An AC zero-crossing compensation method for stress line birefringence in an optical current sensor

Abstract

This invention relates to an AC zero-crossing compensation method for stress line birefringence in an optical current sensor. The optical current sensor includes a laser source, a polarizer, a magneto-optical thin film, and a radial polarization grating arranged sequentially on the same optical path. The method includes the following steps: emitting an optical signal using the laser source, which passes sequentially through the polarizer, the magneto-optical thin film, and the radial polarization grating. Under the influence of the current to be measured, the output signal is superimposed with the Faraday magnetostrictive rotation angle α and the stress line birefringence γ, forming a translated strip-shaped light spot; locating the position of the strip-shaped light spot using a position-sensitive detector and measuring the rotation angle of the polarization plane of the linearly polarized light; detecting the AC zero-crossing point of the current to be measured, and acquiring the rotation angle of the polarization plane measured by the position-sensitive detector at the zero-crossing point as the stress line birefringence γ; and compensating the output signal of the optical current sensor using the acquired stress line birefringence γ.

Description

TECHNICAL FIELD

[0001] The application relates to an alternating current zero compensation method for stress line birefringence of an optical current sensor and belongs to the technical field of optical current sensor correction. BACKGROUND

[0002] An optical current sensor based on a Faraday magneto-optical effect has advantages of passivity, good insulation performance, wide response frequency band, strong anti-interference capability and the like, meets the development demand of a smart power grid in China, and has a good development prospect. However, a magneto-optical material and an optical fiber of the optical current sensor are prone to stress line birefringence. Generally, the stress line birefringence is several times or even dozens of times of a Faraday magneto-optical rotation angle, has a serious extinction effect on the rotation angle, and deteriorates the accuracy of measurement and the reliability of long-term operation of the optical current sensor, thereby becoming a bottleneck restricting practical application for many years and being called a "world problem" in the industry.

[0003] The existing optical current sensor realizes approximate linear measurement of the Faraday magneto-optical rotation angle by detecting output light intensity based on Malus law. The measurement mode has defects of light power dependence and nonlinear measurement, so that the stress line birefringence introduced by the magneto-optical material and the optical material is superimposed with the Faraday magneto-optical rotation angle, and it is difficult to separate and compensate, which is also the crux of the problem that the stress line birefringence has not been effectively solved. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides an alternating current zero compensation method for stress line birefringence of an optical current sensor, direct measurement of the stress line birefringence is realized, and compensation and elimination of the stress line birefringence are realized based on a measurement result.

[0005] The technical scheme of the application is as follows:

[0006] In one aspect, the application provides an alternating current zero compensation method for stress line birefringence of an optical current sensor, the optical current sensor comprises a laser source, a polarizer, a magneto-optical film and a radial polarization grating which are sequentially arranged in the same optical path, and the method comprises the following steps:

[0007] The laser source emits an optical signal, which sequentially passes through the polarizer, the magneto-optical film and the radial polarization grating, and under the action of a measured current, an output signal is superimposed with a Faraday magneto-optical rotation angle alpha and stress line birefringence gamma, and a translation bar-shaped light spot is formed;

[0008] A position sensitive detector is used to position the bar-shaped light spot to measure a polarization plane rotation angle of linearly polarized light;

[0009] An alternating current zero point of the measured current is detected, and the polarization plane rotation angle measured by the position sensitive detector at the zero point is taken as the stress line birefringence gamma;

[0010] The output signal of the optical current sensor is compensated by the acquired stress birefringence γ.

[0011] As a preferred embodiment, the method for measuring the rotation angle of the polarization plane of linearly polarized light by positioning the bar-shaped light spot with the position sensitive detector is specifically:

[0012] The initial position of the dark fringe center of the bar-shaped light spot is positioned by the position sensitive detector;

[0013] In the measurement of the current to be measured, the current position of the dark fringe center of the bar-shaped light spot is positioned by the position sensitive detector, and the light spot displacement Δx is calculated by the current position and the initial position of the dark fringe center;

[0014] The value of the rotation angle of the polarization plane is acquired based on the relationship between the light spot displacement Δx and the rotation angle of the polarization plane.

