A stacked optical current sensor and its anti-external magnetic interference method

Abstract

The present invention discloses a stacked optical current sensor and an anti-external magnetic interference method thereof, which belong to the technical field of electric power sensors. The stacked optical current sensor includes: a sensor device and a stacked optical current sensor real-time signal processor. This optical current sensor includes a lower layer and an upper layer sub-sensor, whose sensing magneto-optical optical path structure is placed on the long side or short side of a symmetrical polygon, and the upper layer sub-sensor is placed after the rotation angle is taken as the center of the lower layer sub-sensor. The anti-external magnetic interference method is that the current conductor to be measured is placed at the center of the stacked optical current sensor, and the interference current conductor can be located at any point outside the stacked optical current sensor. At this time, the magnetic field integrals of the interference current on the sensing magneto-optical optical path structures of the upper and lower layers of sub-sensors show the characteristics of being mutually inverted. The signal processor performs superposition and cancellation processing on the signals obtained from the two layers of sub-sensors to eliminate the influence of the magnetic field of the interference current, and thus obtain a high-precision current measurement result.

Description

Technical Field

[0001] The invention belongs to the technical field of electric power sensors, and in particular relates to a stacked optical current sensor and a method for resisting external magnetic interference thereof. Background Art

[0002] In recent years, with the substantial increase in the operating voltage level of the power grid, electronic sensors have a wider application prospect in the power system. Among them, the optical current transformer based on the Faraday effect has received widespread attention in electronic transformer components in recent years. Due to its advantages such as large dynamic measurement range, wide frequency response range, high accuracy, and making up for the shortcomings of traditional electromagnetic current transformers such as easy ferromagnetic resonance, easy saturation of the iron core, and large size, the optical current transformer is considered to be an ideal substitute for traditional electromagnetic current transformers. The first one proposed by the academic community was the fiber optical current sensor (FOCS), in which the energized conductor is surrounded by optical fiber. The original intention of proposing this structure was to make the transformer measurement structure satisfy the basic Ampere loop law, thereby completely eliminating the influence of external interference current on the transformer measurement accuracy. However, subsequent studies have found that under the combined action of inhomogeneous magnetic field and linear birefringence, FOCT actually cannot satisfy the Ampere loop law. At the same time, the physical properties of optical fiber are also easily affected by temperature, which leads to fluctuations in sensor performance. Therefore, the academic community has proposed a magneto-optical current transformer (MOCS), which uses magneto-optical glass as a sensor measurement unit. According to the different optical path structures, magneto-optical current transformers can be divided into closed optical path transformers and direct optical path transformers. Direct optical path transformers have the advantages of simple optical path structure and easy manufacturing. With the solution of measurement accuracy temperature drift, long-term operation stability, photoelectric conversion noise, manufacturing materials and other issues, direct optical path optical current transformers have initially entered the practical stage.

[0003] The basic measurement principle of the direct optical path magneto-optical current sensor is as follows: Fig.11 As shown, it is the polarization light deflection angle The relationship with current I can be expressed by the following formula:

[0004]

[0005] Where V is the Verdet constant of the magneto-optical material, is the magnetic field intensity generated by the external current, l is the length of the light path, k is the proportional constant, and I is the current to be measured. Malus's law is then used to convert the difficult-to-measure angle signal into an easily-measured light intensity signal, thereby obtaining the measured current.

[0006] From the above formula, it can be concluded that when MOCS measures current, it actually uses the spatial magnetic field information converted from the current information. When there is interference current in space, the interference magnetic field generated by it will be superimposed on the magnetic field generated by the current to be measured in the sensing optical path, resulting in errors in MOCS measurement.

[0007] Although the direct optical path type magneto-optical current sensor has many advantages, its structure naturally cannot meet the basic Ampere loop law. Therefore, resistance to external magnetic field interference has become the first problem that must be solved when applying the direct optical path type magneto-optical current sensor. The academic community has also studied this problem from many aspects and achieved certain results. At present, there are mainly the following methods to solve the problem of optical current sensor's resistance to external magnetic interference:

[0008] 1) Through the magnetic collecting ring and other structures, the magnetic field formed by the current to be measured is enhanced to indirectly suppress the interference of the external magnetic field. However, this method obviously does not fundamentally solve the problem of external magnetic interference. If the interference current increases several times or dozens of times due to some factors, this method will lose its effect. And this method also increases the difficulty of sensor design.

[0009] 2) Magnetic shielding method. Rely on adding additional equipment such as shielding covers to isolate the external magnetic field from the sensor device. The disadvantages of this method are limited shielding effect, complex structure, and reduced insulation performance.

[0010] 3) Zero and anti-magnetic method. The interference current is placed at certain special positions. In theory, the interference current can completely prevent the optical current sensor arranged in a regular polygon from interfering. The biggest disadvantage of this method is that it has strict requirements on the location of the interference current and lacks the ability to adapt to interference currents that may exist at any position in space.

