阅读说明：本技术 一种旋转式双晶体补偿型光学电场传感器及电场传感方法 (Rotary type double-crystal compensation type optical electric field sensor and electric field sensing method ) 是由 刘君 李岩松 李志� 于 2021-08-02 设计创作，主要内容包括：本发明公开了一种旋转式双晶体补偿型光学电场传感器及电场传感方法,包括光源、光学电场传感单元、光电探测器、信号处理系统、驱动装置以及光电转速传感器。进行电场传感时,所述传感器将待测电场施加到传感单元的两个电光晶体上,光源发出的光信号经旋转的光学电场传感单元后到达光电探测器,用光电转速传感器测量传感单元的旋转速度,将光电探测器输出的电信号及光电转速传感器输出的转速分别送到信号处理系统,从而实现电场传感。(The invention discloses a rotary type double-crystal compensation type optical electric field sensor and an electric field sensing method. When electric field sensing is carried out, the sensor applies an electric field to be detected to two electro-optic crystals of the sensing unit, an optical signal sent by the light source reaches the photoelectric detector after passing through the rotating optical electric field sensing unit, the photoelectric rotating speed sensor is used for measuring the rotating speed of the sensing unit, and the electric signal output by the photoelectric detector and the rotating speed output by the photoelectric rotating speed sensor are respectively sent to the signal processing system, so that the electric field sensing is realized.)

1. A rotary bicrystal compensation type optical electric field sensor is characterized by comprising: the device comprises a light source (1), an optical electric field sensing unit (10), a photoelectric detector (11), a signal processing system (16) and a driving device (17); the optical electric field sensing unit (10) comprises a first collimator (2), a polarizer (3), an 1/4 wave plate (4), a first electro-optic crystal (5), a 90-degree Faraday optical rotator (6), a second electro-optic crystal (7), an analyzer (8) and a second collimator (9) which are sequentially packaged in a sensing unit shell made of insulating materials; the photoelectric rotating speed sensor (12) is placed at one end of the optical electric field sensing unit (10) and is respectively connected with the photoelectric detector (11) to a signal processing system (16), and the signal processing system (16) comprises an analog signal data acquisition system (13), a filtering unit (14) and a voltage signal processing unit (15) which are sequentially connected;

the first electro-optical crystal (5) and the second electro-optical crystal (7) are two electro-optical crystals with the same size, and the crystal materials of the two electro-optical crystals are materials with the photoelectric effect.

2. A rotating bicrystal compensated optical electric field sensor according to claim 1, wherein the crystal material of the first (5) and second (7) electro-optical crystals is bismuth germanate or lithium niobate.

3. A rotary bicrystal compensation type optical electric field sensor according to claim 1, wherein the packaging positions of the first electro-optical crystal (5) and the second electro-optical crystal (7) are both coincident with the optical path, but the sensing principal axes of the first electro-optical crystal (5) and the second electro-optical crystal (7) are opposite, that is, the position of the second electro-optical crystal (7) is obtained by rotating the first electro-optical crystal (5) by 180 ° with the optical path direction as a rotation axis.

4. A rotary bicrystal compensated optical electric field sensor as claimed in claim 1, wherein the light passing direction of the first (5) and second (7) electro-optical crystals is perpendicular to the electric field direction of the optical sensing unit (10).

5. The rotating type bicrystal compensation optical electric field sensor according to claim 1, wherein the filter unit (14) is a DSP chip with an extended Kalman filter program programmed therein, and the voltage signal processing unit (15) is a DSP chip with an electric field calculation program programmed therein.

6. A rotary bicrystal compensation type optical electric field sensor as claimed in claim 1, wherein the optical electric field sensing unit (10) is disposed in a plane perpendicular to the direction of the electric field to be measured, and the optical electric field sensing unit (10) is driven by the driving device (17) to rotate around the optical path transmission direction as a rotation axis; the photoelectric rotating speed sensor (12) is used for measuring the rotating speed of the optical electric field sensing unit and sending a rotating speed signal to the signal processing system (16).

