Broadband combined current transformer and broadband current measurement method

Abstract

The application discloses a wide-band combined current transformer and a wide-band current measurement method, and the wide-band combined current transformer comprises a traditional current transformer and a single magnetic resistance single-axis magnetic field sensor; wherein the magnetic resistance single-axis magnetic field sensor is arranged at a relatively fixed position outside the traditional current transformer; the gain change of the magnetic resistance single-axis magnetic field sensor is corrected in real time through the current measurement value of the traditional current transformer at a low frequency band, and a wide-band current signal is measured and acquired. The gain of the magnetic resistance single-axis magnetic field sensor is corrected in real time through the accurate value of the CT at a low frequency, the linear relationship between the magnetic field and the current is utilized, and the core defects of the insufficient high-frequency response of the CT and the position sensitivity of the MR are effectively overcome. The single magnetic resistance sensor is fused with the CT, an array or a special iron core is not needed, the cost and the complexity are significantly reduced, the gain adaptive correction is realized by using a microcontroller, the target conductor can be arbitrarily offset, and the wide-band high-precision measurement capability with strong robustness is achieved.

Description

Technical Field

[0001] This application relates to the fields of power electronics and sensor technology, specifically to a broadband combined current transformer and a broadband current measurement method. Background Technology

[0002] Existing current measurement technologies mainly include various types such as traditional current transformers (CTs) and magnetic field sensors. Traditional current transformers use an iron core structure and measure alternating current through the principle of electromagnetic induction. They have the advantages of low cost and high accuracy in the low-frequency range (50Hz / 60Hz power frequency). However, due to the hysteresis loss and eddy current effect of the iron core, their high-frequency response is limited, and they cannot effectively capture transient signals in the kHz to MHz range, leading to signal attenuation and distortion, which limits their application in high-voltage power grid fault diagnosis. In addition, CTs in high-frequency applications also face increased core losses, non-uniform frequency response, enhanced skin effect, parasitic capacitance and inductive interference, and saturation problems. These factors further limit their reliability in broadband measurements. For example, in high-frequency environments, the iron core material of the CT (such as silicon steel) will heat up due to eddy current losses, leading to a decrease in efficiency. For frequencies above 400Hz, special materials such as amorphous steel are required, which increases cost and complexity. The bandwidth limitation of CT also stems from its low-frequency response lower limit, making it difficult to accurately measure DC or extremely low-frequency signals. Furthermore, in large CT scanners, low permeability increases magnetic flux leakage at high frequencies. Overall, these limitations render CT inadequate for modern high-frequency applications such as new energy equipment or motor drive systems, failing to meet the real-time capture requirements of transient currents.

[0003] On the other hand, magnetic field sensors based on the high-performance magnetoresistive (MR) effect can directly measure magnetic field strength, thereby indirectly calculating current, and have advantages such as wide bandwidth (DC to MHz level), fast response, and low power consumption. In particular, tunnel magnetoresistive (TMR) sensors, with their high sensitivity (magnetoresistivity exceeding 100%), low power consumption (microampere-level current only), and excellent thermal stability, significantly improve measurement accuracy in applications. [5] Compared to other magnetoresistive technologies such as anisotropic magnetoresistive (AMR) or giant magnetoresistive (GMR) sensors, TMR offers higher accuracy and the ability to detect weak magnetic fields, making it suitable for non-contact current measurement. Its advantages also include small package size, temperature stability (drift less than 40 ppm / °C), and high signal-to-noise ratio (resolution up to 5 mA), making it an ideal replacement for traditional shunt resistors in power electronics. However, a single magnetoresistive uniaxial magnetic field sensor is sensitive to the relative distance and orientation of the target conductor. If the position is offset or the angle deviates, the measurement gain changes significantly, leading to a sharp drop in accuracy. Therefore, in current measurement, multiple magnetoresistive uniaxial magnetic field sensor arrays are typically used for compensation, such as circular magnetic field sensor arrays or linear sensor arrays for multiple target conductors, but this significantly increases cost and design complexity.

