Independent double-strip-shaped optical current sensor and external temperature fluctuation interference resisting method thereof

Abstract

The invention discloses an independent double-strip-shaped optical current sensor and an external temperature fluctuation interference resisting method thereof, and belongs to the technical field of intelligent measurement and sensing of a power system. The sensor comprises a sensing unit and a signal processing unit which are connected with each other, the output end of a multi-frequency modal decoupling signal processing device is connected with the input end of a double-strip-shaped optical current sensor signal processing device, and the output end of the double-strip-shaped optical current sensor signal processing device is connected with the input end of a measurement signal output device; the sensing unit is provided with a double-strip-shaped sensing unit main body structure comprising a measurement sensing light path structure and a temperature compensation sensing light path structure, and the vertical distances from the midpoints of the measurement sensing light path structure and the temperature compensation sensing light path structure to the current to be measured are equal. According to the invention, the temperature-resistant measurement function can be realized while the advantages of high long-term operation stability and simple structure of the single straight-through light path type optical current sensor are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent measurement and sensing in power systems, and particularly to an independent double-strip optical current sensor and a method for resisting external temperature fluctuation interference thereof. Background Art

[0002] Traditional ferromagnetic current transformers have problems such as being prone to ferromagnetic resonance, core magnetic saturation, large floor area, and high insulation cost. Therefore, traditional ferromagnetic current transformers have become out of touch with the development trend of grid intelligence and digitization. In order to meet the construction requirements of smart grids and new grids, electronic current transformers represented by optical current transformers have gradually shown application value. Magneto-optical glass optical current sensors (MOCTs) have received extensive attention from researchers due to their advantages of small size and relatively stable physical properties. MOCTs can be further divided into two sensing structures: closed optical path type and direct optical path type according to their sensor structures. Among them, the closed optical path structure has a reflection phase shift due to structural limitations and poor long-term operation stability. However, the direct optical path structure is simple, has a low manufacturing cost, and good long-term operation stability. The invention patent "A laminated optical current sensor and a method for resisting external magnetic interference thereof" with the application number 202210600285.7 disclosed by the Chinese Patent Office solves the problem of external magnetic interference during the measurement process of the direct optical path type MOCT, but does not consider the influence of temperature fluctuation disturbance on the measurement accuracy of the direct optical path type MOCT. With the solution of the external magnetic interference problem, the photoelectric noise problem, and the application of high-performance magneto-optical materials during the measurement process of the direct optical path type MOCT, the direct optical path type MOCT has shown outstanding practical potential, but still faces the influence of temperature interference.

[0003] In view of the linear birefringence problem existing in magneto-optical materials, various solutions have been proposed from different angles in the prior art, which can be listed as follows:

[0004] 1) Separating the Faraday effect and the linear birefringence effect offline. A phase retardation plate is added between the magneto-optical material and the polarizer in the original measurement structure. No external magnetic field is applied outside the magneto-optical material, but incident linearly polarized light is used. By using the calculation method of the Jones matrix, the formula for measuring the linear birefringence inside the magneto-optical material is derived, and the linear birefringence of the magneto-optical material is directly measured. However, this measurement method cannot realize the online simultaneous detection of the Faraday rotation angle and the linear birefringence of the magneto-optical glass, and has low practical potential.

[0005] 2) Using the temperature characteristic curve output by the pre-measured magneto-optical sensing structure to perform temperature compensation on the output signal of the sensor is also a sensor temperature compensation method. However, this method has high requirements for the heat transfer structure of the sensor, and it is difficult to obtain the corresponding relationship between the repeated sensor output signal and the ambient temperature curve, resulting in a large compensation error for the method.

[0006] 3) Optical current sensor based on comparative measurement: A permanent magnet is applied to construct a comparative magneto-optical current sensor, that is, a reference sensing optical path is constructed using a permanent magnet. It can be approximately considered that the reference sensing optical path and the actual measurement optical path are affected by the ambient temperature in the same way. This method can compensate in real time for the problem of the decrease in the measurement accuracy of the optical current sensor caused by temperature influence by using a permanent magnet to construct a standard measurement sensing optical path. However, the practical application of this method is limited by the permanent magnet. The permanent magnet is prone to demagnetization, which will make the long-term operation stability of the comparative measurement method poor.