7. A method for electric field sensing using a rotary bicrystal compensated optical electric field sensor according to any of claims 1-6, comprising the steps of:

step 1: the rotary type double-crystal compensation type optical electric field sensor applies an electric field to be measured to a first electro-optical crystal (5) and a second electro-optical crystal (7) of an optical inductance sensing unit (10), wherein the first electro-optical crystal (5) and the second electro-optical crystal (7) are both bismuth germanate crystals;

step 2: an optical signal emitted by the light source (1) passes through the first collimator (2) and then becomes a parallel light beam, and then becomes a linear polarized light after passing through the polarizer (3), the 1/4 wave plate (4) changes the linear polarized light into a circular polarized light, the circular polarized light is transmitted to the first electro-optic crystal (5) and then is decomposed into two beams of orthogonal linear polarized light, the two beams of orthogonal linear polarized light are respectively transmitted along the directions of two induction main shafts of the first electro-optic crystal (5), the polarization directions of the two beams of orthogonal linear polarized light are rotated by 90 degrees after passing through the optical rotator (6), the polarization plane interchange of the two beams of linear polarized light is realized, then the two beams of orthogonal linear polarized light are transmitted along the directions of the two induction main shafts of the second electro-optic crystal (7), and finally the orthogonal linear polarized light carrying the phase difference delta is transmitted to the analyzer (8) to generate interference and enters the electro-optic detector (11) after passing through the second collimator (9);

and step 3: and (3) converting the optical signal entering in the step (2) into an electric signal by the photoelectric detector (11) and then using the electric signal as an input signal of a signal processing system (16), thereby realizing electric field sensing.

8. The method for sensing an electric field according to claim 7, wherein in the step 2, the phase difference δ is generated after two beams of orthogonal linearly polarized light pass through the first electro-optical crystal (5) and the second electro-optical crystal (7), and the phase difference δ is obtained by the following formula (1):

where λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the electric field intensity applied to the electro-optic crystal, l is the length of the electro-optic crystal, ω is the angular velocity of rotation of the sensing unit (10), and t is the time.

9. The method of claim 7, wherein in step 3, the filtering calculation method of the filtering unit (14) in the signal processing system (16) is as shown in equation (2):

in the formula, Z_kData output by the analog signal data acquisition system; h is_k(x) As an observation function, H_kIs a parameter matrix; a is a state transition matrix;the previous state quantities are calculated for each cycle,calculating a state quantity after each cycle; w and v are zero-mean and incoherent white noise, the covariance of w and v is Q and R respectively, and the value range of Q and R is 0-1; i is an identity matrix.

10. The method of claim 9, wherein the filter unit (14) is a DSP chip programmed with an extended kalman filter, and the state variable is selected asThe filtering program comprises the following specific steps:

the first step is as follows: initialization state x₀Covariance P₀；

The second step is that: state prediction

The third step: observation prediction

The fourth step: state transition matrix

The fifth step: observation matrix

And a sixth step: covariance prediction

The seventh step: kalman gain

Eighth step: status update

The ninth step: covariance update

11. Method of performing electric field sensing according to claim 7,

when measuring a direct current electric field, the calculation of the output light intensity of the optical electric field sensing unit (10), i.e. the light intensity entering the photodetector (11) in step 2, is as shown in formula (3):

in the formula I_iFor input of light intensity, I_oFor output light intensity, λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the DC electric field intensity, l is the length of the electro-optic crystal, omega is the rotating angular speed of the sensing unit (10), t is the time, X is the time_k＝[X₁,X₂,X₃,X₄]^TA is a 4-order unit array;

when measuring an alternating electric field, the calculation of the output light intensity of the optical electric field sensing unit (10), i.e. the light intensity entering the photodetector (11) in step 2, is as shown in formula (4):

in the formula I_iFor input of light intensity, I_oFor output light intensity, λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the direct current electric field intensity, l is the length of the electro-optic crystal, omega is the rotation angular velocity of the sensing unit (10), omega is₀For AC field angular velocity, t is time, where X_k＝[X₁,X₂,X₃,X₄,X₅,X₆]^TA is a 6-order unit array; h ═ H_1k,H_2k,H_3k,H_4k,H_5k,H_6k]；

