Calibration and correction method of current transformer

Abstract

The invention discloses a calibration and correction method of a current transformer, and belongs to the technical field of current measurement. The method comprises the following steps: acquiring a voltage signal output by a current transformer, and obtaining a sampling waveform signal; performing baseline drift detection on the acquired sampling waveform signal; if it is detected that baseline drift exists, dynamic baseline calibration is carried out in a high-altitude proportion scene; performing baseline correction on the sampling waveform signal; calculating the increment of pulse attenuation compensation based on inertial filtering; performing linear interpolation compensation on the positive pulse width in the sampling waveform signal; and outputting the corrected detected current signal. According to the calibration and correction method of the current transformer provided by the invention, the current measurement precision of the current transformer in a high duty ratio scene is improved by monitoring the baseline position and the linear interpolation compensation dynamic correction signal in real time.

Description

Technical Field

[0001] This application belongs to the technical field of current measurement, and particularly relates to a calibration and correction method for a current transformer. Background Art

[0002] Bergoz ACCT is a high-precision, non-truncated current measurement device designed for measuring wide pulses, millisecond-level pulse trains, and low-noise signals, and is widely used in fields such as particle accelerators, plasma research, and precision industrial measurement. Its working principle is based on mutual inductance: the current to be measured passes through the conductor or beam pipe in the center aperture of the ACCT, and a voltage signal proportional to it can be induced at the output end of the ACCT without direct electrical connection, and this voltage signal can be directly input into a high-precision data acquisition system.

[0003] Since the transfer function bandwidth of the ACCT does not include the DC component, it can only respond to AC signals, and the average value of its output signal is always zero. For a low-duty-cycle input current (pulse width much smaller than the repetition period), the baseline of the output signal is close to zero, and the waveform distortion is not obvious. However, for a high-duty-cycle input current, in order to maintain the average value of the output signal at zero, the baseline will drift, resulting in significant waveform distortion, mainly manifested as baseline drift and pulse amplitude attenuation. The specific manifestations are as follows:

[0004] (1) Baseline drift: The baseline of the output signal shifts, and the shift amount changes with the duty cycle. The higher the duty cycle, the more significant the baseline drift. In addition, even at the same duty cycle, the baseline position also shows instability, presenting a characteristic of continuous drift;

[0005] (2) Pulse amplitude attenuation: There is a phenomenon of amplitude attenuation in the ACCT output, and the attenuation amount is less than 2% / ms. Summary of the Invention

[0006] In order to solve the problems of baseline drift and pulse attenuation of Bergoz ACCT at high duty cycles, this application provides a calibration and correction method for a current transformer, which improves the current measurement accuracy of the current transformer in high-duty-cycle scenarios by real-time monitoring of the baseline position and dynamic correction of the signal through linear interpolation compensation.

[0007] The technical solution is as follows:

[0008] Provide a calibration and correction method for a current transformer, including:

[0009] Collect the voltage signal output by the current transformer to obtain a sampled waveform signal;

[0010] Perform baseline drift detection on the obtained sampled waveform signal;

[0011] If baseline drift is detected, dynamic baseline calibration is performed in the high-altitude occupancy scenario;

[0012] Perform baseline correction on the sampled waveform signal;

[0013] Calculate the increment of pulse attenuation compensation based on inertial filtering;

[0014] Perform linear interpolation compensation on the positive pulse width in the sampled waveform signal;

[0015] Output the corrected measured current signal.

[0016] Furthermore, to detect baseline drift in the acquired sampled waveform signal, it is to determine whether the minimum voltage SampleData Min of the sampled waveform signal is less than 0V. If the minimum voltage SampleData Min of the sampled waveform signal is less than 0V, baseline drift is detected and dynamic baseline calibration needs to be performed in the high-altitude occupancy scenario.

[0017] Furthermore, baseline calibration is to calculate the baseline position based on the minimum value of the sampled waveform signal and the value of the last sampling point of the negative pulse.

[0018] Furthermore, the baseline position is to calculate the baseline voltage value SampleData BaseLine , and the calculation formula is:

[0019]

[0020] where SampleData Min is the minimum value of the sampled waveform signal, and SampleData NegFinal is the value of the last sampling point of the negative pulse.

