CN112269050A - LC resonance fluxgate leakage current detection method for inhibiting modulation ripple - Google Patents
LC resonance fluxgate leakage current detection method for inhibiting modulation ripple Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 16
- 230000002401 inhibitory effect Effects 0.000 title claims abstract description 10
- 230000005284 excitation Effects 0.000 claims abstract description 42
- 238000005070 sampling Methods 0.000 claims description 12
- 230000002238 attenuated effect Effects 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 6
- 230000000717 retained effect Effects 0.000 claims description 6
- 238000004804 winding Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 4
- 230000006698 induction Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/56—Testing of electric apparatus
Abstract
The invention discloses a LC resonance fluxgate leakage current detection method for inhibiting modulation ripples, which comprises the following steps of S1: excitation current iex1The first direct current component is generated by the measured current and comprises a first high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave; step S2: excitation current iex2Including a second high frequency component at the same frequency as the fundamental and odd harmonics and a second dc component generated by the current under test. According to the LC resonance fluxgate leakage current detection method for inhibiting the modulation ripple, useless direct current components are filtered through HPL and LPF processing, and high frequency components are mutually offset, so that the modulation ripple is inhibited, and a pure direct current error signal, namely a leakage current signal, is obtained.
Description
Technical Field
The invention belongs to the technical field of fluxgate leakage current detection, and particularly relates to an LC resonance fluxgate leakage current detection method for inhibiting modulation ripples.
Background
In 2014, the three-magnetic-core three-winding closed-loop measurement scheme proposed by G.Velasco-Quesada et al was improved by Yangxue Dawley, Dawley university of Hebei industries, and the two-magnetic-core three-winding closed-loop LC resonant fluxgate current sensor was developed. Although the scheme realizes low cost, the precision is only 0.7 percent because the problems of secondary side modulation ripple and the like are not considered.
In a closed-loop system, an LC resonance fluxgate used as a direct-current zero-flux detector adopts a filtering demodulation mode, the biggest defect is that an output signal has a modulation ripple with a larger amplitude, and the modulation ripple is directly transmitted to a secondary winding through an ampere-turn balance controller as an error signal to form a conduction modulation ripple; and the alternating magnetic flux of the LC resonant fluxgate generates an induction modulation ripple in the secondary winding through a transformer effect. For precision measurement, the secondary side modulation ripple has become a bottleneck limiting the improvement of measurement accuracy, and none of the existing solutions can effectively solve the above problems.
Disclosure of Invention
The invention mainly aims to provide an LC resonance fluxgate leakage current detection method for inhibiting modulation ripples, wherein the LC resonance fluxgate sensing detection realizes tiny leakage current detection through the change of induction signals on the primary side and the secondary side, and because ripple voltage or ripple current with the same frequency as the fundamental wave or odd harmonic wave of excitation magnetic flux (or excitation current) exists in the primary side winding and the secondary side winding of a direct current type current comparison instrument, the modulation ripples are inhibited through HPL and LPF processing to filter useless direct current components, and high frequency components are mutually offset, so that pure direct current error signals, namely leakage current signals, are obtained.
The invention also aims to provide an LC resonance fluxgate leakage current detection method for inhibiting modulation ripples, which adopts an inhibition method for reducing excitation current sampling resistance and excitation current peak value by adding a high-pass filter aiming at conduction modulation ripples caused by a filter demodulation circuit.
Another objective of the present invention is to provide a method for detecting leakage current of an LC resonant fluxgate for suppressing modulation ripple, in which the LC resonant fluxgate is used as a dc zero-flux detector, and a high-pass filter is used to suppress conduction modulation ripple caused by a filter demodulation circuit.
The invention also aims to provide an LC resonance fluxgate leakage current detection method for inhibiting modulation ripples, the measurement precision of a sensor reaches 1.3ppm, and the maximum index of the sensor is improved by 3 orders of magnitude compared with the highest index of 0.2% reached by the existing similar scheme; the modulation ripple is reduced to 0.12 muA, which is reduced by 83 times compared with the prior similar scheme index of 10 muA.
In order to achieve the above object, the present invention provides a method for detecting leakage current of an LC resonant fluxgate with suppressed modulation ripple, for obtaining a pure leakage current signal, comprising the steps of:
step S1: excitation current iex1The first direct current component is generated by the measured current and comprises a first high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave;
step S2: excitation current iex2The second direct-current component is generated by the current to be measured and comprises a second high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave;
step S3: excitation current iex1First high frequency component of (a) and an excitation current iex2Are equal in amplitude and opposite in phase (approximate, but not absolute), and will excite the current iex1And excitation currentStream iex2Through a summing circuit Sum1 to cancel the first high frequency component and the second high frequency component;
step S4: the excitation current i will pass through the summation circuit Sum1ex1And an excitation current iex2Further attenuating the signal by a low pass filter LPF to obtain a pure leakage current signal Vdc(i.e., a dc error signal).
