CN202649279U - Closed-loop optical fiber current transformer - Google Patents
Closed-loop optical fiber current transformer Download PDFInfo
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- CN202649279U CN202649279U CN 201220125163 CN201220125163U CN202649279U CN 202649279 U CN202649279 U CN 202649279U CN 201220125163 CN201220125163 CN 201220125163 CN 201220125163 U CN201220125163 U CN 201220125163U CN 202649279 U CN202649279 U CN 202649279U
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Abstract
The utility model provides a closed-loop optical fiber current transformer which comprises a light source, a light source control unit, a photoelectric detector, an optical device integrated component and a sensor head. The optical path system of the transformer is simple in structure and is convenient for integration and modularization. The used optical element has the advantages of small volume, light weight, no electromagnetic interference and no interference to the measured. A reflective optical path and the simple optical device are used to realize the model exchange of orthogonal polarized light, thus a reciprocal optical path is formed, and the ability of interference resistance of the optical path is improved. The technology of multiple closed-loops is used to effectively overcome light source power attenuation and system measurement error caused by the drift of the half-wave voltage of an optical phase modulator and to improve the operation stability and reliability of the transformer.
Description
Technical field
The present invention relates to a kind of optical fiber current mutual inductor, relate in particular to a kind of current transformer of full optical fiber approach of closed loop, its sensing element and optical signal transmission parts all are optical fiber, and its signal processing adopts a kind of many technology of closed loop of coherent detection scheme.
Background technology
Current transformer is one of the most basic in the electric power power transmission and transformation network, most important checkout equipment, its effect mainly comprises: one, the large current values in the high voltage environment on the transmission line of electricity being dropped to can be with the direct numerical value of measuring of secondary instrument, so that measure with general instrument; Two, provide electric signal for various monitoring and protection equipment, with the safety and stability of monitoring electric system; Three, the secondary device of high voltage primary equipment and low-voltage is isolated.
Therefore, safe, the reliable and Economic Status of the performance of current transformer and electric system is closely related.In the electric system, conventional current detecting equipment is to adopt take the current transformer of undesirable mutual electromagnetic inductance principle as the basis.In high voltage, large electric current and superpower electric system, this conventional current mutual inductor exposes a series of serious shortcomings: potential catastrophic failure danger, insulation difficulty, iron core magnetic saturation, secondary side load open circuit etc.
Optical fiber current mutual inductor is owing to its inherent characteristics possesses the incomparable advantage of traditional electromagnetic current transducer.Along with improving constantly of its reliability, optical fiber current mutual inductor will become that power domain electric energy metrical and protection use mainly selects equipment, progressively becomes domestic and international industry common recognition.
Ampère law is pointed out, when having electric current to flow through in the conductor, can produce closed magnetic field around it, adopts the way of Faraday magnetooptical effect to measure the size that this magnetic field just can obtain current flowing in the conductor.Optical fiber current mutual inductor normally forms a Fibre Optical Sensor unit to external optical fiber around a upper fixing turn.When having electric current to flow through in the conductor, according to Faraday effect, the magnetic field around it will be so that angle of change of polarization of transmission light in the sensor fibre, measures the size of current that the variable quantity of angle just can obtain flowing through in the conductor.Because this angle is very little, take measurement of an angle directly to determine that the size of current precision is very low, therefore adopt the method for interferometry, the polarized light angle is transformed into the phase changing capacity of light, again by interfering rear application to be extracted based on the feeble signal disposal route of the modulation /demodulation of being correlated with.
But there are following shortcomings in existing optical fiber current mutual inductor: 1, light path system complex structure is unfavorable for the system integration; 2, the element in the light path is subject to the impact of the conditions of work such as temperature easily, and measuring error is large, can not realize close-loop feedback.Existing optical fiber current mutual inductor technology is referring to CN100575959C, CN101299147B, CN101364475B, CN101521104B, CN101692401B, CN101915866A, CN101957395A, CN102087307A, CN102082606A etc.
Summary of the invention
The object of the invention is to the following aspects: one, light path system simple in structure, be convenient to integrated and modularization; Two, used optical element volume is little, lightweight, and is not subjected to electromagnetic interference (EMI), does not also disturb measured; Three, utilize reflective light path and simple optical device to realize the modes swap of crossed polarized light, form the reciprocity light path, improve the light path antijamming capability; Four, adopt a plurality of technology of closed loop, effectively overcome the systematic measurement error that light source power is decayed, the drift of optical phase modulator half-wave voltage causes, improve mutual inductor operation stability and reliability.
For simplification system and Effective Raise system reliability, be necessary to carry out integrated design for signal processing unit and the data acquisition unit of sensing.
In view of the foregoing, the invention provides a kind of closed-loop optical fiber current transformer, comprise: light source, light source driving units, photodetector, optical device integrated package, sensing head, wherein, the optical device integrated package, be used for the light of light source output is risen partially and is decomposed into two bunch polarized lights of orthogonal mode, then be coupling in described two bunch polarized lights on two orthogonal modess of same polarization maintaining optical fibre and transfer to sensing head; The light that reception is returned from sensing head and so that the light that returns in described optical device integrated package, interfere; Result of interference is outputed to photodetector; Reception is from the feedback modulation intelligence of signal processing unit, stack bias modulation phase place and feedback phase modulation between two bunch polarized lights; The closed signal processing unit, the output signal of reception photodetector is processed this signal, and signal processing results is fed back to optical device integrated package and light source driving units as the feedback modulation intelligence; Light source driving units is used for providing constant current and temperature control information to light source, receives simultaneously the feedback signal input of signal processing unit, makes the light intensity of light source stable output.