[0015] As a preferred embodiment, the method for acquiring the relationship between the light spot displacement Δx and the rotation angle of the polarization plane is:

[0016] The light vector E1 output by the magneto-optical film is:

[0017]

[0018] Wherein, J r is the transmission matrix, E in is the linearly polarized light obtained by the incident light from the laser source through the polarizer, A represents the input light intensity, and α′=α+γ is the rotation angle of the polarization plane of the linearly polarized light considering the stress birefringence;

[0019] After the vibration components of E1 in x and y directions are combined, a linearly polarized light is obtained, and the amplitude is still A, and the polarization azimuth angle θ is:

[0020]

[0021] Therefore, θ of E1 and α′ satisfy a linear relationship:

[0022] θ=α′;

[0023] After E1 passes through the bar-shaped radial polarization grating for demodulation, it is converted into a bar-shaped light spot, wherein the dark fringe center position corresponds to the polarization plane of E1, and linearly translates with the change of α′, and θ and the light spot displacement Δx satisfy:

[0024]

[0025] Therefore, the following is obtained:

[0026]

[0027] Wherein, l is the length of the grating.

[0028] In another aspect, the present application also provides an AC zero-crossing compensation system for stress line birefringence of an optical current sensor, the optical current sensor comprising a laser source, a polarizer, a magneto-optical film and a radial polarization grating arranged in sequence in the same optical path, the system comprising:

[0029] a starting module for emitting an optical signal by the laser source, the optical signal sequentially passing through the polarizer, the magneto-optical film and the radial polarization grating, under the action of a current to be measured, the output signal superimposing a Faraday magneto-optical rotation angle a and stress line birefringence g, forming a translated bar-shaped light spot;

[0030] a measurement module for measuring a polarization plane rotation angle of linearly polarized light by positioning a position of the bar-shaped light spot by a position sensitive detector;

[0031] an AC zero-crossing detection module for detecting an AC zero-crossing point of the current to be measured;

[0032] a stress line birefringence determination module for obtaining the polarization plane rotation angle measured by the position sensitive detector at the zero-crossing point as the stress line birefringence g;

[0033] a compensation module for compensating the output signal of the optical current sensor by the obtained stress line birefringence g.

[0034] As a preferred embodiment, the measurement module specifically comprises:

[0035] an initial position measurement unit for positioning an initial position of a dark fringe center of the bar-shaped light spot by the position sensitive detector;

[0036] a light spot displacement calculation unit for positioning a current position of the dark fringe center of the bar-shaped light spot by the position sensitive detector when measuring the current to be measured, and calculating a light spot displacement amount Dx by the current position and the initial position of the dark fringe center;

[0037] a polarization plane rotation angle calculation unit for obtaining a value of the polarization plane rotation angle by a relationship between the light spot displacement amount Dx and the polarization plane rotation angle.

[0038] As a preferred embodiment, the method for obtaining the relationship between the light spot displacement amount Dx and the polarization plane rotation angle in the polarization plane rotation angle calculation unit is:

[0039] the light vector E1 output by the magneto-optical film is obtained as:

[0040]

[0041] wherein J r is a transmission matrix, E inThe incident light from the laser source is linearly polarized light through a polarizer, A represents the input light intensity, and alpha' = alpha + gamma is the rotation angle of the linearly polarized light polarization plane considering the stress birefringence;

[0042] E1 is a linearly polarized light after the vibration components in x and y directions are synthesized, the amplitude is still A, and the polarization azimuth angle theta is:

[0043]

[0044] Therefore, theta of E1 and alpha' satisfy a linear relationship:

[0045] Theta = alpha';

[0046] E1 is converted into a bar-shaped light spot after demodulation by the bar-shaped radial polarization grating, wherein the dark line center position corresponds to the polarization plane of E1, and linearly translates with the change of alpha', and theta and the light spot displacement amount Delta x satisfy:

[0047]

[0048] Therefore, the following is obtained:

[0049]

[0050] Wherein, l is the length of the grating.

[0051] In another aspect, the application also provides an electronic device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to realize the AC zero-crossing compensation method for stress birefringence of the optical current sensor according to any one of the embodiments of the application.

