CN111175556B - Current transformer and implementation method - Google Patents
Current transformer and implementation method Download PDFInfo
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- CN111175556B CN111175556B CN202010061964.2A CN202010061964A CN111175556B CN 111175556 B CN111175556 B CN 111175556B CN 202010061964 A CN202010061964 A CN 202010061964A CN 111175556 B CN111175556 B CN 111175556B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/181—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using coils without a magnetic core, e.g. Rogowski coils
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
Abstract
A current transformer and an implementation method belong to the field of transformers and comprise a high-voltage end module and a low-voltage end module; the method is characterized in that: the wireless power supply device also comprises an air core coil and a remote wireless power supply device; one end of the optical fiber is connected with the electro-optical conversion circuit module, and the other end of the optical fiber is connected with the photoelectric conversion circuit module. The intelligent gain control circuit module is adopted to eliminate the manufacturing error of the hollow coil, the parameter deviation of the electronic components and the temperature drift of the electronic circuit caused by the temperature and humidity change, and the measurement precision is high. The current transformer can output the same current magnitude and power as the secondary end of the traditional electromagnetic current transformer through the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter, and is matched with various existing instruments and power distribution cabinets. The remote wireless power supply device solves the power supply problem of the high-voltage end collecting head of the hollow coil type current transformer, has no power supply dead angle and measuring blind area, and is convenient to maintain safely, good in stability and long in service life.
Description
Technical Field
The invention belongs to the field of transformers, and particularly relates to a current transformer and an implementation method thereof.
Background
The current transformer is a device for converting high voltage and large current into low voltage and small current which are convenient for measurement and use according to a certain ratio, and comprises a traditional electromagnetic current transformer and an electronic current transformer, wherein the electronic current transformer mainly uses optical fibers to transmit electric parameters collected by a high-voltage end to a low-voltage end, and the low-voltage end is further processed after being converted into an electric signal through photoelectric conversion. The electronic current transformer can be divided into the following parts in principle: the current transformer comprises three types, namely an optical current transformer, an air core coil current transformer and an iron core coil type low-power current transformer.
The optical current transformer sensing head portion generally does not require a power supply. Because the sensing head part is a more complex optical system, the sensing head part is easily influenced by various environmental factors such as temperature, vibration and the like, the running precision is difficult to ensure, and the long-term stability is poor. A low-power current transformer (LPCT) of the core-coil type is a development of the conventional electromagnetic current transformer, and a core is still used. Because the iron core is provided, and technical parameters such as the material, the shape and the like of the iron core have certain requirements, the cost is higher than that of the hollow coil type. An air-core coil current transformer, also called Rogowski (Rogowski) coil type current transformer, is generally manufactured by uniformly winding an enameled wire on an annular framework, wherein the framework is made of non-ferromagnetic materials such as plastics, ceramics and the like, which is a remarkable characteristic that the air-core coil current transformer is different from a current transformer with an iron core, and most of electronic current transformers adopt an air-core coil as a current collecting device.
However, the electronic current transformer in the current market has the following disadvantages:
1. the degree of intelligence is not sufficient; the existing electronic current transformer can only complete transmission of collected signals to a low-voltage end by a high-voltage end through optical fibers, and the low-voltage end converts received signals into 4V low-voltage analog signals or processes the signals into specified digital signals. The method and the control mode for eliminating the influence of temperature drift caused by manufacturing errors, raw material parameter deviation, temperature change and the like on the measurement precision are relatively extensive and are basically pure hardware. Firstly, the air-core coil is manufactured to ensure that the number of winding turns is the same, and the consistency of other parameters is difficult to ensure, so that the acquired signals have deviation. Secondly, because the voltage signal amplitude that air core coil induced is less needs to amplify, and chip and electronic component in the signal amplification circuit all have numerical deviation, and these chip and electronic component also can receive electromagnetic interference and environmental humiture's influence simultaneously, cause the drift of output signal, also called the temperature drift, reduce the accuracy of measuring signal. In addition, the signal induced by the air-core coil is in a differential relation with the current passing through the air-core coil, so that the waveforms at the two ends of the induction coil generally cannot represent the waveform of the current to be measured, and conversion needs to be carried out through an integrating circuit. The chips and electronics in the integrator circuit also suffer from the problems described above, which reduces the accuracy of the measurement.
2. The application range is narrow; the low-voltage end of the existing electronic current transformer outputs 4V small-voltage analog signals or digital signals. Unless a pure digital power station is newly built, the device cannot be matched with meters (many meters are also pointer type meters) needing to input 5A analog current at all, and a relay device cannot be driven. For old power distribution cabinets and transformer substations which are used and need to be maintained or modified, the electronic current transformer which can only output 4V small-voltage analog signals or digital signals cannot be matched with original instruments and devices, and the application range of the electronic current transformer is greatly limited.