[0011] In view of the above problems existing in the prior art, the inventor provides a novel stacked optical current sensor and a corresponding method for realizing resistance to external magnetic interference. This structure can basically completely eliminate the influence of the magnetic field generated by the interfering current located at any position in space on the measurement accuracy of the sensor, and effectively improve the measurement accuracy of the sensor. Moreover, compared with the ordinary single-layer structure, this structure is particularly suitable for the case where the interfering current is large or the interfering current is close to the current to be measured. Summary of the invention

[0012] The purpose of the present invention is to provide a stacked optical current sensor and a method for resisting external magnetic interference thereof, characterized in that the stacked optical current sensor comprises: a sensor device 18 and a stacked optical current sensor real-time signal processor 22; in the sensor device 18, a stacked structural body 13 is respectively connected to a spectrometer 11 and a beam combiner 14; wherein the spectrometer 11 comprises a 1# spectrometer and a 2# spectrometer, the 1# spectrometer and the 2# spectrometer are respectively connected to a controlled light source 10, and the controlled light source 10 is connected to a highly stable controllable current source 9; the beam combiner 14 is connected to a controllable current source 9; and the controllable current source 10 is connected to a controllable current source 9. 4 comprises a 1# beam combiner and a 2# beam combiner; the 1# beam combiner and the 2# beam combiner are respectively connected to two photodetectors 15, and the two photodetectors 15 are respectively connected to two A / D converters 16; the two A / D converters 16 are respectively connected to the stacked optical current sensor data processing unit 19 in the stacked optical current sensor real-time signal processor 22; the stacked optical current sensor real-time signal processor 22 is composed of the stacked optical current sensor data processing unit 19, the current signal output unit 20, and the signal output synthesis unit 21 connected in series;

[0013] The stacked structure body 13 includes upper and lower sub-sensors, and the upper sensor is placed with an angle of π / k rotated relative to the center of the lower sensor; there is a corresponding positioning boss 8 on the lower insulating cover 7, and the upper sensor is fixed on the insulating disk 6 at a set angle, and the insulating cover 7 covers the sensing magneto-optical optical path structure 12, thereby forming two independent insulating entities; wherein, the sensing magneto-optical optical path structure 12 is composed of an input collimator 1, a polarizer 2, a magneto-optical material 3, an analyzer 4, and a parallel output collimator 5 in series; the sensing magneto-optical optical path structures 12 are connected to form a square structure through input / output optical fibers 23.

[0014] The upper layer sub-sensor or the lower layer sub-sensor contains k identical sensing magneto-optical optical path structures 12, and the entire sensor contains 2k identical sensing magneto-optical optical path structures 12; the effective sensing optical path lengths of the 2k sensing magneto-optical optical path structures 12 along the light-transmitting direction are the same, and the upper and lower layers of sub-sensors together constitute the stacked structural body 13 of the stacked optical current sensor; wherein K>2, K∈N.

[0015] The connection structure of the sensor device includes the following:

[0016] The first connection method is: a highly stable controllable current source 9 is connected to a controlled light source 10 to drive the controlled light source to output a highly stable DC light intensity; the output highly stable DC light intensity enters two identical splitters 11, namely, the 1# splitter and the 2# splitter, and the splitters evenly divide it into k beams of light output, and the output light is connected to k sensing magneto-optical optical path structures 12 in the upper and lower layers through optical fibers, for a total of 2k; the output ends of the k sensing magneto-optical optical path structures in the upper and lower layers are respectively connected to the input ends of two combiners 14. The output ends of the two combiners 14, namely, the 1# combiner and the 2# combiner, are respectively connected to the input ends of two photodetectors 15; the output end of the photodetector is connected to the input end of the A / D converter 16. The output of the A / D converter enters the real-time signal processor 22 of the stacked optical current sensor for signal processing, and finally outputs the current value to be measured;

[0017] The second connection mode is: the output ends of the k sensing magneto-optical optical path structures 12 in the upper and lower layers are independently connected to the input ends of the k photoelectric detectors 15, the output ends of the photoelectric detectors are directly connected to the A / D converter with k input ends, and the A / D converter is then connected to the input end of the real-time signal processor 22, and the other connection modes remain unchanged;

[0018] The third connection method is: cancel the beam splitter, the natural light generated by the light source is directly connected to the input ends of the upper and lower layers of the sensing magneto-optical optical path structure 12, and the k sensing magneto-optical optical path structures 12 contained in each layer are connected by optical fiber, and finally the output light intensity of the upper and lower layers of sub-sensors is respectively connected to the input ends of the photodetector 15; the fourth connection method is: cancel the beam splitter, the light source with k output ends is directly connected to the upper and lower k sensing magneto-optical optical path structures 12, and the output ends of the upper and lower k sensing magneto-optical optical path structures 12 are independently connected to the photodetector 15. The output end of the photodetector is directly connected to the A / D converter with k input ends, and the A / D converter is then connected to the input end of the real-time signal processor 22, and the other connection methods remain unchanged;

[0019] The fifth connection mode, in the stacked optical current sensor, the overall connection mode remains unchanged from the first connection mode; the output ends of the k sensing magneto-optical optical path structures 12 in the upper and lower layers are connected to the k input ends of the beam combiner 14 having k+1 input ends, the k+1th input end of the beam combiner 14 is directly connected to the output end of the controlled light source 10, and the output end of the beam combiner 14 is connected to the input end of the photodetector 15. The output end of the photodetector 15 is further connected to the input end of the A / D converter 16, and the A / D converter 16 is further connected to the input end of the real-time signal processor 22. The photodetector 15 converts the received optical signal into an electrical signal, and the photodetector 15 outputs the detected signal in real time, and sends the output signal to the A / D converter 16, which is converted into a digital signal and sent to the stacked optical current sensor real-time signal processor 22, which removes the external magnetic field interference according to the superposition elimination algorithm and obtains the required current value I to be measured.

