Open-loop current inversion method and sensor array

Abstract

The invention discloses an open-loop current inversion method and a sensor array, and relates to the technical field of current measurement. According to the method, a first sensor and a second sensor are orthogonally arranged outside a to-be-detected wire, an array device is moved, sensor output signals and wire current data under different distances are acquired, and a function model of sensitivity, voltage gradient and distance is established. And carrying out inversion operation on the output of the sensor array by using the model. The first sensor and the second sensor are made of magnetoelectric composite materials; the magnetoelectric composite material is formed by compositing a magnetostrictive material and a piezoelectric material through epoxy resin and is cascaded by adopting a multi-layer structure. The magnetoelectric composite material sensor has the advantages of high sensitivity, low power consumption, miniaturization and the like. The open-loop inversion algorithm disclosed by the invention improves the measurement precision and the anti-interference capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current measurement, in particular to an open-loop current inversion method and a sensor array. BACKGROUND

[0002] With the rapid development of power electronics and intelligent control technology, the demand for current measurement is increasingly significant. As a basic physical quantity of the power system, the measurement accuracy and reliability of the current are directly related to the safe and stable operation of the system. Therefore, the accuracy of the current inversion method and the high precision and wide range of the sensor have become a key technical challenge.

[0003] Current current measurement devices are divided into invasive and non-invasive types according to the deployment method. Invasive measurement requires access to the measured circuit when in use, and wiring errors may cause short circuits or equipment damage. Therefore, although invasive measurement has low cost and simple structure, its installation destructiveness and isolation defects make it gradually replaced by non-invasive solutions in modern high-precision and high-safety scenarios. Non-invasive measurement does not require the circuit to be disconnected and mainly includes clamp (clamping) sensors and array sensors. Clamp sensors such as Hall effect, Rogowski coil, and current transformer, etc. mostly use magnetic concentrators to improve the sensitivity and current inversion accuracy of the sensor. In actual measurement, incomplete closure of the clamp or eccentricity of the wire will cause measurement errors, and the magnetic core may easily saturate, limiting the range. Array sensors use multiple sensing units for distributed measurement and combine inversion algorithms to achieve spatial current distribution monitoring. Existing array current sensors still have limitations in inversion methods in terms of dynamic measurement accuracy and adaptability to complex environments, such as complex calculations and poor anti-interference ability. In terms of sensors, miniaturized TMR sensors are mostly used, which have low sensitivity, resulting in the need for a large number of array elements, limited current measurement accuracy and range. In the fields of modern power electronics, intelligent control, and new energy, the requirements for high precision, wide range, small size, and low power consumption of current measurement are increasingly stringent, and traditional current sensors often face bottlenecks in meeting these requirements, especially in maintaining high precision while covering a wide range.

[0004] Compared with other types of current sensors, magnetoelectric current sensors have the advantages of passive low power consumption, ultra-high sensitivity, and wide dynamic range. Therefore, it is of great engineering significance to develop an open-loop current inversion method based on a magnetoelectric sensor array. SUMMARY

[0005] The technical problem solved by the present application is: in view of the limitations of the existing array current sensor in the current inversion method, and the deficiencies of the sensor array in high precision, wide range, small size and low power consumption, especially in non-intrusive measurement, low sensitivity, poor anti-interference ability, large measurement error and limited range, etc. A kind of open loop current inversion method based on magneto-electric sensor array is proposed, which effectively solves the above problems and realizes high precision, wide range, non-contact and reliable measurement of current in power system and other occasions.

