Error calibration system and method for wide-band and wide-range current transformer

Abstract

The invention discloses an error calibration system and method for a wide-band wide-range current transformer, comprising: a wide-band wide-range standard transformer, a wide-band large current generating device, and a wide-band wide-range transformer calibrator; the wide-band large current generating device provides working current for the primary side of the wide-band wide-range current transformer to be measured and the primary side of the wide-band wide-range standard transformer; the wide-band wide-range transformer calibrator collects the standard current signal of the secondary side of the standard transformer and the current signal to be measured of the secondary side of the wide-band wide-range current transformer to be measured, performs data preprocessing to obtain a calculable digital signal, and performs error calculation to obtain the error of the wide-band wide-range current transformer to be measured; the wide-band wide-range transformer calibrator adopts a multi-position Hall sensor, and the sampling system also has a range switching capability, thereby expanding the range of current measurement, and ensuring the sampling accuracy of low current signals, and having a wider range of frequency adaptability.

Description

Technical Field

[0001] The present invention relates to the technical field of error measurement, and in particular to an error calibration system and method for a wide-band and wide-range current transformer. Background Art

[0002] With the widespread application of power electronic equipment, in some special occasions of the power system, the load variation range is very large and the frequency band is wide. For example, the rapidly developing high-speed rail in China has the characteristics of high speed, large traction, and no direct pollution. The traction substation converts the high-voltage power supply of the public network into a power supply suitable for electric locomotives. When an electric locomotive passes, the current passing through the traction substation can basically reach the rated value or even higher, and in the time period after the electric locomotive passes, the current passing through the traction substation is very small. For special occasions with relatively large load changes, traditional current transformers can no longer meet the needs of measurement. Therefore, wide-band and wide-range current transformers will be more and more widely used. Due to the characteristics of wide-range and wide-frequency wide-band current transformers, traditional current transformer calibration methods (only for 1%-120% of the rated current of the current transformer) are difficult to simply transplant and apply to the error calibration of wide-band and wide-range current transformers. Therefore, it is necessary to design corresponding error calibration methods for wide-band and wide-range current transformers. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a wide-band and wide-range current transformer error calibration system and method, which are used to complete the error verification or calibration of the wide-band and wide-range current transformer.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention provides an error calibration system for a wide-band and wide-range current transformer, comprising: a wide-band and wide-range standard transformer, a wide-band and wide-range large current generating device, and a wide-band and wide-range transformer calibrator;

[0006] The wide-band wide-range transformer calibrator is composed of a multi-position Hall sensor A, a multi-position Hall sensor B, a wide-band wide-range standard transformer, a data processing module A, a data processing module B and a calculation module;

[0007] The primary side of the wide-band and wide-range standard transformer is connected in series with the primary side of the wide-band and wide-range current transformer to be measured and then connected to both ends of the wide-band and wide-range current generating device; the secondary side of the wide-band and wide-range standard transformer is connected to a multi-position Hall sensor A, and the secondary side of the wide-band and wide-range current transformer to be measured is connected to a multi-position Hall sensor B;

[0008] The multi-position Hall sensor A collects the standard current signal on the secondary side of the wide-band and wide-range standard transformer and converts it to output a standard small current signal proportional to it; the multi-position Hall sensor B collects the current signal to be measured on the secondary side of the wide-band and wide-range current transformer to be measured and converts it to output a small current signal to be measured proportional to it;

[0009] The data processing module A converts the standard small current signal into a standard small voltage signal, amplifies it, and then converts it into a digital signal to output to the calculation module; the data processing module B converts the small current signal to be measured into a small voltage signal to be measured, amplifies it, and then converts it into a digital signal to output to the calculation module;

[0010] The calculation module performs error calculation based on the data output by the data processing module A and the data processing module B to obtain the error of the wide-band and wide-range current transformer to be measured.