[0020] A method for realizing anti-external magnetic interference of a stacked optical current transformer is as follows:

[0021] For the lower optical current sensor whose sensing optical path is arranged in a symmetrical polygonal manner, the current conductor 17 to be measured is placed at the center of the optical current sensor, that is, at the pole O of the plane polar coordinate system, and the interference current conductor 24 is located outside the optical current sensor. If the magnitude of the current to be measured is I and the magnitude of the interference current is I 1 , then the magnetic field integral value of the interference current on the k-segment sensing optical path of the lower optical current sensor can be expressed by formula (1):

[0022]

[0023] In formula (1), θ j ′ is the angle formed by the geometric point where the interference current conductor 24 is located and the line connecting the two ends of the j-th sensing optical path; r is the radius of the circumscribed circle of the symmetrical polygon; L is the straight-line distance between the geometric point where the interference current is located and the pole O; θ is the angle formed by the pole O and the line connecting the two ends of the j-th sensing optical path; α is the angle between the interference current and the line connecting the center of MOCS and the polar axis.

[0024] When the optical current sensor structure and the distance L between the interference current and the pole O are determined, k, r, and θ in equation (1) are all constants, and equation (1) will be transformed into equation (2):

[0025]

[0026] Among them, C 1 ,C 2 ,C 3 ,C 4 is a constant term,

[0027] Taking α as the independent variable, the magnetic field integral value of the interference current on the k-segment sensing optical path will show the characteristics of periodic change; therefore, in order to reduce the influence of the interference current magnetic field at any position on the measurement accuracy, the introduced magnetic field integral value should be the magnetic field integral with the same period as the magnetic field integral value represented by equation (2), but with the opposite phase; therefore, consider rotating the optical current sensor counterclockwise around the pole O by a certain angle β. Since the overall structure of the optical current sensor remains unchanged, after the rotation, only the angle α between the interference current and the center line of the optical current sensor and the polar axis changes. The angle after the change is denoted as α′, and we have:

[0028] α′=α-β,(3)

[0029] At this time, the mathematical model of the external magnetic field interference to MOCS is transformed into formula (4):

[0030]

[0031] The function represented by formula (4) is equivalent to the function represented by formula (1) shifted rightward by β units on the α axis. When the structure of MOCS is determined, the integral result reflected by formula (1) will only be related to L and α. In order to analyze the relationship between the external magnetic field interference and α at a certain distance, the formula (1) is differentiated with respect to the variable α, and the derivative is set to 0, and the corresponding α expression is obtained as formula (5):

[0032]

[0033] Due to the cycle Therefore, this expression has only two extreme points in one cycle; further analysis shows that the two extreme points are a maximum point and a minimum point respectively; it is noted that the difference between formula (4) and formula (1) is only the angle between the interference current and the MOCS center line and the polar axis. Therefore, when the rotation angle β takes a certain value a, the maximum and minimum values ​​of formula (1) in one cycle will correspond to the minimum and maximum values ​​of formula (4) in one cycle respectively; angle a is the optimal center deflection angle, and the general calculation formula for the optimal overall deflection angle a is as follows:

[0034]

[0035] Therefore, after rotating the lower optical current sensor by a certain angle according to the optimal overall deflection angle, the magnetic field integral with the same period as the magnetic field integral value represented by equation (2) but with the opposite phase can be obtained; considering the compactness of the sensor, a stacked structure is proposed; the upper and lower layers of the stacked optical current sensor are processed as follows (7):

[0036]

[0037] In the formula, u1n It is the current signal measured by the positive MOCS, which includes two components: the current signal u o With the interference current signal u o1 .u 2n The current signal measured by the tilted MOCS also includes two parts: the current signal to be measured u o With the interference current signal u o2 ; In the final signal processing, u 1n with u 2n After merging, the values ​​are divided by 2, thereby almost completely eliminating the influence of interference current at any location.

[0038] The beneficial effects of the present invention are as follows:

[0039] (1) A mathematical model of external magnetic interference in optical current sensors is proposed, and based on this model, a stacked structure is proposed, which can basically completely eliminate the influence of the magnetic field generated by the interference current located at any position in space on the measurement accuracy of the sensor.

[0040] (2) The present invention changes the structure of the optical current sensor so that the optical current transformer has a stronger ability to resist external magnetic interference generated by interference current located at any position, thereby improving the measurement accuracy of the optical current transformer.

[0041] (3) The present invention does not require the addition of magnetic shielding equipment, nor does it require other means to enhance the magnetic field of the current to be measured to resist external magnetic interference, thereby retaining the advantage of good insulation performance of the optical current sensor.

[0042] (4) Due to the use of the idea of ​​overall superposition to cancel interference, the requirement of the zero-sum magnetic control method for the interference current to be located at a specific position is reduced, and it also has a good anti-interference effect on the interference current offset from the zero-sum point.

[0043] (5) The optical current transformer's small size and light weight are retained. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the lower sub-sensor structure in the stacked optical current sensor; a is the lower sub-sensor composition; b is the lower insulating cover and positioning boss;

[0045] Figure 2 Schematic diagram of the upper sub-sensor structure in the stacked optical current sensor; a is the upper sub-sensor component; b is the upper insulating cover;

[0046] Figure 3 Schematic diagram of the stacked optical current sensor and its signal processing part in Example 1.

[0047] Figure 4 Schematic diagram of the stacked optical current sensor and its signal processing part in Example 2.

[0048] Figure 5 Schematic diagram of the stacked optical current sensor and its signal processing part in Example 3.

[0049] Figure 6 Schematic diagram of the stacked optical current sensor and its signal processing part in Example 4.

[0050] Figure 7 Schematic diagram of the stacked optical current sensor and its signal processing part in Example 5.

[0051] Figure 8 Schematic diagram of the geometric position relationship between the geometric point N where the interference current is located and the k-segment optical sensor units placed in a symmetrical polygon in Example 6.