According to an aspect of the present invention, described optical device integrated package comprises: light splitting splicer spare, polarization maintaining optical fibre, optical phase modulator, light delay device.
According to an aspect of the present invention, described optical device integrated package comprises: light splitting splicer spare, polarization maintaining optical fibre, the light polarizer, optical phase modulator, light delay device.
According to an aspect of the present invention, described optical device integrated package comprises: the first light splitting splicer spare, polarization maintaining optical fibre, Y type optical phase modulator, the second light splitting splicer spare, light delay device.
According to an aspect of the present invention, described closed signal processing unit comprises: simulation amplification filtering unit, AD conversion unit, major loop DLC (digital logic circuit), D/A conversion unit, 2 π voltage control unit and filter units.
According to an aspect of the present invention, adopt square wave bias modulation mode, introducing ± pi/2 bias modulation phase differential between two bundle cross polarization light; Adopt staircase waveform feedback modulation system between two bundle cross polarization light, to introduce the faraday's phase information equal and opposite in direction that forms with the sensing head place, the phase differential of opposite direction; Adopt the way of relevant modulation /demodulation to carry out the signal demodulation.
According to an aspect of the present invention, simulation amplification filtering unit receives the electric signal from photodetector, carries out being input to AD conversion unit after the amplification filtering; AD conversion unit is used for receiving the output of simulation amplification filtering unit, will be digital signal through the analog signal conversion of amplification filtering, then outputs to the major loop DLC (digital logic circuit); The major loop DLC (digital logic circuit) receives AD conversion unit output, and the AD conversion unit output signal is carried out demodulation, and demodulation result is carried out integration thereupon and form digital staircase waveform bench height, and the digital staircase waveform of formation that further adds up; Whether receive the integrated signal of 2 π voltage control units output, detecting has periodic demodulating error, with the automatic adjustment to 2 π feedback driving voltage; Also realize the stack of digital staircase waveform and bias modulation square wave in the described major loop DLC (digital logic circuit), stack result outputs to D/A conversion unit; Described major loop DLC (digital logic circuit) also directly exports the integral result of demodulating information to wave filter; 2 π voltage control units are used for receiving the output of major loop DLC (digital logic circuit), and the signal after the demodulation is carried out integration, obtain characterizing the signal that whether has 2 π voltage reset errors, and described signal is exported to the major loop DLC (digital logic circuit); D/A conversion unit, be used for receiving the output of major loop DLC (digital logic circuit), the stack result of digital staircase waveform and bias modulation square-wave signal is converted to simulating signal, then output analog signal to optical phase modulator, it is poor with the feedback phase modulation to drive optical phase modulator introducing ± pi/2 bias modulation phase place between two bunch polarized lights; Filter unit is used for receiving the output of integral unit, and integrated signal is carried out filtering, and the filtering result is as the output of mutual inductor numeral.
To the detailed description of preferred forms, these and other purposes disclosed by the invention, feature and advantage will be more obvious according to hereinafter.
Description of drawings
Fig. 1 is the theory structure synoptic diagram of an embodiment of optical fiber mutual inductor of the present invention;
Fig. 2 is the structural drawing of an embodiment of closed signal processing unit among Fig. 1;
Fig. 3 is the structural drawing of a plurality of embodiments of optical device integrated package among Fig. 1;
Fig. 4 is the waveform synoptic diagram of square-wave frequency modulation;
Fig. 5 is the waveform synoptic diagram of staircase waveform feedback phase relation.
Embodiment
Fig. 1 is the principle assumption diagram of an embodiment of optical fiber mutual inductor involved in the present invention.According to this embodiment, this optical fiber mutual inductor comprises: light source driving units, light source, optical device integrated package, sensor fibre, catoptron, quarter wave plate, photodetector, closed signal processing unit, power supply.Sensor fibre, catoptron, these three parts of quarter wave plate consist of sensing head.Because sensing head belongs to prior art, therefore in Fig. 1, do not indicate with literal.
In addition, sensing head also can have multiple way of realization, does not belong to content of the present invention, so repeat no more.
Light source is for the light beam of the certain power of output under the control of light source driving units.
The optical device integrated package be used for to receive the light of light source output, and this light of light source output risen is biased into linearly polarized light, again this linearly polarized light is decomposed into immediately two bunch polarized lights of orthogonal mode; In the optical device integrated package, above-mentioned two bunch polarizations are shaken be optically coupled on two orthogonal modess of same polarization maintaining optical fibre, be that the optical device integrated package is sent the linearly polarized light of two bundle orthogonal modes along two orthogonal modes fl transmission of same polarization maintaining optical fibre to sensing head, and receiving subsequently the light beam that this two bunch polarized light returns along the original optical path modes swap after the responsive Faraday magnetooptical effect in sensing head place, the two-beam line that returns interferes in the optical device integrated package; The optical device integrated package also is used for the result of interference of two bunch polarized lights is outputed to photodetector by optical fiber; In addition, the optical device integrated package is accepted the feedback modulation intelligence from the closed signal processing unit, with stack ± pi/2 bias modulation phase place between two bunch polarized lights and with faraday's phase difference
FThe feedback phase modulation φ of equal and opposite in direction, opposite direction
R
Sensing head comprises quarter wave plate, sensor fibre, catoptron, is used for responsive current lead to be measured magnetic field on every side, namely according to Faraday magnetooptical effect, introduces the Faraday magnetooptical effect phase difference between two bundle crossed polarized lights
F
In sensing head, quarter wave plate is used for light beam from the linearly polarized light to the circularly polarized light, or circularly polarized light is to the mode conversion between the linearly polarized light.In the present embodiment, quarter wave plate is used for two bundle orhtogonal linear polarizaiton light of fl transmission are changed into two bundle orthogonal mode circularly polarized lights of left-handed and dextrorotation, and simultaneously the two bundle circularly polarized lights that return from sensor fibre is transformed back into the linearly polarized light of quadrature.Afterwards, the two bunch polarized lights that transform back into return along original optical path.
