CN107607766B - Mirror symmetry true random four-state modulation and demodulation method for optical fiber current transformer - Google Patents
Mirror symmetry true random four-state modulation and demodulation method for optical fiber current transformer Download PDFInfo
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Abstract
The invention discloses a mirror symmetry true random four-state modulation and demodulation method for an optical fiber current transformer, which comprises the following steps: electrifying the optical fiber current transformer, and starting sampling by an A/D converter of the optical fiber current transformer to obtain a sampling number; the A/D converter transmits the sampling number to the data demodulation module, and the data demodulation module generates a random sequence and random modulation times according to the lowest bit AD [0] in the sampling number; and the data demodulation module generates mirror symmetry true random four-state modulation according to the random sequence and the random modulation times. The invention not only has the advantages of the two-state, four-state and four-state random modulation and demodulation method, but also can make up the defects of the two-state, four-state and four-state random modulation, reduce noise, reduce and stably output zero position, and solve the problems of low current test precision and direct current test stability.
Description
Technical Field
The invention belongs to the field of optical fiber current mutual inductance, and particularly relates to a mirror symmetry true random four-state modulation and demodulation method for an optical fiber current mutual inductor.
Background
The optical fiber current transformer serving as novel current measuring equipment has the advantages of being simple in insulation, small in size, safe, reliable, digital, intelligent, integrated in metering, measuring and protecting and the like, is key equipment for intelligent substation construction, is rapidly developed in recent years, has large technical progress, is applied to small-batch intelligent substations, represents the development direction of the transformer industry, and must gradually replace the traditional electromagnetic transformer to become mainstream configuration equipment in the field of power measurement in the future.
The optical fiber current transformer is a mainstream engineering application scheme of the existing optical current transformer, and mainly comprises a light path, a circuit and a modulation and demodulation method, wherein the modulation and demodulation method is an important factor influencing the performance of the optical fiber current transformer. The modulation and demodulation method used by the existing optical fiber current transformer mainly adopts three modulation methods of two-state square wave modulation, four-state step wave modulation and four-state pseudo random modulation, wherein the modulation amplitude of the two-state square wave is +/-pi/2, the modulation period is the intrinsic transition time tau of an interference light path of the optical fiber current transformer, and the modulation is alternately and repeatedly carried out, as shown in figure 1. The modulation amplitude of the four-state step wave is + -pi/2 and + -3 pi/2, the modulation period is half of the intrinsic transit time of the optical fiber current transformer, i.e. tau/2, and + -pi/2 and + -3 pi/2 modulation are also carried out alternately and repeatedly, as shown in fig. 2. The four-state pseudo-random wave modulation amplitude is +/-pi/2 and +/-3 pi/2, the modulation period is half of the intrinsic transit time of the optical fiber current transformer, namely tau/2, and the four modulation amplitudes randomly appear according to a random sequence with determined length, as shown in figure 3. The two-state square wave and the four-state step wave have the advantages that the positive and negative modulation amplitudes are equal in frequency, the output zero position is small and stable, and zero position compensation is not needed. The method has the defects that the modulation period is regular, the modulation mode is determined to be unchanged, the modulation signal is easy to generate interference and acts on the detected signal, larger noise is caused, the linearity is poor, the method is not beneficial to small current testing, and dead zones which cannot be detected can be generated. The four-state pseudo-random modulation has the advantages that the modulation of +/-pi/2 and +/-3 pi/2 occurs randomly, the modulation mode is random, the interference on the detection signal is avoided, the noise is small, the linearity is good, and no dead zone exists. The disadvantages are that the random sequence of + -pi/2 and + -3 pi/2 modulation is generated by a row of random numbers with fixed length, the modulation is implemented according to the random numbers with fixed length, and the modulation is repeated after the modulation is completed, so the modulation is called pseudo-random four-state modulation, the positive and negative modulation amplitudes are unequal, the output zero position is large and easy to fluctuate, and the zero position has asymmetry after the current is reversed.