Wherein H_1k＝cos(2πkT_s(f₀+X_4k))，H_2k＝sin(2πkT_s(f₀+X_4k))，H_3k＝1，H_4k＝2πkT_s(-X_1kH_1k+X_2kH_2k-X_5kH_5k+X_6kH_6k)；H_5k＝cos(2πkT_s(f₀+X_4k))，H_6k＝sin(2πkT_s(f₀+X_4k) ); where k is the sampling time of the analog signal data acquisition system, T_sIs the sampling interval; f. of₀Is the frequency of the alternating current electric field to be measured.

12. The method of claim 7, wherein in step 3, the voltage signal processing unit (15) in the signal processing system (16) is calculated according to equation (5):

wherein E is the electric field strength of the electric field to be measured, K_ESetting a proportionality coefficient for the voltage; for DC and AC electric fields, X₄Namely the rotation frequency of the sensing head of the rotary optical electric field sensor.

Technical Field

The invention belongs to the field of optical voltage sensing, and particularly relates to a rotary type double-crystal compensation type optical electric field sensor and an electric field sensing method.

Background

In recent years, the operation voltage level of the power grid is greatly improved, and the electric field measurement has wider application in power systems, such as power transmission and transformation equipment state monitoring, reasonable selection of electrical equipment, high voltage test and corona discharge research, high voltage system electromagnetic environment analysis and the like. The traditional electric field measuring device is difficult to meet the modern power measurement requirement due to the defects of large volume, difficult insulation, narrow response frequency band, small dynamic range and the like. The optical electric field sensor adopts a crystal material as a sensing medium, and realizes the measurement of an electric field by utilizing the characteristic that the change angle of the polarization direction is in direct proportion to an external electric field when linearly polarized light passes through an electro-optic material arranged in the external electric field. The insulating material has the advantages of good insulating property, strong anti-electromagnetic interference, high stability and the like, and has wide application prospect.

Most of the existing optical electric field sensors are open-loop systems, and the long-term operation stability and the measurement accuracy of the sensors are easily influenced by factors such as temperature, drift charge and the like. At present, people improve the stability and the measurement accuracy of a sensor by a multi-purpose compensation method, typical ideas include a double-light-path method, a double-crystal method, a reference light-path method and the like, and light path systems involved in the methods are in a static state, so that an electro-optic crystal tends to generate a charge accumulation effect under the action of a direct current electric field or an alternating current-direct current mixed electric field, and the effect makes a macroscopic electric field in the crystal weak, thereby greatly influencing the accuracy of the sensor.

Object of the Invention

The present invention is directed to solve the above problems in the prior art, and an object of the present invention is to provide a rotary bicrystal compensation type optical electric field sensor and an electric field sensing method, which can not only overcome the measurement accuracy problem caused by the charge accumulation effect of the electro-optic crystal under the action of the dc electric field, but also compensate the output drift of the sensor caused by the temperature change.

Disclosure of Invention

According to an aspect of the present invention, there is provided a rotary type double crystal compensation type optical electric field sensor, comprising: the device comprises a light source (1), an optical electric field sensing unit (10), a photoelectric detector (11) and a signal processing system (16); the optical electric field sensing unit (10) comprises a first collimator (2), a polarizer (3), an 1/4 wave plate (4), a first electro-optic crystal (5), a 90-degree Faraday optical rotator (6), a second electro-optic crystal (7), an analyzer (8) and a second collimator (9) which are sequentially packaged in a sensing unit shell made of insulating materials; the photoelectric rotating speed sensor (12) is placed at one end of the optical electric field sensing unit (10) and is respectively connected with the photoelectric detector (11) to a signal processing system (16), and the signal processing system (16) comprises an analog signal data acquisition system (13), a filtering unit (14) and a voltage signal processing unit (15) which are sequentially connected;

the first electro-optical crystal (5) and the second electro-optical crystal (7) are two electro-optical crystals with the same size, and the crystal materials of the two electro-optical crystals are materials with the photoelectric effect.