[0004] Several hybrid current sensor solutions exist in the current field, aiming to combine the advantages of different sensing technologies. For example, some solutions combine CT scanners with miniature fluxgate sensors to achieve broadband measurements. However, this approach uses two fluxgate sensors fabricated into a clamp-on probe to ensure a stable spatial relationship between the target circuit and the magnetic field sensor, resulting in a large size, heavy weight, and complex installation. Another solution uses a split-core magnetoelectric sensor with a wireless measurement system of the CT scanner, but this system has a narrow measurement bandwidth, making it unable to effectively measure high-frequency current signals.

[10] Furthermore, one paper proposed using a hybrid approach of a magnetoresistive uniaxial magnetic field sensor and a current transformer to extend bandwidth, but this approach still has the following significant problems:

[0005] 1. This solution requires a special iron core, and the magnetoresistive uniaxial magnetic field sensor is fixed at the notch of the iron core, which greatly increases the difficulty of technical implementation and versatility;

[0006] 2. In this scheme, the magnetoresistive single-axis magnetic field sensor and the analog signal processing circuit of the CT are connected in hardware to achieve signal fusion, and the magnetic field measurement value of the TMR is not compensated. Therefore, when the position and angle of the target line are offset and changed, the fused current measurement signal is less accurate than the low-frequency current value measured by the CT alone.

[0007] In summary, although some technical solutions attempt to combine magnetic field sensors, such as magnetoresistive single-axis magnetic field sensors and fluxgate sensors, with traditional current transformers to expand the measurement bandwidth, these sensors either require specially made notched iron cores and fix the sensor at the notch for measurement, or require complex fixing methods to ensure that the relative position between the target current and the sensor remains unchanged, or require the use of a large number of magnetic field sensors to reduce the impact of changes in the spatial position of the target line on the measurement results. Summary of the Invention

[0008] The technical problems to be solved by this application are: the insufficient high-frequency response of traditional current transformers, which makes it impossible to capture transient signals in the kHz to MHz range; and the technical bottlenecks of gain drift caused by position and angle offset of a single magnetoresistive single-axis magnetic field sensor, which requires compensation by multiple sensor arrays, increasing cost and complexity. The purpose is to provide a broadband combined current transformer that solves the problems of high-frequency signal attenuation and distortion and sensor position sensitivity by fusing the low-frequency accurate measurement value of traditional current transformer with the broadband signal of a single magnetoresistive single-axis magnetic field sensor and dynamically correcting the MR gain in real time based on the value of traditional current transformer.

[0009] This application is achieved through the following technical solution:

[0010] In a first aspect, this application provides a broadband combined current transformer, comprising:

[0011] Traditional current transformers and single magnetoresistive single-axis magnetic field sensors;

[0012] The magnetoresistive single-axis magnetic field sensor is disposed at a relatively fixed position outside the conventional current transformer;

[0013] The broadband combined current transformer is configured to correct the gain change of the magnetoresistive single-axis magnetic field sensor in real time by using the current measurement value of the conventional current transformer in the low-frequency band, and to measure and acquire the broadband current signal.

[0014] A further optimization is that the magnetic field sensing direction of the magnetoresistive uniaxial magnetic field sensor is configured to be perpendicular to the direction of the magnetic field lines generated by the conductor under test.

[0015] A further optimization involves real-time correction of the gain variation of the magnetoresistive uniaxial magnetic field sensor, including calculating the dynamic gain coefficient. It satisfies:

[0016]

[0017] in, The target current value is measured independently by a traditional current transformer. This is the output voltage of the magnetoresistive single-axis magnetic field sensor.

[0018] A further optimization scheme is as follows: and This is the root mean square value calculated within a preset time window.

[0019] A further optimized solution is that the traditional current transformer has a toroidal iron core structure; the magnetoresistive single-axis magnetic field sensor has a sensitivity greater than 1mV / Gauss and a bandwidth greater than 10MHz.

[0020] A further optimization scheme includes a microcontroller configured to receive and process signals from the conventional current transformer and the magnetoresistive single-axis magnetic field sensor, and output a wideband current signal.