In sensing head, catoptron is used for reflection ray, makes the light reverse transfer.In the present embodiment, catoptron is used for so that two bundle circularly polarized light beam modes swap and reverse transfer, namely so that be originally two bundle circularly polarized lights of left-handed and dextrorotation and change dextrorotation and left-handed two bundle circularly polarized lights into and return along sensor fibre.
Photodetector be used for to receive the light signal output of optical device integrated package, utilizes photoelectric effect that light signal is converted to electric signal, and electric signal is outputed to amplification filtering unit in the closed signal processing unit.Photodetector belongs to prior art, and those skilled in the art can learn its specific implementation fully, hereinafter no longer describes in detail.
The closed signal processing unit receives the signal input of photodetector, realizes the digital control of signal and processing, and signal processing results is fed back to optical device integrated package and light source driving units.
Power supply is used for the direct current such as 110V, 220V or electric main are changed into the light current that the circuit board of mutual inductor can be used, i.e. power supply effect is to power to light source driving units and closed signal processing unit.
Light source driving units is used for providing constant current and temperature control information to light source, receives simultaneously the feedback signal input of closed signal processing unit, so that the light source intensity signal of stable output all the time.
As shown in Figure 1, lower in working order, power supply is to light source driving units, the power supply of closed signal processing unit, light source driving units work, control light source luminescent.The light that light source sends enters the optical device integrated package by optical fiber, through the adjustment of optical device integrated package, is divided into again the two-beam line of orthogonal mode behind the formation linearly polarized light, that is, and and the linearly polarized light of X, Y two bundle orthogonal modes.Then this two bundles polarized light is protected inclined to one side Transmission Fibers along same and is transferred to sensing head.
At the sensing head place, the linearly polarized light of X, Y two bundle orthogonal modes at first convert to respectively left-handed by quarter wave plate and (or) circularly polarized light of dextrorotation.When described left-handed and (or) when the circularly polarized light of dextrorotation arrived the catoptron of sensor fibre end, these two kinds of circularly polarized lights produced modes swap, return after the modes swap (be left-handed change dextrorotation, dextrorotation become left-handed).
This two-beam is responsive Faraday magnetooptical effect and arrive quarter wave plate by sensor fibre again, transforms back into linearly polarized light (also having exchanged with linear polarization pattern before) and returns along original optical path through quarter wave plate.
Two-beam interferes after arriving the optical device integrated package, and result of interference is carried out entering after the opto-electronic conversion closed signal processing unit through photodetector and carried out signal and resolve and extract.
The closed signal processing unit is processed according to the signal of photodetector input, the result that obtains is outputed to the optical device integrated package, thereby form the signal feedback to light path devices, be convenient to accurately, stably detect the electric current that passes through in the current carrying conductor.
In addition, the closed signal processing unit also feeds back light source driving units according to the input signal of photodetector, forms the closed-loop control that light source drives.As shown in Figure 1, by the variation to the extraction of DC component in photodetector Output rusults reflection light source power, and this DC component information (i.e. hereinafter I
0) Real-time Feedback is to light source driving units, revises light source drive current size, so that the light source luminous power of stable output all the time.
In the said process, the two bundle polarized lights respectively phase differential size of twice responsive Faraday effect formation are: φ
F=4NVI
Wherein, N is that the sensor fibre number of turns, V are that Verdet constant, the I of sensor fibre is size of current to be measured.φ
FIt is faraday's phase shift.
Afterwards, two bunch polarized lights are passed back in the optical device integrated package, and interfere therein, and result of interference is delivered to photodetector, turn not as entering the follow-up signal processing links behind the telecommunications breath, and the phase informations of the two bundle polarized lights that interfere are extracted.Because the interference light intensity information of mutual inductor is faraday's phase shift φ
FCosine function, namely
I
d＝I
0(1+cosφ
F)
Wherein, I
0It is the light intensity of two bundle relative photo.
By near the character of cosine function zero phase as can be known: (1) interference light intensity can not reflect the symbol of faraday's phase shift, no matter φ
Fpositive and negatively all export same numerical value, thereby can not reflect the flow direction of electric current to be measured; (2) small current measurement sensitivity is low, because cosine function is zero in zero phase place first order derivative.Yet in most application scenario, faraday's phase shift is very little; (3) in optical fiber current mutual inductor, by employed optical device basic parameter restriction, the output voltage that has determined photodetector is the Weak Information of microvolt level, and noise generally is a millivolt magnitude, namely is difficult to directly extract phase information from following formula.
Poor by in the optical device integrated package, introducing phase modulation among the present invention, reach and extract faraday's phase shift φ
FPurpose.Namely by introducing square wave bias modulation and staircase waveform feedback technique, so that the mutual inductor system always works in sensitive area, and be easy to adopt the way of correlation demodulation to extract faraday's phase shift information.
