CN210982602U - High-accuracy three-phase standard electric energy meter with harmonic measurement function - Google Patents
High-accuracy three-phase standard electric energy meter with harmonic measurement function Download PDFInfo
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- CN210982602U CN210982602U CN201921611504.1U CN201921611504U CN210982602U CN 210982602 U CN210982602 U CN 210982602U CN 201921611504 U CN201921611504 U CN 201921611504U CN 210982602 U CN210982602 U CN 210982602U
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Abstract
The utility model provides a high accuracy three-phase standard electric energy meter with harmonic is measured, its three-phase voltage signal sampling circuit, three-phase current signal sampling circuit link to each other with sampling part CPU's input through signal isolation circuit respectively, three-phase current signal sampling circuit is including active compensation current transformer and programme-controlled operational amplifier circuit, sampling part CPU's output links to each other with error calculator, standard table pulse output circuit respectively, human-computer interface CPU, error calculator pass through the serial ports and change RS-485 communication line and be connected with sampling part CPU, human-computer interface CPU and display element, keyboard element link to each other, the output of being examined table pulse input circuit links to each other with the error calculator. The three-phase standard electric energy meter expands the small current range, can improve the measurement precision of small current, can generate fundamental wave or harmonic electric energy, and can be used as a standard for checking the fundamental wave electric energy or the harmonic electric energy of the harmonic electric energy meter.
Description
Technical Field
The utility model relates to a technical field of three-phase electric energy meter, especially a high accuracy three-phase standard electric energy meter with harmonic is measured.
Background
The high-grade three-phase standard electric energy meter with advanced technology at present is based on digital sampling, the sampling frequency is generated according to the captured frequency and the number of sampling points of a cycle, waveform points of three-phase voltage and three-phase current are sampled through a sampling time sequence CPU, and electric quantities such as voltage, current, active power, reactive power, power factors, phases and the like are obtained through calculation. The electric quantities obtained in the calculation process are all full-wave, and the electric quantities of fundamental waves and various harmonics cannot be obtained. Aiming at the use of various harmonic electric energy meters, the standard electric energy meters can not be used as a standard device for verifying the harmonic electric energy meters, and a high-accuracy three-phase standard electric energy meter with harmonic measurement is provided.
Disclosure of Invention
The utility model aims at solving the problem among the prior art, provide a high accuracy three-phase standard electric energy meter with harmonic measurement, expanded the undercurrent range, can improve the measurement accuracy of undercurrent to can produce fundamental wave or harmonic electric energy, can regard as the standard of harmonic electric energy meter inspection fundamental wave electric energy or harmonic electric energy.
In order to achieve the above object, the utility model provides a high accuracy three-phase standard electric energy meter with harmonic is measured, including three-phase voltage signal sampling circuit, three-phase current signal sampling circuit, signal isolation circuit, sampling part CPU, human-computer interface CPU, the display element, keyboard unit, error calculator, examined table pulse input circuit, standard table pulse output circuit, three-phase voltage signal sampling circuit, three-phase current signal sampling circuit link to each other with sampling part CPU's input through signal isolation circuit respectively, and three-phase voltage signal and three-phase current signal are imported respectively to three-phase voltage signal sampling circuit, three-phase current signal sampling circuit includes active compensation current transformer and programme-controlled operational amplifier circuit, and active compensation current transformer includes primary winding N, secondary winding N1 and N2, The device comprises a compensation winding N3 and an excitation winding N4, wherein a primary winding N is connected with a current input terminal, secondary windings N1 and N2 are connected with a sampling resistor R through a relay in a switching mode, a sampling signal is input into a program-controlled operational amplifier circuit, a compensation circuit is connected between the compensation winding N3 and the excitation winding N4, the output end of a sampling part CPU is respectively connected with an error calculator and a standard meter pulse output circuit, a human-computer interface CPU and the error calculator are connected with the sampling part CPU through a serial port-to-RS-485 communication line, the human-computer interface CPU is connected with a display unit and a keyboard unit, and the output end of a detected meter pulse input circuit is connected with the error calculator.
Preferably, the three-phase voltage signal sampling circuit comprises a resistance voltage division circuit, a program-controlled operational amplifier circuit, an ADC conversion circuit and an ADC reference voltage circuit, and the divided signals are amplified by the program-controlled operational amplifier circuit to adapt to full-scale input of ADC input signals.
Preferably, the three-phase current signal sampling circuit further includes an ADC conversion circuit and an ADC reference voltage circuit.
Preferably, the resistance of the three-phase voltage signal sampling circuit and the sampling resistance R of the three-phase current signal sampling circuit both adopt low-temperature floating foil resistance produced by VISIHAY company, the temperature coefficient is 0.05 ppm/DEG C, the ADC conversion circuit adopts an 18-bit AD conversion chip AD7634, the data width is 18-bit, the ADC reference voltage circuit adopts L M399H with extremely low temperature drift, and the temperature drift parameter is 0.5 ppm/DEG C.
Preferably, the number of turns of the secondary winding N1 is 200, and the number of turns of the N2 is 1800.
Preferably, the signal isolation circuit is used for reducing signal interference between the analog circuit and the digital circuit, and the input circuits of the three-phase voltage and the three-phase current are operated by using independent power supplies so as to reduce the signal interference between the phases.
Preferably, the sampling portion CPU has a single-precision floating-point arithmetic unit for shortening an arithmetic time in discrete fourier transform.