[0021] A further optimization is that the microcontroller outputs the wideband current signal in one of the following ways:

[0022] Measurement values ​​of traditional current transformers And the measured values ​​of the magnetoresistive single-axis magnetic field sensor after gain correction Perform a weighted average and output the wideband current signal;

[0023] Directly outputs the measured value of the magnetoresistive single-axis magnetic field sensor after gain correction;

[0024] Frequency domain decomposition was performed on the measured values ​​of the magnetoresistive uniaxial magnetic field sensor, and the low-frequency components were replaced with... Replace the high-frequency component with Then, the signal is reconstructed to form a broadband current signal.

[0025] A further optimization scheme includes a mode switching module, which is configured to switch between pure CT measurement mode and CT-MR fusion measurement mode.

[0026] Secondly, this application provides a broadband current measurement method, applied to a broadband combined current transformer as described in any one of claims 1-8, characterized in that the method includes the following steps:

[0027] The low-frequency measurement value of the target current is obtained through the conventional current transformer. ;

[0028] The output voltage is obtained through the magnetoresistive uniaxial magnetic field sensor. ;

[0029] based on and Calculate the dynamic gain coefficient used to correct the gain of the magnetoresistive uniaxial magnetic field sensor;

[0030] The measured value of the magnetoresistive single-axis magnetic field sensor in the high-frequency band is corrected based on the dynamic gain coefficient to obtain the corrected high-frequency current value.

[0031] By combining the low-frequency measurement value with the corrected high-frequency current value, a wideband current measurement result is output.

[0032] Thirdly, this application provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a broadband combined current transformer program, wherein when the broadband combined current transformer program is executed by a processor, it implements the steps of the broadband combined current transformer as described above.

[0033] Compared with the prior art, this application has the following advantages and beneficial effects:

[0034] By using the real-time correction of MR gain with accurate low-frequency CT values, the linear physical relationship between the magnetic field around the current and the target current is fully utilized, thus solving the inherent defects of insufficient high-frequency response of CT and position sensitivity of MR.

[0035] Using only a single magnetoresistive uniaxial magnetic field sensor, without the need for multi-chip arrays or special iron cores, significantly reduces cost and design complexity;

[0036] The magnetoresistive single-axis magnetic field sensor can be structurally separated from the traditional current transformer without the need for a specially made notched magnetic core, which greatly reduces the difficulty of hardware design.

[0037] It allows arbitrary shifts in the position and angle of the target current, improving the robustness and versatility of the system;

[0038] The signal fusion logic is simple and efficient, can be implemented with a microcontroller, and is suitable for a variety of practical scenarios, improving measurement accuracy and bandwidth performance. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the exemplary embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0040] Figure 1 A schematic diagram of a broadband combined current transformer structure provided in an embodiment of this application;

[0041] Figure 2 This is a measurement diagram illustrating the situation where both the position and angle of the target current shift as provided in an embodiment of this application.

[0042] Figure 3 This is an illustration of the measurement results when the distance increases by 20% in the harmonic interference scenario of Example 1;

[0043] Figure 4 This is an illustration of the measurement results under the harmonic interference scenario in Example 1, with an angle offset of 15°.

[0044] Figure 5 This is an illustration of the measurement results in Example 1 when the distance increases by 20% and the angle shifts by 15° under the harmonic interference scenario;

[0045] Figure 6 This is an illustration of the measurement results when the distance increases by 20% in the short-circuit transient scenario of Example 2;

[0046] Figure 7 This is an illustration of the measurement results under the short-circuit transient scenario in Example 2, when the angle shift is 15°.

[0047] Figure 8 This is an illustration of the measurement results in Example 2 when the distance increases by 20% and the angle shifts by 15° under the short-circuit transient scenario; Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0049] First, some of the technical terms used in this application will be explained to help those skilled in the art understand this application.

[0050] CT: Current Transformer;

[0051] MR: MagnetoResistive;

[0052] MCU: Microcontroller Unit;

[0053] RMS: Root Mean Square;

[0054] DC: Direct Current.