As a further preferable embodiment of the above technical means, step S1 is specifically implemented as the following steps:
step S1.1: the first high-frequency component with the same frequency as the fundamental wave and the odd harmonic and the first direct-current component generated by the measured current are both provided with an exciting current sampling resistor RS1Voltage V onsn1And (4) generating.
As a further preferable embodiment of the above technical means, step S2 is specifically implemented as the following steps:
step S2.1: the second high-frequency component with the same frequency as the fundamental wave and the odd harmonic and the second direct-current component generated by the measured current are both provided with an exciting current sampling resistor RS2Voltage V onsn2Generating;
step S2.2: excitation current iex2The second dc component is filtered out after the first processing, while the second high frequency component is retained and not attenuated.
As a further preferred embodiment of the above technical solution, the step S2.2 is specifically implemented as the following steps:
step S2.2.1: excitation current iex2The second direct current component generated by the measured current does not have a linear relation with the measured current so as to judge the second direct current component as an useless direct current component;
step S2.2.2: exciting current iex2The second direct current component is filtered out by a high pass filter HPL and the second high frequency component is retained and not attenuated.
As a further preferable embodiment of the above technical means, step S3 is specifically implemented as the following steps:
step S3.1: reduce exciting current sampling resistance RS1And RS2；
Step S3.2: reducing the excitation current iex1And an excitation current iex2Peak value of (a).
Drawings
Fig. 1 is a schematic structural diagram of a high-pass filter for suppressing a conduction modulation ripple in the LC resonant fluxgate leakage current detection method for suppressing a modulation ripple according to the present invention.
Detailed Description
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
Referring to fig. 1 of the drawings, fig. 1 is a schematic structural diagram of a high-pass filter for suppressing a conduction modulation ripple according to an LC resonant fluxgate leakage current detection method for suppressing a modulation ripple.
In the preferred embodiment of the present invention, those skilled in the art should note that the high pass filter, the low pass filter, the LC resonant fluxgate average current model, etc. related to the present invention can be regarded as the prior art.
Preferred embodiments.
The invention discloses an LC resonance fluxgate leakage current detection method for inhibiting modulation ripples, which is used for obtaining a pure leakage current signal and comprises the following steps:
step S1: excitation current iex1The first direct current component is generated by the measured current and comprises a first high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave;
step S2: excitation current iex2The second direct-current component is generated by the current to be measured and comprises a second high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave;
step S3: excitation current iex1First high frequency component of (a) and an excitation current iex2Are equal in magnitude andopposite in phase (approximate, but not absolute) and will excite the current iex1And an excitation current iex2Through a summing circuit Sum1 to cancel the first high frequency component and the second high frequency component;
step S4: the excitation current i will pass through the summation circuit Sum1ex1And an excitation current iex2Further attenuating the signal by a low pass filter LPF to obtain a pure leakage current signal Vdc(i.e., a dc error signal).
Specifically, step S1 is implemented as the following steps:
step S1.1: the first high-frequency component with the same frequency as the fundamental wave and the odd harmonic and the first direct-current component generated by the measured current are both provided with an exciting current sampling resistor RS1Voltage V onsn1And (4) generating.
More specifically, step S2 is specifically implemented as the following steps:
step S2.1: the second high-frequency component with the same frequency as the fundamental wave and the odd harmonic and the second direct-current component generated by the measured current are both provided with an exciting current sampling resistor RS2Voltage V onsn2Generating;
step S2.2: excitation current iex2The second dc component is filtered out after the first processing, while the second high frequency component is retained and not attenuated.
Further, step S2.2 is embodied as the following steps:
step S2.2.1: excitation current iex2The second direct current component generated by the measured current does not have a linear relation with the measured current so as to judge the second direct current component as an useless direct current component;
step S2.2.2: exciting current iex2The second direct current component is filtered out by a high pass filter HPL and the second high frequency component is retained and not attenuated.
Further, step S3 is implemented as the following steps:
step S3.1: reduce exciting current sampling resistance RS1And RS2；
Step S3.2: reducing the excitation current iex1And an excitation current iex2Peak value of (a).
Preferably, the probe of the LC resonant fluxgate sensor has an inductive device, the output end of the probe is connected in parallel with a capacitor to form an LC resonant circuit, the LC resonant circuit resonates and amplifies a fundamental wave induction signal output by the pickup coil, and simultaneously suppresses other frequency harmonic signals, thereby achieving an effect of extracting the fundamental wave signal, a change in the current of the fluxgate body causes a change in the inductive inductance, thereby causing a change in the frequency, and finally, a voltage processor reversely deduces whether a leakage current exists according to the frequency.