[0007] According to the above analysis of the defects existing in various temperature compensation methods for MOCT measurement, an independent double-strip optical current sensor and its method for resisting external temperature fluctuation interference are needed to eliminate the influence of ambient temperature fluctuation on the optical current sensor, while maintaining the characteristics of the direct-through optical path type MOCT structure, such as simple structure, low manufacturing cost, and strong long-term operation stability. Summary of the Invention

[0008] The object of the present invention is to propose an independent double-strip optical current sensor and its method for resisting external temperature fluctuation interference.

[0009] An independent double-strip optical current sensor includes a sensing unit and a signal processing unit connected to each other. The signal processing unit includes a multi-frequency mode decoupling signal processing device, a double-strip optical current sensor signal processing device, and a measurement signal output device. Among them, the output end of the multi-frequency mode decoupling signal processing device is connected to the input end of the double-strip optical current sensor signal processing device, and the output end of the double-strip optical current sensor signal processing device is connected to the input end of the measurement signal output device;

[0010] The sensing unit is provided with a double-strip sensing unit main structure including a measurement sensing optical path structure and a temperature compensation sensing optical path structure. The vertical distances from the midpoints of the measurement sensing optical path structure and the temperature compensation sensing optical path structure to the current to be measured are equal.

[0011] Further, both the measurement sensing optical path structure and the temperature compensation sensing optical path structure are sequentially connected in series by a signal input optical fiber, an input collimator, a polarizer, a magneto-optical sensing material, an analyzer, an output collimator, and a signal output optical fiber.

[0012] Further, the relationship between the placement positions of the polarizer and the analyzer in the measurement sensing optical path structure is that their optical axes are 45° apart; the relationship between the placement positions of the polarizer and the analyzer in the temperature compensation sensing optical path structure is that their optical axes are 0° apart.

[0013] Further, the measurement sensing optical path structure and the temperature compensation sensing optical path structure are fixed on an insulating bearing structure; an insulating encapsulation cover is also provided on the insulating bearing structure.

[0014] As a preferred technical solution of the present invention, the internal connection structure of the independent double-strip optical current sensor is as follows:

[0015] The high-precision adjustable current source, the controllable light source, and the optical splitter are connected in sequence. Then, the optical splitter divides into two paths and is respectively connected to the measurement sensing optical path structure and the temperature compensation sensing optical path structure; the measurement sensing optical path structure and the temperature compensation sensing optical path structure are arranged in parallel; the measurement sensing optical path structure is sequentially connected to an input end of the multi-frequency mode decoupling signal processing device through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure is sequentially connected to another input end of the multi-frequency mode decoupling signal processing device through a second photodetector and a second A / D converter.

[0016] As another preferred technical solution of the present invention, the internal connection structure of the independent double-strip optical current sensor is as follows:

[0017] The high-precision adjustable current source is connected to the controllable light source. Then, the controllable light source directly divides into two paths through an optical fiber and is respectively connected to the measurement sensing optical path structure and the temperature compensation sensing optical path structure; the measurement sensing optical path structure and the temperature compensation sensing optical path structure are arranged in parallel; the measurement sensing optical path structure is sequentially connected to an input end of the multi-frequency mode decoupling signal processing device through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure is sequentially connected to another input end of the multi-frequency mode decoupling signal processing device through a second photodetector and a second A / D converter.

[0018] As another preferred technical solution of the present invention, the internal connection structure of the independent double-strip optical current sensor is as follows:

[0019] The high-precision adjustable current source, the controllable light source, and the optical splitter are connected in sequence. Then, the optical splitter divides into two paths and is respectively connected to the measurement sensing optical path structure and the temperature compensation sensing optical path structure; the measurement sensing optical path structure and the temperature compensation sensing optical path structure are arranged perpendicular to each other, and their input ends are not adjacent; the measurement sensing optical path structure is sequentially connected to an input end of the multi-frequency mode decoupling signal processing device through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure is sequentially connected to another input end of the multi-frequency mode decoupling signal processing device through a second photodetector and a second A / D converter.

[0020] As another preferred technical solution of the present invention, the internal connection structure of the independent dual-strip optical current sensor is as follows:

[0021] The high-precision adjustable current source is connected to the controllable light source, and then the controllable light source is directly connected to the measurement sensing optical path structure and the temperature compensation sensing optical path structure through the optical fiber in two paths respectively; the measurement sensing optical path structure and the temperature compensation sensing optical path structure are arranged perpendicular to each other, and their input ends are not adjacent; the measurement sensing optical path structure is connected to an input end of the multi-frequency modal decoupling signal processing device through the first photodetector and the first A / D converter in sequence; the temperature compensation sensing optical path structure is connected to the other input end of the multi-frequency modal decoupling signal processing device through the second photodetector and the second A / D converter in sequence.