3. Power supply is difficult; the high-voltage end collecting head of the electronic current transformer generally has an electronic circuit and can work only by providing a power supply. The power supply of the high-voltage end collecting head is mainly powered by laser or high-voltage bus CT. The laser energy supply mode is that the photoelectric conversion efficiency is too low, usually only about 10%, the usable life of the high-power laser light-emitting tube can not meet the actual use requirement, and a large-diameter optical fiber is needed. The price of the high-power laser light-emitting tube and the large-diameter optical fiber is generally higher, and the danger of replacing the light-emitting tube under the electrified condition is higher, so that the maintenance complexity of a laser energy supply mode is higher. When the bus current is lower than 10A, the bus current is difficult to obtain enough energy, a circuit of a high-voltage end header cannot normally work, and power supply dead angles and measurement blind areas exist. And combine laser energy supply and bus CT power supply, need carry out the switching of laser energy supply and bus CT energy supply, use the laser energy supply when the electric current is little to the setting value promptly, switch to the CT energy supply when the electric current is big to a certain extent. Therefore, the circuit control of the whole system is also more complicated, the total cost of the product becomes higher, and the reliability is lowered.
Disclosure of Invention
The invention aims to solve the problems and provides a current transformer which is safe, stable and intelligent in correction and can output standard 5A current analog quantity and an implementation method.
The invention relates to a current transformer, which comprises a high-voltage end module and a low-voltage end module; the high-voltage end module and the low-voltage end module are connected through optical fibers; the wireless power supply device also comprises an air core coil and a remote wireless power supply device;
the high-voltage end module comprises an impedance matching circuit module, a high-voltage end intelligent gain control circuit module, a digital modulation circuit module, an electro-optical conversion circuit module, a high-voltage end MCU and a high-voltage end temperature sensor. The hollow coil is connected with the input of the impedance matching circuit module; the impedance matching circuit module, the high-voltage end intelligent gain control circuit module, the digital modulation circuit module and the electro-optical conversion circuit module are electrically connected in sequence; the high-voltage end temperature sensor is respectively and electrically connected with the high-voltage end intelligent gain control circuit module and the digital modulation circuit module through a high-voltage end MCU; the power supplies used by the high-voltage intelligent gain control circuit module, the digital modulation circuit module, the electro-optical conversion circuit module, the high-voltage MCU and the high-voltage temperature sensor in the high-voltage module are all electrically connected with the output phase of the remote wireless power supply device; the outputs of the power supply and the remote wireless power supply device used by the high-voltage end intelligent gain control circuit module, the digital modulation circuit module, the electro-optical conversion circuit module, the high-voltage end MCU and the high-voltage end temperature sensor in the high-voltage end module are all 5V.
The low-voltage end module comprises a photoelectric conversion circuit module, a digital demodulation circuit module, an integrating circuit module, a low-voltage end intelligent gain control circuit module, a low-voltage end MCU, a low-voltage end temperature sensor, a pulse width modulation circuit module, an inversion driving circuit module, a power inverter bridge and a low-pass filter; the photoelectric conversion circuit module, the digital demodulation circuit module, the integrating circuit module, the low-voltage end intelligent gain control circuit module, the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter are sequentially and electrically connected; the digital demodulation circuit module and the low-voltage end temperature sensor are electrically connected with the low-voltage end MCU; the low-voltage end MCU is electrically connected with the low-voltage end intelligent gain control circuit module and the pulse width modulation circuit module;
one end of the optical fiber is connected with the electro-optical conversion circuit module, and the other end of the optical fiber is connected with the electro-optical conversion circuit module.
Furthermore, the current transformer of the invention, the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter are electrically connected in sequence to form a circuit which comprises two circuits which are arranged in the same way and are respectively a measuring branch circuit and a protection branch circuit; the measuring branch is used for generating a current signal for measurement; the protection branch circuit is used for generating a current signal for protection. Due to the requirements of practical application, the protection signal generally requires overload with a rated value of 40-50 times, and the measurement signal requires accuracy of 0.2S.
The implementation method of the current transformer comprises the steps that firstly, an air core coil acquires an alternating voltage signal from a bus, and then the alternating voltage signal is transmitted to an impedance matching circuit module, and electromagnetic interference generated on the bus is eliminated through the impedance matching circuit module; the high-voltage end MCU detects the environmental temperature of the high-voltage end module in real time through the high-voltage end temperature sensor, compares the environmental temperature with prestored data, and generates a corresponding high-voltage end gain amplification coefficient by combining the prestored manufacturing error of the hollow coil, the deviation of electronic components and temperature drift data of an electronic circuit; the signal flowing through the high-voltage end intelligent gain control circuit module is subjected to correction, calibration and gain amplification; then the amplified signal and the high-voltage end gain amplification coefficient are converted into a digital pulse signal through a digital modulation circuit module, laser is generated by a laser emission tube in an electro-optical conversion circuit module, and the signal is transmitted to a low-voltage end module through an optical fiber; the working power supply of the high-voltage circuit is provided by a remote wireless power supply device.
The output of the high-voltage intelligent gain control circuit module is intelligently adjusted by a high-voltage MCU. The high-voltage end MCU prestores data such as manufacturing errors of the air-core coil, deviation of electronic components, temperature drift of an electronic circuit and the like during production and debugging. During actual work, the MCU samples the signal size and the ambient temperature in real time, compares the signal size and the ambient temperature with prestored data, and automatically adjusts the gain amplification coefficient of the gain amplification circuit by using the digital potentiometer. The difference generated by coil production and manufacturing, electronic component deviation and the like is eliminated, the temperature drift caused by temperature and humidity change to an electronic circuit is eliminated, the nonlinearity of an acquisition system is compensated, and the precision of measuring an output signal is ensured.