[0052] Fig. 9 This is a general schematic diagram of the stacked structure in Example 6.

[0053] Fig.10 The schematic diagram of the specific structure when k=3, 4, and 5 are taken for the stacked structure respectively; wherein a, k=3; bk=4c, k=5;

[0054] Fig.11 This is the MOCS measurement schematic.

[0055] Figure numerals: 1-input collimator; 2-polarizer; 3-magneto-optical material; 4-analyzer; 5-parallel output collimator; 6-insulating disk; 7-insulating cover; 8-boss for positioning; 9-high stability controllable current source; 10-controlled light source; 11-beam splitter; 12-sensing magneto-optical optical path structure; 13-stacked structure body; 14-beam combiner; 15-photodetector; 16-A / D converter; 17-current conductor to be measured; 18-sensor device (stacked optical current sensor); 19-stacked optical current sensor data processing unit; 20-current signal output unit; 21-signal output integration unit; 22-stacked optical current sensor real-time signal processor; 23-input / output optical fiber; 24-interference current conductor DETAILED DESCRIPTION

[0056] The present invention provides a stacked optical current sensor and a method for resisting external magnetic interference thereof, which will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0057] Figure 1 The figure shows the schematic diagram of the structure of the lower layer sub-sensor in the stacked structure optical current sensor;

[0058] Figure 2It is a schematic diagram of the structure of the upper sub-sensor in the stacked optical current sensor;

[0059] In the sensor device 18, the stacked structure body 13 is respectively connected to the spectrometer 11 and the beam combiner 14; wherein the spectrometer 11 includes a 1# spectrometer and a 2# spectrometer, the 1# spectrometer and the 2# spectrometer are respectively connected to the controlled light source 10, and the controlled light source 10 is connected to the highly stable controllable current source 9; the beam combiner 14 includes a 1# beam combiner and a 2# beam combiner; the 1# beam combiner and the 2# beam combiner are respectively connected to two photodetectors 15, and the two photodetectors 15 are respectively connected to two A / D converters 16; the two A / D converters 16 are respectively connected to the stacked optical current sensor data processing unit 19 in the stacked optical current sensor real-time signal processor 22; the stacked optical current sensor real-time signal processor 22 is composed of a stacked optical current sensor data processing unit 19, a current signal output unit 20, and a signal output synthesis unit 21 connected in series;

[0060] The stacked structure body 13 includes upper and lower sub-sensors, and the upper sensor is placed with an angle of π / k rotated relative to the center of the lower sensor; there is a corresponding positioning boss 8 on the lower insulating cover 7, and the upper sensor is fixed on the insulating disk 6 at a set angle, and the insulating cover 7 covers the sensing magneto-optical optical path structure 12, thereby forming two independent insulating entities; wherein, the sensing magneto-optical optical path structure 12 is composed of an input collimator 1, a polarizer 2, a magneto-optical material 3, an analyzer 4, and a parallel output collimator 5 in series; the sensing magneto-optical optical path structures 12 are connected to form a square structure through input / output optical fibers 23.

[0061] The upper layer sub-sensor or the lower layer sub-sensor contains k identical optical sensing units, and the entire sensor contains 2k identical sensing magneto-optical optical path structures (12); the effective sensing optical path lengths of the 2k sensing magneto-optical optical path structures (12) along the light transmission direction are the same, and the upper and lower layers of sub-sensors together constitute a stacked structural body (13) of the stacked optical current sensor; wherein K>2, K∈N.

[0062] Example 1

[0063] Combination Figure 1 , 2, 3 illustrate the present embodiment 1, wherein, Figure 1 The figure shows the schematic diagram of the structure of the lower layer sub-sensor in the stacked structure optical current sensor; Figure 2 It is a schematic diagram of the structure of the upper sub-sensor in the stacked optical current sensor; Figure 3 The first connection mode of the sensor device is shown, including a schematic diagram of a stacked optical current sensor structure and its signal processing part;

[0064] like Figure 3As shown, the stacked optical current sensor includes a sensor device 18 and a stacked optical current sensor real-time signal processor 22. In the sensor device 18, the stacked structure body 13 is respectively connected to the spectrometer 11 and the beam combiner 14; wherein the spectrometer 11 includes a 1# spectrometer and a 2# spectrometer, the 1# spectrometer and the 2# spectrometer are respectively connected to the controlled light source 10, and the controlled light source 10 is connected to the highly stable controllable current source 9; the beam combiner 14 includes a 1# beam combiner and a 2# beam combiner; the 1# beam combiner and the 2# beam combiner are respectively connected to two photodetectors 15, and the two photodetectors 15 are respectively connected to two A / D converters 16; the two A / D converters 16 are respectively connected to the stacked optical current sensor data processing unit 19 in the stacked optical current sensor real-time signal processor 22; the stacked optical current sensor real-time signal processor 22 is composed of a stacked optical current sensor data processing unit 19, a current signal output unit 20, and a signal output synthesis unit 21 connected in series;

[0065] The stacked structure body 13 includes upper and lower sub-sensors (such as Figure 1 , 2 As shown in the figure, the upper sensor is placed with an angle of π / k rotated relative to the center of the lower sensor; there is a corresponding positioning boss 8 on the lower insulating cover 7, and the upper sensor is fixed on the insulating disk 6 at a set angle. The insulating cover 7 covers the sensing magneto-optical optical path structure 12, thereby forming two independent insulating entities; wherein, the sensing magneto-optical optical path structure 12 is composed of an input collimator 1, a polarizer 2, a magneto-optical material 3, an analyzer 4, and a parallel output collimator 5 in series; the sensing magneto-optical optical path structures 12 are connected to form a square structure through input / output optical fibers 23.