[0055] Firstly, such as Figure 1 As shown, this application provides a broadband combined current transformer, comprising:

[0056] The traditional current transformer 10 and a single magnetoresistive uniaxial magnetic field sensor 20 are used. The traditional current transformer is a current measuring device based on the principle of electromagnetic induction. It adopts an iron core structure and is mainly used for measuring alternating current. It has the advantages of high accuracy and low cost in the low frequency range (such as 50Hz / 60Hz power frequency), but its high frequency response is limited due to hysteresis loss and eddy current effect. The magnetoresistive uniaxial magnetic field sensor 20 is only sensitive to the magnetic field component in a single direction. This characteristic is the basis of its measurement principle and subsequent gain correction algorithm. Using only a single magnetoresistive uniaxial magnetic field sensor 20 eliminates the need for multiple arrays or special iron cores, significantly reducing cost and design complexity.

[0057] The magnetoresistive single-axis magnetic field sensor 20 is located at a relatively fixed position outside the conventional current transformer 10, ensuring structural separation without the need for a special iron core or complex fixing device.

[0058] The broadband combined current transformer is configured to correct the gain change of the magnetoresistive single-axis magnetic field sensor 20 in real time by using the current measurement value of the conventional current transformer 10 in the low-frequency band, and to measure and acquire broadband current signals in order to accurately capture low-frequency and high-frequency current signals.

[0059] The broadband combined current transformer provided in this application achieves accurate capture of low-frequency (<1kHz) and high-frequency (>1kHz) current signals by combining the signal fusion of a traditional current transformer 10 and a single high-performance magnetoresistive single-axis magnetic field sensor 20, based on the linear physical relationship between the magnetic field surrounding the current and the target current (Biosavart's law). Its core lies in using the accurate measurement value of the traditional current transformer 10 in the low-frequency band to correct the gain change of the magnetoresistive single-axis magnetic field sensor 20 in real time, thereby overcoming the shortcomings of insufficient high-frequency response of the traditional current transformer 10 and the position / angle sensitivity of the high-performance magnetoresistive single-axis magnetic field sensor 20.

[0060] In one embodiment, the magnetic field sensing direction of the magnetoresistive uniaxial magnetic field sensor 20 is configured to be as perpendicular as possible to the direction of the magnetic field lines generated by the conductor under test, and the sensing axis direction of the magnetoresistive uniaxial magnetic field sensor 20 is configured to be parallel to the direction of the magnetic field generated by the conductor under test (i.e., the tangential direction of the magnetic field lines) to minimize the influence of position and angular offset on the measurement.

[0061] In one embodiment, a conventional current transformer uses a toroidal core structure and measures current through electromagnetic induction, primarily responsible for accurate measurement in the low-frequency band.

[0062] In one embodiment, a magnetoresistive uniaxial magnetic field sensor is placed outside the conventional current transformer, within 10 mm of the target conductor, with its direction as perpendicular as possible to the magnetic field lines. This sensor senses the magnetic field strength generated by the target conductor passing through the interior of the conventional current transformer. Its bandwidth covers DC (i.e., lower limit 0 Hz) to 10 MHz, suitable for high-frequency signal capture. The sensitivity of the magnetoresistive uniaxial magnetic field sensor is greater than 1 mV / Gauss, and its bandwidth is greater than 10 MHz. The uniaxial magnetoresistive uniaxial magnetic field sensor is fixed to a relatively fixed position outside the conventional current transformer via a support structure or clips, ensuring a fixed relative position between the individual magnetoresistive uniaxial magnetic field sensor and the conventional current transformer.

[0063] The output voltage of the magnetoresistive uniaxial magnetic field sensor 20 in this application is... With target current The relationship is based on Biot-Savart's law. At the sensor location (distance) ) or angle ( When the angle between the sensitive direction of the MR magnetic field and the direction of the magnetic field deviates, the measurement diagram is as follows: Figure 2As shown. If the gain of the reluctance uniaxial magnetic field sensor 20 is not corrected, the current value calculated using a fixed gain will have a very large measurement error. However, since the traditional current transformer 10 uses a closed iron core to completely surround the target current for measurement, its measurement result will not have a significant error. At this point, the data fusion of the reluctance uniaxial magnetic field sensor 20 and the traditional current transformer 10 will actually significantly reduce the measurement accuracy of the CT. According to Biot-Savart's law, it can be analyzed that even if the position and angle of the target current shift, at this time... Still with the target current The relationship is linear, and its theoretical derivation is as follows:

[0064]

[0065] in, The output voltage of the magnetoresistive uniaxial magnetic field sensor 20 is related to the magnetic field strength in its measurement direction component. The ratio between them is related to the sensor chip parameters and the external gain amplifier circuit. This is the angle between the measurement direction of the magnetoresistive uniaxial magnetic field sensor 20 and the direction of the magnetic field generated by the target current at this location. Let be the magnetic permeability of air. This is the distance between the magnetoresistive single-axis magnetic field sensor 20 and the target line.