Preferably, the crystal material is bismuth germanate or lithium niobate.

Furthermore, the packaging positions of the first electro-optical crystal (5) and the second electro-optical crystal (7) are both superposed with the light path, but the directions of the induction main shafts of the first electro-optical crystal (5) and the second electro-optical crystal (7) are opposite, namely the position of the second electro-optical crystal (7) is obtained by rotating the first electro-optical crystal (5) by 180 degrees by taking the direction of the light path as a rotating shaft.

Further, the light passing direction of the first electro-optical crystal (5) and the second electro-optical crystal (7) is perpendicular to the electric field passing direction of the optical sensing unit (10).

Preferably, the filtering unit (14) is a DSP chip burned with an extended kalman filtering program, and the voltage signal processing unit (15) is a DSP chip burned with an electric field calculation program.

Furthermore, the optical electric field sensing unit (10) is arranged in a plane vertical to the direction of the electric field to be measured, and the optical electric field sensing unit (10) is driven by the driving device (17) to rotate by taking the optical path transmission direction as a rotating shaft; the photoelectric rotating speed sensor (12) is used for measuring the rotating speed of the optical electric field sensing unit and sending a rotating speed signal to the signal processing system (16).

According to another aspect of the present invention, there is provided a method for sensing an electric field by using the above-mentioned rotary bicrystal compensation type optical electric field sensor, comprising the following steps:

step 1: the rotary type double-crystal compensation type optical electric field sensor applies an electric field to be measured to a first electro-optical crystal (5) and a second electro-optical crystal (7) of an optical inductance sensing unit (10), wherein the first electro-optical crystal (5) and the second electro-optical crystal (7) are both bismuth germanate crystals;

step 2: an optical signal emitted by the light source (1) passes through the first collimator (2) and then becomes a parallel light beam, and then becomes a linear polarized light after passing through the polarizer (3), the 1/4 wave plate (4) changes the linear polarized light into a circular polarized light, the circular polarized light is transmitted to the first electro-optic crystal (5) and then is decomposed into two beams of orthogonal linear polarized light, the two beams of orthogonal linear polarized light are respectively transmitted along the directions of two induction main shafts of the first electro-optic crystal (5), the polarization directions of the two beams of orthogonal linear polarized light are rotated by 90 degrees after passing through the optical rotator (6), the polarization plane interchange of the two beams of linear polarized light is realized, then the two beams of orthogonal linear polarized light are transmitted along the directions of the two induction main shafts of the second electro-optic crystal (7), and finally the orthogonal linear polarized light carrying the phase difference delta is transmitted to the analyzer (8) to generate interference and enters the electro-optic detector (11) after passing through the second collimator (9);

and step 3: and (3) converting the optical signal entering in the step (2) into an electric signal by the photoelectric detector (11) and then using the electric signal as an input signal of a signal processing system (16), thereby realizing electric field sensing.

In step 2, the phase difference δ is generated after the two orthogonal linearly polarized light beams pass through the first electro-optical crystal (5) and the second electro-optical crystal (7), and the phase difference δ is obtained by equation (1):

where λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the electric field intensity applied to the electro-optic crystal, l is the length of the electro-optic crystal, ω is the angular velocity of rotation of the sensing unit (10), and t is the time.

