Non-intrusive evaluation method for current distribution eccentric state

Abstract

The invention provides a non-intrusive evaluation method for a current distribution eccentric state, and the method comprises the following steps: placing a segmented Rogowski coil at the peripheral side of a to-be-tested element, and measuring the output voltage of the segmented Rogowski coil after the to-be-tested element is electrified; integrating the induced voltage to obtain an intermediate voltage integral quantity; and constructing a proportional function relationship between the current of the to-be-measured element and the intermediate voltage integral quantity, and obtaining point location information of non-uniform current distribution in the to-be-measured element and corresponding current eccentric state information based on the proportional function relationship. According to the method, the current distribution state of the device is evaluated through mutual inductance between the sectional Rogowski coil and the element to be measured, the original packaging structure of the device does not need to be damaged, the leakproofness and insulativity of the device are guaranteed, meanwhile, compared with an existing non-intrusive measurement method, the method is more accurate in measurement result, and the measurement efficiency is improved. And the current distribution state can be evaluated.

Description

Technical Field

[0001] The invention relates to the technical field of electric power appliances, and in particular to a non-invasive evaluation method for an eccentric state of current distribution. Background Art

[0002] Press-fit power electronic devices are widely used in the field of high-voltage direct current transmission due to their high reliability, good heat dissipation performance, and low thermal resistance. However, with the increase in the area and number of parallel chips, the problems related to current imbalance caused by device aging and pressure imbalance have become more prominent. When a press-fit power electronic device has a serious current imbalance, it will seriously reduce the performance of the device and affect the safe operation of the equipment. Therefore, it is of great engineering significance to detect the current imbalance state inside the press-fit power electronic device.

[0003] In the prior art, there are two main methods for detecting unbalanced current inside a crimped power electronic device, namely, invasive measurement and non-invasive measurement.

[0004] Among them, the intrusive measurement requires opening the device package, placing the Rogowski coil inside the device, and detecting the current of each chip separately. This intrusive measurement solution can provide full-bandwidth current measurement results for all parallel chips in the press-fit power electronic device. However, it will destroy the airtightness and insulation of the device, and the intrusive sensor cannot be installed inside the whole wafer press-fit power electronic devices, such as diodes and integrated gate commutation thyristors.

[0005] Compared with invasive measurement, non-invasive measurement uses the principle that changes in the internal current distribution of crimped power electronic devices will cause changes in the external magnetic field. There is no need to place the Rogowski coil inside the device. The changes in the internal current distribution can be inferred through changes in the external magnetic field, which does not affect the airtightness and insulation of the device. At the same time, the current conditions inside the crimped power electronic devices of the entire wafer can be measured.

[0006] However, although the above non-invasive measurement scheme can perform measurement without opening the device housing, it also has some defects, as follows:

[0007] 1. The flat structure of the crimping device causes the magnetic field generated by its own current to account for a very small proportion of the external magnetic field, and the magnetic field interference of the first busbar is serious, resulting in low measurement accuracy;

[0008] 2. The busbar is usually not perpendicular to the surface of the crimped power electronic device, which leads to non-uniform effects on the magnetic field at different locations and complicates the separation of device current related quantities from the measurement results.

[0009] Therefore, the existing methods can only reveal the changes in current distribution through changes in the magnetic field, but cannot directly evaluate the current distribution state. Furthermore, a segmented Rogowski coil and crimped power electronic device current distribution detection method is disclosed in Chinese patent application CN116679106A. According to the external dimensions of the device under test, the structure corresponding to the segmented Rogowski coil skeleton is determined; after the coil skeleton structure is determined, the wire is evenly wound around the coil skeleton, and the two terminals of the wire are led out and connected to the measuring device; according to the different shapes, the number of coils arranged around the device under test is different. Although this technical solution can reflect the changes in the current distribution inside the device to a certain extent, it is still unable to accurately evaluate the bias of the current distribution.

[0010] In summary, a corresponding accurate evaluation method needs to be provided for existing non-invasive detection solutions. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention provides a non-invasive evaluation method which has simple steps and can accurately evaluate the current distribution eccentricity state of a crimped power electronic device.