[0022] A method for resisting external temperature fluctuation interference of an independent dual-strip optical current sensor, with the axis direction perpendicular to the light transmission direction as the x-axis, and the angle between the optical axis of the analyzer and the x-axis is The angle between the optical axis of the polarizer and the x-axis is θ, then considering any angle between the optical axes of the polarizer and the analyzer, the optical current sensing model of the optical current sensing structure is shown as the following formula:

[0023]

[0024] Where:

[0025]

[0026] cos(χ) = (δ / Δ)

[0027] sin(χ) = (2γ / Δ)

[0028] In the formula, E o represents the total output electric vector of the light; E o1 , E o2 respectively represent the electric vectors in the x and y directions of the output light; sin(χ), cos(χ) represent variables related to the dielectric tensor matrix of the magneto-optical material, and their values can be determined by γ and δ. δ is the linear birefringence of the magneto-optical material, and the environmental temperature interference information is mixed in the output signal of the optical current sensor in the form of linear birefringence. γ is the Faraday rotation angle value containing the current information to be measured, and Δ is the mixed quantity of the linear birefringence δ and the Faraday rotation angle γ; and δ >> γ, so Δ ≈ δ, which is a constant under the same temperature environment. j is the imaginary unit. When considering any angle between the polarizer and the analyzer, the light intensity signals J O output by the measurement sensing optical path structure and the temperature compensation sensing optical path structure are both as follows:

[0029]

[0030] When the relative angle θ between the optical axis of the polarizer (3) and the x-axis is 45°, the light intensity signal JO Becomes:

[0031]

[0032] In the formula, J i is the intensity of the incident light; keeping the relative angle θ between the incident plane of the incident linearly polarized light and the x-axis at 45°, and setting the relative angle between the optical axis of the analyzer of the measurement sensing optical path structure and the x-axis to be 90°, then the electrical signal u1 output by the measurement sensing optical path structure is expressed as:

[0033]

[0034] In the formula, J o1 is the intensity of the outgoing light output by the measurement sensing optical path structure; setting the angle between the optical axis of the analyzer of the temperature compensation sensing optical path structure and the x-axis to be 45°, and the relative angle between the optical axis of the polarizer and the x-axis θ to be 45°, then the output signal u2 of the temperature compensation sensing optical path structure is expressed as:

[0035]

[0036] In the formula, J o2 is the intensity of the outgoing light output by the temperature compensation sensing optical path structure; from this, it can be obtained that the signals output by the measurement sensing optical path structure and the temperature compensation sensing optical path structure are both AC-DC mixed signals, and because noise will be generated in the signal during the acquisition process of the photodetector and the analog-to-digital conversion process, so a multi-frequency modal decoupling signal processing device is used to obtain the AC signal related to the information of the current to be measured near the frequency of the current to be measured, that is, 50Hz, and the temperature compensation signal information:

[0037]

[0038] u4 = cos(Δ)

[0039] Obtain the measurement value of the Faraday rotation angle containing only the information of the current to be measured after eliminating the influence of linear birefringence, and then obtain the value of the current to be measured. In actual measurement, the value of the Faraday rotation angle is less than 90°, and because the value range of the arcsine function is [-π / 2, π / 2], so the formula for resisting external temperature fluctuation interference is obtained as:

[0040]

[0041] It is also known that the basic principle formula of the Faraday magneto-optical effect of optical current sensing is given as follows:

[0042]

[0043] Wherein, V is the Verdet constant of the magneto-optical material, with the unit of rad / A, which is an important parameter characterizing the magneto-optical properties of the material; is the magnetic field information to be measured, with the unit of A / m; l represents the length of the sensing optical path, with the unit of m; I is the value of the current to be measured, with the unit of A; N is a constant, characterizing the number of turns of the linearly polarized light around the current loop; therefore, the final measurement signal output device outputs the measured signal as follows:

[0044]

[0045] Place the polarizers of the measurement sensing optical path structure and the temperature compensation sensing optical path structure according to the requirements of the same-angle anti-temperature fluctuation perturbation method for polarizers, and then the high-precision optical current sensing measurement value that eliminates the temperature interference information can be obtained.

[0046] The beneficial effects of the present invention are as follows:

[0047] 1. The independent double-strip optical current sensor structure proposed by the present invention can basically eliminate the influence of environmental temperature fluctuations on the measurement accuracy decline of the optical current sensor.