[0006] In order to achieve the above purpose, the present application is realized by adopting the following technical scheme: the method comprises:

[0007] Step 1, the first sensor is vertically placed outside the measured wire, that is, the sensitive axis direction of the sensor is perpendicular to the wire, the second sensor is parallel to the first sensor, and the distance is the baseline length of the array; The sensor array and the axial direction of the current-carrying wire are in orthogonal geometric relationship;

[0008] Step 2, keep the posture of the first sensor and the second sensor (i.e. two-element sensor) stable, measure the distance R from the center of the wire to the center of the first sensor in the current state, and synchronously collect the output signals of the first sensor and the second sensor, and the current value of the wire at this time;

[0009] Step 3, move the two-element sensor device in the direction away from the wire and ensure the vertical orthogonal relationship in step 1, move a certain distance, repeat step 2 to record the distance R, the output signal of the two-element sensor device and the current value of the wire again;

[0010] Repeat the process of step 1-step 2 to obtain a data set that meets the processing condition;

[0011] Step 4, process and fit the data set obtained in step 3 to obtain the sensitivity-distance and voltage gradient function, and complete the calibration process;

[0012] Step 5, place the non-intrusive current sensor based on magneto-electric composite material in the distribution state of step 1 within the effective distance in the data set obtained in step 3, that is, any value between the maximum and minimum values of R in the data set, according to the fitting function obtained in step 4, the measured current value I is obtained by searching algorithm iteration mv The measurement result is displayed through the upper computer.

[0013] In one scheme, the step 4 comprises:

[0014] Step 401, according to the above step 3, the distance R is obtained each time;

[0015] Specifically, the instantaneous current of the lead is I, the magnetic induction intensity of the ring magnetic field excited at the distance R is calculated according to the Biot-Savart law, and the magnetic induction intensity at the center of the first sensor body and the second sensor at the distance R is obtained.

[0016] According to step 401, the magnetic induction intensity gradient under unit current at the distance R is calculated as:

[0017]

[0018] Where B1 is the magnetic induction intensity at the center of the first sensor body at the distance R, and B2 is the magnetic induction intensity at the center of the second sensor body at the distance R, and the magnetic induction intensity gradient under unit current is also a function of R as the independent variable.

[0019] The output signal of the non-intrusive current measurement device of the sensor is a voltage signal, and the magnetic induction intensity gradient under unit current The output voltage gradient under unit current differs by a sensitivity coefficient S, which is simple and efficient in data acquisition process, and the output voltage gradient The function is used for current calculation:

[0020]

[0021] Step 402, according to a series of distances R obtained in step 3, repeat step 401 to obtain the sensitivity function with R as the independent variable.

[0022] Step 403, according to the above step 3, the output voltage values of the first sensor and the second sensor at the distance R are obtained, the output voltage difference value is compared with the current and the baseline distance, and the voltage gradient under unit current is calculated, and the voltage gradient function with distance R as the independent variable is obtained by moving the distance R each time.

[0023] In one scheme, the step 5 comprises:

[0024] Step 501, initialize the distance R;

[0025] Step 502, according to the output voltage gradient Function, the inversion current value I3 is calculated;

[0026] Step 503, the sensitivity S1 of the first sensor and the sensitivity S2 of the second sensor corresponding to the distance R are calculated;

[0027] Step 504, according to the sensitivity S1 and the sensitivity S2 obtained in step 503, the measured current I1 obtained by the first sensor and the measured current I2 obtained by the second sensor are calculated respectively according to the Biot-Savart law.

[0028] Step 505, the difference between I1 and I2 is calculated, if the difference is greater than the maximum current error allowed, return to step 502 to recalculate, if the current error meets the requirements, output the current I mv .

[0029] In still another aspect, a sensor array suitable for the open-loop current inversion method, the sensor array comprising: a first sensor and a second sensor;

[0030] The first sensor and the second sensor are both single-axis sensors and the sensitive axis directions are kept parallel, forming a two-element array;

[0031] The first sensor is symmetrically placed vertically outside the measured wire, that is, the sensitive axis direction of the sensor is perpendicular to the wire, and the spatial position of the second sensor forms a spatial baseline with the first sensor, which is in orthogonal geometric relationship with the axial direction of the current-carrying wire;

[0032] The baseline distance d of the first sensor and the second sensor is fixed and unchanged.

[0033] In one scheme, the first sensor and the second sensor are composed of a magnetoelectric composite material;

[0034] The magnetoelectric composite material is composed of magnetostrictive material and piezoelectric material by epoxy resin compounding, and adopts a multilayer structure for cascade connection;

[0035] The piezoelectric material in the magnetoelectric composite material is one of piezoelectric ceramic, piezoelectric single crystal, piezoelectric polymer and piezoelectric macroscopic fiber composite material;

[0036] The magnetostrictive material in the magnetoelectric composite material is a soft magnetic alloy, including one of Metglas, Fe-Ga alloy, Terfernol alloy and metal Ni.