The photoelectric conversion circuit module of the low-voltage end module completes photoelectric conversion after receiving the optical signal transmitted by the optical fiber, and the analog signal and the high-voltage end gain amplification factor of the high-voltage end are restored by the digital demodulation circuit module; sending the gain amplification coefficient of the high-voltage end into the MCU of the low-voltage end; meanwhile, the low-voltage end MCU acquires the temperature information of the environment of the low-voltage end circuit in real time through a low-voltage end temperature sensor, compares the temperature information with prestored data, and generates a corresponding low-voltage end gain amplification coefficient by combining the received high-voltage end gain amplification coefficient information for adjusting gain amplification; the restored analog signal is converted into a signal which is in the same phase relation with the current of the tested bus through the integral circuit module, and then the signal is amplified through the low-voltage end intelligent gain control circuit module, the low-voltage end gain amplification coefficient of the signal comes from data generated by the low-voltage end MCU in real time, the amplitude and the phase of the output signal of the low-voltage end intelligent gain control circuit module are adjusted, and the analog signal is calibrated; the calibrated analog signals are respectively sent to a pulse width modulation circuit module at the measuring end and a pulse width modulation circuit module at the protection end to generate SPWM signals, the SPWM signals drive a power inverter bridge through an inverter driving circuit module, and the output of the power inverter bridge generates required current signals through a low-pass filter.
Further, in the implementation method of the current transformer of the present invention, the obtaining of the gain amplification factor of the high voltage terminal includes the following steps:
1) acquiring coil difference values: testing and comparing the wound hollow coil with a standard hollow coil under the same bus current, uniformly selecting 3 or more current test points between 1-200% of rated primary current respectively, testing the output voltage difference value of the two coils on the test points, and storing the difference value into a high-voltage end MCU (microprogrammed control Unit);
2) obtaining the gain amplification factor of the application circuit: sine wave signals with the same amplitude are input into the tested high-voltage end intelligent gain control circuit and the standard gain amplification circuit, the standard gain amplification circuit is placed at a temperature of +25 ℃, the tested high-voltage end intelligent gain control circuit is placed at a temperature of-55 ℃ to +90 ℃, 3 or more temperature test points are uniformly selected, the amplification coefficient of the temperature test points is adjusted at the temperature points, the amplitude of output signals of the temperature test points is the same as that of the standard gain amplification circuit, and the temperature value of each temperature point and the corresponding gain amplification coefficient value are stored into the high-voltage end MCU.
Further, in the implementation method of the current transformer of the present invention, the obtaining of the gain amplification factor of the low voltage end includes the following steps:
1) obtaining a gain amplification coefficient of a measuring branch: placing the tested circuit at a temperature of-55 ℃ to +90 ℃, selecting a plurality of temperature points, selecting a plurality of points between 3% and 150% of the current output by the tested circuit at the temperature, and storing a gain amplification coefficient meeting the 0.2S precision and a corresponding temperature value in a low-voltage end MCU (microprogrammed control Unit);
2) obtaining a gain amplification coefficient of a protection branch circuit: the tested circuit is placed at the temperature of minus 55 ℃ to plus 90 ℃, a plurality of temperature points are selected, and under the temperature, the error of the tested circuit is smaller than plus or minus 1% within 120% of the current of 5A, the gain amplification coefficient with the composite error smaller than plus or minus 3% within 3000% and the corresponding temperature value are stored in the MCU of the low-voltage end.
Furthermore, the high-voltage end circuit of the current transformer is powered by a remote wireless power supply device. The remote wireless power supply device comprises a transmitting end, a receiving end, a transmitting circuit module and a rectification, filtering and voltage stabilizing circuit module; the transmitting end is connected with the receiving end through an insulating support;
the transmitting terminal comprises a transmitting terminal insulating shell and a transmitting terminal resonant circuit module; the transmitting end resonant circuit module is arranged in the transmitting end insulating shell; the transmitting end resonant circuit module is electrically connected with the transmitting circuit module;
the receiving end comprises a receiving end insulating shell and a receiving end resonant circuit module; the receiving end resonant circuit module is arranged in the receiving end insulating shell; and the receiving end resonance circuit module is electrically connected with the rectification, filtering and voltage stabilizing circuit module.
One end of the insulating support is fixedly connected with the transmitting end insulating shell, and the other end of the insulating support is fixedly connected with the receiving end insulating shell; a plurality of insulating umbrellas are arranged on the insulating support; the length of the insulating support is greater than or equal to 100 mm.
Further, according to the current transformer, an insulating filling material is arranged in the transmitting end insulating shell; the transmitting end resonant circuit module is arranged in an insulating filling material; an insulating filling material is arranged in the receiving end insulating shell; the receiving end resonant circuit module and the rectification filtering and voltage stabilizing circuit module are arranged in the insulating filling material. The insulating shell and the insulating filling material are high-voltage-resistant epoxy resin or high-voltage silicon rubber.