[0048] 2. By proposing a new structural design of the temperature compensation signal sensing arm, the present invention realizes the separate detection of the measured current measurement signal and the environmental temperature interference signal, and through the reasonable detection of the two signals, a higher-precision optical current sensing measurement result can be obtained.

[0049] 3. The independent double-strip optical current sensor of the present invention can realize the temperature-resistant measurement function while ensuring the advantages of strong long-term operation stability and simple structure of the single-strip direct-through optical path type optical current sensor.

[0050] 4. The present invention adopts the method of changing the angle of the polarizer to realize the construction of the optical current sensing measurement structure and the temperature compensation structure, which has the advantages of simple operation and simple manufacturing process, and improves the temperature-resistant practical performance of the MOCT.

[0051] 5. The present invention utilizes the independent characteristics of each single-strip direct-through optical path type optical current sensor, and can be combined with the strip direct-through optical path type MOCT structure that resists other physical fields, such as external magnetic interference fields, etc., laying a foundation for realizing multi-physical field anti-interference. Description of the Drawings

[0052] Figure 1 (a), (b), and (c) are respectively the structure diagrams of the independent double-strip optical current sensors placed in parallel at equal distances, placed vertically at equal distances, and the schematic diagram of the insulating encapsulation cover;

[0053] Figure 2 is the schematic diagram of the independent double-strip optical current sensor and its signal processing device in Embodiment 1;

[0054] Figure 3 Schematic diagram of the independent double-strip optical current sensor and its signal processing device in Embodiment 2;

[0055] Figure 4 Schematic diagram of the independent double-strip optical current sensor and its signal processing device in Embodiment 3;

[0056] Figure 5 Schematic diagram of the independent double-strip optical current sensor and its signal processing device in Embodiment 4;

[0057] Figure 6 Schematic diagram of the Faraday magneto-optical effect of the MOCT measurement principle;

[0058] In the figure: 1 - input signal optical fiber; 2 - light source input collimator; 3 - polarizer; 4 - magneto-optical sensing material; 5 - analyzer; 6 - light source output collimator; 7 - output signal optical fiber; 8 - measurement sensing optical path structure; 9 - temperature compensation sensing optical path structure; 10 - insulating carrier structure; 11 - insulating encapsulation cover; 12 - high-precision adjustable current source; 13 - controllable light source; 14 - optical splitter; 15 - double-strip sensing unit main structure; 16 - photodetector; 17 - A / D converter; 18 - multi-frequency mode decoupling signal processing device; 19 - double-strip optical current sensor signal processing device; 20 - measurement signal output device; 21 - sensing unit; 22 - signal processing unit; 23 - current conductor to be measured. Specific embodiments

[0059] The present invention proposes an independent double-strip optical current sensor and a method for resisting interference from external temperature fluctuations. The following further describes the present invention with reference to the accompanying drawings and specific embodiments.

[0060] Figure 1 (a), (b), and (c) are respectively the structural diagrams of the independent double-strip optical current sensors placed in parallel at equal distances, placed vertically at equal distances, and the schematic diagram of the insulating encapsulation cover.

[0061] The vertical distances from the midpoints of the two independent optical current sensing optical path structures to the current 23 to be measured are equal; two optical current sensing optical path structures are placed on the insulating carrier structure 10 and fixed; the insulating encapsulation cover 11 is placed above the double-strip sensing unit main structure 15 and together with the insulating carrier structure 10 forms an insulating isolation device of the independent double-strip optical current sensing device; the measurement sensing optical path structure 8 is connected in series by the signal input optical fiber 1, input collimator 2, polarizer 3, magneto-optical sensing material 4, analyzer 5, output collimator 6, and signal output optical fiber 7; the temperature compensation sensing optical path structure 9 and the measurement sensing optical path structure 8 are composed of exactly the same types and sequences of components; the difference between the temperature compensation sensing optical path structure 9 and the measurement sensing optical path structure 8 lies in the optical axis angle difference of the analyzer.

[0062] The positional relationship between the polarizer 3 and the analyzer 5 in the measurement sensing optical path structure 8 is that the optical axes are 45° different; the positional relationship between the polarizer 3 and the analyzer 5 in the temperature compensation sensing optical path structure 9 is that the angle between the optical axes is 0°; the two independent measurement sensing optical path structures 8 and temperature compensation sensing optical path structures 9 together constitute the magneto-optical sensing part of the double-strip sensing unit main structure 15 in the independent double-strip optical current sensor's independent double-strip sensing unit.

