Temperature drift noise compensation method for optical voltage sensor based on synchronous sampling of Newton circular polarization grating and merging unit

Abstract

The present invention proposes a method for compensating for temperature drift noise in an optical voltage sensor based on synchronous sampling using a Newton circular polarization grating and a merging unit. This method addresses the problem that temperature drift and vibration generate stress line birefringence in electro-optical crystals and transmission optical fibers, which is mixed with electro-optical phase delay and is difficult to separate and compensate for. The present invention uses a Newton circular polarization grating to linearly demodulate the electro-optical phase delay of an optical voltage sensor. When stress line birefringence is present, the output of the optical voltage sensor is a linear superposition of the electro-optical phase delay and the stress line birefringence. Synchronous sampling using the merging unit is used to obtain the output signal of the optical voltage sensor to determine the zero-crossing moment of the AC voltage to be measured. At this time, the electro-optical phase delay is zero, and the output signal of the optical voltage sensor is the stress line birefringence, which can be detected and eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of high voltage measurement, and in particular relates to a temperature drift noise compensation method for an optical voltage sensor based on synchronous sampling of a Newton circular polarization grating and a merging unit. Background Art

[0002] As a key device on the primary side of the power grid, voltage transformers (VTs), with their accuracy and stability, are crucial for energy metering, relay protection, and power system dispatching. Currently, traditional electromagnetic VTs are no longer able to meet the demands of the power system's ultra-high voltage and high-capacity trends. In recent years, electronic VTs have rapidly developed, effectively overcoming the shortcomings of electromagnetic VTs. Optical VTs, a key branch of electronic VTs, offer advantages such as small size, light weight, excellent insulation performance, a wide dynamic range, and a wide frequency response, demonstrating promising application prospects.

[0003] However, the long-term stability and reliability of optical voltage sensors are difficult to meet practical requirements. The main reason is that the problem of stress line birefringence in electro-optical crystals has not been solved. The main sources of stress birefringence in electro-optical crystals include: ① The influence of the production process makes it inevitable that some impurities are contained in the electro-optical crystal, and natural linear birefringence is generated during the growth, processing and annealing process. ② The hard connection between the crystal and devices such as prisms and wave plates forms an external constraint. When the temperature changes, external stress birefringence is generated due to the different linear expansion coefficients of different materials; ③ The temperature gradient within the crystal causes different degrees of thermal expansion and contraction of each part, resulting in uneven internal stress birefringence. The stress line birefringence of electro-optical crystals is obviously random, and there is currently no effective solution. Summary of the Invention

[0004] The problem that temperature drift and vibration generate stress line birefringence in electro-optic crystals and transmission optical fibers, and together with electro-optic phase delay aliasing, it is difficult to separate and compensate.

[0005] The optical voltage sensor, based on a Newton circular polarization grating, can linearly demodulate the electro-optical phase delay. When stress line birefringence is present, the output of the optical voltage sensor is a linear superposition of the electro-optical phase delay and the stress line birefringence. The output signal of the optical voltage sensor is obtained by synchronous sampling using a merging unit to determine the zero-crossing moment of the AC voltage being measured. At this moment, the electro-optical phase delay is zero, and the output signal of the optical voltage sensor is the stress line birefringence, which can be detected and eliminated.

[0006] Based on a linear measurement mode, the optical voltage sensor can extract and compensate for stress line birefringence when the AC voltage crosses zero. The optical voltage sensor can linearly demodulate the electro-optical phase delay. When stress line birefringence is present, its output is a linear superposition of the electro-optical phase delay and the stress line birefringence. According to the Pockels effect, when the AC voltage to be measured crosses zero, the electro-optical phase delay of the electro-optical crystal is also zero. At this time, the output signal of the optical voltage sensor is the stress line birefringence. The zero-crossing moment of the AC voltage to be measured is determined by synchronous sampling of the merging unit, and the stress line birefringence at this time is obtained and eliminated.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A method for compensating temperature drift noise of an optical voltage sensor based on synchronous sampling of a Newton circular polarization grating and a merging unit is characterized by: linearly demodulating the electro-optical phase delay of the optical voltage sensor based on the Newton circular polarization grating; when stress line birefringence exists, the output of the optical voltage sensor is a linear superposition of the electro-optical phase delay and the stress line birefringence; synchronous sampling of the merging unit is used to obtain the output signal of the optical voltage sensor to determine the zero-crossing moment of the AC voltage to be measured. At this moment, the electro-optical phase delay is zero, and the output signal of the optical voltage sensor is the stress line birefringence, which is detected and eliminated.