[0011] A further optimization scheme is that the data processing module A or B includes: a sampling resistor, a programmable operational amplifier module, an AD conversion module, a bottom 32-bit microcomputer and an embedded 32-bit microcomputer; the programmable operational amplifier module amplifies the collected small voltage signal by a specified multiple;

[0012] The sampling resistor converts the small current signal collected by the multi-speed Hall sensor A and the multi-speed Hall sensor B into a small voltage signal;

[0013] The AD conversion module converts the voltage signal amplified by the programmable operational amplifier module into a digital signal output;

[0014] The bottom 32-bit microcomputer controls the data processing module A and the data processing module B to sample simultaneously, and converts the digital signal output by the AD conversion module into operable data and transmits it to the embedded 32-bit microcomputer;

[0015] The embedded 32-bit microcomputer performs digital filtering, integration operation and error calculation on the digital signal transmitted from the bottom 32-bit microcomputer to obtain the error of the wide-band and wide-range current transformer to be tested.

[0016] In the wide-band and wide-range transformer calibrator: the standard current signal passes through the standard current sampling circuit composed of the sampling resistor R1 and the operational amplifier A1, and outputs a standard small voltage signal proportional to the standard current;

[0017] The measured current signal passes through the measured current sampling loop composed of the sampling resistor R2 and the operational amplifier A2, and outputs a measured small voltage signal proportional to the measured current.

[0018] The standard small voltage signal is converted into a standard digital signal by AD1;

[0019] The small voltage signal to be measured is converted into a digital signal to be measured by AD2.

[0020] FPGA (bottom-level 32-bit microcomputer) controls the AD1 conversion module and the AD2 conversion module to sample simultaneously, reads the standard digital signal converted by the AD1 conversion module and the standard digital signal converted by the AD2 conversion module, converts the standard digital signal and the standard digital signal into a calculable data format and sends them to the embedded 32-bit microcomputer. The calculable data is subjected to digital filtering, Fourier operation, error calculation and other processes in the embedded 32-bit microcomputer to obtain the error data of the measured transformer, and the embedded 32-bit microcomputer finally sends the results and related data to the human-machine interface. The waveform, effective value, error and other related information are displayed in the human-machine interface.

[0021] A further optimization solution is that the AD conversion module outputs the digital signal to the underlying 32-bit microcomputer through the SPI bus.

[0022] A further optimization scheme is that the sampling resistor is used to convert the standard small current signal / the small current signal to be measured into a standard small voltage signal / the small voltage signal to be measured, and output it to the programmable operational amplifier module, and the sampling resistor adopts a high-precision, low-temperature drift precision resistor.

[0023] A further optimized solution is that the multi-speed Hall sensor is composed of a selector switch and a broadband sensor, and the broadband sensor has multiple input terminals;

[0024] The input end of the selector switch is connected to a standard transformer with a wide frequency and a wide range or a current transformer with a wide frequency and a wide range to be measured, and the output end of the selector switch is selectively connected to an input terminal of a wide frequency sensor.

[0025] A further optimization scheme is that the selector switch is composed of multiple high-current relays and their drive circuits.

[0026] The selector switches K1 and K2 are composed of multiple high-current relays and their drive circuits, which are used to access standard current signals. According to the control signal of FPGA (the underlying 32-bit microcomputer), the standard current signals are connected to the terminals of the wide-band sensor; the wide-band sensor adopts a high-precision multi-speed Hall sensor module to convert the standard current signal and output a proportional standard small current signal to the sampling resistor.

[0027] A further optimization scheme is that the wide-band and wide-range transformer calibrator also includes a human-computer interaction module, which is used for parameter setting, graphics and data display.

[0028] The wide-band and wide-range standard transformer adopts zero-flux current transformer technology and provides an accuracy of not less than 0.05 within the range of 0.1% to 200% of the rated current.