In the present invention, in the optical device integrated package, optical phase modulator is set, its objective is introducing ± pi/2 bias modulation phase place and close-loop feedback phase modulation φ between two bundle coherent lights
R, wherein feed back phase modulation φ
RIn order to offset faraday's phase difference
F, so that system always works in sensitive area.
The optical device integrated package is mainly realized several functions such as a minute actinic light, light rise partially, polarized light decomposition, optically-coupled, light phase modulation.The optical device integrated package can have multiple embodiment.
Fig. 3 is the structural drawing of a plurality of embodiments of optical device integrated package among Fig. 1.
Shown in Fig. 3 (a), the optical device integrated package comprises light splitting splicer spare 1, polarization maintaining optical fibre, optical phase modulator, light delay device.Except the sensing head part, the light path scheme of optical fiber current mutual inductor is all risk insurance folk prescription case in this scheme, and namely all optical fiber and device tail optical fiber all are polarization maintaining optical fibres.The linearly polarized light that sends in high polarisation source transmits in same polarization maintaining optical fibre through the 45° angle of tail optical fiber welding is divided into orthogonal mode to axle two bunch polarized light X, Y after through light splitting splicer spare, behind optical phase modulator and light delay device (light delay device itself is extremely one section polarization maintaining optical fibre of thousands of meters of a hop count rice), then two orthogonal modess along same polarization maintaining optical fibre transfer to sensing head.After returning from sensing head, this two-beam modes swap is passed through optical phase modulator again, reaches 45 ° of fusion point places and satisfies interference condition, interferes, and result of interference is coupled into photodetector through light splitting splicer spare 1.
Shown in Fig. 3 (b), the optical device integrated package comprises light splitting splicer spare 1, polarization maintaining optical fibre, the light polarizer, optical phase modulator, light delay device.Behind the light process light splitting splicer spare and the light polarizer that light source sends, welding is divided into orthogonal mode to axle two bunch polarized light X, Y transmit in same polarization maintaining optical fibre through the 45° angle of protecting inclined to one side tail optical fiber, behind optical phase modulator and light delay device (light delay device itself is extremely one section polarization maintaining optical fibre of thousands of meters of a hop count rice), then two orthogonal modess along same polarization maintaining optical fibre transfer to sensing head.After returning from sensing head, this two-beam modes swap is passed through optical phase modulator again, reaches 45 ° of fusion point places and satisfies interference condition, interferes, and result of interference is coupled into photodetector through the light polarizer and light splitting splicer spare.
Shown in Fig. 3 (c), the optical device integrated package comprises the first light splitting splicer spare (being light splitting splicer spare 1), polarization maintaining optical fibre, Y type optical phase modulator, the second light splitting splicer spare (being light splitting splicer spare 2), light delay device.The light that light source sends arrives Y type optical phase modulator behind the first light splitting splicer spare.Y type optical phase modulator has that light rises partially, the function of light beam splitting, optical modulation.Y type optical phase modulator belongs to prior art, no longer describes in detail.At Y type optical phase modulator place, light reaches the second light splitting splicer spare along its two tail optical fiber propagated forward respectively after being polarized and being divided into the identical linearly polarized light of two bundle polarization modes.Before this, tail optical fiber by Y type optical phase modulator and 90 ° of angles of a tail optical fiber of the second light splitting splicer spare are to the axle welding so that above-mentioned two bunch polarized lights from the second light splitting splicer spare out after pattern orthogonally along same polarization maintaining optical fibre propagated forward.Similarly, the polarized light of this two bundles orthogonal mode returns and through behind the second light splitting splicer spare from sensing head, again because the welding to axle at above-mentioned 90 ° of angles becomes two identical bunch polarized lights of pattern, and interfere at Y type optical phase modulator place, result of interference is coupled into photodetector through the first light splitting splicer spare.
Shown in Fig. 3 (d), the optical device integrated package comprises the first light splitting splicer spare (being light splitting splicer spare 1), polarization maintaining optical fibre, Y type optical phase modulator, the second light splitting splicer spare (being light splitting splicer spare 2), light delay device.The light that light source sends arrives Y type optical phase modulator behind the first light splitting splicer spare, at Y type optical phase modulator place, light reaches the second light splitting splicer spare along its two tail optical fiber propagated forward respectively after being polarized and being divided into the identical linearly polarized light of two bundle polarization modes.Second light splitting splicer spare can assemble the linearly polarized light of the identical polarization mode in two tail optical fibers of forward path two bunch polarized lights of orthogonal mode and protect inclined to one side tail optical fiber continuation propagated forward along same, two bunch polarized light of protecting orthogonal mode in the inclined to one side tail optical fiber in the backward channel can also be changed into two bunch polarized lights of model identical, and propagate along its two backward channel tail optical fibers respectively, namely can be the polarization angle half-twist of a branch of polarized light in the two bundle polarized lights of propagating therein.Above-mentioned two bunch polarized lights from the second light splitting splicer spare out after pattern orthogonally along same polarization maintaining optical fibre propagated forward.Similarly, the polarized light of this two bundles orthogonal mode returns and through behind the second light splitting splicer spare from sensing head, change again two identical bunch polarized lights of pattern into, and interfere at Y type optical phase modulator place, result of interference is coupled into photodetector through the first light splitting splicer spare.
More than listed the several specific embodiments about the optical device integrated package that to realize in this patent, but anyly can realize that the design of above-mentioned functions is all within the protection domain of this patent.