Further, according to the current transformer, the transmitting end resonant circuit module comprises a transmitting coil and a transmitting resonant capacitor which are sequentially connected; the receiving end resonant circuit module comprises a receiving coil and a receiving resonant capacitor which are connected in sequence; the transmitting coil is cylindrical in shape; the receiving coil is disc-shaped; the cylindrical transmitting coil is used for focusing and enhancing the energy in the radiation direction; the disk-shaped receiver coil, like the splayed antenna, achieves the maximum range of received energy.
Further, according to the current transformer, the transmitting circuit module comprises a high-frequency oscillating circuit, a power driving circuit and a power amplifying circuit which are electrically connected in sequence; the power amplification circuit is electrically connected with the transmitting coil and the transmitting resonant capacitor, and the transmitting circuit module is powered by the switching power supply when working.
Further, in the current transformer of the present invention, the rectification filter and voltage regulator circuit module includes a rectification filter circuit and a voltage regulator output circuit electrically connected in sequence; and the rectification filter circuit is electrically connected with the receiving resonant capacitor.
The intelligent gain control circuit module has the advantages that the manufacturing error of the air-core coil, the parameter deviation of the electronic components and the temperature drift of the electronic circuit caused by temperature and humidity changes can be eliminated by adopting the intelligent gain control circuit module, and the measurement precision is high. The current transformer can output the same 5A current value and the maximum 50VA power as the secondary end of the traditional electromagnetic current transformer by arranging the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter, and can be matched with various existing instruments and power distribution cabinets. When the circuit module is matched with a corresponding circuit module, 4V small-voltage analog signals and standard digital signals can be output, and the application occasions of the circuit module are increased. Due to the adoption of the remote wireless power supply device, the power supply problem of the collecting head at the high-voltage end of the hollow coil type current transformer is effectively solved, no power supply dead angle and measurement blind area exist, the safety maintenance is convenient, the stability is good, and the service life is long.
Drawings
FIG. 1 is a circuit diagram of a high-side module according to the present invention;
FIG. 2 is a circuit diagram of a low voltage side module according to the present invention;
FIG. 3 is a comparison of the output characteristics of the intelligent gain control circuit of the present invention with the output characteristics of other circuits;
FIG. 4 is a SPWM signal generation and low pass filtered post-reduction waveform in accordance with the present invention;
FIG. 5 is a circuit diagram of a remote wireless power supply apparatus according to the present invention;
FIG. 6 is a schematic diagram of a remote wireless power supply apparatus according to the present invention;
the device comprises a transmitting coil 1, a transmitting resonant capacitor 2, a transmitting end insulating shell 3, a transmitting circuit module 4, a high-voltage insulating lead 5, an insulating support 6, an insulating umbrella 7, a receiving coil 8, a rectifying, filtering and voltage stabilizing circuit module 9 and a receiving resonant capacitor 10.
Detailed Description
The current transformer and the implementation method of the invention are explained in detail by the drawings and the embodiments.
The invention relates to a current transformer, which comprises a high-voltage end module and a low-voltage end module; the high-voltage end module and the low-voltage end module are connected through optical fibers; the wireless power supply device also comprises an air core coil and a remote wireless power supply device.
As shown in fig. 1, the high-voltage terminal module includes an impedance matching circuit module (composed of R, L, C1 and C2), a high-voltage terminal intelligent gain control circuit module (Ug 1 and Ug 2), a digital modulation circuit module (Ug 5), an electro-optical conversion circuit module (Ug 6), a high-voltage terminal MCU (Ug 3), and a high-voltage terminal temperature sensor (Ug 4). The hollow coil is connected with the input of the impedance matching circuit module; the impedance matching circuit module, the high-voltage end intelligent gain control circuit module, the digital modulation circuit module and the electro-optical conversion circuit module are electrically connected in sequence; the high-voltage end temperature sensor is electrically connected with the high-voltage end intelligent gain control circuit module through a high-voltage end MCU; the high-voltage end MCU is electrically connected with the digital modulation circuit module; the high-voltage end intelligent gain control circuit module, the digital modulation circuit module, the electro-optical conversion circuit module, the high-voltage end MCU and the high-voltage end temperature sensor in the high-voltage end module are all provided by a remote wireless power supply device.
As shown in fig. 2, the low-voltage end module includes a photoelectric conversion circuit module (U1), a digital demodulation circuit module (U2), an integrating circuit module (U3), a low-voltage end intelligent gain control circuit module (U4, U5), a low-voltage end MCU (U6), a low-voltage end temperature sensor (U7), a pulse width modulation circuit module (U8, U9), an inverter driving circuit module (U10, U11, V1-V4), a power inverter bridge (T1-T4), and a low-pass filter (Lo, Co). The photoelectric conversion circuit module, the digital demodulation circuit module, the integrating circuit module, the low-voltage end intelligent gain control circuit module, the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter are electrically connected in sequence; and the digital demodulation circuit module, the pulse width modulation circuit module and the low-voltage end temperature sensor are electrically connected with the low-voltage end MCU.