[0012] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0013] The present invention provides a non-invasive evaluation method for the eccentricity state of current distribution, which comprises the following steps:

[0014] At least one segmented Rogowski coil is placed around the component to be tested, and the output voltage of the segmented Rogowski coil is measured after the component to be tested is powered on;

[0015] calculating the induced voltage of the segmented Rogowski coil according to the output voltage and the electrical parameters of the segmented Rogowski coil;

[0016] Integrating the induced voltage to obtain an intermediate voltage integral;

[0017] Constructing a proportional function relationship between the current of the component under test and the integral of the intermediate voltage;

[0018] Based on the proportional function relationship, the point information of the uneven current distribution in the component to be tested and the corresponding current information are obtained.

[0019] Optionally, the number of the segmented Rogowski coil is 1;

[0020] The output voltage measurement process also includes the following steps:

[0021] The segmented Rogowski coil is placed at different positions for measurement for multiple times, and multiple output voltages are obtained.

[0022] Optionally, the number of the segmented Rogowski coils is multiple;

[0023] The output voltage measurement process also includes the following steps:

[0024] A plurality of the segmented Rogowski coils are placed at different positions for measurement, and a plurality of the output voltages are obtained simultaneously or in batches.

[0025] Optionally, the number of the segmented Rogowski coils is 2, and the sum of the segmented angles of the segmented Rogowski coils ranges from 180° to 225°;

[0026] The two segmented Rogowski coils are symmetrically placed, and the range of the center line angle is 80°-120°.

[0027] Optionally, the sum of the segment angles of the segmented Rogowski coil is 197°, and the centerline angle is 90°;

[0028] The placement angles of the center lines of the two segmented Rogowski coils relative to the busbar are 225° and 315° respectively.

[0029] Optionally, the process of solving the induced voltage includes:

[0030] Obtaining an equivalent circuit diagram of the segmented Rogowski coil based on a circuit analysis method;

[0031] Obtaining a transfer function between the output voltage and the induced voltage according to the equivalent circuit diagram;

[0032] The induced voltage is obtained by solving the transfer function and the output voltage.

[0033] Optionally, the intermediate voltage integral calculation method includes:

[0034] The induced voltage is time-integrated to obtain the intermediate voltage integral amount.

[0035] Optionally, the solution result of the proportional function relationship is an equivalent mutual inductance;

[0036] The equivalent mutual inductance is the ratio of the integrated value of the intermediate voltage to the current of the element to be measured.

[0037] Optionally, the method for solving the point information and the current information includes:

[0038] Solving the equivalent points based on the equivalent mutual inductance of the segmented Rogowski coils at different positions;

[0039] The point information includes the position information of the equivalent point; the current information includes the current intensity of the component to be measured corresponding to the equivalent point.

[0040] Optionally, the method for obtaining the point information and the current information further includes:

[0041] Draw a mutual inductance diagram of the element to be tested, and mark the equivalent mutual inductance contour lines of the segmented Rogowski coil at different positions in the mutual inductance diagram, and mark the intersection points of multiple equivalent mutual inductance contour lines;

[0042] Connecting the intersection point with the center point of the mutual inductance diagram to obtain a current distribution eccentricity vector;

[0043] The point information includes the direction of the current distribution eccentricity vector; the current information includes the amplitude of the current distribution eccentricity vector.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention evaluates the current distribution state of the device through the mutual inductance between the segmented Rogowski coil and the component to be measured. There is no need to destroy the original packaging structure of the device, thus ensuring the airtightness and insulation of the device. Compared with the existing non-invasive measurement method, this method has more accurate measurement results and can also evaluate the current distribution state. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 is a flow chart of the method of the present invention;

[0048] Figure 2 The equivalent circuit diagram of the segmented Rogowski coil of the present invention;

[0049] Figure 3 is a schematic diagram of the evaluation method of the present invention;

[0050] Figure 4 A current eccentricity vector diagram indicated by the intersection of equivalent mutual inductance contour lines of two segmented Rogowski coils in a specific embodiment of the present invention;

[0051] Figure 5 The mutual inductance of the 197-degree segmented Rogowski coil used in the specific embodiment of the present invention to the busbar and the mutual inductance to the device at different placement positions;

[0052] Figure 6 The figure is a mutual inductance characteristic diagram of the 197-degree segmented Rogowski coil used in a specific embodiment of the present invention to the device area current;

[0053] Figure 7 The measurement results of the induced voltage and device current of the segmented Rogowski coil in the specific embodiment of the present invention;

[0054] Figure 8 FIG. 4 is a current eccentricity vector diagram of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0057] In the description of the present invention, “plurality” means two or more than two, unless otherwise clearly and specifically defined.