[0029] The programmable operational amplifier module uses an operational amplifier with controllable amplification factor to amplify the standard small voltage signal / the small voltage signal to be tested by a specified multiple according to the control signal of the FPGA, and outputs the amplified signal to the AD module;

[0030] The AD module uses a wide-band, high-precision 24-bit ADC chip as the core device, and forms a high-precision analog-to-digital conversion circuit with auxiliary circuits such as differential circuits. According to the configuration instructions of the FPGA (the underlying 32-bit microcomputer), the standard voltage signal / voltage signal to be tested output by the program-controlled operation module is converted into an analog-to-digital signal, and converted into a digital signal through the SPI bus and output to the underlying 32-bit microcomputer;

[0031] FPGA (bottom-layer 32-bit microcomputer) uses Intel's high-performance FPGA chip, and uses hardware description language to generate AD module controller, op amp controller, and switch controller in FPGA, which are used to control the working status of each module such as AD1 module, AD2 module, selection switch K1, selection switch K2, program-controlled op amp module A1, program-controlled op amp module A2 and exchange information, and pre-process the data obtained from the module, and then exchange data with the embedded 32-bit microcomputer through a parallel bus;

[0032] The embedded 32-bit microcomputer adopts the ARM chip of STMicroelectronics, exchanges data with the underlying 32-bit microcomputer through the parallel bus FSMC, processes the data according to the instructions of the human-computer interaction module, and outputs the calculation results to the human-computer interaction module; the human-computer interaction module: adopts the Windows operating system and provides a rich information display interface for parameter setting, graphics and data display.

[0033] Based on the error calibration system of the wide-band and wide-range current transformer, the present invention also provides a corresponding method, comprising the following steps:

[0034] S1. Make the broadband high current generating device provide working current for the primary side of the broadband wide range current transformer to be tested and the primary side of the broadband wide range standard transformer;

[0035] S2. The wide-band wide-range current transformer tester collects the standard current signal of the secondary side of the standard current transformer and the current signal to be measured on the secondary side of the wide-band wide-range current transformer to be measured and performs data preprocessing to obtain a digital signal that can be calculated;

[0036] S3. The wide-band and wide-range current transformer tester performs error calculation based on operable digital signals to obtain the error of the wide-band and wide-range current transformer to be tested.

[0037] The working current of the existing current transformer tester is 50Hz, and it has good adaptability to frequencies near 50Hz. However, for low-frequency and high-frequency signals, the adaptability will gradually decrease as the frequency moves away from the power frequency, and the current passing rate will gradually decrease to 0%. In order to improve the stability and accuracy of the instrument, the current input end of the instrument usually adopts a multi-tap current transformer design. The frequency adaptability of the current transformer is relatively poor, and high-frequency and low-frequency signals other than 50Hz will be attenuated when passing through the current transformer. The wide-band and wide-range current transformer uses a Hall sensor made by the Hall effect at the current input end. The output of the Hall sensor is only related to the input current size, but not to the frequency. Therefore, the wide-band and wide-range has a wide range of frequency adaptability, and the wide-band and wide-range transformer tester has good adaptability from DC to high frequency.

[0038] The working current input range of existing current transformer calibrators is usually 0-6A, and the calibration accuracy is difficult to guarantee at 0.001A current; while the working current input range of wide-band and wide-range current transformer calibrators is greater than 0-10A, and still has high accuracy at 0.001A.