One end of the optical fiber is electrically connected with the electro-optical conversion circuit module at the high-voltage end, and the other end of the optical fiber is electrically connected with the electro-optical conversion circuit module at the low-voltage end.
According to the current transformer, the high-voltage end circuit is powered by a remote wireless power supply device. As shown in fig. 5, the remote wireless power supply device includes a transmitting end, a receiving end, a transmitting circuit module 4 and a rectifying, filtering and voltage-stabilizing circuit module 9. The transmitting end and the receiving end are connected through an insulating support 6.
The transmitting terminal comprises a transmitting terminal insulating shell 3 and a transmitting terminal resonant circuit module; the transmitting end resonant circuit module is arranged in the transmitting end insulating shell 3; the transmitting end resonant circuit module is electrically connected with the transmitting circuit module 4;
the receiving end comprises a receiving end insulating shell and a receiving end resonant circuit module; the receiving end resonant circuit module is arranged in the receiving end insulating shell; and the receiving end resonance circuit module is electrically connected with the rectification, filtering and voltage stabilizing circuit module.
One end of the insulating support 6 is fixedly connected with the transmitting end insulating shell 3, and the other end of the insulating support is fixedly connected with the receiving end insulating shell; a plurality of insulating umbrellas 7 are arranged on the insulating support 6; the length of the insulating support 6 is equal to 100 mm. Fig. 6 shows a schematic structural diagram of a remote wireless power supply device according to the present invention. An insulating filling material is arranged in the transmitting end insulating shell 3; the transmitting end resonant circuit module is arranged in an insulating filling material; an insulating filling material is arranged in the receiving end insulating shell; the receiving end resonance circuit module and the rectification filtering and voltage stabilizing circuit module 9 are arranged in the insulating filling material. The transmitting end resonant circuit module comprises a transmitting coil 1 and a transmitting resonant capacitor 2 which are connected in sequence; the transmitting coil 1 is wound into a hollow cylinder shape and is connected with the transmitting resonant capacitor 2 in series, and an excitation signal of the transmitting coil comes from a transmitting circuit module 4 connected with a high-voltage-resistant insulated wire 5; the receiving end resonance circuit module comprises a receiving coil 8 and a receiving resonance capacitor 10 which are connected in sequence; the transmitting coil 1 is cylindrical in shape; the receiving coil 8 is disc-shaped. The transmitting circuit module 4 comprises a high-frequency oscillation circuit, a power driving circuit and a power amplifying circuit which are electrically connected in sequence; the power amplifying circuit is electrically connected with the transmitting coil 1 and the transmitting resonant capacitor 2. The rectification filter and voltage stabilizing circuit module 9 comprises a rectification filter circuit and a voltage stabilizing output circuit which are electrically connected in sequence; the rectifying and filtering circuit is electrically connected with the receiving resonant capacitor 10.
The realization process of the remote wireless power supply device is as follows: after the transmitting end circuit is electrified, the high-frequency oscillation circuit generates high-frequency signals of about 1MHz, and the high-frequency signals are converted into two mutually-reversed pulse paths through the power driving circuit to drive the two power tubes of the power amplifying circuit to work alternately. The output of the power tube is applied to a series resonance circuit composed of a transmitting coil 1 and a transmitting resonance capacitor 2 to generate a high-frequency electromagnetic field and a high-frequency electromagnetic wave to radiate energy.
The wireless receiving circuit of the receiving end consists of a receiving coil 8 and a receiving resonant capacitor 10, which are adjusted to have the same frequency as the transmitting end and form resonant coupling with the transmitting circuit, and the obtained energy is maximum at the moment. The received electric signal is converted into a direct current signal by the rectifying and filtering circuit, the voltage is regulated by the voltage stabilizing output circuit, and the electric energy required by the operation of the high-voltage collecting head circuit is output.
The implementation process of the current transformer comprises the following steps:
the high-voltage end collecting head is realized by the following steps: firstly, an air core coil acquires current from a bus to obtain an alternating voltage signal, and then the alternating voltage signal is transmitted to an impedance matching circuit module, and electromagnetic interference generated on the bus is eliminated through the impedance matching circuit module; the high-voltage end MCU detects the environmental temperature of the high-voltage end module in real time through the high-voltage end temperature sensor, compares the environmental temperature with prestored data, and generates a corresponding high-voltage end gain amplification coefficient by combining the prestored manufacturing error of the hollow coil, the deviation of electronic components and temperature drift data of an electronic circuit; carrying out intelligent correction and calibration on signals flowing through the high-voltage end intelligent gain control circuit module and simultaneously carrying out gain amplification; and then the amplified signal and the high-voltage end gain amplification coefficient are converted into a digital pulse signal through a digital modulation circuit module, laser is generated by an electro-optical conversion circuit module, and the signal is transmitted to a low-voltage end module through an optical fiber.