[0052] In another aspect, the application also provides a computer readable storage medium, which stores a computer program, wherein the program is executed by a processor to realize the AC zero-crossing compensation method for stress birefringence of the optical current sensor according to any one of the embodiments of the application.

[0053] The application has the following beneficial effects:

[0054] The AC zero-crossing compensation method for stress birefringence of the optical current sensor is based on the bar-shaped light spot output superimposed with the Faraday magneto-optical rotation angle alpha and the stress birefringence gamma of the bar-shaped radial polarization grating, and the direct linear measurement of the polarization plane rotation angle is realized through light spot positioning. Based on the principle that the current magnetic field is zero when the measured AC current crosses zero, the stress birefringence is detected and compensated at the AC zero-crossing point, so as to realize the purpose of eliminating the stress birefringence. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1The flow chart of the method of the embodiment one of the present application;

[0056] Figure 2 The principle diagram of the zero-crossing compensation in the embodiment of the present application;

[0057] Figure 3 The simulation diagram of the output light spot of the optical current sensor realized based on the bar radial polarization grating;

[0058] Figure 4 The principle diagram of the zero-crossing detection circuit in the embodiment of the present application.

[0059] The reference signs in the drawings are:

[0060] 1, laser source; 2, polarizer; 3, magneto-optical film; 4, bar radial polarization grating; 5, position sensitive detector; 6, bar light spot; 7, zero-crossing detection circuit; 8, bar light spot corresponding to the Faraday magneto-optical rotation angle; 9, bar light spot corresponding to the stress line birefringence. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work under the premise that the embodiments are within the scope of protection of the present application.

[0062] It should be understood that the step numbers used herein are only for the convenience of description, and are not limited to the execution sequence of the steps.

[0063] It should be understood that the terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clear from the context, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0064] The terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or sets thereof.

[0065] The term "and / or" means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0066] Embodiment one:

[0067] Reference is made to Figure 1 and Figure 2The application discloses an AC zero-crossing compensation method for stress linear birefringence of an optical current sensor, the optical current sensor comprising a laser source 1, a polarizer 2, a magneto-optical film 3 and a radial polarization grating 4 arranged in sequence in the same light path.

[0068] S100, a laser source 1 emits an optical signal, the optical signal emitted by the laser source 1 passes through the polarizer 2 to obtain linearly polarized light, the linearly polarized light passes through the magneto-optical film 3, under the action of a magnetic field, the polarization plane of the polarized light rotates, and the rotation angle is a Faraday magneto-optic rotation angle alpha; however, temperature change and vibration also produce stress linear birefringence gamma in the magneto-optical film 3 and a transmission optical fiber, and the stress linear birefringence gamma is superimposed on the alpha, so that the polarization plane of the output linearly polarized light co-rotates by an angle of alpha+gamma, the linearly polarized light is demodulated by the bar-shaped radial polarization grating 4 to be converted into a bar-shaped light spot 6 superimposed with the Faraday magneto-optic rotation angle alpha and the stress linear birefringence gamma, and the bar-shaped light spot 6 linearly translates with the change of the polarization plane of the linearly polarized light.

[0069] S200, the position of the emitted bar-shaped light spot 6 is located by a position-sensitive detector 5 to measure the rotation angle of the polarization plane of the linearly polarized light.

[0070] S300, according to the Faraday magneto-optic effect, when the measured AC current passes through zero, the alpha of the magneto-optical film is zero, at this time, the output signal of the sensor is the gamma, so that the zero-crossing point of the measured current can be determined by using a zero-crossing detection circuit 7, at this time, alpha=0, and the rotation angle of the polarization plane measured by the position-sensitive detector is the stress linear birefringence gamma.

[0071] S400, the output signal of the optical current sensor is compensated by the obtained stress linear birefringence gamma.