The two-state square wave, four-state step wave and four-state pseudo-random wave modulation all have inherent advantages and disadvantages, and error factors caused by the two-state square wave, the four-state step wave and the four-state pseudo-random wave modulation inevitably exist. The small current testing precision and the electric quantity metering application are influenced by overlarge noise. The zero size and stability can seriously affect the accuracy of direct current testing. Therefore, the fiber-optic current transformer can take necessary measures to inhibit or eliminate the problems when carrying out small current test or direct current test. In general, the prior art approach can be solved by the following methods: firstly, through optimizing current transformer interference light path, reduce the noise level, improve the measuring accuracy. And secondly, the sensitive signal-to-noise ratio is improved and the noise is reduced by increasing the winding number of the sensitive ring. And thirdly, the influence of the zero position is eliminated by modeling and compensating the output zero position of the current transformer. Fourthly, noise suppression and null size control are carried out by improving and optimizing a modulation and demodulation method. In the current technical level, the optimized light path is limited by the technical level of the domestic existing optical devices, and the noise reduction is limited. The noise level of the optical fiber current transformer can be greatly improved by increasing the number of winding turns of the sensitive ring, but the difficulty of a multi-turn winding process is higher, the yield is lower, the cost is increased, and batch production cannot be realized. Due to poor zero repeatability and fluctuation and asymmetry of the optical fiber current transformer, a zero modeling compensation result is not ideal. Innovating the modulation and demodulation method is an important method for reducing noise and stabilizing zero, but the effect is not ideal at present.
Disclosure of Invention
The technical problem solved by the invention is as follows: the mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer overcomes the defects of the prior art, has the advantages of two-state, four-state and four-state random modulation and demodulation methods, can make up the defects of two-state, four-state and four-state random modulation, can reduce noise, reduce and stably output zero, and solves the problems of low current test precision and direct current test stability.
The purpose of the invention is realized by the following technical scheme: a mirror symmetry true random four-state modulation and demodulation method for an optical fiber current transformer comprises the following steps:
(1) electrifying the optical fiber current transformer, and starting sampling by an A/D converter of the optical fiber current transformer to obtain a sampling number;
(2) the A/D converter transmits the sampling number in the step (1) to a data demodulation module, and the data demodulation module generates a random sequence and random modulation times according to the lowest bit AD [0] in the sampling number;
(3) and (3) the data demodulation module generates mirror symmetry true random four-state modulation according to the random sequence and the random modulation times in the step (2).
The mirror symmetry true random four-state modulation and demodulation method for the optical fiber current transformer further comprises the following steps: (3-1) mirror symmetry true random four-state modulation is applied to the Y waveguide after passing through the A/D converter and the operational amplifier circuit.
In the mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer, in the step (3), generating mirror symmetry true random four-state modulation includes the following steps:
(4) the data demodulation module generates true random four-state modulation according to the random sequence, the data demodulation module applies modulation according to the random modulation times in the step (2), and when the applied modulation times are larger than the random modulation times in the step (2), whether the generated true random four-state modulation meets mirror symmetry is judged;
(5) when mirror symmetry is met, carrying out mirror image implementation on true random four-state modulation which is greater than the applied modulation times of the random modulation times in the step (2) in the step (4) to form mirror image symmetry true random four-state modulation;
(6) and (5) when the mirror symmetry is not met, continuing to apply the modulation until the mirror symmetry condition is met, and repeating the step.
In the mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer, in the step (4), mirror symmetry conditions are as follows: the modulation amplitude difference between the current modulation sequence and the last modulation sequence of the true random four-state modulation is + -pi/2 or + -3 pi/2.
In the mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer, in the step (4), the applied modulation times are 4-10 times.
In the mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer, in the step (3), the true random four-state modulation is generated continuously by taking AD (analog to digital) lowest bit AD 0 as a random source, the random number has no repetition and no period, and the modulation sequence generated by the random number is completely random.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention effectively improves the signal-to-noise ratio, reduces the noise of output test current and improves the detection sensitivity;
(2) the zero output stability of the optical fiber current transformer is improved, and the asymmetry of the zero output after the current is reversed is restrained.