The output of the high-voltage intelligent gain control circuit module is intelligently adjusted by a high-voltage MCU. The high-voltage end MCU prestores data such as manufacturing errors of the air-core coil, deviation of electronic components, temperature drift of an electronic circuit and the like during production and debugging. During actual work, the MCU samples the signal size and the ambient temperature in real time, compares the signal size and the ambient temperature with prestored data, and automatically adjusts the gain amplification factor of the gain amplification circuit by using the digital potentiometer (Ug 2). The difference generated by coil production and manufacturing, electronic component deviation and the like is eliminated, the temperature drift caused by temperature and humidity change to an electronic circuit is eliminated, the nonlinearity of an acquisition system is compensated, and the precision of measuring an output signal is ensured. As shown in fig. 3, according to the experimental test, the same signal is input, when the signal is loaded on the non-correction circuit, the amplitude of the output signal has large fluctuation due to the influence of temperature change and element parameter difference, and the linear relation between the input and the output cannot be maintained; in the same circuit structure, when an element with smaller temperature drift and lower parameter dispersion is selected, the fluctuation of an output signal is obviously reduced, and the linear relation between input and output is relatively close; when the intelligent gain control mode is adopted, even if components made of common materials are selected, the output and the input signal can keep a quite good linear relation.
The acquisition of the gain amplification factor of the high-voltage end comprises the following steps:
1) acquiring coil difference values: testing and comparing the wound hollow coil with a standard hollow coil under the same bus current, uniformly selecting 3 or more current test points between 1-200% of rated primary current respectively, testing the output voltage difference value of the two coils on the test points, and storing the difference value into a high-voltage end MCU (microprogrammed control Unit);
2) obtaining the gain amplification factor of the application circuit: sine wave signals with the same amplitude are input into the tested high-voltage end intelligent gain control circuit and the standard gain amplification circuit, the standard gain amplification circuit is placed at a temperature of +25 ℃, the tested high-voltage end intelligent gain control circuit is placed at a temperature of-55 ℃ to +90 ℃, 3 or more temperature test points are uniformly selected, the amplification coefficient of the temperature test points is adjusted at the temperature points, the amplitude of output signals of the temperature test points is the same as that of the standard gain amplification circuit, and the temperature value of each temperature point and the corresponding gain amplification coefficient value are stored into the high-voltage end MCU.
The implementation method of the low-voltage end module comprises the following steps: the photoelectric conversion circuit module of the low-voltage end module completes photoelectric conversion after receiving the optical signal transmitted by the optical fiber, and the analog signal and the high-voltage end gain amplification factor of the high-voltage end are restored by the digital demodulation circuit module; sending the gain amplification coefficient of the high-voltage end to the low-voltage end MCU; meanwhile, the low-voltage end MCU acquires the temperature information of the environment of the low-voltage end circuit in real time through a low-voltage end temperature sensor, compares the temperature information with prestored data, and generates a corresponding low-voltage end gain amplification coefficient by combining the received high-voltage end gain amplification coefficient information for adjusting gain amplification; the restored analog signal is converted into a signal which is in the same phase relation with the current of the tested bus through the integral circuit module, and then the signal is amplified through the low-voltage end intelligent gain control circuit module, the low-voltage end gain amplification coefficient of the signal comes from data generated by the low-voltage end MCU in real time, the amplitude and the phase of the output signal of the low-voltage end intelligent gain control circuit module are adjusted, and the analog signal is calibrated; the triangular wave signal generated by the MCU is amplified and then sent to the pulse width modulation circuit module together with the calibrated analog signal to generate an SPWM signal, the SPWM signal drives the power inverter bridge through the inverter driving circuit module, and the output of the power inverter bridge generates a current signal through the low-pass filter. The low-voltage end module is provided with two pulse width modulation circuit modules, an inversion driving circuit module, a power inversion bridge and a low-pass filter, and the two pulse width modulation circuit modules, the inversion driving circuit module, the power inversion bridge and the low-pass filter are respectively used for generating a current signal for measurement and a current signal for protection. The output of the circuit structure shown in fig. 2 is a measurement part, and the difference of the protection part is that the supply voltage of the inverter bridge is 350V. As shown in fig. 4, the signal is a sine wave which is restored after integration and has the same phase relation with the current of the bus to be measured, the signal is input to the positive end of the comparator after amplification and correction, and the triangular wave signal generated by the MCU is input to the negative end of the comparator after amplification; when the amplitude of the triangular wave is larger than that of the sine wave signal, the comparator outputs a negative polarity signal; on the contrary, when the sine wave signal is larger than the triangular wave signal, the comparator outputs a positive polarity signal; the signal is a pulse signal with the width changing along with the amplitude of the sine wave, namely an SPWM signal; because the change of the SPWM signal has relevance with the amplitude change of the sine wave signal, the sine wave signal can be recovered through the low-pass filter; the signal is output in a current form, namely a sine wave current signal.
The low-voltage end gain coefficient adjusting process comprises the following steps:
1) obtaining a gain amplification coefficient of a measuring branch: placing the tested circuit at a temperature of-55 ℃ to +90 ℃, selecting a plurality of temperature points, selecting a plurality of points between 3% and 150% of the current output by the tested circuit at the temperature, and storing a gain amplification coefficient meeting the 0.2S precision and a corresponding temperature value in a low-voltage end MCU (microprogrammed control Unit);
2) obtaining a gain amplification coefficient of a protection branch circuit: the tested circuit is placed at the temperature of minus 55 ℃ to plus 90 ℃, a plurality of temperature points are selected, and under the temperature, the error of the tested circuit is smaller than plus or minus 1% within 120% of the current of 5A, the gain amplification coefficient with the composite error smaller than plus or minus 3% within 3000% and the corresponding temperature value are stored in the MCU of the low-voltage end.