[0037] The present application has the following advantages:

[0038] The non-invasive current sensor based on the magnetoelectric composite material and the current inversion method according to the present application can realize high-precision current measurement by only ensuring that the sensor is placed near the wire in the above-mentioned vertical orthogonal relationship when measuring the current. The present application has low sensitivity to installation distance, reduces the influence of different diameter wires on measurement results, eliminates common mode noise through gradient calculation, greatly improves system stability, has low calculation complexity, and can realize high-precision current measurement in a non-contact situation. BRIEF DESCRIPTION OF DRAWINGS

[0039] The accompanying drawings, which constitute a part of this specification, are included to provide a further understanding of the present application, and are incorporated herein by reference. These drawings merely

[0040] Figure 1 is a schematic diagram of a current-carrying wire measured by the open-loop current sensor based on magnetoelectric composite material according to the present application;

[0041] Figure 2 is a flow chart of the current inversion method of the open-loop current sensor based on magnetoelectric composite material according to the present application.

[0042] In the figure: sensor 1 - first sensor, sensor 2 - second sensor. DETAILED DESCRIPTION

[0043] For the purpose of promoting an understanding of the principles of the application, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the application is thereby intended, such alterations and further modifications in the illustrated device being contemplated as falling within the scope of the application. It is to be understood that the application is not limited to the specific devices illustrated herein, but encompasses any and all devices which can possibly be developed from or through the concepts herein taught, and lies in the appropriate combination of form, function and concept.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for describing particular embodiments only and is not intended to be limiting of the application. For the purpose of promoting an understanding of the principles of the application, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the application is thereby intended, such alterations and further modifications in the illustrated device being contemplated as falling within the scope of the application. It is to be understood that the application is not limited to the specific devices illustrated herein, but encompasses any and all devices which can possibly be developed from or through the concepts herein taught, and lies in the appropriate combination of form, function and concept.

[0045] The present application is directed to the problems of the prior art that the installation of current sensor is complex, the flexibility is not high, the open-loop array current sensor measurement is greatly affected by distance, etc., and provides an open-loop current sensor based on magnetoelectric composite material and a current inversion method.

[0046] Embodiment one

[0047] As Figure 1As shown, the embodiment of the present application provides an open-loop current sensor based on a magneto-electric composite material. The magnetostrictive material used in the magneto-electric composite material is made of Metglas, the size of the Metglas strip used is 40mmx2mmx0.125mm, 5 layers of Metglas strip are bonded together to form a single magnetostrictive laminate, and the size of the piezoelectric single crystal lead-lead magnesium lead titanate used is 40mmx2mmx0.4mm. The composite structure adopts a laminated configuration in which the magnetostrictive layer (Metglas laminate) and the piezoelectric single crystal layer are alternately stacked, and is bonded into a three-layer magneto-electric composite structure by epoxy resin glue. The non-intrusive current sensor based on the magneto-electric composite material comprises: a sensor 1 (first sensor) and a sensor 2 (second sensor). The sensor 1 and the sensor 2 are both made of the above-mentioned magneto-electric composite material, wherein the optimal bias magnetic field of the magnetostrictive material is provided by a pair of neodymium-iron-boron permanent magnets. The sensor 1 and the sensor 2 are both single-axis sensors and the sensitive axis directions are kept parallel, forming a two-element array form.

[0048] The baseline distance d of the sensor 1 and the sensor 2 has a great influence on the performance of the current sensor device: first, considering that the volume of the two-element current sensor array should be as small as possible to make the calculation more consistent with the infinite straight wire in theory, so the baseline distance d cannot be too large; second, considering the sensitivity of the sensitive axis direction of the sensor 1 and the sensor 2, if the baseline distance d is too small, when calculating the magnetic induction gradient, the gradient value may be overwhelmed by noise, which cannot accurately reflect the real magnetic field change, thereby reducing the measurement resolution and reliability. In summary, the embodiment of the present application sets d to 15mm and keeps it unchanged.