Drawings
FIG. 1 is a schematic diagram of a prior art two-state square wave modem;
FIG. 2 is a schematic diagram of a four-state step wave modem in the prior art;
FIG. 3 is a diagram of a prior art pseudo-random four-state modem;
FIG. 4 is a schematic diagram of the overall scheme of the fiber optic current transformer of the present invention;
FIG. 5 is a mirror symmetry true random four-state modem schematic of the present invention;
fig. 6 is a flow chart of the mirror symmetry true random four-state modulation and demodulation method of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 4, under the action of a driving refrigeration circuit, light emitted by a light source enters an integrated optical device through a coupler a, the light is phase-modulated by a Y waveguide integrated optical device, and then two beams of linearly polarized light are output, wherein one beam of light is modulated, the two beams of linearly polarized light enter a delay line through a coupler B along the fast axis and the slow axis of a polarization maintaining optical fiber respectively, and are converted into two beams of circularly polarized light through a lambda/4 wave plate, wherein one beam of circularly polarized light is left-handed, the other beam of circularly polarized light enters a sensitive optical fiber of an optical fiber ring for propagation, and the two beams of elliptically polarized light generate a phase difference under the combined action of the Faraday magneto-optical effect and measured
Two-beam ellipseCircularly polarized light is transmitted to a reflector to be reflected and then enters a sensitive optical fiber again, the original left-handed light is changed into right-handed light, the original right-handed light is changed into left-handed light, and phase difference is generated under the combined action of Faraday magneto-optical effect and measured current
At this time, the total phase difference becomes
Two beams of elliptically polarized light carrying current information are converted into linearly polarized light again through a lambda/4 wave plate, meanwhile, the linearly polarized light originally transmitted along a slow axis is converted into linearly polarized light which is transmitted along a fast axis, the linearly polarized light originally transmitted along the slow axis is converted into linearly polarized light which is transmitted along the slow axis, and finally, the linearly polarized light returns to a Y waveguide integrated optical device to interfere, the interference light is output to a photoelectric detector through the integrated optical device and a coupler A, the detector converts an optical signal into an electric signal, the electric signal is sampled through an A/D, a detected signal is output after the digital signal is demodulated and demodulated according to an applied modulation signal, meanwhile, a modulation signal, a feedback step wave and an error feedback signal are generated, and finally, the modulation signal, the step wave and the error feedback are applied to the Y.
Fig. 6 is a flow chart of the mirror symmetry true random modem method of the present invention. As shown in fig. 6, the mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer includes the following steps:
(1) electrifying the optical fiber current transformer, and starting sampling by an A/D converter of the optical fiber current transformer to obtain a sampling number;
(2) the A/D converter transmits the sampling number in the step (1) to a data demodulation module, and the data demodulation module generates a random sequence and random modulation times according to the lowest bit AD [0] in the sampling number;
(3) the data demodulation module generates mirror symmetry true random four-state modulation according to the random sequence and the random modulation times in the step (2);
(3-1) mirror symmetry true random four-state modulation is applied to the Y waveguide after passing through the A/D converter and the operational amplifier circuit.
In step (3), generating mirror symmetry true random four-state modulation comprises the following steps:
(4) the data demodulation module generates true random four-state modulation according to the random sequence, the modulation sequence is generated by the random number output by the random source AD [0], the random number is not repeated and has no period, therefore, the modulation amplitude is formed by the complete random combination of + -pi/2 or + -3 pi/2. The data demodulation module applies modulation according to the random modulation times in the step (2), and when the applied modulation times is larger than the random modulation times in the step (2), whether the generated true random four-state modulation meets mirror symmetry is judged; the mirror symmetry conditions are: the modulation amplitude difference between the current modulation sequence and the last modulation sequence of the true random four-state modulation is + -pi/2 or + -3 pi/2. As shown in fig. 5, the current modulation sequence is the modulation being applied, the modulation adjacent thereto that has been applied is the last modulation sequence, and the modulation adjacent thereto that is to be applied is the next modulation sequence.
(5) When mirror symmetry is met, performing modulation implementation on the true random four-state modulation which is greater than the modulation frequency applied in the step (2) in the step (4) in a mirror image mode to form complete mirror symmetry true random four-state modulation;
(6) and (5) when the mirror symmetry is not met, continuing to apply the modulation until the mirror symmetry condition is met, and repeating the step.