[0072] Based on the embodiment, the stress linear birefringence can be extracted and compensated when the AC current passes through zero through the linear measurement mode. The optical current sensor directly converts the Faraday magneto-optic rotation angle into synchronous translation of a light spot image based on the bar-shaped radial polarization grating, and directly linearly measures the rotation angle through light spot positioning. Temperature change and vibration produce stress linear birefringence in the magneto-optical film and the transmission optical fiber, and have a harmful extinction effect on the Faraday magneto-optic rotation angle. Based on the above linear measurement mode, the output of the sensor is linear superposition of the Faraday magneto-optic rotation angle and the stress linear birefringence. When the measured AC current passes through zero, the current magnetic field is zero, so that the Faraday magneto-optic rotation angle is zero, at this time, the output signal of the sensor is the stress linear birefringence. Then, the zero-crossing point of the measured AC current is determined by using a zero-crossing detection circuit, at this time, the stress linear birefringence can be detected and compensated, and the purpose of eliminating the stress linear birefringence is achieved.

[0073] As a preferred embodiment of the present embodiment, in step S200, the method for measuring the rotation angle of the polarization plane of linearly polarized light by positioning the bar-shaped light spot with the position-sensitive detector is specifically:

[0074] S201, positioning the initial position of the dark fringe center of the bar-shaped light spot with the position-sensitive detector;

[0075] S202, positioning the current position of the dark fringe center of the bar-shaped light spot with the position-sensitive detector when measuring the current to be measured, and calculating the light spot displacement amount Δx from the current position and the initial position of the dark fringe center;

[0076] S203, obtaining the value of the rotation angle of the polarization plane based on the relationship between the light spot displacement amount Δx and the rotation angle of the polarization plane.

[0077] As a preferred embodiment of the present embodiment, the method for obtaining the relationship between the light spot displacement amount Δx and the rotation angle of the polarization plane is:

[0078] Specifically refer to Figure 2 , the incident light from the laser source 1 is linearly polarized light Ein through the polarizer 2:

[0079]

[0080] Where A represents the input light intensity.

[0081] The linearly polarized light passes through the magneto-optical film 3, and under the action of the magnetic field of the current to be measured, the polarization plane of the linearly polarized light rotates, and the rotation angle is the Faraday magneto-optical rotation angle α, and the transmission matrix J E can be expressed as:

[0082]

[0083] Affected by temperature changes and vibrations, stress birefringence γ is generated in the magneto-optical film 3 and the transmission optical fiber, at this time J E can be rewritten as J r :

[0084]

[0085] Where α' = α + γ is the rotation angle of the polarization plane of the linearly polarized light considering the stress birefringence.

[0086] Therefore, the Jones vector of the linearly polarized light after passing through the magneto-optical film is:

[0087]

[0088] The vibration components of the output light vector E1 in x and y directions are combined to obtain a linearly polarized light, and the amplitude is still A, and the polarization azimuth angle θ is:

[0089]

[0090] Therefore, θ in E1 and α' satisfy a linear relationship:

[0091] θ = α' (6)

[0092] E1 is converted into a bar-shaped light spot after demodulation by the bar-shaped radial polarization grating, wherein the dark stripe center position corresponds to the polarization plane of E1 and linearly translates with the change of α'. θ and the light spot displacement Δx satisfy:

[0093]

[0094] wherein l is the length of the grating. When θ = 0°, the dark stripe center position is on the 0° grating unit of the bar-shaped polarization grating. Based on the Matlab simulation, the light intensity distribution after the polarization grating detection is shown in FIG. 4. Figure 3 It can be seen that the dark stripe center of the light spot synchronously translates with the change of θ, and therefore the direct measurement of θ can be realized by measuring the translation amount of the dark stripe center of the light spot.

[0095] Combining formula (6) and (7), we obtain:

[0096]

[0097] Therefore, the linear measurement result of the optical current sensor is the linear superposition of α and γ. According to the Faraday magneto-optical effect, the measured magnetic field H and α satisfy:

[0098] α = VHL M (9)

[0099] wherein V is the Verdet constant, and LM is the light path length of the magneto-optical material along the magnetic field direction. When H = 0, α = 0, that is, at the zero crossing of the alternating current, the output signal α' of the optical current sensor is γ, and at this moment, the dark stripe center position of the bar-shaped light spot 8 corresponding to α = 0 is at zero, while the dark stripe position 9 of the output light spot of the optical current sensor corresponds to γ. By positioning the light spot, γ can be detected and compensated, achieving the purpose of eliminating γ.