[0066] The upper layer sub-sensor or the lower layer sub-sensor contains k identical optical sensing units, and the entire sensor contains 2k identical sensing magneto-optical optical path structures (12); the effective sensing optical path lengths of the 2k sensing magneto-optical optical path structures (12) along the light transmission direction are the same, and the upper and lower layers of sub-sensors together constitute the stacked structural body 13 of the stacked optical current sensor; wherein K>2, K∈N.

[0067] Figure 3The first connection mode of the sensor device is shown as follows: a highly stable controllable current source 9 is connected to a controlled light source 10 to drive the controlled light source to output a highly stable DC light intensity; the output highly stable DC light intensity enters two identical spectrometers 11, namely, the 1# spectrometer and the 2# spectrometer, and the spectrometers evenly divide it into k beams of light output, and the output light is connected to k sensing magneto-optical optical path structures 12 in the upper and lower layers through optical fibers, for a total of 2k; the output ends of the k sensing magneto-optical optical path structures in the upper and lower layers are connected to the input ends of the two beam combiners 14 respectively. The output ends of the two beam combiners 14, namely the 1# beam combiner and the 2# beam combiner, are respectively connected to the input ends of the two photodetectors 15; the output ends of the photodetectors are connected to the input ends of the A / D converter 16; the photodetector 15 converts the received optical signal into an electrical signal, outputs a detection signal in real time, sends the output signal to the A / D converter 16 to convert it into a digital signal, and then sends it to the stacked optical current sensor real-time signal processor 22, which removes the external magnetic field interference according to the superposition elimination algorithm and obtains the required current value I to be measured;

[0068] The output information of the k sensing magneto-optical optical path structures 12 in the upper and lower layers is input into the photodetector 15 after passing through the beam combiner, so the photodetector 15 only needs one input port.

[0069] Example 2

[0070] Figure 4 Schematic diagram of the stacked optical current sensor and its signal processing part in Example 2. Figure 4 The second connection method of the sensor device is shown; in the stacked optical current sensor of this embodiment, the overall connection method remains unchanged from Example 1; the output ends of the k sensing magneto-optical optical path structures 12 in the upper and lower layers are independently connected to the input ends of k photodetectors 15, and the output ends of the photodetectors are directly connected to the A / D converter with k input ends, and the A / D converter is further connected to the input end of the real-time signal processor 22; the photodetector 15 converts the received optical signal into an electrical signal, and outputs the detection signal in real time, and sends the output signal to the A / D converter 16 with k input ports to convert it into a digital signal and then sends it to the stacked optical current sensor real-time signal processor 22; the real-time signal processor removes the external magnetic field interference according to the superposition elimination algorithm and obtains the required current value I to be measured.

[0071] The output information of the k photodetectors 15 in the upper and lower layers is directly output to the corresponding A / D converter 16, which requires the A / D converter 16 to have at least k input ports.

[0072] Example 3

[0073] Figure 5The third connection mode of the stacked optical current sensor in Example 3 and its signal processing part schematic diagram. In the stacked optical current sensor of this embodiment, the overall connection mode remains unchanged from that of Example 1; however, the light propagation direction of the upper and lower layers should be consistent, the beam splitter is eliminated, the natural light generated by the light source is directly connected to the input ends of the upper and lower sensing magneto-optical optical path structures 12, and the k sensing magneto-optical optical path structures 12 contained in each layer are connected by optical fibers, and finally the output light intensity of the upper and lower sub-sensors is respectively connected to the input ends of the photodetector 15; the output ends of the upper and lower sub-sensors are directly connected to the input ends of the photodetector 15. The photodetector 15 converts the received optical signal into an electrical signal, detects the output signal of the photodetector 15 in real time, sends the output signal to the A / D converter 16 to convert it into a digital signal, and then sends it to the stacked optical current sensor real-time signal processor 22. The real-time signal processor removes the external magnetic field interference according to the superposition elimination algorithm and obtains the required current value I to be measured.

[0074] The inputs and outputs of the k sensing magneto-optical optical path structures 12 in the upper and lower layers are connected in series, so the photoelectric detector 15 only needs one input port.

[0075] Example 4

[0076] Figure 6 Schematic diagram of the fourth connection mode of the stacked optical current sensor and its signal processing part in Example 4. In the stacked optical current sensor of this embodiment, the overall connection mode remains unchanged from the first connection mode;

[0077] The optical splitter is eliminated, and the light source with k output ends is directly connected to the upper and lower k sensing magneto-optical optical path structures 12 respectively, and the output ends of the upper and lower k sensing magneto-optical optical path structures 12 are independently connected to the photodetector 15. The output end of the photodetector is directly connected to the A / D converter with k input ends, and the A / D converter is further connected to the input end of the real-time signal processor 22, and the other connection methods remain unchanged; the photodetector 15 converts the received optical signal into an electrical signal, detects the output signal of the photodetector 15 in real time, and sends the output signal to the A / D converter 16 with k input ports, which is converted into a digital signal and sent to the stacked optical current sensor real-time signal processor 22, which removes the external magnetic field interference according to the superposition elimination algorithm and obtains the required current value I to be measured.

[0078] The output information of the k photodetectors 15 in the upper and lower layers is directly output to the corresponding A / D converter 16, which requires the A / D converter 16 to have at least k input ports.