[0058] It is worth noting that the methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products, and their sources are not specifically limited unless otherwise specified.

[0059] It should also be noted that in the specific embodiment of the present invention, the component to be tested is described as a crimped power electronic device, which has multiple chips inside. The segmented Rogowski coil is obtained by segmenting the classic circular Rogowski coil. It is no longer a complete circle, but its winding method is the same as that of the classic Rogowski coil. Specifically, the segmented Rogowski coil used in the present invention is made using a multi-layer printed circuit board. The top layer and the bottom layer are used as shielding layers, and the coil is located in the middle and is provided with leads for collecting electrical signals.

[0060] like Figure 1 As shown, this embodiment provides a non-invasive evaluation method for the eccentricity state of current distribution, comprising the following steps:

[0061] At least one segmented Rogowski coil (SRC) is placed around the DUT, and the output voltage of the segmented Rogowski coil is measured after the DUT is powered on. The equivalent circuit of the segmented Rogowski coil is as follows: Figure 2 As shown, L S , R S and C Sare the parasitic self-inductance, parasitic resistance and parasitic capacitance of SRC respectively. M is the sampling resistor. S_i and v SRC_i are the induced voltage and output voltage of the i-th SRC respectively.

[0062] Optionally, in this step, the number of segmented Rogowski coils is considered and described in different situations:

[0063] When there is only one segmented Rogowski coil, the output voltage measurement process also includes the following steps:

[0064] The segmented Rogowski coil is placed at different positions around the component to be tested for multiple times. The placement position is specifically the side of the component to be tested and is placed at different angles along a fixed circle. After measurement, multiple output voltages are obtained, and then the induced voltage of the segmented Rogowski coil is calculated based on the output voltage and the electrical parameters of the segmented Rogowski coil.

[0065] When there are multiple segmented Rogowski coils, the output voltage measurement process also includes the following steps:

[0066] Place multiple segmented Rogowski coils at different positions for measurement. The placement position is specifically lateral to the component to be measured, and they are placed at different angles along a fixed circle. Afterwards, multiple output voltages are obtained simultaneously or in batches. The induced voltage of the segmented Rogowski coil is then calculated using the output voltage and the electrical parameters of the segmented Rogowski coil. Specifically, in this embodiment, two segmented Rogowski coils are taken as an example for explanation. They are placed lateral to the segmented Rogowski coil and together form an arc. Since the position will affect the measurement result during the specific placement process, in order to increase the measurement accuracy, the sum of the segmented angles Seg of the segmented Rogowski coil is in the range of 180°-225°, and the two segmented Rogowski coils are placed symmetrically, and the center line angle is in the range of 80°-120°. Among them, the sum of the segmented angles Seg is the sum of the arc angles corresponding to the two segmented Rogowski coils, and the center line is the angle formed by the center lines of the two segmented Rogowski coils after the midpoint of the coil is connected to the geometric center of the component to be measured. In this embodiment, reference Figure 3 and Figure 4 As shown; among them, Figure 3 The output voltage measurement results of the two segmented Rogowski coils are obtained. The equivalent mutual inductance of the two coils can be calculated based on the measurement results and the total current of the device. Figure 4 is the intersection of two isolines of mutual inductance, and its vector is the evaluation result of current distribution eccentricity. The preferred design is that the sum of the segment angles of the segmented Rogowski coil is 197°. Figure 5 The mutual inductance M of two SRCs (SRC#1 and SRC#2) with Seg=197° and the busbar at different initial angles α is shown. Bus and central mutual inductance M CenterThe figure shows that when the center line of SRC is placed at an angle of 225° and 315° relative to the busbar, the busbar mutual inductance M Bus Close to 0, the coupling of bus current can be reduced and the sensitivity of SRC can be enhanced. The bus is a connector of crimping type device. Therefore, the two SRCs are placed at 225° and 315° of the center line, and the center line angle is 90°. Figure 6 The figure shows the mutual inductance of the SRC with Seg = 197° to the current of the crimped power electronic device. It can be seen that the minimum to maximum mutual inductance ratio of the selected SRC is 0.34, which balances the mutual inductance change and the sensing distance.