[0100] In one embodiment, the zero-crossing detection circuit 7 is used to determine the zero crossing of the measured alternating current, and the circuit principle is shown in FIG. 5. Figure 4 U2A and U2B are two comparators of LM339, Vi is the input signal, Vo is the output signal, V2 and V3 are the upper limit value and lower limit value of the reference voltage of the comparator respectively; 7408N is an integrated double-input four AND gate circuit. Its working principle is: in a period, when Vi > V2, Vo is low; when V3 < Vi < V2, Vo is high; when Vi < V3, Vo is low. Therefore, by adjusting the values of V2 and V3, the zero crossing of the alternating current can be detected.

[0101] In the embodiment, the laser source 1 is a single longitudinal mode laser with a wavelength of 808 nm; the magneto-optical film 3 is a Bi-Gd-YIG type; the strip radial polarization grating 4 is made by an electron beam direct writing method, with a processing error of ±5 nm, a length of 12 mm, a height of 1.5 mm, a period of 200 nm, a duty cycle of 0.5, a grating ridge height of 150 nm, and a maximum measurable Faraday magneto-optical rotation angle of ±50°; the position sensitive detector 5 is used to detect the spot displacement, which is an S3932 type with a light sensitive area of 1*12 mm, a wavelength response range of 760-1100 nm, and a peak wavelength of 960 nm; the zero-crossing detection circuit is used to detect the zero-crossing point of the alternating current to be measured, and the reference is attached Figure 4 ;

[0102] To verify the effectiveness of the method proposed in the embodiment, a high-low temperature alternating humidity test box is used to provide different temperature environments, with a temperature range of-40℃-85℃ and a temperature fluctuation of ±0.5℃. The optical current sensor is placed in the inner tank of the temperature box, and the temperature cycle experiment is carried out in the temperature range of-40℃-85℃. The zero-crossing detection circuit 7 is used to detect the zero-crossing point to determine the stress line birefringence introduced in each cycle and to compensate it. Finally, the basic accuracy of the optical current sensor is recorded by the calibration instrument, as shown in Table 1. Under the temperature cycle condition, the optical current sensor can meet the requirement of 0.5 level accuracy.

[0103] Table 1 Basic accuracy experimental data

[0104]

[0105] Embodiment two:

[0106] The embodiment proposes an alternating current zero-crossing compensation system for stress line birefringence of an optical current sensor, which comprises a laser source, a polarizer, a magneto-optical film and a radial polarization grating arranged in sequence in the same optical path, and the system comprises:

[0107] A starting module is used to emit an optical signal by the laser source, which passes through the polarizer, the magneto-optical film and the radial polarization grating in sequence, and under the action of the current to be measured, the output signal is superimposed with the Faraday magneto-optical rotation angle α and the stress line birefringence γ, forming a translated strip light spot. This module is used to realize the function of step S100 in embodiment one, and will not be described here.

[0108] A measurement module is used to measure the polarization plane rotation angle of linearly polarized light by positioning the strip light spot position by the position sensitive detector. This module is used to realize the function of step S200 in embodiment one, and will not be described here.

[0109] An alternating current zero-crossing detection module is used to detect the alternating current zero-crossing point of the current to be measured.

[0110] a stress birefringence determination module for obtaining the polarization plane rotation angle measured by the position sensitive detector at the zero-crossing moment as the stress birefringence γ; the AC zero-crossing detection module and the stress birefringence determination module together realize the function of step S300 in Embodiment One, and thus will not be described here again;

[0111] a compensation module for compensating the output signal of the optical current sensor by the obtained stress birefringence γ; this module realizes the function of step S400 in Embodiment One, and thus will not be described here again.

[0112] As a preferred embodiment of the present embodiment, the measurement module specifically comprises:

[0113] an initial position measurement unit for measuring the initial position of the dark fringe center of the bar-shaped light spot by the position sensitive detector;

[0114] a light spot displacement calculation unit for calculating the light spot displacement amount Δx by the current position of the dark fringe center of the bar-shaped light spot measured by the position sensitive detector and the initial position of the dark fringe center when measuring the current to be measured;

[0115] a polarization plane rotation angle calculation unit for obtaining the value of the polarization plane rotation angle by the relationship between the light spot displacement amount Δx and the polarization plane rotation angle.