[0079] Example 5

[0080] Figure 7Schematic diagram of the stacked optical current sensor and its signal processing part in Example 5.

[0081] This embodiment specifically describes the fifth connection method of the stacked optical current sensor. In the stacked optical current sensor of this embodiment, the overall connection method remains unchanged from the first connection method; the output ends of the k sensing magneto-optical optical path structures 12 of the upper and lower layers are connected to the k input ends of the beam combiner 14 having k+1 input ends, and the k+1th input end of the beam combiner 14 is directly connected to the output end of the controlled light source 10, and the output end of the beam combiner 14 is connected to the input end of the photodetector 15. The output end of the photodetector 15 is then connected to the input end of the A / D converter 16, and the A / D converter 16 is then connected to the input end of the real-time signal processor 22. The photodetector 15 converts the received optical signal into an electrical signal, and the photodetector 15 outputs the detected signal in real time, and sends the output signal to the A / D converter 16, which is converted into a digital signal and sent to the stacked optical current sensor real-time signal processor 22, which removes the external magnetic field interference according to the superposition elimination algorithm and obtains the required current value I to be measured.

[0082] Example 6

[0083] Figure 8 The figure shows the geometric position relationship between the geometric point N where the interference current conductor 24 is located and the k-segment optical sensing units arranged in a symmetrical polygon in Example 6.

[0084] This embodiment is a specific and detailed definition of the first to fifth connection modes. Figure 2 ) should be rotated to the angle specified below. Figure 1 ) are placed on the long side or short side of the symmetrical 2k-gon. The current conductor 17 to be measured is located at the center of the symmetrical 2k-gon. The 2k vertices of the symmetrical 2k-gon are all located on its circumscribed circle, such as Fig. 9 A general schematic diagram of the stacked structure in the sixth embodiment and Fig.10 The specific structural schematic diagram is shown when k=3, 4, and 5 for the stacked structure, wherein the positive direction of each section of the sensing magneto-optical optical path structure can be clockwise or counterclockwise. Figure 8 As shown, the center of the symmetrical 2k-gon is taken as the pole O, and the line connecting the midpoint of any section of the sensing magneto-optical optical path structure and the pole is taken as the polar axis to establish the corresponding polar coordinate system.

[0085] Embodiment 7: A method for realizing resistance to external magnetic interference of a stacked optical current transformer

[0086] like Figure 8As shown, the geometric point where the interference current conductor 24 is located outside the symmetrical 2k-gon is marked as point N; the length of the line connecting point N and the pole O is L, the angle with the polar axis is α, and the angle formed by the pole O and the connecting line at both ends of any section of the sensing magneto-optical optical path structure is θ. The radius of the corresponding circumscribed circle is r, the length of each section of the sensing magneto-optical optical path structure is a, and the vertical distance between the midpoint and the pole O is b.

[0087] According to the above definition, the magnetic field integral value of the interference current on the k-segment sensing magneto-optical optical path structure of the sensor can be expressed as:

[0088]

[0089] It can be seen from formula (1) that the factors affecting the magnetic field integral of the interference current on the MOCS include: the distance L between the interference current conductor and the center point of the MOCS, the number of sensing optical path sections k, the angle α between the line connecting the interference current conductor and the center of the MOCS and the polar axis, the length of the sensing optical path a, and the vertical distance b between the magneto-optical glass sensing optical path and the pole O.

[0090] According to formula (1), after the MOCS structure and the distance L between the interference current conductor and the center point are determined, the variables k, r, and θ in the formula are all fixed values. Formula (1) will be converted into formula (2),

[0091]

[0092] Among them, C 1 ,C 2 ,C 3 ,C 4 is a constant term.

[0093] Therefore, with α as the independent variable, the magnetic field integral value of the interference current on the k-segment sensing optical path will show the characteristics of periodic change. In order to reduce the influence of the interference current magnetic field at any position on the measurement accuracy, consider introducing a signal with the same period as the magnetic field integral value represented by equation (1) but opposite phase. Consider rotating the MOCS counterclockwise around the center point by a certain angle β. Since the overall structure of the MOCS remains unchanged, after the rotation, only the angle α between the interference current and the center line of the MOCS and the polar axis changes. The changed angle is denoted as α′, and we have:

[0094] α′=α-β (3)

[0095] At this time, the mathematical model of the external magnetic field interference to MOCS is transformed into formula (4):

[0096]

[0097] The function represented by formula (4) is equivalent to the function represented by formula (1) shifted right by β units on the α axis. When the structure of MOCS is determined, the integral result reflected by formula (4) will only be related to L and α. In order to analyze the relationship between the external magnetic field interference and α at a certain distance, the formula (4) is differentiated with respect to the variable α, and the derivative is set to 0, and the corresponding α expression is obtained as formula (5):

[0098]

[0099] Due to the cycle Therefore, this expression has only two extreme points in one cycle. Further analysis shows that the two extreme points are a maximum point and a minimum point respectively. Note that the difference between formula (1) and formula (4) is only the angle between the interference current and the MOCS center line and the polar axis. Therefore, when the rotation angle β takes a certain value a, the maximum and minimum values ​​in one cycle will correspond to the minimum and maximum values ​​in one cycle of formula (4), that is, the integral value represented by formula (1) and the integral value represented by formula (4) are in an inverse relationship with each other. This article calls angle a the optimal center deflection angle, and the general calculation formula for the optimal overall deflection angle a is as follows:

[0100]

[0101] Combined with formula (6), it can be seen that by rotating the normal-placed sensing structure clockwise or counterclockwise by a certain angle, a signal with an opposite phase to the integrated value of the interference current on the normal-placed sensing structure can be introduced. According to the Faraday magneto-optical effect, the incident light in the optical current transformer is deflected by an angle after passing through the sensing optical path. The relationship with current I can be expressed as:

[0102]

[0103] In formula (7), V is the Verdet constant of the magneto-optical material, H is the magnetic field intensity generated by the external current, and l is the length of the light path. By superimposing the introduced anti-phase signal with the magnetic field signal of the original interference current, the magnetic field integral part in formula (7) can only contain the magnetic field information of the current to be measured, thereby improving the measurement accuracy of the sensor. Moreover, since the overall signal is superimposed, there is no special requirement for the interference current position.