[0066] Therefore, this application provides accurate current measurements using conventional current transformers in the low-frequency range (<1kHz). (Error <2%), used as a reference. The output of the magnetoresistive single-axis magnetic field sensor. by and The influence of this causes gain drift. To compensate for this drift, the dynamic gain coefficient... The calculation is as follows:

[0067]

[0068] Dynamic gain coefficient It reflects the combined effects of position and angle deviations, and is used to correct the measurement values ​​of high-frequency (>1kHz) magnetoresistive monoaxial magnetic field sensors, calculating the correction value for MR current measurement. .

[0069] To improve measurement stability, and The dynamic gain coefficient can be calculated using the root mean square (RMS) value over a period of time (e.g., a 1-second window). As shown in the following formula, to significantly reduce the impact of target AC signals and noise (such as electromagnetic interference) and ensure system robustness, the RMS calculation is implemented through the MCU's internal algorithm, requiring no additional hardware:

[0070]

[0071] In one embodiment, the broadband combined current transformer provided in this application further includes a microcontroller;

[0072] The microcontroller is configured to receive and process signals from the conventional current transformer and the magnetoresistive single-axis magnetic field sensor, and output a broadband current signal. The final output signal can be a weighted average of the measured values ​​from the conventional current transformer and the magnetoresistive single-axis magnetic field sensor, a pure magnetoresistive single-axis magnetic field sensor measured value after gain correction based on the current value of the conventional current transformer, or a fusion value of the low-frequency conventional current transformer current value and high-frequency MR data after Fourier series decomposition. Specifically, the microcontroller outputs the broadband current signal in one of the following ways. :

[0073] Method 1: Weighted average. Specifically, by adjusting the set weight w, the low-frequency reliability (e.g., <1kHz) of the traditional current transformer and the high-frequency response (e.g., >1kHz) of the magnetoresistive single-axis magnetic field sensor are dynamically balanced to output a fused signal. This directly generates a wideband output.

[0074]

[0075] in, The weights can also be changed based on real-time measurement needs or frequency.

[0076] Method 2: Pure MR correction:

[0077]

[0078] Relying on the measurement values ​​of the magnetoresistive monoaxial magnetic field sensor after CT low-frequency calibration, and utilizing the inherent broadband characteristics (DC to 10MHz) of the magnetoresistive monoaxial magnetic field sensor measurement values, the high-frequency signal fidelity is ensured, making it suitable for high-frequency current signal feature capture.

[0079] Method 3: Fourier decomposition and fusion:

[0080] Intelligent segmentation is performed in the frequency domain, and a Fourier transform is applied to the target current signal, replacing the low-frequency component (<1kHz) with... Replace high-frequency components (>1kHz) with By reconstructing and seamlessly integrating high and low frequency components, an optimized wideband signal is generated.

[0081] All three methods output wideband current signals. By integrating the low-frequency accurate measurement value of the traditional current transformer with the high-frequency broadband signal of the magnetoresistive sensor, they ensure complete bandwidth coverage from DC to high frequency, thus realizing full-band current measurement.

[0082] In one embodiment, such as Figure 1 As shown, the combined current transformer includes a conventional current transformer, a single magnetoresistive single-axis magnetic field sensor, a support structure or clip (for fixing the magnetoresistive single-axis magnetic field sensor to a relatively fixed position outside the conventional current transformer), external circuitry, and a microcontroller.

[0083] In one embodiment, the broadband combined current transformer provided in this application further includes a mode switching module, which is configured to switch between a pure CT measurement mode and a CT-MR fusion measurement mode.