[0116] As a preferred embodiment of the present embodiment, the method for obtaining the relationship between the light spot displacement amount Δx and the polarization plane rotation angle in the polarization plane rotation angle calculation unit is:

[0117] the light vector E1 output by the magneto-optical film is obtained as:

[0118]

[0119] wherein, J r is the transmission matrix, E in is the linearly polarized light obtained by the polarizer from the incident light from the laser source, A represents the input light intensity, and α' = α + γ is the rotation angle of the polarization plane of the linearly polarized light considering the stress birefringence;

[0120] the vibration components of E1 in the x and y directions are combined to obtain a linearly polarized light, and the amplitude of the linearly polarized light is still A, and the polarization azimuth angle θ is:

[0121]

[0122] Therefore, θ of E1 and α' satisfy a linear relationship:

[0123] θ = α';

[0124] E1 is converted into a bar-shaped light spot after demodulation by the bar-shaped radial polarization grating, wherein the dark stripe center position corresponds to the polarization plane of E1 and linearly translates with the change of a', and θ and the light spot displacement Δx satisfy:

[0125]

[0126] Therefore, we have:

[0127]

[0128] wherein, l is the length of the grating.

[0129] Embodiment three:

[0130] The embodiment provides an electronic device, including a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the AC zero-crossing compensation method for stress line birefringence of an optical current sensor according to any embodiment of the application when executing the program.

[0131] Embodiment four:

[0132] The embodiment provides a computer readable storage medium, which stores a computer program, and the program is executable on a processor to implement the AC zero-crossing compensation method for stress line birefringence of an optical current sensor according to any embodiment of the application.

[0133] In the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects. "At least one of the following" and the like means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b and c can mean: a, b, c, a and b, a and c, b and c, or a and b and c, wherein a, b, and c can be single or multiple.

[0134] Those of ordinary skill in the art can realize that the units and algorithm steps described in the embodiments disclosed herein can be realized by electronic hardware, computer software and a combination of electronic hardware and computer software. Whether the functions are realized in hardware or software mode depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0135] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the system, device and unit described above can refer to the corresponding processes in the foregoing method embodiments, and will not be described here.

[0136] In several embodiments provided in the present application, any function, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (Read-Only Memory; hereinafter referred to as: ROM), a random access memory (Random Access Memory; hereinafter referred to as: RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0137] The above is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. An AC zero-crossing compensation method for stress-birefringence in optical current sensors, characterized in that, The optical current sensor comprises a laser source, a polarizer, a magneto-optical film and a radial polarization grating arranged in sequence in the same light path, and the method comprises the following steps: The laser source is used to emit an optical signal which passes through the polarizer, the magneto-optical film and the radial polarization grating in sequence, and under the action of the current to be measured, the output signal is superimposed with a Faraday magneto-optical rotation angle α and a stress linear birefringence γ, forming a translated strip-shaped light spot; The position of the strip-shaped light spot is located by a position sensitive detector to measure the rotation angle of the polarization plane of linearly polarized light; The AC zero-crossing point of the current to be measured is detected, and the rotation angle of the polarization plane measured by the position sensitive detector at the zero-crossing point is taken as the stress linear birefringence γ; The output signal of the optical current sensor is compensated by the obtained stress linear birefringence γ.

2. An AC zero-crossing compensation method of stress-birefringence in an optical current sensor according to claim 1, characterized in that, The method for measuring the rotation angle of the polarization plane of linearly polarized light by locating the strip-shaped light spot by the position sensitive detector is specifically: The initial position of the dark fringe center of the strip-shaped light spot is located by the position sensitive detector; In the measurement of the current to be measured, the current position of the dark fringe center of the strip-shaped light spot is located by the position sensitive detector, and the displacement amount Δx of the light spot is calculated by the current position and the initial position of the dark fringe center; The value of the rotation angle of the polarization plane is obtained based on the relationship between the displacement amount Δx of the light spot and the rotation angle of the polarization plane.