Specifically, in the step (1) and the step (2), the A/D conversion chip starts sampling at the moment when the modulation and demodulation circuit of the optical fiber current transformer is powered on, and outputs are provided under the condition of the existence of the measured current, because the A/D conversion chip outputs in multiple bits, the lowest bit AD [0] of the A/D conversion chip is 0 and 1 random quantity, the AD [0] is used as a random number sequence source, a true random sequence is generated, and the random modulation times are set.
In step (3), the true random four-state modulation is a random modulation sequence generated by random number output by random source AD [0], the random number is not repeated and has no period, so the modulation amplitude is formed by the complete random combination of + -pi/2 or + -3 pi/2.
In the step (4), completely random modulation is applied according to a random sequence, so that the difference of modulation amplitude between the previous modulation sequence and the next modulation sequence is +/-pi/2 or +/-3 pi/2, and the modulation frequency of the modulation sequence is randomly set to be 4-10 times or more.
In the step (5) and the step (6), after the random modulation sequence reaches the set times, symmetrical judgment is carried out, and the condition of the symmetrical judgment is that the modulation amplitude difference between the current modulation sequence and the next modulation sequence is +/-pi/2 or +/-3 pi/2. If the symmetry condition is satisfied, the symmetry judgment is finished. If the symmetric condition is not met, the random symmetric waveform is continuously applied until the symmetric condition is met, so that the modulation times of one symmetric random modulation waveform are not completely equal to the set value.
After the symmetric judgment is satisfied, the random modulation waveform applied before is subjected to mirror image implementation, and complete symmetric true random four-state modulation is completed. After that, the next symmetric random modulation is performed, as shown in fig. 5. In fig. 5, the previous symmetric random modulation period is 8 τ, the next symmetric random modulation period is 4 τ after the boundary, and the modulation period is determined according to the randomly set number of times and the judgment condition.
After the system is powered on, parameter initialization is completed, a light intensity signal generated after phase difference generated by magneto-optical Faraday effect is interfered is converted into an electric signal through a photoelectric detector, the electric signal is subjected to signal demodulation through A/D sampling, a random sequence and random modulation times are generated at the same time, a random modulation waveform is generated by the modulation sequence and the modulation times, symmetrical judgment is carried out after the modulation times are larger than the set modulation times, if the symmetrical conditions are met, mirror image random modulation is carried out, if the symmetrical conditions are not met, random modulation is continuously carried out until the symmetrical conditions are met, and then mirror image is carried out. Mirror symmetry true random four-state modulation is applied to the Y waveguide after passing through the A/D converter and the operational amplifier circuit. The mirror symmetry true random four-state modulation and demodulation method has the characteristics of symmetry and randomness, has the advantages of equal occurrence frequency of positive and negative +/-pi/2 and +/-3 pi/2 modulation amplitudes of square waves, has the advantages of random occurrence of pseudo random four-state modulation +/-pi/2 and +/-3 pi/2, has completely random sequences and random modulation periods, and can effectively overcome the defects of poor detection sensitivity, high noise, reverse asymmetry of zero position and zero position fluctuation caused by the original modulation method.
The mirror symmetry true random modulation is shown in fig. 5, where fig. 5 collectively includes two complete mirror symmetry true random modulation waveforms, the two complete modulation waveforms are separated by a boundary, the modulation frequency of the modulation waveform before the boundary is 16 times, the period is 8 τ, the first 8 modulations are true random modulations, and the last 8 modulations are mirror images of the first 8 modulations with a symmetry axis. Since the modulation frequency is randomly set to 4 to 10 times, the mirror symmetry modulation frequency is 8 times after the boundary, and the period is 4 τ. In addition, the modulation needs to be subjected to symmetry judgment, even if the modulation frequency is greater than the set modulation frequency, random modulation is continuously carried out when the symmetry judgment is not met, mirror image implementation is not carried out until the symmetry condition is met, and the modulation period also has randomness. Therefore, the modulation sequence and the modulation period of the mirror symmetry true random modulation and demodulation method have random characteristics.
The invention effectively improves the signal-to-noise ratio, reduces the noise of output test current and improves the detection sensitivity; the zero output stability of the optical fiber current transformer is improved, and the asymmetry of the zero output after the current is reversed is restrained.