[0084] Secondly, this application provides a broadband current measurement method, applied to the broadband combined current transformer described above, the method comprising the following steps:

[0085] Step S1: Obtain the low-frequency measurement value of the target current using the conventional current transformer. ;

[0086] Step S2: Obtain the output voltage of the magnetoresistive uniaxial magnetic field sensor. ;

[0087] Step S3: Based on and Calculate the dynamic gain coefficient used to correct the gain of the magnetoresistive uniaxial magnetic field sensor. As shown in the following formula:

[0088]

[0089] in, The target current value is measured independently by a traditional current transformer. This is the output voltage of the magnetoresistive single-axis magnetic field sensor.

[0090] In one embodiment, to improve measurement stability, and The dynamic gain coefficient can be calculated using the root mean square (RMS) value over a period of time (e.g., a 1-second window). This ensures the stability of the measurement system and the accuracy of the measurement results, significantly reducing the impact of target AC signals and noise (such as electromagnetic interference) and ensuring system robustness. RMS calculation is implemented through an internal algorithm of the MCU, requiring no additional hardware.

[0091]

[0092] According to Biosavart's law, Even when there is a deviation in the sensor angle (the direction of the sensor's magnetic field sensitivity is not perfectly orthogonal to the direction of the magnetic field) or a change in the distance between the sensor and the target current, the following equation still holds:

[0093]

[0094] in, The output voltage of the magnetoresistive uniaxial magnetic field sensor is related to the magnetic field strength in its measurement direction component. The ratio between them is related to the sensor chip parameters and the external gain amplifier circuit. This is the angle between the measurement direction of the magnetoresistive uniaxial magnetic field sensor and the direction of the magnetic field generated by the target current at this location. Let be the magnetic permeability of air. This represents the distance between the magnetoresistive single-axis magnetic field sensor and the target circuit.

[0095] Depend on From the calculation formula, we can see that the distance and angle After the change, With target current It still exhibits a linear relationship, which is the gain coefficient. This coefficient can be applied to high-frequency current calculations;

[0096] Step S4: Based on the dynamic gain coefficient, correct the measurement value of the magnetoresistive single-axis magnetic field sensor in the high-frequency band to obtain the corrected high-frequency current value:

[0097]

[0098] Where k is the dynamic gain coefficient calculated in step S3. This is the output voltage measured in real time by the magnetoresistive single-axis magnetic field sensor. The core of this formula lies in using the precise proportional relationship calibrated by a traditional current transformer (CT) in the low-frequency band to calibrate the measurement value of the magnetoresistive single-axis magnetic field sensor in the high-frequency band in real time, thereby eliminating gain errors caused by position or angle offset and ensuring accurate capture of high-frequency current signals.

[0099] Step S5: Combine the low-frequency measurement value with the corrected high-frequency current value to output a wideband current measurement result, as shown in the following formula:

[0100]

[0101] in, It is the accurate measurement value of a traditional current transformer in the low-frequency range (<1kHz). It is the high-frequency current value (>1kHz) corrected by the dynamic gain coefficient k, and w is a configurable weight (usually dynamically adjusted according to frequency characteristics or actual needs). This formula achieves signal fusion through a microcontroller (MCU), and finally outputs the wideband current measurement result Ifusion covering DC to 10MHz, combining low-frequency accuracy with high-frequency response capability.

[0102] The following two specific embodiments, combined with MATLAB simulation, verify the performance of the broadband combined current transformer provided in this application.

[0103] The simulation settings are as follows:

[0104] Target current range: 0-200A, sampling rate: 100kHz, simulation duration: 1 second;

[0105] The CT model uses a second-order Butterworth low-pass filter (cutoff frequency 1kHz) to accurately measure low-frequency components (<1kHz) but attenuate high frequencies.

[0106] The MR model is full-band (DC-10MHz), with a sensitivity of 0.05V / Gauss and a magnetic field measurement noise standard deviation of 4.27μT (laboratory measurement value), but the gain is affected by the conductor position offset;

[0107] Simulate three types of offsets:

[0108] (1) The distance increases by 20% (the nominal distance increases from 8mm to 9.6mm, and the gain decreases by about 16.7%).