[0021] Furthermore, to perform baseline correction on the sampled waveform signal, it is to add the calibrated baseline voltage value SampleData BaseLine to each sampling value.

[0022] Furthermore, the formula for calculating the increment of compensation for the attenuated part is:

[0023]

[0024] where Rise represents the SampleData Rise sampling point index number; Min represents the SampleData Min sampling point index number, and Δ is the compensation increment.

[0025] Furthermore, the inertial filtering algorithm is used to smooth the baseline and stabilize the increment calculation, and the formula is:

[0026] Δ = α×Δ+(1 - α)×Δ pre

[0027] where α is the smoothing coefficient, and Δ pre is the compensation increment calculated in the previous time.

[0028] Further, linear interpolation compensation is performed on the positive pulse width in the sampled waveform signal. Specifically, linear interpolation compensation starts from the sampling point where the amplitude exceeds the set threshold of the maximum sampling value SampleData Max and gradually increases the compensation increment Δ until the positive pulse ends.

[0029] This technical solution at least includes the following technical effects:

[0030] To solve the problems of baseline drift and pulse attenuation of Bergoz ACCT under high duty cycle, this technical solution adopts single - sensor output signal processing. By real - time monitoring and calibrating the baseline position of the ACCT output signal, and dynamically correcting the signal through linear interpolation compensation, it synchronously corrects the baseline drift and pulse attenuation under high duty cycle to reconstruct a complete and accurate output signal waveform, and finally ensures the accuracy of current measurement.

[0031] It should be understood that the above general description and the following detailed description are only exemplary and do not limit this application. Description of the Drawings

[0032] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0033] Figure 1 Schematic diagram of the output distortion phenomenon of the current transformer;

[0034] Figure 2 Flow chart of the calibration and correction method of a current transformer provided by a preferred embodiment of this application;

[0035] Figure 3 Schematic diagram of high - duty - cycle baseline calibration provided by a preferred embodiment of this application;

[0036] Figure 4 Schematic diagram of pulse attenuation compensation provided by a preferred embodiment of this application;

[0037] Figure 5 Oscilloscope measurement diagram of the electronics output of the Bergoz ACCT current transformer at the starting point of the positive pulse provided by a preferred embodiment of this application;

[0038] Figure 6Oscilloscope measurement diagram of the electronic output of the Bergoz ACCT current transformer at the end point of the positive pulse provided by a preferred embodiment of the present application;

[0039] Figure 7 Waveform diagram of the Bergoz ACCT output after calibration and correction provided by a preferred embodiment of the present application. Detailed implementation manners

[0040] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0041] Explanation of related terms:

[0042] ACCT is short for Alternating Current Current Transformer (alternating current current transformer), which is a non-contact current sensor.

[0043] Bergoz is a French company specialized in the production of high-precision electronic measurement equipment, and its products are widely used in fields such as particle accelerators, nuclear physics experiments, and medical equipment (such as proton therapy).

[0044] The present application provides a calibration and correction method for a current transformer. In order to solve the problems of baseline drift and pulse attenuation of Bergoz ACCT under high duty cycle, a correction method combining baseline dynamic calibration and linear interpolation compensation is proposed, which is different from the general baseline processing technology. The single-sensor output signal is processed, and through baseline calibration based on the minimum value and the negative pulse point, combined with linear interpolation and inertial filtering algorithms to compensate for attenuation.

[0045] As shown in the attached Figure 1 and Figure 2 figures, the present application provides a calibration and correction method for a current transformer, and the specific steps are as follows:

[0046] Step S10: Collect the voltage signal output by the current transformer to obtain a sampled waveform signal. Specifically: collect the voltage signal output by the ACCT electronics, the period of this signal is T1, and the positive pulse width is T2. Set the number of sampling points of the data acquisition system to 1000, and adjust the sampling frequency so that the sampling period meets the requirement to ensure that a complete positive pulse waveform is collected. In the present invention, the AD value range of sampling is 0 to 32767, and the corresponding voltage range is -10V to 10V.

[0047] Step S20: Detect the baseline drift of the acquired sampled waveform signal, and determine whether there is baseline drift in the ACCT output signal, that is, determine the minimum value SampleData of the sampled signal Min whether it is less than 0V. If the minimum voltage value SampleData of the sampled waveform signal Min is less than 0, it is detected that there is baseline drift, and dynamic baseline calibration needs to be performed in the high-duty-cycle scenario.