The above-described embodiments are merely preferred embodiments of the present invention, and general changes and substitutions by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.
Claims (5)
1. A mirror symmetry true random four-state modulation and demodulation method for an optical fiber current transformer is characterized by comprising the following steps:
step 1: electrifying the optical fiber current transformer, and starting sampling by an A/D converter of the optical fiber current transformer to obtain a sampling number;
step 2: the A/D converter transmits the sampling number in the step 1 to a data demodulation module, and the data demodulation module generates a random sequence and random modulation times according to the lowest bit AD [0] in the sampling number;
and step 3: the data demodulation module generates mirror symmetry true random four-state modulation according to the random sequence and the random modulation times in the step 2; wherein the content of the first and second substances,
in the step 3, generating mirror symmetry true random four-state modulation includes the following steps:
step 3-1: the data demodulation module generates true random four-state modulation according to the random sequence, the data demodulation module applies modulation according to the random modulation times in the step 2, and when the applied modulation times are larger than the random modulation times in the step 2, whether the generated true random four-state modulation meets the mirror symmetry condition is judged;
step 3-2: when the mirror symmetry condition is met, carrying out mirror image implementation on the true random four-state modulation which is greater than the random modulation times in the step 2 and is before the applied modulation times in the step 3-1 to form mirror symmetry true random four-state modulation;
step 3-3: and when the mirror symmetry condition is not met, continuing to apply modulation until the mirror symmetry condition is met, and repeating the step 3-2.
2. The mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer according to claim 1, further comprising the steps of: and 4, step 4: mirror symmetry true random four-state modulation is applied to the Y waveguide after passing through an A/D converter and an operational amplifier circuit.
3. The mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer according to claim 1, characterized in that: in the step 3-1, the mirror symmetry condition is: the modulation amplitude difference between the current modulation sequence and the last modulation sequence of the true random four-state modulation is + -pi/2 or + -3 pi/2.
4. The mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer according to claim 1, characterized in that: in the step 3-1, the number of times of modulation applied is 4 to 10.
5. The mirror symmetry true random four-state modulation and demodulation method for the fiber current transformer according to claim 1, characterized in that: in the step 3, mirror symmetry true random four-state modulation is generated continuously by taking the lowest bit AD [0] in the sampling number as a random source, the random number has no repetition and no period, and the modulation sequence generated by the random number is completely random.
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| CN107422166B (en) * | 2017-08-07 | 2020-02-11 | 北京航天时代光电科技有限公司 | Modulation and demodulation method for suppressing light power fluctuation for optical fiber current transformer |
| CN109631871B (en) * | 2018-12-09 | 2021-03-09 | 西安航天精密机电研究所 | Random modulation and demodulation method for inhibiting cross coupling of optical fiber gyroscope |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6700928B1 (en) * | 2000-05-11 | 2004-03-02 | The Boeing Company | Tetrahedron modem |
| CN1844853A (en) * | 2006-05-19 | 2006-10-11 | 北京航空航天大学 | Four-state modulation and demodulation method for automatically tracking optical fiber gyro 2pai voltage |
| CN101246009A (en) * | 2008-02-29 | 2008-08-20 | 北京航空航天大学 | Digital closed-loop optic fiber gyroscope accidental modulating method based on four-state markov chain |
| CN105911503A (en) * | 2016-07-08 | 2016-08-31 | 中国能源建设集团湖南省电力设计院有限公司 | On-line verification system for all-fiber optical current transformer |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6700928B1 (en) * | 2000-05-11 | 2004-03-02 | The Boeing Company | Tetrahedron modem |
| CN1844853A (en) * | 2006-05-19 | 2006-10-11 | 北京航空航天大学 | Four-state modulation and demodulation method for automatically tracking optical fiber gyro 2pai voltage |
| CN101246009A (en) * | 2008-02-29 | 2008-08-20 | 北京航空航天大学 | Digital closed-loop optic fiber gyroscope accidental modulating method based on four-state markov chain |
| CN105911503A (en) * | 2016-07-08 | 2016-08-31 | 中国能源建设集团湖南省电力设计院有限公司 | On-line verification system for all-fiber optical current transformer |
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