3. An AC zero-crossing compensation method of stress-birefringence in an optical current sensor according to claim 2, characterized in that, The method for obtaining the relationship between the displacement amount Δx of the light spot and the rotation angle of the polarization plane is: The output light vector E1 of the magneto-optical film is: where J r is the transmission matrix, E in is the linearly polarized light from the incident light from the laser source through the polarizer, A represents the input light intensity, and a' = a + y is the rotation angle of the polarization plane of the linearly polarized light when the stress linear birefringence is considered. After the vibration components of E1 in x and y directions are combined, a linearly polarized light is obtained, the amplitude of which is still A, and the polarization azimuth angle θ is: Therefore, θ of E1 and α' satisfy a linear relationship: θ = α'; After E1 passes through the strip-shaped radial polarization grating for demodulation, it is converted into a strip-shaped light spot, wherein the dark fringe center position corresponds to the polarization plane of E1, and linearly translates with the change of α', and θ and the displacement amount Δx of the light spot satisfy: Therefore, the following is obtained: Wherein, l is the length of the grating.

4. An AC zero-crossing compensation system for stress-birefringence in an optical current sensor, characterized in that The optical current sensor comprises a laser source, a polarizer, a magneto-optical film and a radial polarization grating arranged in sequence in the same light path, and the system comprises: A starting module is configured to emit an optical signal by a laser source, which passes through a polarizer, a magneto-optical film and a radial polarization grating in sequence, and under the action of the current to be measured, the output signal is superimposed with a Faraday magneto-optical rotation angle α and a stress linear birefringence γ, forming a translated strip-shaped light spot; A measurement module is configured to measure the rotation angle of the polarization plane of linearly polarized light by locating the position of the strip-shaped light spot by a position sensitive detector; An AC zero-crossing point detection module is configured to detect the AC zero-crossing point of the current to be measured; A stress linear birefringence determination module is configured to take the rotation angle of the polarization plane measured by the position sensitive detector at the zero-crossing point as the stress linear birefringence γ; A compensation module is configured to compensate the output signal of the optical current sensor by the obtained stress linear birefringence γ.

5. An optical current sensor stress line birefringence AC zero-crossing compensation system according to claim 4, characterized in that, The measurement module specifically comprises: An initial position measurement unit is configured to locate the initial position of the dark fringe center of the strip-shaped light spot by the position sensitive detector; A light spot displacement calculation unit is configured to locate the current position of the dark fringe center of the strip-shaped light spot by the position sensitive detector in the measurement of the current to be measured, and calculate the displacement amount Δx of the light spot by the current position and the initial position of the dark fringe center. A polarization plane rotation angle calculation unit is configured to obtain a value of the polarization plane rotation angle according to a relationship between the spot displacement amount Δx and the polarization plane rotation angle.

6. An optical current sensor stress line birefringence AC zero-crossing compensation system according to claim 5, wherein, The method for obtaining the relationship between the spot displacement amount Δx and the polarization plane rotation angle in the polarization plane rotation angle calculation unit is: The light vector E1 output by the magneto-optical film is: where J r is the transmission matrix, E in is the linearly polarized light obtained by passing the incident light from the excitation laser source through a polarizer, A represents the input light intensity, and a' = a + y is the rotation angle of the polarization plane of the linearly polarized light when the stress linear birefringence is taken into account. After the vibration components of E1 in the x and y directions are combined, a linearly polarized light is obtained, the amplitude of which is still A, and the polarization azimuth angle θ is: Therefore, θ of E1 and α' satisfy a linear relationship: θ = α'; After E1 is demodulated by the strip radial polarization grating, it is converted into a strip light spot, the dark line center position of which corresponds to the polarization plane of E1 and linearly translates with the change of α', and θ and the spot displacement amount Δx satisfy: Therefore, the following is obtained: Wherein, l is the length of the grating.

7. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the alternating current zero-crossing compensation method for stress line birefringence of the optical current sensor according to any one of claims 1 to 3.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the alternating current zero-crossing compensation method for stress line birefringence of the optical current sensor according to any one of claims 1 to 3.

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