[0063] Embodiment 1

[0064] Figure 2 It is a schematic diagram of the independent double-strip optical current sensor and its signal processing device in Embodiment 1. This method is described as follows: The high-precision adjustable current source 12 drives the controllable light source 13 to output a stable and reliable light source signal; the light source signal is split into two beams by the optical splitter 14; among them, one beam of light serves as the input light signal of the measurement sensing optical path structure 8; the other beam of light serves as the input light signal of the temperature compensation sensing optical path structure 9; the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are placed symmetrically parallel to the upper and lower sides of the current to be measured 23, and the vertical distances from the midpoints of their optical path structures to the current to be measured 23 are equal; the output light intensity signals modulated by the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are respectively input into the first A / D converter and the second A / D converter of the A / D converter 17 through the first photodetector and the second photodetector; the optical signals output by the first A / D converter and the second A / D converter are comprehensively processed by the multi-frequency mode decoupling signal processing device 18, the double-strip optical current sensor signal processing device 19, and the measurement signal output device 20, and then the accurate optical current sensing measurement result after temperature disturbance resistance is output.

[0065] Embodiment 2

[0066] Figure 3 It is a schematic diagram of the independent double-strip optical current sensor and its signal processing device in Embodiment 2. The independent double-strip optical current sensor in this embodiment is represented in the following form. Remove the optical splitter 14, and directly use the natural light generated by the stable and reliable controllable light source 13 as the input light signals of the sensing structure measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 respectively; and input the output light intensity signals generated by the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 into the first photodetector and the second photodetector of the photodetector 16 respectively and simultaneously; the signals output by the first photodetector and the second photodetector then output the output light intensity modulation signal to the first A / D converter and the second A / D converter of the A / D converter 17; the light intensity signal output by the A / D converter 17 is input into the signal processing unit 22 for signal processing, and then the measurement result of the current to be measured with temperature disturbance resistance is output.

[0067] In this embodiment, it is necessary to ensure that the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are symmetrically and equidistantly placed on the upper and lower sides of the current to be measured.

[0068] Embodiment 3

[0069] Figure 4 It is a schematic diagram of an independent double-strip optical current sensor and its signal processing device in Embodiment 3. The independent double-strip optical current sensor in this embodiment is expressed in the following form, retaining the optical splitter 14; the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are placed at 90°, and the centers of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are vertically and equidistantly placed on the upper and left sides of the current 23 to be measured respectively; and the natural light signal generated by the controllable light source 13 is respectively input into the input ends of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 through the optical splitter 14; the output signals of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are respectively input into the first photodetector and the second photodetector of the photodetector 16 at the same time; the signals output by the first photodetector and the second photodetector are then output to the first A / D converter and the second A / D converter of the A / D converter 17 as output optical intensity modulation signals; the optical intensity signals output by the A / D converter 17 are input into the signal processing unit 22 for signal processing and then the measurement result of the current to be measured with temperature disturbance resistance is output.

[0070] In this embodiment, it is necessary to ensure that the input ends of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are not adjacent, in order to conform to the direction consistency of the external magnetic field.

[0071] Embodiment 4

[0072] Figure 5Schematic diagram of the independent dual-strip optical current sensor and its signal processing device in Embodiment 4; the independent dual-strip optical current sensor in this embodiment is represented in the following form, removing the optical splitter 14; the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are placed at a 90° angle, and the centers of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are placed on the upper and left sides of the current to be measured 23 perpendicular to and equidistant from the current to be measured 23; the natural light input signal emitted by the controllable light source 13 is directly input into the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9; the measurement signal of the current to be measured and the optical current sensing temperature compensation signal generated by modulation through the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are respectively collected and processed by the first photodetector and the second photodetector of the photodetector 16 and then input into the first A / D converter and the second A / D converter of the A / D converter 17; the current electrical signal to be measured and the optical current sensing temperature compensation signal output by the first A / D converter and the second A / D converter are further comprehensively processed by the multi-frequency mode decoupling signal processing device 18, the dual-strip optical current sensor signal processing device 19, and the measurement signal output device 20; the signal processing unit 22 finally outputs an accurate optical current sensing measurement result resistant to temperature disturbance.

[0073] In this embodiment, it is necessary to ensure that the input ends of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are not adjacent, conforming to the direction consistency of the external magnetic field.