[0067] Optionally, according to the above design, the mutual inductance values ​​of the two SRCs need to be calibrated before the test officially begins.

[0068] The calculation formula used for calibration is:

[0069]

[0070] Where M Device For Figure 6 The calculated mutual inductance, M, is shown Device_Cali is the mutual inductance value after calibration. Calibration coefficient k Cali is determined by a calibration experiment in which a current is passed through the center of a metal module. In this experiment, k Cali Equal to the actual mutual inductance M measured at the center Center Divided by the theoretical mutual inductance M Device (0mm,0°).

[0071] Furthermore, the induced voltage v of the i-th SRC S_i It can be expressed as:

[0072]

[0073] In the formula, J(dS) and M Device_i (dS) are the current density and mutual inductance per unit area of ​​the press-fit power electronic device, and S is the area of ​​the press-fit power electronic device.

[0074] Therefore, in order to solve the induced voltage, the solution process includes: based on the equivalent circuit diagram of the aforementioned segmented Rogowski coil, the transfer function of the output voltage and the induced voltage is obtained according to the equivalent circuit diagram, and the function formula is:

[0075]

[0076] Where s is a complex variable in Laplace transform. The induced voltage is obtained by solving the above transfer function and output voltage.

[0077] Integrate the induced voltage to obtain the intermediate voltage integral. Since the output voltage v of SRC SRC_i It shows a differential characteristic relative to the device current. Therefore, the induced voltage is integrated over time to obtain the intermediate voltage integral v Int_i The formula is:

[0078] v Int_i =∫v S_i dt=∫∫ S M Device_i (dS)J(dS)dS

[0079] Construct a proportional function relationship between the current of the component under test and the integral of the intermediate voltage. Among them, due to the mutual inductance between the SRC and the crimped power electronic device showing the characteristic of "large near and small far", v Int_i It can be effectively used as a ruler to measure current distribution. Based on the above analysis, the equivalent mutual inductance between SRC and the press-fit power electronic device is defined as M Eq_i , and the equivalent mutual inductance is the ratio of the intermediate voltage integral to the current of the component to be measured. Therefore, the formula for the proportional function relationship is:

[0080]

[0081] Where, for each SRC, M Eq_i It can be obtained through experimental measurement and calculation, and the output voltage v SRC_i The current i of the press-fit power electronic device SUM The relationship formula is:

[0082]

[0083] Based on the proportional function relationship, the point information of uneven current distribution in the component to be tested and the corresponding current information are obtained.

[0084] Optionally, the method for obtaining the point information and current information includes:

[0085] Based on the equivalent mutual inductance of the segmented Rogowski coils at different positions, the equivalent points are solved; Figure 3 As shown, SRC#1 and SRC#2 are placed at the aforementioned positions, respectively, according to v SRC_1 , v SRC_2 and i SUM To calculate the equivalent mutual inductance M of the two SRCs Eq_1 and M Eq_2 , find M in the mutual inductance calculation results of SRC#1 and SRC#2 respectively. Eq_1 and M Eq_2 The equivalent value points are thus obtained, whereby the point information includes the position information of the equivalent value points, and the current information includes the current intensity of the component to be measured corresponding to the equivalent value points.

[0086] Based on the above evaluation results, there is a more intuitive evaluation method, that is, the method for solving point information and current information also includes:

[0087] First, define the vector To evaluate the current distribution state in the crimped power electronic device, its amplitude represents the degree of current imbalance in the crimped power electronic device, and its angle indicates the direction of the current imbalance.

[0088] Further, if Figure 3 As shown, draw the mutual inductance diagram of the component to be tested, mark the equivalent mutual inductance contour lines of SRC#1 and SRC#2 in the mutual inductance diagram, and mark the intersection of the equivalent mutual inductance contour lines; the intersection point is the current unbalance point.