As shown in Figure 2, according to an embodiment of the invention, the closed signal processing unit comprises simulation amplification filtering unit, AD conversion unit (A/D), major loop DLC (digital logic circuit), D/A conversion unit (D/A), 2 π voltage control unit and filter units.
Wherein, simulation amplification filtering unit is used for receiving the electric signal from photodetector, carries out amplification filtering in order to the input as the analog to digital conversion link.
AD conversion unit is used for receiving the output of simulation amplification filtering unit, will be digital signal through the analog signal conversion of amplification filtering, then outputs to the major loop DLC (digital logic circuit), carries out logical operation.
The major loop DLC (digital logic circuit), the output of reception AD conversion unit is carried out demodulation to the AD conversion unit output signal, demodulation result is carried out the bench height that integration forms the feedback staircase waveform thereupon, take time τ as step-length above-mentioned bench height is added up afterwards, form digital staircase waveform.Step-length τ is the transmission time of light in the mutual inductor light path.According to the figure place of follow-up link D/A conversion unit, digital staircase waveform can automatically overflow and make zero, and realizes automatically reseting of feedback modulation.If when occuring when automatically reseting, the corresponding feedback modulation of staircase waveform overall height 2 π phase differential, so this automatically reseting can not exert an influence to the measuring accuracy of mutual inductor.In addition, owing to the half-wave voltage of light phase modulation may produce drift along with the variation of environment and time, will be transferred to simultaneously through the signal of demodulation in the 2 π voltage control units in the present embodiment; In addition, this logical circuit also receives the integrated signal of 2 π voltage control units output, and whether detect has periodic demodulating error, in order to the automatic adjustment to 2 π feedback driving voltage; Also realize in addition the stack of digital staircase waveform and bias modulation square wave in the major loop DLC (digital logic circuit), stack result outputs to D/A conversion unit; In addition, the major loop DLC (digital logic circuit) also directly exports wave filter to the integral result of demodulating information, and the filtering result is as the output of mutual inductor numeral, to characterize size of current to be measured.
2 π voltage control units, be used for receiving the output of major loop DLC (digital logic circuit), signal after the demodulation is carried out integration, obtain to characterize the signal that whether has 2 π voltage reset errors, and this signal exported to the major loop DLC (digital logic circuit), in order to 2 π resetting voltages are adjusted automatically.
D/A conversion unit, be used for receiving the output of major loop DLC (digital logic circuit), the stack result of digital staircase waveform and bias modulation square-wave signal is converted to simulating signal, then output analog signal to optical phase modulator, thereby drive optical phase modulator with introducing ± pi/2 bias modulation phase place and φ between two bunch polarized lights
RThe feedback phase modulation is poor.
Filter unit is used for receiving the output of integral unit, and integrated signal is carried out filtering, and the filtering result is as the output of mutual inductor numeral, to characterize size of current to be measured.
According to an embodiment of the invention, in this embodiment, the major loop DLC (digital logic circuit) comprises signal demodulation unit, integral unit and cumulative unit at least.
According to an embodiment of the invention, in this embodiment, 2 π voltage control units comprise 2 π voltage error signal demodulating unit and digital integrators.
Signal demodulation unit receives the output of AD conversion unit, and the output signal of AD conversion unit is carried out demodulation.The method of demodulation is: the adjacent front and back semiperiod of the periodic signal of AD conversion unit output is taken a sample respectively do cumulatively, accumulation result subtracts each other again, and subtracting each other the result namely is demodulation result.Then demodulation result is sent to 2 π voltage error signal demodulating units in the 2 π voltage control units.
2 π voltage error signal demodulating units carry out to the received signal demodulation and judge, judge whether to exist periodic control information, and formation demodulation judged result is sent in the digital integrator, form further update information, and feed back to the major loop DLC (digital logic circuit), in order to 2 π feedback voltages are adjusted automatically.
Integral unit is exported to filter unit with integral result, and integral result is transferred in the totalizer to be added up by totalizer forms digital staircase waveform, as shown in Figure 5.The digital staircase waveform that forms is sent in the D/A conversion unit after superposeing with the bias modulation square wave.The bias modulation square wave as shown in Figure 4.D/A conversion unit is input to transformation result in the optical phase modulator, thereby it is poor with the feedback phase modulation to introduce corresponding bias modulation phase place in the middle of light path.
According to a specific embodiment of the present invention, Fig. 4 has described a kind of embodiment of square-wave frequency modulation.Upper and lower, right three parts that Fig. 4 can be divided into.The sinogram longitudinal axis of part represents the later light intensity of two bundle polarized light interferences on Fig. 4, and transverse axis represents that two bundle cross polarization light phases are poor.Part is that two bundle cross polarization light are carried out ± modulated square wave of pi/2 bias modulation under Fig. 4, and its vertical pivot is the time, and transverse axis represents the square wave amplitude, and just in time can be between two bundle cross polarization light during the square wave which amplitude modulation introducing ± pi/2 bias modulation phase differential.Fig. 4 right half is that two bundle polarized light interference results are through the output waveform after the square-wave frequency modulation, wherein partially left part is waveform in measured physical quantity=0 o'clock, the side that takes over partly is to be not equal to 0 o'clock waveform at measured physical quantity, when the flat part in bottom represents to be in the square wave which amplitude modulation, spike then is that two bundle polarized light interference results in square wave peak-peak amplitude jump form through peaks.