[0049] The signals output by the sensors can be used to achieve high-precision measurement of the current, such as Figure 1 As shown, the sensor 1 is symmetrically placed vertically outside the measured wire, that is, the sensitive axis direction of the sensor is perpendicular to the wire, and the spatial position of the sensor 2 and the sensor 1 constitutes a spatial baseline, which is in orthogonal geometric relationship with the axial direction of the current-carrying wire (∠α=90°±Δα, Δα≤1°).

[0050] Embodiment two:

[0051] The embodiment of the present application also provides a current inversion method of an open-loop current sensor based on a magneto-electric composite material, comprising:

[0052] Step 1, the first sensor is symmetrically placed vertically outside the measured wire, that is, the sensitive axis direction of the sensor is perpendicular to the wire, and the second sensor is parallel to the first sensor with a spacing of the baseline length of the array. The sensor array and the axial direction of the current-carrying wire are in orthogonal geometric relationship (∠α=90°±Δα, Δα≤1°).

[0053] Step 2, under the vertical orthogonal relationship described in step 1, measure the shortest distance R from the center line of the conductor to the center line of the sensor 1, the above-mentioned sensor center line is a straight line parallel to its longest edge and intersecting the center lines of the width and height directions at the geometric center in the cross section, and simultaneously collect the output signals of the sensor 1 and the sensor 2, and the current value of the conductor at this time.

[0054] Step 3, move the two-element current sensor device in a direction away from the conductor and ensure the vertical orthogonal relationship described in step 1, move a certain distance, repeat the above-mentioned step 2 to record the distance R, the output signals of the two-element current sensor device and the current value of the conductor again. Repeat the above process to obtain a data set that meets the processing conditions.

[0055] Step 4, process the data set obtained in step 3 to obtain the sensitivity_distance function and the voltage gradient function.

[0056] The step 4 specifically comprises a sensitivity_distance function and a voltage gradient function fitting process: step 401, according to the distance R obtained by moving each time in the above-mentioned step 3, let the instantaneous current of the conductor be I, according to the Biot-Savart law, the magnetic induction intensity of the annular magnetic field excited at the distance R, that is, the magnetic induction intensity at the center of the first sensor body, is:

[0057]

[0058] The magnetic induction intensity of the annular magnetic field excited by the instantaneous current of the conductor at the distance R+d, that is, the magnetic induction intensity at the center of the second sensor body, is:

[0059]

[0060] Where μ0 is the magnetic permeability of vacuum;

[0061] The sensitivities of the first sensor and the second sensor at the distance R can be calculated by the formula:

[0062]

[0063] Where V1 represents the output voltage signal of the first sensor, V2 represents the output voltage signal of the second sensor, S1 represents the calculated sensitivity of the first sensor, and S2 represents the calculated sensitivity of the second sensor;

[0064] Step 402, according to the above-mentioned step 3, a series of distances R can be obtained, and the above-mentioned step 401 can be repeated to obtain a sensitivity function (S_R function) with R as the independent variable:

[0065]

[0066] Wherein f1 is the fitting function of the first sensor sensitivity-distance curve, f2 is the fitting function of the second sensor sensitivity-distance curve;

[0067] Step 403, according to the above step 401, the magnetic induction intensity gradient under unit current at distance R is calculated as:

[0068]

[0069] Wherein B1 is the magnetic induction intensity at the first sensor body center at distance R, B2 is the magnetic induction intensity at the second sensor body center at distance R, the magnetic induction intensity gradient under unit current is also a function of R, since the output signal of the above-mentioned non-intrusive current measurement device based on two-element magneto-electric sensor is a voltage signal, and the magnetic induction intensity gradient under unit current The output voltage gradient under unit current Difference by a sensitivity coefficient S, so in practical application, in order to obtain data process relatively simple and efficient, the output voltage gradient Function is used for current calculation:

[0070]

[0071] Step 5, the non-intrusive current sensor based on magneto-electric composite material is placed in the data set at distance R obtained in the above step 3, that is, any value between the maximum and minimum value of R in the data set, according to the fitting function obtained in step 4, the measured current value is obtained by searching algorithm iteration, and the measurement result is displayed through the upper computer.