[0109] (2) Angle shift of 15° (gain decreases by approximately 3.4%);

[0110] (3) The distance increases by 20% and the angle shifts by 15° (the gain decreases by about 19.7%).

[0111] The fusion algorithm calculates the dynamic gain coefficient k based on the RMS value within a 0-0.5s window, corrects the measurement value of the magnetoresistive uniaxial magnetic field sensor, and directly uses it as the fusion result. Output.

[0112] Environmental noise includes CT measurement noise (standard deviation 0.5A) and MR magnetic field noise (standard deviation 4.27μT).

[0113] Example 1: Harmonic Interference Measurement in High-Voltage Power Grid Fault Monitoring

[0114] In high-voltage power grid fault monitoring scenarios, a commercially available magnetoresistive single-axis magnetic field sensor (sensitivity 0.05V / Gauss, bandwidth >10MHz) and a ring current transformer (core diameter 10cm, secondary turns 200) were selected. The magnetoresistive single-axis magnetic field sensor was placed outside the conventional current transformer, nominally 8mm away from the conductor, perpendicular to the magnetic lines of force, and fixed with clips. The signal was amplified and input to a microcontroller (e.g., STM32) via an ADC. The simulation signal was a 50Hz fundamental frequency (amplitude 50A) superimposed with harmonic interference (3kHz and 5kHz harmonics, amplitudes 20A and 10A respectively, added from 0.5s). Three position offsets were verified:

[0115] Figure 3 (a) shows a comparison between CT measurements and true values;

[0116] Figure 3 (b) is a comparison chart of uncorrected MR measurements and true values;

[0117] Figure 3 (c) is a comparison chart of the corrected fusion result and the true value.

[0118] (1) Distance increased by 20%

[0119] like Figure 3 As shown in (a), CT measurements retain the 50Hz fundamental frequency but lack the 3kHz and 5kHz harmonics; as Figure 3 As shown in (b), the uncorrected MR measurement captures harmonics but has a significant amplitude deviation; the average RMS value of the target current is 37.081 A, while the RMS value measured by the uncorrected magnetoresistive uniaxial magnetic field sensor is only 30.902 A. Figure 3 As shown in (c), the fusion result recovers the harmonic characteristics with an error of <1%.

[0120] Figure 4 (a) shows a comparison between CT measurements and true values;

[0121] Figure 4 (b) is a comparison chart of uncorrected MR measurements and true values;

[0122] Figure 4 (c) is a comparison chart of the corrected fusion result and the true value.

[0123] (2) Angular offset θ = 15°:

[0124] like Figure 4 As shown in (a), CT measurements still lack harmonics; as Figure 4 As shown in (b), the uncorrected MR measurement amplitude deviation is slightly lower than the increase in distance, but it is still inaccurate; Figure 4 As shown in (c), the fusion result error is <1%, accurately restoring the full waveform.

[0125] Example 2: Short-circuit transient detection in new energy equipment

[0126] In new energy equipment (such as photovoltaic inverters), the same hardware configuration as in Example 1 is used to address short-circuit transient faults. The simulation signal is a 50Hz fundamental frequency (amplitude 50A) superimposed with a short-circuit transient (a 10kHz attenuating pulse is added starting from 0.5s, with an initial amplitude of 100A and an attenuation constant of 100s^-1). Three position offsets are verified:

[0127] Figure 6 (a) shows a comparison between CT measurements and true values;

[0128] Figure 6 (b) is a comparison chart of uncorrected MR measurements and true values;

[0129] Figure 6 (c) is a comparison chart of the corrected fusion result and the true value.

[0130] (1) Distance increased by 20%

[0131] like Figure 6 As shown in (a), CT measurements show a smoothed-out 10kHz pulse; as Figure 6 As shown in (b), the uncorrected MR measurement ( Figure 6 b) Captures pulses but with large amplitude deviations; fusion results ( Figure 6 c) Exactly matches the true value with an error of <1%.

[0132] Figure 7 (a) shows a comparison between CT measurements and true values;

[0133] Figure 7 (b) is a comparison chart of uncorrected MR measurements and true values;

[0134] Figure 7 (c) is a comparison chart of the corrected fusion result and the true value.