Claims (9)
1. A current transformer comprises a high-voltage end module and a low-voltage end module; the high-voltage end module and the low-voltage end module are connected through optical fibers; the method is characterized in that: the device also comprises an air coil and a remote wireless power supply device;
the high-voltage end module comprises an impedance matching circuit module, a high-voltage end intelligent gain control circuit module, a digital modulation circuit module, an electro-optical conversion circuit module, a high-voltage end MCU and a high-voltage end temperature sensor; the hollow coil is connected with the input of the impedance matching circuit module; the impedance matching circuit module, the high-voltage end intelligent gain control circuit module, the digital modulation circuit module and the electro-optical conversion circuit module are electrically connected in sequence; the high-voltage end temperature sensor is respectively and electrically connected with the high-voltage end intelligent gain control circuit module and the digital modulation circuit module through a high-voltage end MCU; the power supplies used by the high-voltage intelligent gain control circuit module, the digital modulation circuit module, the electro-optical conversion circuit module, the high-voltage MCU and the high-voltage temperature sensor in the high-voltage module are all electrically connected with the output phase of the remote wireless power supply device;
the low-voltage end module comprises a photoelectric conversion circuit module, a digital demodulation circuit module, an integrating circuit module, a low-voltage end intelligent gain control circuit module, a low-voltage end MCU, a low-voltage end temperature sensor, a pulse width modulation circuit module, an inversion driving circuit module, a power inverter bridge and a low-pass filter; the photoelectric conversion circuit module, the digital demodulation circuit module, the integrating circuit module, the low-voltage end intelligent gain control circuit module, the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter are sequentially and electrically connected; the digital demodulation circuit module and the low-voltage end temperature sensor are electrically connected with the low-voltage end MCU; the low-voltage end MCU is electrically connected with the low-voltage end intelligent gain control circuit module and the pulse width modulation circuit module;
one end of the optical fiber is connected with the electro-optical conversion circuit module, and the other end of the optical fiber is connected with the electro-optical conversion circuit module;
the remote wireless power supply device comprises a transmitting end and a receiving end; the transmitting end comprises a transmitting end resonant circuit module; the receiving end comprises a receiving end resonant circuit module; the transmitting end resonant circuit module comprises a transmitting coil (1) and a transmitting resonant capacitor (2) which are connected in sequence; the receiving end resonance circuit module comprises a receiving coil (8) and a receiving resonance capacitor (10) which are connected in sequence; the transmitting coil (1) is cylindrical in shape; the receiving coil (8) is disc-shaped.
2. The current transformer of claim 1, wherein: the pulse width modulation circuit module, the inversion driving circuit module, the power inversion bridge and the low-pass filter are electrically connected in sequence to form a circuit which comprises two paths which are arranged in the same way and are respectively a measurement branch and a protection branch; the measuring branch is used for generating a current signal for measurement; the protection branch circuit is used for generating a current signal for protection.
3. The method for implementing the current transformer according to claim 2, wherein: firstly, an alternating voltage signal is acquired by an air-core coil from a bus and then transmitted to an impedance matching circuit module, and electromagnetic interference generated on the bus is eliminated through the impedance matching circuit module; the high-voltage end MCU detects the environmental temperature of the high-voltage end module in real time through the high-voltage end temperature sensor, compares the environmental temperature with prestored data, and generates a corresponding high-voltage end gain amplification coefficient by combining the prestored manufacturing error of the hollow coil, the deviation of electronic components and temperature drift data of an electronic circuit; carrying out correction, calibration and gain amplification on a signal flowing through the high-voltage-end intelligent gain control circuit module; then the amplified signal and the high-voltage end gain amplification coefficient are converted into a digital pulse signal through a digital modulation circuit module, laser is generated by a laser emission tube in an electro-optical conversion circuit module, and the signal is transmitted to a low-voltage end module through an optical fiber;
the photoelectric conversion circuit module of the low-voltage end module completes photoelectric conversion after receiving the optical signal transmitted by the optical fiber, and the analog signal and the high-voltage end gain amplification factor of the high-voltage end are restored by the digital demodulation circuit module; sending the gain amplification coefficient of the high-voltage end into the MCU of the low-voltage end; meanwhile, the low-voltage end MCU acquires the temperature information of the environment of the low-voltage end circuit in real time through a low-voltage end temperature sensor, compares the temperature information with prestored data, and generates a corresponding low-voltage end gain amplification coefficient by combining the received high-voltage end gain amplification coefficient information for adjusting gain amplification; the restored analog signal is converted into a signal which is in the same phase relation with the current of the tested bus through the integral circuit module, and then the signal is amplified through the low-voltage end intelligent gain control circuit module, the low-voltage end gain amplification coefficient of the signal comes from data generated by the low-voltage end MCU in real time, the amplitude and the phase of the output signal of the low-voltage end intelligent gain control circuit module are adjusted, and the analog signal is calibrated; the calibrated analog signals are respectively sent to a pulse width modulation circuit module at the measuring end and a pulse width modulation circuit module at the protection end to generate SPWM signals, the SPWM signals drive a power inverter bridge through an inverter driving circuit module, and the output of the power inverter bridge generates required current signals through a low-pass filter.
