offset vector corresponding to each of the surface-mounted flux coils is determined by comparing the central mutual inductance value with the real-time mutual inductance value.

3. The method according to claim 2, characterized in that, The mutual inductance characteristic matrix is ​​obtained in the following way: Based on the multi-turn parallel winding coaxial series structure of the surface-mount flux coil, the magnetic field generated by the equivalent current-carrying conductor of the square IGBT device in the single-turn coil region is calculated according to the Biot-Savart law. The magnetic flux of the single-turn coil is obtained by integrating the magnetic field in the region of the single-turn coil. The total magnetic flux of the surface-mounted flux coil is obtained by summing the magnetic flux of all turns. Based on the relationship between total magnetic flux and current, the mutual inductance characteristic matrix of the surface-mounted magnetic flux coil is calculated.

4. The method according to claim 3, characterized in that, The time-varying current of the equivalent current-carrying conductor I ( t Any point within the online turn area R = ( x , y , z The generated magnetic field is expressed by the following formula: ； in, The permeability of free space, B Represents any point within the coil area R The generated magnetic field l This is the equivalent current-carrying conductor length; The magnetic flux through the coil in a single turn is: ； in, For the first i The magnetic flux of the coil, for the first turn i The coils form a closed region in the YZ plane with a length of [missing information]. b , width is a The inner edge distance is the equivalent current-carrying conductor distance. d .

5. The method according to claim 1, characterized in that, The layout of the surface-mount flux coil satisfies the following conditions: The surface-mount flux coil is mounted close to the ceramic housing surface of the square IGBT device; The normal direction of the surface-mount flux coil is orthogonal to the current direction of the equivalent current-carrying conductor of the square IGBT device. The direction of the current in the equivalent current-carrying conductor is defined as the vertical direction passing through the center of the upper and lower electrodes of the square IGBT device.

6. The method according to claim 1, characterized in that, The offset vector is calculated using the following formula: ； in, For the first i The offset vector of a surface-mounted flux coil. For the first i The unit normal vector of a surface-mounted flux coil. This is the offset coefficient. For the first i The actual mutual inductance value of a surface-mounted flux coil For the first i The center mutual inductance value of a surface-mounted flux coil when the current distribution is balanced. For the first i Normalized coefficients of a surface-mounted flux coil.

7. The method according to claim 6, characterized in that, The normalization coefficient This is used to map changes in mutual inductance to changes in spatial location; the mapping process uses an offset coefficient. Substitutional normalization coefficient This is indicated in the following manner: when When the current concentration point is close to the surface-mounted flux coil; when When the current concentration point is far away from the surface-mounted flux coil; when When the current is evenly distributed, it indicates that the current distribution is balanced.

8. The method according to claim 1, characterized in that, The composite vector is calculated using the following formula: ； in, For the synthesized vector, For the first i The offset vector of a surface-mounted flux coil.

9. The method according to claim 1, characterized in that, The step of evaluating the current distribution state inside the square IGBT based on the synthesized vector includes: Based on the direction of the synthesized vector in the two-dimensional plane, determine the azimuth angle of the current concentration point relative to the center of the square IGBT device; Calculate the magnitude of the synthesized vector as an index value used to quantify the degree of balance in current distribution; By combining the azimuth angle and the module length, a comprehensive evaluation of the location of the current concentration point and the degree of imbalance inside the square IGBT device is completed.

10. A current distribution evaluation system for square IGBTs based on surface-mount flux coils, characterized in that, include: Multiple surface-mount flux coils are mounted on the housing surface of the square IGBT device to couple alternating magnetic fields and output induced voltage; The measuring unit is connected to the surface-mounted magnetic flux coil and is used to measure the induced voltage of each surface-mounted magnetic flux coil. The processing unit, connected to the measurement unit, is used to: calculate the mutual inductance value of each surface-mounted flux coil based on the induced voltage; calculate the offset vector based on the change in the mutual inductance value of each surface-mounted flux coil; superimpose the offset vectors to obtain a composite vector; and evaluate the current distribution state inside the square IGBT based on the composite vector.

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