Further, in step 3, a filtering calculation method of the filtering unit (14) in the signal processing system (16) is as shown in equation (2):

in the formula, Z_kData output by the analog signal data acquisition system; h is_k(x) As an observation function, H_kIs a parameter matrix; a is a state transition matrix;calculating the pre-state for each cycleThe amount of state is,calculating a state quantity after each cycle; w and v are zero-mean and incoherent white noise, the covariance of w and v is Q and R respectively, and the value range of Q and R is 0-1; i is an identity matrix.

Preferably, the filtering unit (14) is a DSP chip burned with an extended Kalman filtering program, and the state variable is selected asThe filtering program comprises the following specific steps:

the first step is as follows: initialization state x₀Covariance P₀；

The second step is that: state prediction

The third step: observation prediction

The fourth step: state transition matrix

The fifth step: observation matrix

And a sixth step: covariance prediction

The seventh step: kalman gain

Eighth step: status update

The ninth step: covariance update

Further, when measuring the dc electric field, the calculation of the output light intensity of the optical electric field sensing unit (10), i.e. the light intensity entering the photodetector (11) in step 2, is as shown in formula (3):

in the formula I_iFor input of light intensity, I_oFor output light intensity, λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the DC electric field intensity, l is the length of the electro-optic crystal, omega is the rotating angular speed of the sensing unit (10), t is the time, X is the time_k＝[X₁,X₂,X₃,X₄]^TA is a 4-order unit array;

further, when measuring the ac electric field, the calculation of the output light intensity of the optical electric field sensing unit (10), i.e. the light intensity entering the photodetector (11) in step 2, is as shown in formula (4):

in the formula I_iFor input of light intensity, I_oFor output light intensity, λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the direct current electric field intensity, l is the length of the electro-optic crystal, omega is the rotation angular velocity of the sensing unit (10), omega is₀For AC field angular velocity, t is time, where X_k＝[X₁,X₂,X₃,X₄,X₅,X₆]^TA is a 6-order unit array; h ═ H_1k,H_2k,H_3k,H_4k,H_5k,H_6k]；

Wherein H_1k＝cos(2πkT_s(f₀+X_4k))，H_2k＝sin(2πkT_s(f₀+X_4k))，H_3k＝1，H_4k＝2πkT_s(-X_1kH_1k+X_2kH_2k-X_5kH_5k+X_6kH_6k)；H_5k＝cos(2πkT_s(f₀+X_4k))，H_6k＝sin(2πkT_s(f₀+X_4k) ); where k is the sampling time of the analog signal data acquisition system, T_sIs the sampling interval; f. of₀Is the frequency of the alternating current electric field to be measured.

Further, in step 3, the calculation method of the voltage signal processing unit (15) in the signal processing system (16) is as shown in equation (5):

wherein E is the electric field strength of the electric field to be measured, K_ESetting a proportionality coefficient for the voltage; for DC and AC electric fields, X₄Namely the rotation frequency of the sensing head of the rotary optical electric field sensor.

Drawings

FIG. 1 is a schematic diagram of a rotary type double-crystal compensation type optical electric field sensor and a signal processing device thereof;

FIG. 2 is a schematic diagram of a mechanical structure of a rotary type double-crystal compensation optical electric field sensor;

FIG. 3 is a circuit diagram of a signal acquisition system;

FIG. 4 is a block diagram of a filtering unit;

reference numerals: 1-a light source; 2-a first collimator; 3-a polarizer; 4-1/4 wave plate; 5-a first electro-optic crystal; 6-an optical rotator; 7-a second electro-optic crystal; 8, a polarization analyzer; 9-a second collimator; 10-optical electric field sensing unit; 11-a photodetector; 12-a photoelectric rotation speed sensor; 13-analog signal data acquisition system; 14-a filtering unit; 15-voltage signal processing unit; 16-a signal processing system; 17-a drive device; 18-a sensing housing; 19-fixing the sleeve; 20-a gear; 21-supporting the base; 22-a mounting plate with an optical fiber slip ring; 23-bearing.