[0039] In order to ensure the measurement accuracy, the existing current transformer calibrator usually uses a current transformer to convert input currents of different sizes into current signals within a specified range, so that the input signal of the sampling system is kept within a certain range, which can effectively reduce the sampling error. Due to the size limitation, the instrument current transformer does not have many taps, which limits the measurement range of the current transformer. Excessive input current will cause signal clipping, and the sampling error of too small input current will increase, making it impossible to guarantee accuracy. The wide-band and wide-range current transformer calibrator uses a multi-position Hall device, and the sampling system also has the ability to switch the range, thereby expanding the range of current measurement and ensuring the sampling accuracy of low current signals.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] The present invention provides a wide-band wide-range current transformer error calibration system and method, wherein a wide-band large current generating device provides working current for the primary side of the wide-band wide-range current transformer to be measured and the primary side of the wide-band wide-range standard transformer; the wide-band wide-range transformer calibrator collects the standard current signal of the secondary side of the standard transformer and the current signal to be measured on the secondary side of the wide-band wide-range current transformer to be measured, performs data preprocessing to obtain a calculable digital signal, and performs error calculation to obtain the error of the wide-band wide-range current transformer to be measured. The wide-band wide-range current transformer calibrator uses a multi-position Hall device, and the sampling system also has the ability to switch the range, thereby expanding the range of current measurement, and ensuring the sampling accuracy of low current signals, and having a wider range of frequency adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention.

[0043] Figure 1 It is a schematic diagram of the structure of the error calibration system of the wide-band and wide-range current transformer of the present invention;

[0044] Figure 2 The working principle diagram of the error calibration system of the wide-band and wide-range current transformer of the present invention;

[0045] Figure 3 Design schematic diagram for wide-band and wide-range calibrator;

[0046] Figure 4 This is a verification connection diagram of an error calibration system for a wide-band and wide-range current transformer according to an embodiment. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1

[0049] like Figure 1 As shown, the error calibration system of the wide-band and wide-range current transformer comprises: a wide-band and wide-range standard transformer, a wide-band and wide-range large current generating device, and a wide-band and wide-range transformer calibrator;

[0050] The wide-band and wide-range transformer calibrator is composed of a multi-position Hall sensor A, a multi-position Hall sensor B, a wide-band and wide-range standard transformer, a data processing module A, a data processing module B and a calculation module;

[0051] The primary side of the wide-band and wide-range standard transformer is connected in series with the primary side of the wide-band and wide-range current transformer to be measured and then connected to both ends of the wide-band and wide-range current generating device; the secondary side of the wide-band and wide-range standard transformer is connected to a multi-position Hall sensor A, and the secondary side of the wide-band and wide-range current transformer to be measured is connected to a multi-position Hall sensor B;

[0052] The multi-position Hall sensor A collects the standard current signal on the secondary side of the wide-band and wide-range standard transformer and converts it to output a standard small current signal proportional to it; the multi-position Hall sensor B collects the current signal to be measured on the secondary side of the wide-band and wide-range current transformer to be measured and converts it to output a small current signal to be measured proportional to it;

[0053] The data processing module A converts the standard small current signal into a standard small voltage signal, amplifies it, and then converts it into a digital signal to output to the calculation module; the data processing module B converts the small current signal to be measured into a small voltage signal to be measured, amplifies it, and then converts it into a digital signal to output to the calculation module;

[0054] The calculation module performs error calculation based on the data output by the data processing module A and the data processing module B to obtain the error of the wide-band and wide-range current transformer to be measured.

[0055] like Figure 2 As shown, the data processing module A or B includes: sampling resistors (sampling resistors R1 and R2), programmable operational amplifier modules (A1 and A2), AD conversion modules (AD1 and AD2), bottom 32-bit microcomputers and embedded 32-bit microcomputers; the programmable operational amplifier modules (A1 and A2) amplify the collected small voltage signals by a specified multiple;

[0056] The sampling resistor R1 converts the standard small current signal collected by the multi-speed Hall sensor A into a standard small voltage signal. The sampling resistor R2 converts the small current signal to be measured collected by the multi-speed Hall sensor B into a small voltage signal to be measured.

[0057] The AD conversion module (module AD1 and module AD2) converts the voltage signal amplified by the programmable operational amplifier module into a digital signal output;

[0058] The bottom 32-bit microcomputer controls the data processing module A and the data processing module B to sample simultaneously, and converts the digital signal output by the AD conversion module into operable data and transmits it to the embedded 32-bit microcomputer;

[0059] The embedded 32-bit microcomputer performs digital filtering, integration operation and error calculation on the digital signal transmitted from the bottom 32-bit microcomputer to obtain the error of the wide-band and wide-range current transformer to be tested.