[0009] The specific implementation process includes: the optical signal emitted by the laser source (1) passes through the polarizer (2) to obtain linearly polarized light; under the action of an external electric field, the electro-optical crystal (3) becomes a biaxial crystal, and after the linearly polarized light enters the crystal, it is decomposed into two linearly polarized lights o and e with orthogonal polarization directions along the induction axis direction, and an electro-optical phase delay is generated. And due to temperature drift and vibration factors, stress line birefringence is generated in the electro-optical crystal, introducing additional phase delay θ, which is superimposed on the electro-optical phase delay; with phase delay The o-light and e-light are synthesized into linearly polarized light under the action of the quarter wave plate (4), and the phase delay is converted into the rotation of the polarization plane of the linearly polarized light;

[0010] The linearly polarized light emitted from the 1 / 4 wave plate is polarized by the Newton circular polarization grating (5). The center position of the dark pattern of the circular light spot corresponds to the polarization plane of the linearly polarized light and rotates synchronously with the electro-optical phase delay. The rotation angle of the emitted circular light spot (7) is detected by the four-quadrant detector (6), thus realizing direct and linear measurement of the phase delay. According to the Pockels effect, when the AC voltage to be measured passes through zero, At this time, the output signal of the optical voltage sensor is θ; based on the synchronous sampling unit (8), the output signal of the optical voltage sensor is obtained, and the zero-crossing point of the AC voltage waveform (9) is determined. At this moment, θ corresponds to the annular light spot (10), and the rotation angle (11) of the light spot output by the optical voltage sensor is θ. By positioning the light spot, θ is detected and compensated, so as to achieve the purpose of eliminating θ.

[0011] The present invention and its preferred solution specifically solve the problem that temperature drift and vibration generate stress line birefringence in electro-optic crystals and transmission optical fibers, and together with electro-optical phase delay aliasing, are difficult to separate and compensate. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0013] Figure 1 This is a schematic diagram of a method for compensating for stress line birefringence in an optical voltage sensor based on synchronous sampling of a Newton circular polarization grating and a merging unit according to an embodiment of the present invention;

[0014] Figure 2 This is the output spot diagram of the optical voltage sensor according to an embodiment of the present invention;

[0015] Among them, 1 is the laser, 2 is the polarizer, 3 is the electro-optic crystal, 4 is the 1 / 4 wave plate, 5 is the Newton circular polarization grating, 6 is the four-quadrant detector, 7 is the output spot of the optical voltage sensor, 8 is the synchronous sampling unit, 9 is the AC voltage waveform obtained by the synchronous sampling unit, 10 is the annular spot corresponding to the electro-optical phase delay of zero, and 11 is the annular spot corresponding to stress birefringence. DETAILED DESCRIPTION

[0016] To make the features and advantages of this patent more clearly understood, the following embodiments are specifically described in detail as follows:

[0017] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art to which this application belongs.

[0018] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0019] The following is a further detailed description of this embodiment with reference to the accompanying drawings:

[0020] like Figure 1 As shown in the figure, in order to realize the scheme designed by the present invention, in this embodiment, the optical signal emitted by the laser source 1 passes through the polarizer 2 to obtain linearly polarized light. Under the action of the external electric field, the electro-optical crystal 3 becomes a biaxial crystal. After the linearly polarized light enters the crystal, it is decomposed into two linearly polarized lights o and e with orthogonal polarization directions along the sensing axis, and an electro-optical phase delay is generated. In addition, due to factors such as temperature drift and vibration, stress line birefringence is generated in the electro-optical crystal, introducing an additional phase delay θ, which is superimposed on the electro-optical phase delay. The o-light and e-light are synthesized into linearly polarized light under the action of the 1 / 4 wave plate 4, and the phase delay is converted into the rotation of the polarization plane of the linearly polarized light. The linearly polarized light emitted from the 1 / 4 wave plate is polarized by the Newton circular polarization grating 5. The center position of the dark pattern of the annular light spot corresponds to the polarization plane of the linearly polarized light and rotates synchronously with the electro-optical phase delay. The rotation angle of the output annular light spot 7 is detected by the four-quadrant detector 6, and the direct and linear measurement of the phase delay can be achieved. According to the Pockels effect, when the AC voltage to be measured passes through zero, At this point, the output signal of the optical voltage sensor is θ. Synchronous sampling unit 8 obtains the output signal of the optical voltage sensor and determines the zero-crossing point of the AC voltage 9. At this moment, the annular light spot corresponding to θ is 10, and the rotation angle 11 of the optical voltage sensor output light spot is θ. By positioning the light spot, θ can be detected and compensated for, achieving the purpose of eliminating θ.

[0021] The following is a verification of the compensation principle of stress line birefringence in this embodiment based on the Jones matrix.

[0022] The incident light is polarized by the polarizer, and the polarization direction is parallel to the x-axis. The polarization light vector E is:

[0023]

[0024] Where A represents the incident light intensity.