[0074] Figure 6 Schematic diagram of the MOCT measurement principle of the Faraday magneto-optical effect. The method for the independent dual-strip optical current sensor to achieve anti-interference from ambient temperature fluctuations is as follows:

[0075] As Figure 1 shown, the centers of the current measurement structure 8 to be measured and the temperature compensation measurement structure 9 are placed on both sides of the current to be measured 23 at equal distances from the connection line of the current to be measured 23, ensuring the consistency of the magnetic field information measured by the two sensing arms.

[0076] Taking the axis direction perpendicular to the light transmission direction as the x-axis, let the angle between the optical axis of the analyzer and the x-axis be the angle between the optical axis of the polarizer and the x-axis be θ, then considering any angle between the optical axes of the analyzer and the polarizer, the light intensity information output by the optical current sensing structure can be obtained as shown in the following formula:

[0077]

[0078] In the formula:

[0079] cos(χ) = (δ / Δ)

[0080] sin(χ) = (2γ / Δ)

[0081] In the formula, E o represents the total output electric vector of light; E o1 , E o2 respectively represent the electric vectors in the x and y directions of the output light; sin(χ) and cos(χ) represent variables related to the dielectric tensor matrix of the magneto-optical material, and their values can be determined by γ and δ. δ is the linear birefringence of the magneto-optical material, and the environmental temperature interference information is mixed in the output signal of the optical current sensor in the form of linear birefringence; γ is the Faraday rotation angle value containing the information of the current to be measured; Δ is the mixing amount of the linear birefringence δ and the Faraday rotation angle γ; and δ >> γ, so Δ ≈ δ, and it can be considered that Δ is a constant under the same temperature environment; the angle between the optical axis of the analyzer 5 and the x-axis is j is the imaginary unit. When considering any angle of the analyzer, the light intensity signals J output by the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are O both given by the following formula:

[0082]

[0083] When the relative angle θ between the optical axis of the polarizer and the x-axis is 45°, the light intensity signal J O becomes:

[0084]

[0085] In the formula, J i is the light intensity of the incident light; keeping the relative angle θ between the incident plane of the incident linearly polarized light and the x-axis at 45°, and setting the relative angle between the optical axis of the analyzer of the measurement sensing optical path structure 8 and the x-axis to be 90°, then the light intensity information u1 output by the measurement sensing optical path structure 8 can be expressed as:

[0086]

[0087] In the formula, J o1 is the light intensity of the outgoing light output by the measurement sensing optical path structure 8; setting the angle between the optical axis of the polarizer-analyzer of the temperature compensation sensing optical path structure 9 and the x-axis to be 45°, and the relative angle θ between the incident plane of the incident linearly polarized light and the x-axis to be 45°, then the output signal u2 of the temperature compensation sensing optical path structure 9 can be expressed as:

[0088]

[0089] In the formula, J o2is the intensity of the outgoing light output by the temperature compensation sensing optical path structure 9; it can be obtained that the signals output by the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 are both AC-DC mixed signals, and due to the noise generated in the signal during the acquisition process of the photodetector and the analog-to-digital conversion process, the multi-frequency mode decoupling signal processing device can be used to obtain the AC signal related to the information of the current to be measured near the frequency of the current to be measured, that is, 50 Hz, and the temperature compensation signal information. The specific signal expression can be represented as:

[0090]

[0091] u4 = cos(Δ)

[0092] The measured value of the Faraday rotation angle that eliminates the influence of linear birefringence can be obtained, and then the value of the current to be measured can be obtained. It should be noted that in actual measurement, the value of the Faraday rotation angle is less than 90°. Also, since the value range of the arcsine function is [-π / 2, π / 2], the principle formula of the temperature-resistant disturbance method can be obtained:

[0093]

[0094] It is also known that the basic principle formula of the MOCT sensing Faraday magneto-optical effect is given as follows:

[0095]

[0096] In the formula, V is the Verdet constant of the magneto-optical material, with the unit of rad / A, which is an important parameter characterizing the magneto-optical properties of the material;

[0097] is the information of the magnetic field to be measured, with the unit of A / m; l represents the length of the sensing optical path, with the unit of m; I is the value of the current to be measured, with the unit of A; N is a constant, characterizing the number of turns of the linearly polarized light around the current loop. Therefore, the signal output by the final measurement signal output device 20 is as follows:

[0098]

[0099] By placing the polarizer of the measurement sensing optical path structure 8 and the temperature compensation sensing optical path structure 9 according to the requirements of the polarizer co-angle temperature-resistant disturbance method, the high-precision optical current sensing measurement value that eliminates the temperature interference information can be obtained.