The interference light intensity information of mutual inductor is faraday's phase shift φ
FCosine function, namely
I
d＝I
0(1+cosφ
F)
In the following formula, I
0The light intensity of two bundle relative photo, φ
F=4NVI be two bunch polarized lights in faraday's phase shift of sensing head place sensitivity, wherein N is that sensor fibre twines the number of turns, V is that sensor fibre Verdet constant, I are size of current to be measured.
As shown in Figure 4, at first driving modulation pull-in frequency by optical phase modulator by square wave at the optical phase modulator place is the square wave phase bias modulation (wherein τ is that two bunch polarized lights are formed into the mistiming that finally interferes) of 1/ (2 τ), stack ± pi/2 phase is poor between two bunch polarized lights, improves the sensitivity of mutual inductor system; By introducing the square wave bias modulation, on frequency domain, output signal spectrum is moved to high frequency by low frequency range simultaneously, avoid the 1/f noise of low frequency range, reduced the impact of low-frequency noise.At this moment interfere and be output as
By bias modulation, be superimposed upon direct current I interfering output to be modulated into one
0On amplitude be I
0Sin φ
FSquare-wave signal, the square wave amplitude has reflected faraday's phase shift size.In order further to reduce system's output nonlinear error and to increase range of dynamic measurement, introduce a feedback compensation phase shift φ with faraday phase shift equal and opposite in direction, opposite direction by optical phase modulator by the modulation of staircase waveform feedback at the optical phase modulator place
R, form closed-loop control system.At this moment, the interference of two-beam is output as
Because φ
F+ φ
R≈ 0, so this moment, the mutual inductor system always worked in the best zero phase near zone of the linearity, it is the highest therefore to measure sensitivity; Owing to realize the closed loop detection, also enlarged the measurement range of system simultaneously.At this moment the correlation demodulation result of system is (semiperiod is subtracted each other the result before and after the periodic signal that following formula represents):
Δ＝n·I
0·sin(φ
F+φ
R)≈n·I
0·(φ
F+φ
R)
Wherein, Δ is the intermediate quantity that signal demodulation link occurs, and it represents demodulation result, is a small quantity, forms digital staircase waveform bench height by the integration to this small quantity.It results from the signal demodulation unit in the major loop DLC (digital logic circuit), outputs to integral unit and 2 π voltage control units.
According to one embodiment of present invention, Fig. 5 has provided the embodiment of staircase waveform feedback phase relation.As shown in Figure 5, Fig. 5 is divided into up and down two parts.Wherein in the first half of Fig. 5, the longitudinal axis is phase differential, and transverse axis is the time.Solid line staircase waveform wherein represents t feedback staircase waveform constantly, and the dotted line staircase waveform represents t+ τ feedback staircase waveform constantly, the size of the bench height actual feedback amount of staircase waveform.The latter half of Fig. 5 is corresponding with the first half, is subtracted each other by the solid line of the first half and dotted line to obtain, and its is actual, and what characterize is the bench height of staircase waveform.At periodic recessed portion, sign be the height value of staircase waveform equally, just herein staircase waveform phase-accumulated formation resets to 2 π, so non-highly low 2 π in the place that resets of its aspect ratio.
Adopt the modulation of staircase waveform feedback to produce the poor φ of feedback phase in the present embodiment
RThe described demodulation result of following formula is made cumulative integration, form the bench height So (So is intermediate quantity, does not indicate) of digital staircase waveform in Fig. 5.So forms analogue step ripple rear drive optical phase modulator through D/A conversion unit on the one hand, differs φ to introduce compensation between two-beam
R, So numeral as mutual inductor after further filtering is processed is exported simultaneously, the size and Orientation of reflection mutual inductor input current.
If the analogue step ripple that forms through digital-to-analog conversion is Δ V
R(t)=V
R(t)-V
R(t-τ), its codomain be (∞ ,+∞), the additional phase shift that then produces between two bunch polarized lights is:
φ
R＝K
fpV
R(t)-K
fpV
R(t-τ)
＝K
fp(V
R(t)-V
R(t-τ))
＝K
fpΔV
R(t)
τ is the transit time of light beam in fibre delay line in the following formula, and Kfp is the phase-modulator index of modulation.The following formula explanation, the phase differential that the staircase waveform modulation produces is directly proportional with the staircase waveform bench height.FW among Fig. 5 (solid line) expression t feedback staircase waveform constantly, BW (dotted line) expression t+ τ feedback staircase waveform constantly; V
R(t) absolute altitude of expression analogue step ripple step.
But obviously, the codomain scope (∞ ,+∞) the upper staircase waveform that constantly rises is impossible realize.Owing to interfere output signal take 2 π as the cycle, so in this closed loop policy, adopting shape codomain scope as shown in Figure 5 be that the staircase waveform of (0,2 π) replaces codomain for (∞ ,+∞) staircase waveform is namely worked as staircase waveform phase modulation K
FpV
R(t)=automatically reset during 2 π.
The closed signal that realizes optical fiber current mutual inductor by above method detects.But in mutual inductor long-term work process, the half-wave voltage of optical phase modulator can be drifted about, i.e. K
FpV
R(t) ≠ 2 at this moment π just needs the automatic corrective loop of design 2 π resetting voltages, as shown in Figure 2.