[0060] The AD conversion modules (module AD1 and module AD2) output digital signals to the underlying 32-bit microcomputer via the SPI bus.

[0061] The sampling resistors (sampling resistor R1 and sampling resistor R2) are precision resistors.

[0062] like Figure 3 As shown, the multi-position Hall sensor is composed of a selector switch and a wide-band sensor, and the wide-band sensor has 4 input terminals;

[0063] The input ends of the selector switch K1 and the selector switch K2 are connected to a standard transformer with a wide frequency and a wide range or a current transformer with a wide frequency and a wide range to be measured, and the output ends of the selector switch K1 and the selector switch K2 are selectively connected to one of the input terminals of the wide frequency sensor.

[0064] The selector switch (K1 and K2) is composed of multiple high-current relays and their drive circuits.

[0065] The wide-band and wide-range transformer calibrator further comprises a human-computer interaction module, which is used for parameter setting, graph and data display.

[0066] Example 2

[0067] like Figure 4 As shown, the program-controlled broadband large current generating device is responsible for the output of the primary working current. The frequency range of the AC current is 5Hz to 2kHz. The output 50Hz fundamental AC current range is 0.1% to 200% of 600A. The current stability ensures the accuracy and stability of the measurement error. When each harmonic is output, the output capacity of the program-controlled broadband large current generating device is reduced accordingly. The 2kHz AC current output capacity is not less than 60A.

[0068] The wide-band and wide-range transformer calibrator adopts the principle of difference measurement, which is responsible for measuring the secondary current of the standard current transformer and the secondary current of the current transformer to be measured and calculating the ratio difference and phase difference of the current transformer to be measured. The wide-band and wide-range transformer calibrator adopts Fourier algorithm to decompose the in-phase component and the orthogonal component, without the need for an orthogonal phase shifter.

[0069] The basic accuracy level of the wide-band and wide-range transformer calibrator is level 2. To ensure the measurement of harmonic signals, the AD module in the wide-band and wide-range transformer calibrator adopts a technology that combines variable sampling rate and variable sampling points, which not only meets the measurement accuracy but also meets the measurement speed. When measuring the fundamental wave error, the sampling rate is 20k / s, and the number of sampling points per cycle reaches 400 points.

[0070] The wide-band and wide-range standard current transformer adopts zero-flux current transformer technology and provides an accuracy of no less than 0.05 within the range of 0.1% to 200% of the rated current.

[0071] Example 3

[0072] When the error calibration system of the wide-band and wide-range current transformer is used and the multi-position Hall sensors are set to select switches with the same transformation ratio, the system can perform self-calibration. The specific self-calibration data (accuracy level is 0.02) are shown in Tables 1 and 2 below:

[0073] Table 1

[0074]

[0075] Table 2

[0076]

[0077] Using the error calibration system of wide-band and wide-range current transformer, the multi-position Hall sensor is set to other positions, and the data obtained by calibration based on the standard transformer (accuracy level is 0.2) are as follows Table 3 and Table 4:

[0078] Table 3

[0079]

[0080] Table 4

[0081]

[0082] From the above content, it can be seen that the error calibration system of the wide-band and wide-range current transformer can perform error calibration for the situation of 0.1%-200% of the rated current of the current transformer, and both self-calibration and standard current transformers can be realized.