[0100] The sensing signal processing unit 22 of the independent double-strip optical current sensor can simultaneously perform real-time comprehensive processing on the output measurement signals of the measurement sensing optical path structure 8 for the current to be measured and the temperature compensation measurement sensing optical path structure 9 to obtain the high-precision measurement result of the high-precision temperature-resistant disturbance independent double-strip optical current sensor.

[0101] The present invention can basically eliminate the influence of environmental temperature fluctuations on the measurement accuracy degradation of the optical current sensor. It can achieve the temperature-resistant measurement function while ensuring the advantages of strong long-term operation stability and simple structure of the single straight-through optical path type optical current sensor. It can be combined with the strip-shaped straight-through optical path type MOCT structure that resists other physical fields, such as external magnetic interference fields, etc., laying a foundation for realizing multi-physical field anti-interference.

Claims

1. An independent double-strip optical current sensor, comprising a sensing unit (21) and a signal processing unit (22) connected to each other, characterized in that, The signal processing unit (22) includes a multi-frequency mode decoupling signal processing device (18), a double-strip optical current sensor signal processing device (19), and a measurement signal output device (20). Among them, the output end of the multi-frequency mode decoupling signal processing device (18) is connected to the input end of the double-strip optical current sensor signal processing device (19), and the output end of the double-strip optical current sensor signal processing device (19) is connected to the input end of the measurement signal output device (20). The sensing unit (21) is provided with a double-strip sensing unit main structure (15) including a measurement sensing optical path structure (8) and a temperature compensation sensing optical path structure (9). The vertical distances from the midpoints of the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) to the current to be measured (23) are equal.

2. The independent double-strip optical current sensor according to claim 1, characterized in that, Both the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are sequentially composed of a signal input optical fiber (1), an input collimator (2), a polarizer (3), a magneto-optic sensing material (4), an analyzer (5), an output collimator (6), and a signal output optical fiber (7) connected in series.

3. The independent double-strip optical current sensor according to claim 2, wherein The positional relationship between the polarizer (3) and the analyzer (5) in the measurement sensing optical path structure (8) is that the optical axes are 45° different; the positional relationship between the polarizer (3) and the analyzer (5) in the temperature compensation sensing optical path structure (9) is that the optical axes are 0° different.

4. The independent double-strip optical current sensor according to claim 3, wherein The measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are fixed on an insulating carrier structure (10); an insulating encapsulation cover (11) is also provided on the insulating carrier structure (10).

5. The independent double-strip optical current sensor according to claim 1, wherein The internal connection structure of the independent double-strip optical current sensor is as follows: A high-precision adjustable current source (12), a controllable light source (13), and a beam splitter (14) are connected in sequence. Then, the beam splitter (14) is divided into two paths and respectively accesses the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9); the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are arranged in parallel; the measurement sensing optical path structure (8) is sequentially connected to an input end of the multi-frequency mode decoupling signal processing device (18) through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure (9) is sequentially connected to another input end of the multi-frequency mode decoupling signal processing device (18) through a second photodetector and a second A / D converter.

6. The independent double-strip optical current sensor according to claim 1, characterized in that, The internal connection structure of the independent double-strip optical current sensor is as follows: The high-precision adjustable current source (12) is connected to the controllable light source (13). Then, the controllable light source (13) is directly divided into two paths through an optical fiber and respectively accesses the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9); the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are arranged in parallel; the measurement sensing optical path structure (8) is sequentially connected to an input end of the multi-frequency mode decoupling signal processing device (18) through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure (9) is sequentially connected to another input end of the multi-frequency mode decoupling signal processing device (18) through a second photodetector and a second A / D converter.

7. The independent double-strip optical current sensor according to claim 1, characterized in that, The internal connection structure of the independent double-strip optical current sensor is as follows: A high-precision adjustable current source (12), a controllable light source (13), and a beam splitter (14) are connected in sequence. Then, the beam splitter (14) is divided into two paths and respectively connected to the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9); the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are arranged vertically, and their input ends are not adjacent; the measurement sensing optical path structure (8) is sequentially connected to an input end of a multi-frequency mode decoupling signal processing device (18) through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure (9) is sequentially connected to the other input end of the multi-frequency mode decoupling signal processing device (18) through a second photodetector and a second A / D converter.