4. The method for implementing the current transformer according to claim 3, wherein: the acquisition of the gain amplification factor of the high-voltage end comprises the following steps:
1) acquiring a coil difference value: testing and comparing the wound hollow coil with a standard hollow coil under the same bus current, uniformly selecting 3 or more current test points between 1-200% of rated primary current respectively, testing the output voltage difference value of the two coils on the test points, and storing the difference value into a high-voltage end MCU (microprogrammed control Unit);
2) obtaining the gain amplification factor of the application circuit: sine wave signals with the same amplitude are input into the tested high-voltage end intelligent gain control circuit and the standard gain amplification circuit, the standard gain amplification circuit is placed at a temperature of +25 ℃, the tested high-voltage end intelligent gain control circuit is placed at a temperature of-55 ℃ to +90 ℃, 3 or more temperature test points are uniformly selected, the amplification coefficient of the temperature test points is adjusted at the temperature points, the amplitude of output signals of the temperature test points is the same as that of the standard gain amplification circuit, and the temperature value of each temperature point and the corresponding gain amplification coefficient value are stored into the high-voltage end MCU.
5. The method for implementing the current transformer according to claim 3, wherein: the acquisition of the low-voltage end gain amplification factor comprises the following steps:
1) obtaining a gain amplification coefficient of a measuring branch: placing the tested circuit at a temperature of-55 ℃ to +90 ℃, selecting a plurality of temperature points, selecting a plurality of points between 3% and 150% of the current output by the tested circuit at the temperature, and storing a gain amplification coefficient meeting the 0.2S precision and a corresponding temperature value in a low-voltage end MCU (microprogrammed control Unit);
2) obtaining a gain amplification coefficient of a protection branch circuit: the tested circuit is placed at the temperature of minus 55 ℃ to plus 90 ℃, a plurality of temperature points are selected, and under the temperature, the error of the tested circuit is smaller than plus or minus 1% within 120% of the current of 5A, the gain amplification coefficient with the composite error smaller than plus or minus 3% within 3000% and the corresponding temperature value are stored in the MCU of the low-voltage end.
6. The current transformer according to claim 1 or 2, characterized in that: the remote wireless power supply device also comprises a transmitting circuit module (4) and a rectification, filtering and voltage stabilizing circuit module (9); the transmitting end and the receiving end are connected through an insulating strut (6);
the transmitting end comprises a transmitting end insulating shell (3); the transmitting end resonant circuit module is arranged in the transmitting end insulating shell (3); the transmitting end resonance circuit module is electrically connected with the transmitting circuit module (4);
the receiving end comprises a receiving end insulating shell; the receiving end resonant circuit module is arranged in the receiving end insulating shell and is electrically connected with the rectification filtering and voltage stabilizing circuit module (9);
one end of the insulating support column (6) is fixedly connected with the transmitting end insulating shell (3), and the other end of the insulating support column is fixedly connected with the receiving end insulating shell; a plurality of insulating umbrellas (7) are arranged on the insulating support (6); the length of the insulating support post (6) is more than or equal to 100 mm.
7. The current transformer of claim 6, wherein: an insulating filling material is arranged in the transmitting end insulating shell (3); the transmitting end resonant circuit module is arranged in an insulating filling material; an insulating filling material is arranged in the receiving end insulating shell; the receiving end resonance circuit module and the rectification filtering and voltage stabilizing circuit module (9) are arranged in the insulating filling material.
8. The current transformer of claim 7, wherein: the transmitting circuit module (4) comprises a high-frequency oscillation circuit, a power driving circuit and a power amplifying circuit which are electrically connected in sequence; the power amplification circuit is electrically connected with the transmitting coil (1) and the transmitting resonant capacitor (2).
9. The current transformer of claim 8, wherein: the rectification filter and voltage stabilizing circuit module (9) comprises a rectification filter circuit and a voltage stabilizing output circuit which are sequentially and electrically connected; the rectifying and filtering circuit is electrically connected with the receiving resonant capacitor (10).
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| CN113759158A (en) * | 2021-07-26 | 2021-12-07 | 国家电网有限公司 | Mutual inductor for multi-node station domain information fusion and data acquisition method |
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| CN104122427A (en) * | 2014-08-04 | 2014-10-29 | 山东理工大学 | Analogue electric signal transmission method and analogue electric signal transmission device applied to current transformer |
| CN206930779U (en) * | 2017-07-19 | 2018-01-26 | 北醒（北京）光子科技有限公司 | A kind of infrared acquisition and measurement apparatus |
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| CN102590576B (en) * | 2012-02-22 | 2014-03-12 | 西安交通大学 | Active photoelectric current transformer with wireless induction power supply function |
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| CN104122427A (en) * | 2014-08-04 | 2014-10-29 | 山东理工大学 | Analogue electric signal transmission method and analogue electric signal transmission device applied to current transformer |
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