[0104] To achieve the above requirements, Fig.10 As shown in FIG. 1 , the current conductor to be measured is placed at the center of the optical current sensor. At the same time, based on the original single-layer sensor, an additional layer with the same structure is added, but rotated around the center. The two layers of sensors measure the current to be measured. The two layers of sensors together form a stacked structure body 13; Fig. 9 The schematic diagram of the stacked structure main body is shown when k = 3, 4, 5.

[0105] The measurement signals of the upper and lower MOCS layers in the stacked MOCS are processed as shown in formula (8):

[0106]

[0107] In the formula, u 1n It is the current signal measured by the positive MOCS, which includes two components: the current signal u o With the interference current signal u o1 .u 2n The current signal measured by the tilted MOCS also includes two parts: the current signal to be measured u o With the interference current signal u o2 . In the final signal processing, u 1n with u 2n After merging, the values ​​are divided by 2, thereby almost completely eliminating the influence of interference current at any location.

[0108] Specific implementation method seven of the above embodiment: Figure 8 With attached Fig. 9 The method of using a stacked structure to achieve resistance to external magnetic field interference for an optical current transformer is further described.

[0109] The method is a method for processing the measurement signal, which can be implemented by the stacked optical current sensor real-time signal processing system 22 .

Claims

1. A stacked optical current sensor, It is characterized in that The stacked optical current sensor comprises: a sensor device (18) and a stacked optical current sensor real-time signal processor (22); in the sensor device (18), the stacked structural body (13) is respectively connected to a beam splitter (11) and a beam combiner (14); wherein the beam splitter (11) comprises a 1# beam splitter and a 2# beam splitter, the 1# beam splitter and the 2# beam splitter are respectively connected to a controlled light source (10), and the controlled light source (10) is connected to a highly stable controllable current source (9); the beam combiner (14) comprises a 1# beam combiner and a 2# beam combiner; the 1# beam combiner The device and the 2# beam combiner are respectively connected to two photodetectors (15), and the two photodetectors (15) are respectively connected to two A / D converters (16); the two A / D converters (16) are respectively connected to a stacked optical current sensor data processing unit (19) in a stacked optical current sensor real-time signal processor (22); the stacked optical current sensor real-time signal processor (22) is composed of a stacked optical current sensor data processing unit (19), a current signal output unit (20), and a signal output synthesis unit (21) connected in series; The stacked structure body (13) comprises upper and lower sub-sensors, wherein the upper sub-sensor is rotated at an angle of π / k relative to the center of the lower sub-sensor; a corresponding positioning boss (8) is provided on the lower insulating cover (7), and the upper sub-sensor is fixed on the insulating disk (6) at a set angle, and the insulating cover (7) covers the sensing magneto-optical optical path structure (12), thereby forming two mutually independent insulating entities; wherein the sensing magneto-optical optical path structure (12) is composed of an input collimator (1), a polarizer (2), a magneto-optical material (3), an analyzer (4), and a parallel output collimator (5) connected in series; and the sensing magneto-optical optical path structures (12) are connected to form a square structure through input / output optical fibers (23); The upper layer sub-sensor and the lower layer sub-sensor each contain k identical sensing magneto-optical optical path structures (12), and the entire sensor contains 2k identical sensing magneto-optical optical path structures (12); the effective sensing optical path lengths of the 2k sensing magneto-optical optical path structures (12) along the light transmission direction are the same, and the upper and lower layers of sub-sensors together constitute a stacked structural body (13) of the stacked optical current sensor; wherein k>2, k∈N.