[0025] Assume that the electro-optical phase delay is The additional phase delay introduced by stress line birefringence is θ, and the Jones matrix J of the electro-optical crystal can be expressed as:

[0026]

[0027] The Jones matrix of the quarter wave plate is:

[0028]

[0029] After the incident light passes through the electro-optic crystal and the quarter-wave plate, the Jones vector E1 is:

[0030]

[0031] It can be seen that E1 is linearly polarized light, and the angle α between its polarization plane and the x-axis satisfies:

[0032]

[0033] Therefore, α and Satisfy between:

[0034]

[0035] By detecting the rotation angle α of the emitted annular light spot, the The linear measurement of different The exit spot when Figure 2 shown.

[0036] Therefore, the measurement result of the optical voltage sensor is According to the Pockels electro-optic effect, the voltage to be measured U is linearly superimposed with θ. satisfy:

[0037]

[0038] Among them U π is the half-wave voltage of the crystal. Therefore, when U=0, δ=0, and the output signal of the optical voltage sensor when the AC voltage passes through zero is At this moment, you can Detect and compensate for it.

[0039] This embodiment obtains the output signal of the optical voltage sensor based on the merging unit synchronous sampling method, and implements sampling by accessing a unified synchronous clock through all the merging units of the station, which has high synchronization accuracy, thereby determining the AC zero-crossing point to be measured.

[0040] In combination with the above design, this embodiment provides a specific test example:

[0041] The laser used as the light source is an 808nm laser with an output power of 10mW, and its spot size is 10mm. The electro-optical crystal is a cylindrical 001-face bismuth germanium oxide crystal with a diameter of 10mm and a length of 50mm, and a half-wave voltage of 41.3kV. An OSQ100-IC four-quadrant detector is used to capture the output spot image. A high-low temperature alternating humidity test chamber provides a variable temperature environment, ranging from -40°C to 85°C, with a temperature fluctuation of ±0.5°C. In this example, the optical voltage sensor's optical path is placed within the chamber's inner chamber, and temperature cycling experiments are conducted within the -40°C to 85°C range. A zero-crossing detection circuit detects the zero-crossing point, determines the stress line birefringence introduced in each cycle, and applies compensation. Finally, the basic accuracy of the optical voltage sensor is recorded using a calibrator, as shown in Table 1. Under temperature cycling conditions, the optical voltage sensor meets the Class 0.5 accuracy requirement.

[0042] Table 1 Basic accuracy experimental data

[0043] Rated voltage percentage / % Ratio difference / % Angular difference / (′) 80 0.401 15.57 100 0.475 12.29 120 0.433 －18.53

[0044] Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

[0046] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive various other forms of optical voltage sensor temperature drift noise compensation methods based on Newton circular polarization grating and merging unit synchronous sampling under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of this invention should be covered by this patent.

Claims

1. A method for compensating temperature drift noise of an optical voltage sensor based on synchronous sampling of a Newton circular polarization grating and a merging unit, characterized by: The electro-optical phase delay of the optical voltage sensor is linearly demodulated using a Newton circular polarization grating. When stress line birefringence exists, the output of the optical voltage sensor is a linear superposition of the electro-optical phase delay and the stress line birefringence. The output signal of the optical voltage sensor is obtained by synchronous sampling using a merging unit to determine the zero-crossing moment of the AC voltage to be measured. At this time, the electro-optical phase delay is zero, and the output signal of the optical voltage sensor is the stress line birefringence, which is detected and eliminated. The light signal emitted by the laser source (1) passes through the polarizer (2) to obtain linearly polarized light; under the action of the external electric field, the electro-optical crystal (3) becomes a biaxial crystal. After the linearly polarized light enters the crystal, it is decomposed into two linearly polarized lights, o light and e light, with orthogonal polarization directions, along the direction of the sensing axis, and an electro-optical phase delay is generated. φ Due to temperature drift and vibration factors, stress line birefringence is generated in the electro-optical crystal, introducing additional phase delay. θ, and superimposed on the electro-optical phase delay; with phase delay ( φ+θ )'s o-light and e-light are synthesized into linearly polarized light under the action of the quarter wave plate (4), and the phase delay is converted into the rotation of the polarization plane of the linearly polarized light; The linearly polarized light emitted from the 1 / 4 wave plate is polarized by the Newton circular polarization grating (5). The center position of the dark pattern of the circular light spot corresponds to the polarization plane of the linearly polarized light and rotates synchronously with the electro-optical phase delay. The rotation angle of the emitted circular light spot (7) is detected by the four-quadrant detector (6), thus realizing direct and linear measurement of the phase delay. According to the Pockels effect, when the AC voltage to be measured passes through zero, φ =0, then the output signal of the optical voltage sensor is θ Based on the synchronous sampling unit (8), the output signal of the optical voltage sensor is obtained and the zero-crossing point of the AC voltage waveform (9) is determined. At this moment θ Corresponding to the annular light spot (10), the rotation angle (11) of the light spot output by the optical voltage sensor is θ , by positioning the spot to detect θ and compensate for it to eliminate θ purpose.

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