[0048] Step S30: If it is detected that there is baseline drift, perform dynamic baseline calibration in the high-duty-cycle scenario. The baseline calibration is based on the minimum value of the sampled waveform signal and the value of the last sampled point of the negative pulse to calculate the baseline position.

[0049] It should be noted that when the duty cycle of the measured current signal is small, the baseline of the ACCT output signal usually does not shift. At this time, there is no need for calibration and correction, and the acquired waveform is directly displayed; when the duty cycle of the measured current signal is large, the baseline of the ACCT output signal will shift, and the minimum voltage value of the sampled signal is less than 0V. At this time, it is necessary to monitor the change of the baseline in real time, calibrate the baseline position, and record the baseline value.

[0050] Step S40: Perform baseline correction on the sampled waveform signal, that is, add the calibrated baseline voltage value SampleData to each sampled value BaseLine .

[0051] Monitor the baseline change in real time, calibrate the position of the baseline, record the baseline value and perform baseline correction. The specific method is as follows: Record the minimum value in the sampled data ( Figure 3 the point ① shown in), and the value of the last sampled point of the negative pulse ( Figure 3 the point ② shown in). The baseline position ( Figure 3 the point ③ shown in), the calculation formula is:

[0052]

[0053] where SampleData Min is the minimum value of the sampled waveform signal, SampleData NegFinal is the value of the last sampled point of the negative pulse, and SampleData BaseLine is the baseline voltage value.

[0054] Perform baseline compensation correction on the sampled waveform, that is, superimpose the baseline value on each sampled data point to eliminate the influence of baseline drift.

[0055] Step S50: Calculate the increment of pulse decay compensation based on inertial filtering. Since the output of the ACCT has a linear decay of less than 2% / ms, calculate the increment that needs to be compensated for the decaying part;

[0056] Step S60: Perform linear interpolation compensation on the positive pulse width in the sampled waveform signal, that is, starting from the sampling point where the amplitude exceeds the set threshold of the maximum sampled value SampleData Max , perform linear interpolation compensation, gradually increasing the compensation increment Δ until the positive pulse ends.

[0057] Step S70: Output the corrected measured current signal, that is, by linearly interpolating to compensate for the amplitude attenuation of the positive pulse, and finally obtain the true measured current signal value.

[0058] When measuring a high duty cycle input current, the output of the ACCT shows an amplitude attenuation phenomenon, and the attenuation amount is less than 2% / ms. In a preferred embodiment, based on the baseline calibration of the minimum value and the negative pulse point, combined with linear interpolation and inertial filtering algorithms to compensate for the attenuation. This compensation process first needs to determine the rising edge starting point and calculate the compensation increment of the attenuation part. At the same time, in order to prevent the influence of continuous baseline drift on the increment calculation, an inertial filtering algorithm is used to smooth the baseline and stabilize the increment calculation.

[0059] Determine the rising edge starting point: By comparing the values of adjacent sampling points, such as Figure 4 the values of point ④ and point ⑤ shown in. When the value of the latter sampling point is greater than the set threshold of the former sampling point, then Figure 4 mark point ④ shown in as the rising edge starting point, denoted as SampleData Rise . At the same time, record the minimum value in the sampling data, denoted as SampleData Min ( Figure 4 point ① shown in);

[0060] Calculate the compensation increment: The compensation increment calculation formula is where Rise represents the sampling point index number of SampleData Rise ; Min represents the sampling point index number of SampleData Min , and Δ is the compensation increment.

[0061] Smoothing the increment value based on inertial filtering: In order to prevent the instability of baseline drift, inertial filtering is used to smooth the baseline and stabilize the increment calculation formula as Δ = α×Δ + (1 - α)×Δ pre α, where is the smoothing coefficient, and Δ pre is the compensation increment calculated last time;

[0062] Linear interpolation compensation: Starting from the sampling point where the amplitude exceeds the set threshold of the maximum sampled value SampleData Max , perform linear interpolation compensation, gradually increasing the compensation increment Δ until the positive pulse ends.

[0063] Through the above steps, the amplitude attenuation of the pulse signal can be compensated, and finally the true value of the measured current signal can be obtained.