At first need to extract the error signal of 2 π resetting voltage corrective loops, minute K
FpV
R(t)＞2 π, K
FpV
R(t)＜2 π, K
FpV
R(t)=2 three kinds of situations of π.Work as K
FpV
R(t) ≠ during 2 π, the photo-detector output power can produce a transient, this transient resets at staircase waveform and constantly can obtain according to the System Dependent demodulation result, this demodulation result is as the 2nd closed loop, it is the two the input error signal of signal circuit of major loop DLC (digital logic circuit) and 2 π voltage control units among Fig. 2, then use by digital integrator it is processed, again the digital signal behind the integration is transformed into simulating signal by digital-to-analogue, remove to control the gain of D/A conversion unit or the digital to analog converter reference voltage that mutual inductor major loop DLC (digital logic circuit) produces staircase waveform, thereby 2 π resetting voltage corrective loops have been formed, 2 π resetting voltages are controlled in real time, make it can produce all the time accurately 2 π phase places, thereby guarantee the no-load voltage ratio performance of mutual inductor.
According to an aspect of the present invention, the closed signal processing unit can be realized by technology such as FPGA, DSP.Said units can be designed to integrated device or independent module according to demand in the situation that function is determined, be designed in the situation of integrated device, and the device of light path, circuit all is easy to modularization and integrated, and reciprocity is good, is convenient to Networking Design.
It will be understood by those of skill in the art that in the scope and equivalency range thereof of claims, according to designing requirement and other factors, various modifications, merging, subitem merging and variation can occur.
Claims (11)
1. closed-loop optical fiber current transformer, comprising: light source, light source driving units, photodetector, optical device integrated package, sensing head is characterized in that:
The optical device integrated package is used for the light of light source output is risen partially and is decomposed into two bunch polarized lights of orthogonal mode, then is coupling in described two bunch polarized lights on two orthogonal modess of same polarization maintaining optical fibre and transfers to sensing head; The light that reception is returned from sensing head and so that the light that returns in described optical device integrated package, interfere; Result of interference is outputed to photodetector; Reception is from the feedback modulation intelligence of signal processing unit, stack bias modulation phase place and feedback phase modulation between two bunch polarized lights;
The closed signal processing unit, the output signal of reception photodetector is processed this signal, and signal processing results is fed back to optical device integrated package and light source driving units as the feedback modulation intelligence;
Light source driving units is used for providing constant current and temperature control information to light source, receives simultaneously the feedback signal input of signal processing unit, makes the light intensity of light source stable output.
2. closed-loop optical fiber current transformer according to claim 1, it is characterized in that: described optical device integrated package comprises: light splitting splicer spare, polarization maintaining optical fibre, optical phase modulator, light delay device.
3. closed-loop optical fiber current transformer according to claim 2 is characterized in that: adopt all risk insurance folk prescription case, namely all optical fiber that relate to or optoelectronic device tail optical fiber are polarization maintaining optical fibre in this light path; Behind the linearly polarized light process light splitting splicer spare that light source sends, be divided into two bunch polarized lights of orthogonal mode through the 45° angle fusion point place of polarization maintaining optical fibre, through behind the optical phase modulator, then two orthogonal modess along same polarization maintaining optical fibre transfer to sensing head; After returning from sensing head, this two-beam modes swap is passed through optical phase modulator again, reaches described 45° angle fusion point place and interferes, and result of interference is coupled to photodetector through light splitting splicer spare.
4. closed-loop optical fiber current transformer according to claim 1, it is characterized in that: described optical device integrated package comprises: light splitting splicer spare, polarization maintaining optical fibre, the light polarizer, optical phase modulator, light delay device.
5. closed-loop optical fiber current transformer according to claim 4, it is characterized in that: behind the light process light splitting splicer spare and the light polarizer that light source sends, be divided into two bunch polarized lights of orthogonal mode through the 45° angle fusion point place of polarization maintaining optical fibre, through behind the optical phase modulator, then two orthogonal modess along same polarization maintaining optical fibre transfer to sensing head; After returning from sensing head, this two-beam modes swap is passed through optical phase modulator again, reaches described 45° angle fusion point place and interferes, and result of interference is coupled to photodetector through the light polarizer and light splitting splicer spare.
6. closed-loop optical fiber current transformer according to claim 1, it is characterized in that: described optical device integrated package comprises: the first light splitting splicer spare, polarization maintaining optical fibre, Y type optical phase modulator, the second light splitting splicer spare, light delay device.
7. closed-loop optical fiber current transformer according to claim 6 is characterized in that: tail optical fiber of Y type optical phase modulator and a tail optical fiber of the second light splitting splicer spare with 90 ° of angles to the axle welding; The light that light source sends arrives Y type optical phase modulator behind the first light splitting splicer spare, at Y type optical phase modulator place, after light was polarized and is divided into the identical linearly polarized light of two bundle polarization modes, two tail optical fibers propagation along described Y type optical phase modulator reached the second light splitting splicer spare respectively; The two-beam line that returns from sensing head through the second light splitting splicer spare after, the place interferes in Y type optical phase modulator, result of interference is coupled to photodetector through the first light splitting splicer spare.
8. closed-loop optical fiber current transformer according to claim 6, it is characterized in that: the second light splitting splicer spare assembles the linearly polarized light of the identical polarization mode in two tail optical fibers of forward path two bunch polarized lights of orthogonal mode and protects inclined to one side tail optical fiber continuation propagated forward, the polarization angle half-twist of a branch of linearly polarized light in the two bunch polarized lights that also will propagate therein along same; The light that light source sends arrives Y type optical phase modulator behind the first light splitting splicer spare, at Y type optical phase modulator place, after light was polarized and is divided into the identical linearly polarized light of two bundle polarization modes, two tail optical fibers propagation along described Y type optical phase modulator reached the second light splitting splicer spare respectively; The two-beam line that returns from sensing head through the second light splitting splicer spare after, change two identical bunch polarized lights of pattern into, the place interferes in Y type optical phase modulator, result of interference is coupled into photodetector through the first light splitting splicer spare.