[0072] The searching algorithm in the step 5 specifically includes:

[0073] Step 501, initializing distance R;

[0074] Step 502, according to the above Function, the inversion current value I3 is calculated;

[0075] Step 503, according to the above S_R function, the sensitivity S1 of the first sensor corresponding to the distance R at this time is calculated, and the sensitivity S2 of the second sensor is calculated;

[0076] Step 504, according to the sensitivity S1 and the sensitivity S2 obtained in step 503, the measured current I1 obtained by the first sensor and the measured current I2 obtained by the second sensor are calculated through the Biot-Savart law respectively;

[0077] Step 505, the difference between I1 and I2 is calculated, if the difference is greater than the maximum current error allowed, R = R + AR (AR is the preset increment of R of each iteration) is returned to the above-mentioned step 502 to recalculate, if the current error meets the requirement, the current I at this time is output mv :

[0078] I mv =(I1+I2+I3) / 3 (7).

[0079] The non-intrusive current sensor based on the magnetoelectric composite material and the current inversion method described in the above embodiment of the application, the baseline distance d of the sensor is 15 mm, the energized current is a series of values of about 10A-200A, the measurement accuracy of the non-intrusive current sensor based on the magnetoelectric composite material and the current inversion method is tested through experiments, the given current true value I is calibrated by Micsig alternating current probe ACP1000, and the measurement results are shown in Table 1:

[0080] Table 1 Sensor current measurement error

[0081] Experimental group Current true value I (A) Indication I mv (A) Relative error (%) 1 14.8014 14.7832 0.12 2 24.1119 24.2508 0.75 3 77.9658 77.675 0.14 4 109.22 108.587 0.58 5 232.76 231.307 0.89

[0082] Embodiment three:

[0083] Based on the inversion method proposed in embodiment one, the current measurement in double return conductors and three-phase cables is carried out.

[0084] In the scene of double return conductors or three-phase cables and the like, through reasonable arrangement of the sensor array and in combination with the distribution characteristics of the spatially superposed magnetic field, the inversion algorithm of embodiment one can be referred to for multivariate fitting and separation processing of the sensor array output signals, and independent inversion measurement of the current in each conductor can be realized. The method effectively improves the high-precision, wide-range, non-contact and reliable measurement under a multi-loop and three-phase system.

[0085] The non-intrusive current sensor based on the magnetoelectric composite material and the current inversion method described in the above embodiment of the application can realize open-loop non-intrusive high-precision current measurement in the case of unknown target conductor distance, the sensor has small volume, the measurement method is simple and convenient, the application has low sensitivity to installation distance, and at the same time, the influence of different diameter conductors on the measurement result is reduced, the common mode noise is eliminated through gradient calculation, and the system stability is greatly improved.

[0086] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing relevant hardware, and the program can be stored in a computer readable storage medium. When the program is executed, the program can include the processes of the above-mentioned embodiment methods. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM) or a random access memory (RAM), etc.

[0087] It should be understood that the above detailed description of the technical solutions of the present application by means of the preferred embodiments is illustrative rather than limiting. Those skilled in the art can modify the technical solutions recorded in each embodiment or make equivalent replacement for part of the technical features on the basis of the description of the present application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present application.

Claims

1. An open-loop current inversion method, characterized in that: The method includes: Step 1: Place the first sensor vertically outside the conductor to be tested, i.e., the sensor's sensitive axis is perpendicular to the conductor. The second sensor is parallel to the first sensor, and the distance between them is the baseline length of the array. The sensor array is orthogonal to the axial direction of the current-carrying conductor. Step 2: Keep the first sensor and the second sensor (i.e., the two-element sensor) in stable attitude, measure the distance R from the center of the conductor to the center of the first sensor in the current state, and simultaneously collect the output signals of the first sensor and the second sensor, as well as the current value of the conductor at this time. Step 3: Move the two-element sensor device away from the wire while maintaining the perpendicular orthogonal relationship of Step 1. Move it a certain distance, repeat Step 2, and record the distance R, the output signal of the two-element sensor device, and the wire current value again. Repeat steps 1-2 to obtain a dataset that meets the processing conditions; Step 4: Process the dataset obtained in Step 3, fit the sensitivity-distance and voltage gradient functions to complete the calibration process; Step 5: Place the non-invasive current sensor based on magnetoelectric composite material within the effective distance of the dataset obtained in Step 3, i.e., any value between the maximum and minimum values ​​of R in the dataset, according to the distribution state obtained in Step 1. Then, based on the fitting function obtained in Step 4, iteratively obtain the measured current value I through a search algorithm. mv The measurement results are displayed on the host computer.