[0083] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An error calibration system for a wide-band and wide-range current transformer, characterized in that: include: Wide-band and wide-range standard transformer, wide-band and wide-current generator, wide-band and wide-range transformer calibrator; The wide-band wide-range transformer calibrator is composed of a multi-position Hall sensor A, a multi-position Hall sensor B, a wide-band wide-range standard transformer, a data processing module A, a data processing module B and a calculation module; The data processing module A or B includes: a sampling resistor, a programmable operational amplifier module, an AD conversion module, a bottom 32-bit microcomputer and an embedded 32-bit microcomputer; the programmable operational amplifier module amplifies the collected small voltage signal by a specified multiple; the sampling resistor converts the small current signal collected by the multi-speed Hall sensor A and the multi-speed Hall sensor B into a small voltage signal; The AD conversion module converts the voltage signal amplified by the programmable operational amplifier module into a digital signal output; The bottom 32-bit microcomputer controls the data processing module A and the data processing module B to sample simultaneously, and converts the digital signal output by the AD conversion module into operable data and transmits it to the embedded 32-bit microcomputer; The embedded 32-bit microcomputer performs digital filtering, integration operation and error calculation on the digital signal transmitted by the underlying 32-bit microcomputer to obtain the error of the wide-band and wide-range current transformer to be measured; the primary side of the wide-band and wide-range standard transformer is connected in series with the primary side of the wide-band and wide-range current transformer to be measured and then connected to both ends of the wide-band and large current generating device; the secondary side of the wide-band and wide-range standard transformer is connected to the multi-position Hall sensor A, The secondary side of the wide-band and wide-range current transformer to be measured is connected to a multi-position Hall sensor B; the multi-position Hall sensor A collects the standard current signal on the secondary side of the wide-band and wide-range standard transformer and converts it to output a standard small current signal proportional to it; the multi-position Hall sensor B collects the current signal to be measured on the secondary side of the wide-band and wide-range current transformer to be measured and converts it to output a small current signal to be measured proportional to it; the data processing module A converts the standard small current signal into a standard small voltage signal, amplifies it, and then converts it into a digital signal to output to the calculation module; the data processing module B converts the small current signal to be measured into a small voltage signal to be measured, amplifies it, and then converts it into a digital signal to output to the calculation module; the calculation module performs error calculation based on the data output by the data processing module A and the data processing module B to obtain the error of the wide-band and wide-range current transformer to be measured; The AD conversion module outputs the digital signal to the underlying 32-bit microcomputer via the SPI bus; the sampling resistor uses a precision resistor; The multi-position Hall sensor is composed of a selector switch and a broadband sensor, and the broadband sensor has a plurality of input terminals; The input end of the selector switch is connected to a standard transformer with a wide frequency and a wide range or a current transformer with a wide frequency and a wide range to be measured, and the output end of the selector switch is selectively connected to an input terminal of a wide frequency sensor.

2. The error calibration system for a wide-band and wide-range current transformer according to claim 1, characterized in that: The selector switch is composed of multiple high-current relays and their drive circuits.

3. The error calibration system for a wide-band and wide-range current transformer according to claim 1, characterized in that: The wide-band and wide-range transformer calibrator further comprises a human-computer interaction module, which is used for parameter setting, graph and data display.

4. The error calibration system for a wide-band and wide-range current transformer according to claim 1, characterized in that: The wide-band and wide-range standard transformer adopts zero-flux current transformer technology and provides an accuracy of not less than 0.05 within the range of 0.1% to 200% of the rated current.

5. A method for error calibration of a wide-band and wide-range current transformer, characterized in that: The error calibration system of a wide-band and wide-range current transformer according to claim 1 is implemented, comprising the following steps: S1. Make the broadband high current generating device provide working current for the primary side of the broadband wide range current transformer to be tested and the primary side of the broadband wide range standard transformer; S2. The wide-band wide-range current transformer tester collects the standard current signal of the secondary side of the standard current transformer and the current signal to be measured on the secondary side of the wide-band wide-range current transformer to be measured and performs data preprocessing to obtain a digital signal that can be calculated; S3. The wide-band and wide-range current transformer tester performs error calculation based on operable digital signals to obtain the error of the wide-band and wide-range current transformer to be tested.

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