Detailed Description

The rotary bicrystal compensation type optical electric field sensing method of the present invention is further described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a rotary type double-crystal compensation optical electric field sensor and a signal processing device thereof, as shown in fig. 1, including: the device comprises a light source (1), an optical electric field sensing unit (10), a photoelectric detector (11) and a signal processing system (16); the optical electric field sensing unit (10) comprises a first collimator (2), a polarizer (3), an 1/4 wave plate (4), a first electro-optic crystal (5), an optical rotator (6), a second electro-optic crystal (7), an analyzer (8) and a second collimator (9) which are sequentially packaged in a sensing unit shell made of insulating materials; the photoelectric rotating speed sensor (12) is placed at one end of the optical electric field sensing unit (10), the photoelectric rotating speed sensor and the photoelectric detector (11) are respectively connected to the signal processing system (16), and the signal processing system (16) comprises an analog signal data acquisition system (13), a filtering unit (14) and a voltage signal processing unit (15) which are sequentially connected.

The first electro-optical crystal (5) and the second electro-optical crystal (7) are of two cuboid structures with the same size, and the cuboid structures are formed by directionally cutting the same bismuth germanate crystal along the direction of the induction main shaft.

The encapsulation positions of the first electro-optical crystal (5) and the second electro-optical crystal (7) are coincided with the light path, but the induction main shaft directions of the first electro-optical crystal (5) and the second electro-optical crystal (7) are opposite, namely the position of the second electro-optical crystal (7) is obtained by rotating the first electro-optical crystal (5) by 180 degrees by taking the light path direction as a rotating shaft.

The light passing direction of the first electro-optical crystal (5) and the second electro-optical crystal (7) is vertical to the direction of the electric field of the optical sensing unit (10).

The optical electric field sensing unit (10) is arranged in a plane perpendicular to the direction of an electric field to be measured, the sensing unit (10) rotates by taking the transmission direction of a light path as a rotating shaft under the driving of the driving device (17), and the photoelectric rotating speed sensor (12) is used for measuring the rotating speed of the optical electric field sensing unit and sending signals to the signal processing system (16).

The rotary double-crystal compensation type optical electric field sensing method applies an electric field to be measured to a first bismuth germanate crystal (5) and a second bismuth germanate crystal (7); the light signal emitted by the light source (1) is changed into parallel light beams after passing through the first collimator (2), then the linearly polarized light is converted into linearly polarized light after passing through the polarizer (3), the 1/4 wave plate (4) converts the linearly polarized light into circularly polarized light, transmits the circularly polarized light to the first electro-optical crystal (5), is decomposed into two beams of orthogonal linearly polarized light, respectively transmits the two beams of orthogonal linearly polarized light along the directions of the two induction main shafts of the first electro-optical crystal (5), rotates 90 degrees in the polarization directions of the two beams of orthogonal linearly polarized light after passing through the optical rotator (6), realizes the polarization plane interchange of the two beams of linearly polarized light, then the light propagates along the two induction main axes of the second electro-optical crystal (7), finally orthogonal linear polarized light carrying the total phase difference is transmitted to an analyzer (8) to generate interference, and enters the photoelectric detector (11) after passing through the second collimator (9), and the photoelectric detector (11) changes the optical signal into an electric signal which is then used as an input signal of the signal processing system (16).

The sensing unit generates a phase difference delta after orthogonal linearly polarized light passes through a first electro-optical crystal (5) and a second electro-optical crystal (7) under the action of an electric field, and the phase difference delta is obtained through the following formula:

where λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the electric field intensity applied to the electro-optic crystal, l is the length of the electro-optic crystal, ω is the angular velocity of rotation of the sensing unit (10), and t is the time.