[0135] (2) Angle offset of 15°:

[0136] like Figure 7 As shown in (a), CT measurements show missing pulses; Figure 7 As shown in (b), the uncorrected MR measurement amplitude deviation is approximately 3.4%; Figure 7 As shown in (c), the fusion result error is <1%, and the pulse characteristics are recovered.

[0137] Figure 5 (a) shows a comparison between CT measurements and true values;

[0138] Figure 5 (b) is a comparison chart of uncorrected MR measurements and true values;

[0139] Figure 5 (c) is a comparison chart of the corrected fusion result and the true value.

[0140] (3) Combined offset (distance increased by 20%, θ=15°):

[0141] like Figure 5 As shown in (a), CT measurements show missing harmonics; Figure 5 As shown in (b), the uncorrected MR measurement amplitude deviation is relatively large; as Figure 5 As shown in (c), the fusion result error is <1%, preserving harmonic characteristics.

[0142] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A broadband combined current transformer, characterized in that, include: Traditional current transformers and single magnetoresistive single-axis magnetic field sensors; The magnetoresistive single-axis magnetic field sensor is disposed at a relatively fixed position outside the conventional current transformer; The broadband combined current transformer is configured to correct the gain change of the magnetoresistive single-axis magnetic field sensor in real time by using the current measurement value of the conventional current transformer in the low-frequency band, and to measure and acquire the broadband current signal.

2. The broadband combined current transformer according to claim 1, characterized in that, The magnetic field sensing direction of the magnetoresistive uniaxial magnetic field sensor is configured to be perpendicular to the direction of the magnetic field lines generated by the conductor under test.

3. The broadband combined current transformer according to claim 1, characterized in that, The real-time correction of the gain change of the magnetoresistive uniaxial magnetic field sensor includes calculating the dynamic gain coefficient. It satisfies: ； in, The target current value is measured independently by a traditional current transformer. This is the output voltage of the magnetoresistive single-axis magnetic field sensor.

4. The broadband combined current transformer according to claim 3, characterized in that, The and This is the root mean square value calculated within a preset time window.

5. The broadband combined current transformer according to claim 1, characterized in that, The conventional current transformer has a toroidal iron core structure; the magnetoresistive single-axis magnetic field sensor has a sensitivity greater than 1mV / Gauss and a bandwidth greater than 10MHz.

6. The broadband combined current transformer according to claim 1, characterized in that, It also includes a microcontroller configured to receive and process signals from the conventional current transformer and the magnetoresistive single-axis magnetic field sensor, and output a wideband current signal.

7. The broadband combined current transformer according to claim 6, characterized in that, The microcontroller outputs the wideband current signal in one of the following ways: Measurement values ​​of traditional current transformers And the measured values ​​of the magnetoresistive single-axis magnetic field sensor after gain correction Perform a weighted average and output the wideband current signal; Directly outputs the measured value of the magnetoresistive single-axis magnetic field sensor after gain correction; Frequency domain decomposition was performed on the measured values ​​of the magnetoresistive uniaxial magnetic field sensor, and the low-frequency components were replaced with... Replace the high-frequency component with Then, the signal is reconstructed to form a broadband current signal.

8. The broadband combined current transformer according to claim 1, characterized in that, It also includes a mode switching module, which is configured to switch between a pure CT measurement mode and a CT-MR fusion measurement mode.

9. A broadband current measurement method, applied to a broadband combined current transformer as described in any one of claims 1-8, characterized in that, The method includes the following steps: The low-frequency measurement value of the target current is obtained through the conventional current transformer. ; The output voltage is obtained through the magnetoresistive uniaxial magnetic field sensor. ; based on and Calculate the dynamic gain coefficient used to correct the gain of the magnetoresistive uniaxial magnetic field sensor; The measured value of the magnetoresistive single-axis magnetic field sensor in the high-frequency band is corrected based on the dynamic gain coefficient to obtain the corrected high-frequency current value. By combining the low-frequency measurement value with the corrected high-frequency current value, a wideband current measurement result is output.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a broadband combined current transformer program, wherein when the broadband combined current transformer program is executed by a processor, it implements the steps of the broadband combined current transformer as described in claim 9.

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