Preferably, the basic principle of the High Pass Filter (HPF) to suppress the conduction modulation ripple is as shown in fig. 1. According to the basic principle of the average current model of the LC resonance fluxgate, the excitation current iex1Contains both the useless high-frequency component with the same frequency as the fundamental wave and odd harmonic wave and the useful DC component generated by the measured current, wherein the useless high-frequency component and the useful DC component can be sampled by an exciting current sampling resistor RS1Voltage V onsn1Thus obtaining the product. Also, an excitation current iex2Also contains high frequency components having the same frequencies as the fundamental wave and odd harmonics, however, iex2The direct current component generated by the measured current does not have a linear relation with the measured current, and therefore, the direct current component is regarded as a useless signal. Excitation current iex2The middle high frequency component and the direct current component can be sampled by the exciting current sampling resistor RS2Voltage V onsn2Thus obtaining the product. If the time constant of the HPF is sufficiently large, signal iex2After passing through the HPF, the useless direct current component is filtered out, and the useful high frequency component is not attenuated. If iex1And iex2The high frequency components in the two are just equal in amplitude and opposite in phase, and then they are cancelled out by each other after passing through the Sum circuit Sum 1. Due to iex2Has been filtered out, so that iex1The useful DC component generated by the measured current is not due to the sum of iex2Added and attenuated to obtain a signal V theoretically free of high-frequency componentssn12。
In practical application, iex1And iex2The high frequency components in the medium will not be equal in absolute magnitudeAnd opposite in phase, resulting in the output signal of the summing circuit Sum1 containing high frequency components of a certain magnitude, which can be further attenuated by a Low Pass Filter (LPF), resulting in a cleaner dc error signal Vdc。
It should be noted that the technical features of the high-pass filter, the low-pass filter, the LC resonant fluxgate average current model, etc. related to the present patent application should be regarded as the prior art, and the specific structure, the operation principle, the control mode and the spatial arrangement mode of the technical features may be conventional choices in the field, and should not be regarded as the invention point of the present patent, and the present patent is not further specifically described in detail.
It will be apparent to those skilled in the art that modifications and equivalents may be made in the embodiments and/or portions thereof without departing from the spirit and scope of the present invention.
Claims (5)
1. A method for detecting leakage current of an LC resonant fluxgate for inhibiting modulation ripples is used for obtaining a pure leakage current signal, and is characterized by comprising the following steps:
step S1: excitation current iex1The first direct current component is generated by the measured current and comprises a first high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave;
step S2: excitation current iex2The second direct-current component is generated by the current to be measured and comprises a second high-frequency component with the same frequency as the fundamental wave and the odd harmonic wave;
step S3: excitation current iex1First high frequency component of (a) and an excitation current iex2Are equal in amplitude and opposite in phase, and will excite the current iex1And an excitation current iex2Through a summing circuit Sum1 to cancel the first high frequency component and the second high frequency component;
step S4: the excitation current i will pass through the summation circuit Sum1ex1And an excitation currentiex2Further attenuating the signal by a low pass filter LPF to obtain a pure leakage current signal Vdc。
2. The method for detecting the leakage current of the LC resonant fluxgate with suppressed modulation ripple according to claim 1, wherein the step S1 is implemented as the following steps:
step S1.1: the first high-frequency component with the same frequency as the fundamental wave and the odd harmonic and the first direct-current component generated by the measured current are both provided with an exciting current sampling resistor RS1Voltage V onsn1And (4) generating.
3. The method for detecting the leakage current of the LC resonant fluxgate with suppressed modulation ripple according to claim 2, wherein the step S2 is implemented as the following steps:
step S2.1: the second high-frequency component with the same frequency as the fundamental wave and the odd harmonic and the second direct-current component generated by the measured current are both provided with an exciting current sampling resistor RS2Voltage V onsn2Generating;
step S2.2: excitation current iex2The second dc component is filtered out after the first processing, while the second high frequency component is retained and not attenuated.
4. The LC resonant fluxgate leakage current detection method for suppressing the modulation ripple according to claim 3, wherein the step S2.2 is embodied as the following steps:
step S2.2.1: excitation current iex2The second direct current component generated by the measured current does not have a linear relation with the measured current so as to judge the second direct current component as an useless direct current component;
step S2.2.2: exciting current iex2The second direct current component is filtered out by a high pass filter HPL and the second high frequency component is retained and not attenuated.
5. The LC resonant fluxgate leakage current detection method for suppressing the modulation ripple according to claim 4, wherein the step S3 is implemented as the following steps:
step S3.1: reduce exciting current sampling resistance RS1And RS2；
Step S3.2: reducing the excitation current iex1And an excitation current iex2Peak value of (a).
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