The theoretical value of the light intensity detected by the photoelectric detector (11) can be obtained by the following formula:

wherein, I_oIs the intensity of the emergent light, I_iIs the incident light intensity, λ is the wavelength of the incident light, n₀Is the refractive index, gamma, of the electro-optic crystal₄₁Is the electro-optic coefficient of the electro-optic crystal, E is the electric field intensity applied to the electro-optic crystal, l is the length of the electro-optic crystal, ω is the angular velocity of rotation of the sensing unit (10), T is the time, k is the sampling interval, T is the time_sIs the sampling time;is the phase; and C is a direct current component of the signal.

Fig. 2 is a schematic diagram of a mechanical structure of a rotary bicrystal compensation type optical electric field sensor, as shown in fig. 2, which includes a sensing housing (18), a fixing sleeve (19), a gear (20), a supporting base (21), an installation plate (22) equipped with an optical fiber slip ring, and a bearing (23).

The optical sensing unit (10) is packaged in a sensing shell (18), two ends of the sensing shell (18) are fixedly connected with a fixed sleeve (19) through a mounting plate (22) provided with an optical fiber slip ring, and the fixed sleeve (19) is connected with a mounting base through a bearing (23).

The gear is fixed on the outer side of the fixed sleeve (19), the driving device (17) drives the gear of the sensing head to rotate through transmission, and then the rotary type double-crystal compensation type optical electric field sensor rotates at a certain frequency.

Fig. 3 is a circuit diagram of a signal acquisition system, which converts an input voltage analog signal into a digital signal, and the sampling value of the voltage signal output by the rotary type double-crystal compensation type optical electric field sensor is as follows:

or

Wherein A is the amplitude of the alternating current component, omega is the rotating angular speed of the sensing unit (10), f is the rotating frequency, T is the time, k is the sampling interval, T_sIs the sampling time;is the phase; and C is a direct current component of the signal.

FIG. 4 is a block diagram of a filtering unit, wherein the filtering unit (14) is a DSP chip with an extended Kalman filtering program, and the state variable is selected asThe filtering program comprises the following specific steps:

the first step is as follows: initialization state x₀Covariance P₀

The second step is that: state prediction

The third step: observation prediction

The fourth step: state transition matrix

The fifth step: observation matrix

And a sixth step: covariance prediction

The seventh step: kalman gain

Eighth step: status update

The ninth step: covariance update

The voltage signal processing unit (15) is a DSP chip with an electric field calculation program burned therein, and the calculation method is as follows:

E＝K_E(I_AC/I_DC)

e is the field strength of the electric field to be measured, K_ESetting a proportionality coefficient for the voltage; for DC and AC electric fields, X₄Namely the rotation frequency of the sensing head of the rotary optical electric field sensor;

the rotary type double-crystal compensation type optical electric field sensing method utilizes the optical rotator to realize the exchange of the polarization planes of two beams of orthogonal linearly polarized light, and eliminates additional birefringence caused by temperature change by a double-crystal method, thereby improving the measurement precision and the temperature stability of the sensor. The rotary structure of the sensing unit can effectively avoid the charge accumulation effect of the electro-optic crystal under the action of the direct current electric field, and improve the measurement accuracy of the sensor for measuring the direct current electric field or the alternating current-direct current mixed field.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adopts a double-crystal compensation method, and utilizes a 90-degree Faraday optical rotator to realize the exchange of the polarization planes of two beams of orthogonal linearly polarized light, thereby eliminating additional birefringence caused by temperature change and improving the measurement precision and the temperature stability of the sensor.

2. The invention adopts the rotary structure of the sensing unit, can effectively avoid the charge accumulation effect of the electro-optic crystal under the action of the direct current electric field, and improves the measurement precision of the sensor for measuring the direct current electric field or the alternating current-direct current mixed field.

3. The signal processing system greatly eliminates the noise in the measured voltage signal and the noise of the photoelectric detector through filtering, and improves the measurement accuracy.

4. The optical electric field sensing method realizes the non-contact measurement of the electric field and the voltage, and solves the insulation problem of the measuring device.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.