2. A stacked optical current sensor according to claim 1, It is characterized in that The connection structure of the sensor device includes the following: The first connection mode is: a highly stable controllable current source (9) is connected to a controlled light source (10) to drive the controlled light source to output a highly stable DC light intensity; the output highly stable DC light intensity enters two identical optical splitters (11), namely, optical splitter 1# and optical splitter 2#, and the optical splitters evenly divide it into k beams of light for output, and the output light is connected to k sensing magneto-optical optical path structures (12) in the upper and lower layers respectively through optical fibers, for a total of 2k sensing magneto-optical optical path structures (12); the output ends of the k sensing magneto-optical optical path structures in the upper and lower layers are respectively connected to the input ends of two beam combiners (14); the output ends of the two beam combiners (14), namely, beam combiner 1# and beam combiner 2#, are respectively connected to the input ends of two photodetectors (15); the output end of the photodetector is connected to the input end of an A / D converter (16); the output of the A / D converter enters a real-time signal processor (22) of a stacked optical current sensor for signal processing, and finally outputs the current value to be measured; The second connection mode is: the output ends of the k sensing magneto-optical optical path structures (12) in the upper and lower layers are independently connected to the input ends of the k photoelectric detectors (15), the output ends of the photoelectric detectors are directly connected to the A / D converter with k input ends, and the A / D converter (16) is further connected to the input end of the real-time signal processor (22), and the rest of the connection modes remain unchanged from the first connection mode; The third connection method is: the beam splitter is eliminated, and the natural light generated by the light source is directly connected to the input ends of the upper and lower layers of the sensing magneto-optical optical path structure (12), and the k sensing magneto-optical optical path structures (12) contained in each layer are connected by optical fibers, and finally the output light intensity of the upper and lower layers of sub-sensors is respectively connected to the input ends of the photoelectric detector (15); the rest of the connection methods remain unchanged from the first connection method; The fourth connection method is: The optical splitter is eliminated, and a light source having k output ends is directly connected to the upper and lower k sensing magneto-optical optical path structures (12), respectively; the output ends of the upper and lower k sensing magneto-optical optical path structures (12) are independently connected to a photodetector (15); the output end of the photodetector is directly connected to an A / D converter having k input ends, and the A / D converter is then connected to the input end of a real-time signal processor (22), and the rest of the connection methods remain unchanged; The fifth connection method, in the stacked optical current sensor, the overall connection method remains unchanged from the first connection method; The output ends of the k sensing magneto-optical optical path structures (12) in the upper and lower layers are connected to the k input ends of a beam combiner (14) having k+1 input ends, and the k+1th input end of the beam combiner (14) is directly connected to the output end of the controlled light source (10), and the output end of the beam combiner (14) is connected to the input end of a photodetector (15); the output end of the photodetector (15) is further connected to the input end of an A / D converter (16), and the A / D converter (16) is further connected to the input end of a real-time signal processor (22). The photodetector (15) converts the received optical signal into an electrical signal, and the photodetector (15) outputs the detected signal in real time, and sends the output signal to the A / D converter (16), which is converted into a digital signal and then sent to the stacked optical current sensor real-time signal processor (22). The real-time signal processor removes external magnetic field interference according to a superposition elimination algorithm and obtains the required current value I to be measured.

3. A method for realizing resistance to external magnetic interference of the stacked optical current sensor according to claim 1 or 2, It is characterized in that For the lower optical current sensor in which the sensing optical path is arranged in a symmetrical polygonal manner, the current conductor (17) to be measured is placed at the center of the optical current sensor, that is, at the pole O of the plane polar coordinate system, and the interference current conductor (24) is located outside the optical current sensor. If the magnitude of the current to be measured is I and the magnitude of the interference current is I 1 , then the magnetic field integral value of the interference current on the k-segment sensing optical path of the lower optical current sensor can be expressed by formula (1): In formula (1), θ′ j is the angle formed by the geometric point where the interference current conductor (24) is located and the line connecting the two ends of the j-th sensing optical path; r is the radius of the circumscribed circle of the symmetrical polygon; L is the straight-line distance between the geometric point where the interference current conductor (24) is located and the pole O; θ is the angle formed by the pole O and the line connecting the two ends of the j-th sensing optical path; α is the angle between the interference current and the center line of the MOCS and the polar axis; When the optical current sensor structure and the distance L between the interference current conductor and the pole O are determined, k, r, and θ in equation (1) are all constants, and equation (1) will be transformed into equation (2): Among them, C 1 ,C 2 ,C 3 ,C 4 is a constant term, Taking α as the independent variable, the magnetic field integral value of the interference current on the k-segment sensing optical path will show the characteristics of periodic change; therefore, in order to reduce the influence of the interference current magnetic field at any position on the measurement accuracy, the introduced magnetic field integral value should be the magnetic field integral with the same period as the magnetic field integral value represented by equation (2), but with the opposite phase; therefore, consider rotating the optical current sensor counterclockwise around the pole O by a certain angle β. Since the overall structure of the optical current sensor remains unchanged, after the rotation, only the angle α between the interference current and the center line of the optical current sensor and the polar axis changes. The angle after the change is denoted as α′, and we have: α′＝α-β， (3) At this time, the mathematical model of the external magnetic field interference to MOCS is transformed into formula (4): The function represented by formula (4) is equivalent to the function represented by formula (1) shifted rightward by β units on the α axis. When the structure of MOCS is determined, the integral result reflected by formula (1) will only be related to L and α. In order to analyze the relationship between the external magnetic field interference and α at a certain distance, the formula (1) is differentiated with respect to the variable α, and the derivative is set to 0, and the corresponding α expression is obtained as formula (5): Due to the cycle Therefore, this expression has only two extreme points in one cycle; further analysis shows that the two extreme points are a maximum point and a minimum point respectively; it is noted that the difference between formula (4) and formula (1) is only the angle between the interference current and the MOCS center line and the polar axis. Therefore, when the rotation angle β takes a certain value a, the maximum and minimum values ​​of formula (1) in one cycle will correspond to the minimum and maximum values ​​of formula (4) in one cycle respectively; angle a is the optimal overall deflection angle, and the general calculation formula for the optimal overall deflection angle a is as follows: Therefore, after rotating the upper optical current sensor by a certain angle according to the optimal overall deflection angle, a magnetic field integral with the same magnetic field integral value period as that represented by equation (2) but with an opposite phase can be obtained; considering the compactness of the sensor, a stacked structure is proposed; the upper and lower layers of the stacked optical current sensor are processed as follows (7): In the formula, u 1n It is the current signal measured by the positive MOCS, which includes two components: the current signal u o With the interference current signal u o1 ;u 2n The current signal measured by the tilted MOCS also includes two parts: the current signal to be measured u o With the interference current signal u o2 ; In the final signal processing, u 1n with u 2n After merging, the values ​​are divided by 2, thereby almost completely eliminating the influence of interference current at any location.

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