[0089] Connect the intersection point with the center point of the mutual inductance diagram to obtain the current distribution eccentricity vector

[0090] In a specific experiment, the experimental waveform of a certain type of crimped power electronic device was obtained through a double pulse test bench. Figure 7 As shown in the figure, the total device current and the output voltage of the two segmented Rogowski coils are shown, where the horizontal axis is time. According to the relationship between the output voltage of the segmented Rogowski coil and the device current, two equivalent mutual inductances can be calculated. Using the corrected mutual inductance, Figure 6 The mutual inductance contours shown are Figure 4 The method shown can obtain the current distribution eccentricity evaluation results. In this experiment, the current distribution evaluation shows that is 41.1∠269.7°, such as Figure 8 As shown. Therefore, the experimental results show that the current in the press-fit power electronic device is unbalanced and mainly flows through the left side of the device. This imbalance may be attributed to the shorter current path of the chip on the left side of the press-fit device, which leads to lower parasitic inductance; the evaluation results are intuitive and accurate, which significantly shortens the fault evaluation time, increases the detection accuracy, and is conducive to the subsequent design and production guidance of the device.

[0091] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A non-invasive evaluation method for the eccentricity of current distribution, characterized in that: The steps include: At least one segmented Rogowski coil is placed around the component to be tested, and the output voltage of the segmented Rogowski coil is measured after the component to be tested is powered on; calculating the induced voltage of the segmented Rogowski coil according to the output voltage and the electrical parameters of the segmented Rogowski coil; Integrating the induced voltage to obtain an intermediate voltage integral; Constructing a proportional function relationship between the current of the component under test and the integral of the intermediate voltage; Based on the proportional function relationship, the point information of the uneven current distribution in the component to be tested and the corresponding current information are obtained.

2. The non-invasive evaluation method for the current distribution eccentricity state according to claim 1, characterized in that: The number of the segmented Rogowski coil is 1; The output voltage measurement process also includes the following steps: The segmented Rogowski coil is placed at different positions for measurement for multiple times, and multiple output voltages are obtained.

3. The non-invasive evaluation method of the current distribution eccentricity state according to claim 1, characterized in that: The number of the segmented Rogowski coils is multiple; The output voltage measurement process also includes the following steps: A plurality of the segmented Rogowski coils are placed at different positions for measurement, and a plurality of the output voltages are obtained simultaneously or in batches.

4. The non-invasive evaluation method of the current distribution eccentricity state according to claim 3, characterized in that: The number of the segmented Rogowski coils is 2, and the sum of the segment angles of the segmented Rogowski coils is in the range of 180°-225°; The two segmented Rogowski coils are symmetrically placed, and the range of the center line angle is 80°-120°.

5. The non-invasive evaluation method of the current distribution eccentricity state according to claim 4, characterized in that: The sum of the segment angles of the segmented Rogowski coil is 197°, and the center line angle is 90°; The placement angles of the center lines of the two segmented Rogowski coils relative to the busbar are 225° and 315° respectively.

6. The non-invasive evaluation method of the current distribution eccentricity state according to claim 1, characterized in that: The process of solving the induced voltage includes: Obtaining an equivalent circuit diagram of the segmented Rogowski coil based on a circuit analysis method; Obtaining a transfer function between the output voltage and the induced voltage according to the equivalent circuit diagram; The induced voltage is obtained by solving the transfer function and the output voltage.

7. The non-invasive evaluation method of the current distribution eccentricity state according to claim 1, characterized in that: The intermediate voltage integral amount calculation method comprises: The induced voltage is time-integrated to obtain the intermediate voltage integral amount.

8. The non-invasive evaluation method of the current distribution eccentricity state according to claim 7, characterized in that: The solution result of the proportional function relationship is the equivalent mutual inductance; The equivalent mutual inductance is the ratio of the integrated value of the intermediate voltage to the current of the element to be measured.

9. The non-invasive evaluation method of the current distribution eccentricity state according to claim 8, characterized in that: The method for solving the point information and the current information includes: Solving the equivalent points based on the equivalent mutual inductance of the segmented Rogowski coils at different positions; The point information includes the position information of the equivalent point; the current information includes the current intensity of the component to be measured corresponding to the equivalent point.

10. The non-invasive evaluation method for the current distribution eccentricity state according to claim 8 or 9, characterized in that: The method for solving the point information and the current information also includes: Draw a mutual inductance diagram of the element to be tested, and mark the equivalent mutual inductance contour lines of the segmented Rogowski coil at different positions in the mutual inductance diagram, and mark the intersection points of multiple equivalent mutual inductance contour lines; Connecting the intersection point with the center point of the mutual inductance diagram to obtain a current distribution eccentricity vector; The point information includes the direction of the current distribution eccentricity vector; the current information includes the amplitude of the current distribution eccentricity vector.

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