2. The open-loop current inversion method according to claim 1, characterized in that: Step 4 includes: Step 401: Based on step 3 above, obtain the distance R for each movement; Specifically: Let the instantaneous current of the conductor be I, calculate the magnetic induction intensity of the ring magnetic field excited at a distance R according to the Biot-Savart law, and obtain the magnitude of the magnetic induction intensity at the center of the first sensor body and the second sensor at a distance R; Step 402: Based on the series of distances R obtained in step 3, repeat step 401 to obtain the sensitivity function with R as the independent variable; Step 403: Based on step 3 above, obtain the output voltage values ​​of the first sensor and the second sensor at a distance R. Compare the output voltage difference with the current and the baseline distance to calculate the voltage gradient under unit current. Each time the distance R is moved, obtain the voltage gradient function with distance R as the independent variable. According to step 401, the magnetic flux density gradient at a distance R under a unit current is calculated as follows: Where B1 is the magnitude of the magnetic induction intensity at the center of the first sensor body at a distance of R, and B2 is the magnitude of the magnetic induction intensity at the center of the second sensor body at a distance of R. The magnetic induction intensity gradient under unit current is also a function with R as the independent variable. The sensor's non-invasive current measurement device outputs a voltage signal, and the magnetic flux density gradient per unit current is... Output voltage gradient under unit current The difference is a sensitivity coefficient S. To simplify and improve the data acquisition process, the output voltage gradient is used. Functions for current calculation:

3. The open-loop current inversion method according to claim 1, characterized in that: Step 5 includes: Step 501, initialize distance R; Step 502, based on the output voltage gradient The function is used to calculate the inversion current value I3; Step 503: Calculate the sensitivity S1 of the first sensor and the sensitivity S2 of the second sensor corresponding to the distance R. Step 504: Based on the sensitivity S1 and sensitivity S2 obtained in step 503, calculate the measured current I1 obtained by the first sensor and the measured current I2 obtained by the second sensor respectively using the Biot-Savart law. Step 505: Calculate the difference between I1 and I2. If the difference is greater than the maximum allowable current error, return to step 502 above to recalculate. If the current error meets the requirements, output the current I at this time. mv .

4. A sensor array, said sensor array being applicable to the open-loop current inversion method according to any one of claims 1-3, characterized in that: The sensor array includes: a first sensor and a second sensor; Both the first and second sensors are single-axis sensors and their sensitive axis directions are parallel, forming a two-element array. The first sensor is placed vertically and symmetrically outside the conductor to be tested, that is, the sensitive axis of the sensor is perpendicular to the conductor. The spatial position of the second sensor and the spatial baseline formed by the first sensor are orthogonal to the axial direction of the current-carrying conductor. The baseline distance d between the first sensor and the second sensor remains constant.

5. A sensor array according to claim 4, characterized in that: The first and second sensors are made of magnetoelectric composite materials; The magnetoelectric composite material is made of magnetostrictive material and piezoelectric material through epoxy resin, and adopts a multi-layer structure for cascading. The piezoelectric material in the aforementioned magnetoelectric composite material is one of piezoelectric ceramics, piezoelectric single crystals, piezoelectric polymers, and piezoelectric macroscopic fiber composite materials; The magnetostrictive material in the aforementioned magnetoelectric composite material is a soft magnetic alloy, including one of Metglas, Fe-Ga alloy, Terfernol alloy, and metallic Ni.

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