9. closed-loop optical fiber current transformer according to claim 1, it is characterized in that: described closed signal processing unit comprises: simulation amplification filtering unit, AD conversion unit, major loop DLC (digital logic circuit), D/A conversion unit, 2 π voltage control unit and filter units.
10. one of according to claim 1-9 described closed-loop optical fiber current transformer is characterized in that, adopts square wave bias modulation mode, introducing ± pi/2 bias modulation phase differential between two bundle cross polarization light; Adopt staircase waveform feedback modulation system between two bundle cross polarization light, to introduce the faraday's phase information equal and opposite in direction that forms with the sensing head place, the phase differential of opposite direction; Adopt the way of relevant modulation /demodulation to carry out the signal demodulation.
11. closed-loop optical fiber current transformer according to claim 9 is characterized in that:
Simulation amplification filtering unit receives the electric signal from photodetector, carries out being input to AD conversion unit after the amplification filtering;
AD conversion unit is used for receiving the output of simulation amplification filtering unit, will be digital signal through the analog signal conversion of amplification filtering, then outputs to the major loop DLC (digital logic circuit);
The major loop DLC (digital logic circuit) receives AD conversion unit output, and the AD conversion unit output signal is carried out demodulation, and demodulation result is carried out integration thereupon and form digital staircase waveform bench height, and the digital staircase waveform of formation that further adds up; Whether receive the integrated signal of 2 π voltage control units output, detecting has periodic demodulating error, with the automatic adjustment to 2 π feedback driving voltage; Also realize the stack of digital staircase waveform and bias modulation square wave in the described major loop DLC (digital logic circuit), stack result outputs to D/A conversion unit; Described major loop DLC (digital logic circuit) also directly exports the integral result of demodulating information to wave filter;
2 π voltage control units are used for receiving the output of major loop DLC (digital logic circuit), and the signal after the demodulation is carried out integration, obtain characterizing the signal that whether has 2 π voltage reset errors, and described signal is exported to the major loop DLC (digital logic circuit);
D/A conversion unit, be used for receiving the output of major loop DLC (digital logic circuit), the stack result of digital staircase waveform and bias modulation square-wave signal is converted to simulating signal, then output analog signal to optical phase modulator, it is poor with the feedback phase modulation to drive optical phase modulator introducing ± pi/2 bias modulation phase place between two bunch polarized lights;
Filter unit is used for receiving the output of integral unit, and integrated signal is carried out filtering, and the filtering result is as the output of mutual inductor numeral.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102628884A (en) * | 2012-03-29 | 2012-08-08 | 扬州永阳光电科贸有限公司 | Closed-loop optical fiber current transformer |
| CN106291040A (en) * | 2016-07-26 | 2017-01-04 | 胡朝年 | Magneto-opitcal current transducer |
| CN107741244A (en) * | 2017-11-10 | 2018-02-27 | 广东复安科技发展有限公司 | A kind of M Z optical interference circuit structures with the inclined function of all risk insurance |
| WO2019090706A1 (en) * | 2017-11-10 | 2019-05-16 | 广东复安科技发展有限公司 | Mach-zehnder interference optical path structure having full polarization maintenance function |
| CN111198289A (en) * | 2018-11-20 | 2020-05-26 | 许继集团有限公司 | Control method of optical fiber type current measuring device |
| CN113960346A (en) * | 2021-09-23 | 2022-01-21 | 国网江苏省电力有限公司电力科学研究院 | Light source timely constant power control device and method applied to optical fiber current transformer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102628884A (en) * | 2012-03-29 | 2012-08-08 | 扬州永阳光电科贸有限公司 | Closed-loop optical fiber current transformer |
| CN102628884B (en) * | 2012-03-29 | 2017-01-18 | 扬州永阳光电科贸有限公司 | Closed-loop optical fiber current transformer |
| CN106291040A (en) * | 2016-07-26 | 2017-01-04 | 胡朝年 | Magneto-opitcal current transducer |
| CN106291040B (en) * | 2016-07-26 | 2018-12-18 | 胡朝年 | Magneto-opitcal current transducer |
| CN107741244A (en) * | 2017-11-10 | 2018-02-27 | 广东复安科技发展有限公司 | A kind of M Z optical interference circuit structures with the inclined function of all risk insurance |
| WO2019090706A1 (en) * | 2017-11-10 | 2019-05-16 | 广东复安科技发展有限公司 | Mach-zehnder interference optical path structure having full polarization maintenance function |
| US11493693B2 (en) | 2017-11-10 | 2022-11-08 | Guangdong Fu'an Technology Development Co., Ltd. | M-Z interface light path structure with all polarization-maintaining function |
| CN111198289A (en) * | 2018-11-20 | 2020-05-26 | 许继集团有限公司 | Control method of optical fiber type current measuring device |
| CN113960346A (en) * | 2021-09-23 | 2022-01-21 | 国网江苏省电力有限公司电力科学研究院 | Light source timely constant power control device and method applied to optical fiber current transformer |
| CN117310260A (en) * | 2023-11-28 | 2023-12-29 | 华中科技大学 | Phase gradient correction and light path difference wide-amplitude current measurement system and method |
| CN117310260B (en) * | 2023-11-28 | 2024-02-20 | 华中科技大学 | Phase gradient correction and light path difference wide-amplitude current measurement system and method |
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