[0064] In one embodiment, a computer program product, such as a computer-readable program carrier, is provided, which contains or stores computer program instructions. When the computer program instructions are executed by a processor, the steps of the above method are at least assisted to be implemented.

[0065] In actual tests, taking the input current signal pulse width as 2.4 ms and the device sampling rate in the present invention as 5 Msps as an example. The current measurement range of the tested Bergoz ACCT is 0 - 30 mA, and its attenuation amount is 0.86% / ms after being tested by the device manufacturer. The output voltage range of its ACCT is 0 - 10 V, and an oscilloscope is used to measure the output waveform of Bergoz ACCT electronics. When the input current pulse width is 2.4 ms, the baseline drifts, as Figure 5 and Figure 6 shown, and the baseline position is -1.52 V.

[0066] As Figure 5 and Figure 6 shown, the voltage values corresponding to the start point and end point of the positive pulse are 7 V and 8.64 V, and the calculated current values are and Since there is an amplitude attenuation of 0.86% / ms in the ACCT during the test, the actual current value corresponding to the end point of the positive pulse should be 8.64 V × (1 + 2.4 ms × 0.86% / ms) = 8.82 V, and the corresponding actual current value should be

[0067] Before correction: The current values corresponding to the start point and end point of the positive pulse are 21.0 mA and 25.92 mA respectively.

[0068] Theoretically after correction: The current values corresponding to the start point and end point of the positive pulse are 21.0 mA and 26.5 mA respectively.

[0069] Comparing the theoretically corrected result with the actually corrected waveform output, as Figure 7 shown, after being processed by the calibration and correction method proposed in this application, the output signal of Bergoz ACCT under the same input conditions is measured again, Figure 7 and the current values corresponding to the start point and end point of the positive pulse in

[0070] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once they learn the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0071] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A calibration and correction method for a current transformer, characterized in that, Including: Collect the voltage signal output by the current transformer to obtain the sampled waveform signal; Perform baseline drift detection on the obtained sampled waveform signal; If baseline drift is detected, perform dynamic baseline calibration in the high altitude occupancy scenario; Perform baseline correction on the sampled waveform signal; Calculate the increment of pulse attenuation compensation based on inertial filtering; Perform linear interpolation compensation on the positive pulse width in the sampled waveform signal; Output the corrected measured current signal.

2. The calibration and correction method of the current transformer according to claim 1, characterized in that Detecting the baseline drift of the acquired sampled waveform signal is to determine whether the minimum voltage SampleData of the sampled waveform signal Min is less than 0V. If the minimum voltage SampleData of the sampled waveform signal Min is less than 0V, it is detected that there is baseline drift, and dynamic baseline calibration needs to be performed in the high air occupancy scenario.

3. The calibration and correction method of the current transformer according to claim 2, characterized in that, The baseline calibration calculates the baseline position based on the minimum value of the sampled waveform signal and the value of the last sampling point of the negative pulse.

4. The calibration and correction method of the current transformer according to claim 3, characterized in that The baseline position is the calculated baseline voltage value SampleData BaseLine , and the calculation formula is: Among them, SampleData Min is the minimum voltage of the sampled waveform signal, and SampleData NegFinal is the value of the last sampling point of the negative pulse.

5. The calibration and correction method of the current transformer according to claim 4, characterized in that, Performing baseline correction on the sampled waveform signal is to add the baseline voltage value SampleData obtained by calibration to each sampled value BaseLine .

6. The calibration and correction method of the current transformer according to claim 1, characterized in that, The formula for calculating the increment of pulse attenuation compensation is: Among them, Rise represents SampleData Rise Sampling point index number; Min represents SampleData Min Sampling point index number, and Δ is the compensation increment.

7. The calibration and correction method of the current transformer according to claim 6, characterized in that The inertial filtering algorithm is used to smooth the baseline and stabilize the increment calculation formula as: Δ = α×Δ+(1 - α)×Δ pre where α is the smoothing coefficient, and Δ pre is the compensation increment calculated in the previous time.

8. The calibration and correction method of the current transformer according to claim 1, characterized in that, Perform linear interpolation compensation on the positive pulse width in the sampled waveform signal, specifically starting from the sampling points where the amplitude exceeds the set threshold of the maximum sampled value SampleData Max and performing linear interpolation compensation, gradually increasing the compensation increment Δ until the positive pulse ends.

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