8. The independent double-strip optical current sensor according to claim 1, wherein, The internal connection structure of the independent double-strip optical current sensor is as follows: The high-precision adjustable current source (12) is connected to the controllable light source (13). Then, the controllable light source (13) is directly divided into two paths through an optical fiber and respectively connected to the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9); the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are arranged vertically, and their input ends are not adjacent; the measurement sensing optical path structure (8) is sequentially connected to an input end of a multi-frequency mode decoupling signal processing device (18) through a first photodetector and a first A / D converter; the temperature compensation sensing optical path structure (9) is sequentially connected to the other input end of the multi-frequency mode decoupling signal processing device (18) through a second photodetector and a second A / D converter.

9. A method for anti-interference of the independent double-strip optical current sensor according to claim 4 against external temperature fluctuation, characterized in that, Taking the axis direction perpendicular to the optical transmission direction as the x-axis, the included angle between the optical axis of the analyzer (5) and the x-axis is If the included angle between the optical axis of the polarizer (3) and the x-axis is θ, then when considering that the included angle between the optical axes of the analyzer and polarizer is arbitrary, the optical current sensing model of the optical current sensing structure is shown as follows: Where: cos(χ) = (δ / Δ) sin(χ) = (2γ / Δ) Where, E o represents the total output electric vector of light; E o1 , E o2 respectively represent the electric vectors in the x and y directions of the output light; sin(χ), cos(χ) represent variables related to the dielectric tensor matrix of the magneto-optic material, and their values can be determined by γ and δ. δ is the linear birefringence of the magneto-optic material, and the environmental temperature interference information is mixed in the output signal of the optical current sensor in the form of linear birefringence. γ is the value of the Faraday rotation angle containing the information of the current to be measured, and Δ is the mixed amount of the linear birefringence δ and the Faraday rotation angle γ; and δ >> γ, so Δ ≈ δ, which is a constant under the same temperature environment. j is the imaginary unit. When considering any angle of the polarizer, the light intensity signals J O output by the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are both given by the following formula: When the relative angle θ between the optical axis of the polarizer (3) and the x-axis is 45°, the light intensity signal J O becomes: where J i is the intensity of the incident light; keeping the relative angle θ between the incident plane of the incident linearly polarized light and the x-axis at 45°, and setting the relative angle between the optical axis of the analyzer of the measurement sensing optical path structure (8) and the x-axis to be 90°, then the electrical signal u1 output by the measurement sensing optical path structure (8) is expressed as: Where, J o1 is the light intensity of the outgoing light output by the measurement sensing optical path structure (8); set the included angle between the optical axis of the analyzer of the temperature compensation sensing optical path structure (9) and the x-axis to be 45°, and the relative included angle θ between the optical axis of the polarizer and the x-axis is 45°, then the output signal u2 of the temperature compensation sensing optical path structure (9) is expressed as: where J o2 is the intensity of the outgoing light output by the temperature compensation sensing optical path structure (9); thus, it can be obtained that the signals output by the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) are both AC-DC mixed signals. Moreover, since noise will be generated in the signal during the acquisition process by the photodetector and the analog-to-digital conversion process, a multi-frequency mode decoupling signal processing device is used to obtain the AC signal related to the information of the current to be measured near the frequency of the current to be measured, i.e., 50 Hz, and the temperature compensation signal information: u4 = cos(Δ) A Faraday rotation angle measurement value containing only the information of the current to be measured, which eliminates the influence of linear birefringence, is obtained, and then the value of the current to be measured is obtained. In actual measurement, the value of the Faraday rotation angle is less than 90°. Also, since the value range of the arcsine function is [-π / 2, π / 2], the formula for resisting the interference of external temperature fluctuations is obtained as follows: Also, the basic principle formula of the optical current sensing Faraday magneto-optical effect is given as follows: In the formula, V is the Verdet constant of the magneto-optical material, with the unit of rad / A, which is an important parameter characterizing the magneto-optical properties of the material; is the magnetic field information to be measured, with the unit of A / m; l represents the length of the sensing optical path, with the unit of m; I is the current value to be measured, with the unit of A; N is a constant, characterizing the number of turns of the linearly polarized light around the current loop; therefore, the final measurement signal output by the measurement signal output device (20) is as follows: By arranging the polarizers of the measurement sensing optical path structure (8) and the temperature compensation sensing optical path structure (9) according to the requirements of the same-angle anti-temperature fluctuation disturbance method of the polarizers, a high-precision optical current sensing measurement value that eliminates temperature interference information is obtained.

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