The utility model has the advantages that: the utility model discloses a switching of current transformer secondary winding number of turns has expanded the undercurrent range to can calculate through discrete Fourier transform and obtain fundamental wave and each time harmonic electric quantity, produce fundamental wave or harmonic electric energy, can regard as the standard of harmonic electric energy meter inspection fundamental wave electric energy or harmonic electric energy.
The features and advantages of the present invention will be described in detail by embodiments with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic block diagram of a high-accuracy three-phase standard electric energy meter with harmonic measurement according to the present invention;
fig. 2 is the utility model relates to a high accuracy three-phase standard electric energy meter's electric quantity transformer principle with harmonic is measured.
Detailed Description
Referring to fig. 1 and 2 the utility model relates to a high accuracy three-phase standard electric energy meter with harmonic is measured, including three-phase voltage signal sampling circuit 1, three-phase current signal sampling circuit 2, signal isolation circuit 3, sampling part CPU4, human-computer interface CPU5, display element 6, keyboard unit 7, error calculator 8, examined table pulse input circuit 9, standard table pulse output circuit 10, three-phase voltage signal sampling circuit 1, three-phase current signal sampling circuit 2 link to each other with the input of sampling part CPU4 through signal isolation circuit 3 respectively, and three-phase voltage signal and three-phase current signal are inputed to three-phase voltage signal sampling circuit 1, three-phase current signal sampling circuit 2 respectively, three-phase current signal sampling circuit 2 includes active compensation current transformer and programme-controlled operational amplifier circuit, and active compensation current transformer includes primary winding N, the last winding, The secondary winding N1 and N2, compensation winding N3 and excitation winding N4, the primary winding N links to each other with the current input terminal, secondary winding N1 and N2 are connected with sampling resistance R through the relay switching, the sampling signal inputs the programme-controlled operational amplifier circuit, it is connected with a compensation circuit between compensation winding N3 and the excitation winding N4, draw the excitation current with the excitation winding, through the compensation circuit, produce the appropriate compensation current, pour into the compensation winding. The compensation current generates magnetic flux in the auxiliary iron core, the main iron core reaches zero magnetic flux, and therefore errors are reduced, the output end of the sampling part CPU4 is respectively connected with the error calculator 8 and the standard meter pulse output circuit 10, the human-computer interface CPU5 and the error calculator 8 are connected with the sampling part CPU4 through a serial port-to-RS-485 communication line, the human-computer interface CPU5 is connected with the display unit 6 and the keyboard unit 7, and the output end of the detected meter pulse input circuit 9 is connected with the error calculator 8.
Furthermore, the three-phase voltage signal sampling circuit 1 comprises a resistance voltage division circuit, a program-controlled operational amplifier circuit, an ADC conversion circuit and an ADC reference voltage circuit, wherein the divided signals are amplified through the program-controlled operational amplifier circuit so as to adapt to full-scale input of ADC input signals and improve sampling accuracy.
Further, the three-phase current signal sampling circuit 2 further includes an ADC conversion circuit and an ADC reference voltage circuit.
Furthermore, the resistance of the three-phase voltage signal sampling circuit 1 and the sampling resistance R of the three-phase current signal sampling circuit 2 are both low-temperature floating foil resistance produced by VISIHAY company, the temperature coefficient is 0.05 ppm/DEG C, the ADC conversion circuit adopts an 18-bit AD conversion chip AD7634, the data width is 18-bit, the ADC reference voltage circuit adopts L M399H with extremely low temperature drift and the temperature drift parameter is 0.5 ppm/DEG C, the stability of an analog input signal is guaranteed, the resolution of a digital signal converted by the ADC is improved, and the stability and the accuracy of the measurement of a standard electric energy meter are improved.
Further, referring to fig. 2, the number of turns of the secondary winding N1 is 200, and the number of turns of N2 is 1800. In the conventional current range, K1 of a secondary winding N1 is connected to a resistor R, K2 of N1 is switched to K3 of N2 through S1, K4 of N2 is switched to a sampling resistor R through S1, and the sampling resistor R is connected to K1 of N1 and K2 of N2 (2000T). When the small current is in a 20mA range, the sampling resistor R is connected to K1 and K2 (200T) of N1 through switching of S1 and S2, and a voltage signal acquired by the sampling resistor R during small current measurement is improved so as to adapt to full-range input of an ADC input signal and improve sampling accuracy.
Further, the signal isolation circuit 3 is used for reducing signal interference between the analog circuit and the digital circuit, and the input circuits of the three-phase voltage and the three-phase current all use separate power supplies to work so as to reduce the signal interference between the phases.
Furthermore, the sampling part CPU4 adopts STM32F4xx series ARM core with main frequency as high as 168 MHz, and has 32-bit multiplier and divider with single precision floating point arithmetic unit. The discrete Fourier transform needs a large amount of floating point operation, and the CPU is provided with a floating point operation unit, so that the operation time during the discrete Fourier transform is greatly shortened.
The utility model discloses the working process:
the three-phase voltage signal and the three-phase current signal are input into the three-phase voltage signal sampling circuit 1 and the three-phase current signal sampling circuit 2, and the sampling part CPU4 generates sampling time sequence pulse according to the captured input signal frequency and the sampling point number of a cycle to control the ADC conversion rate; the sampling part CPU4 reads sampling point data of three-way voltage and three-way current in an external interrupt program according to the sampling time sequence, and stores the sampling point data into six arrays respectively; in the main cycle program, the data in the six arrays are used for respectively calculating the electric quantities such as voltage, current, active power, reactive power, phase and the like.
When harmonic analysis is needed, discrete Fourier transform is carried out on sampled waveform points, and effective values RMS and phases of fundamental waves and each subharmonic of the waveform signals are obtained through calculation; according to the calculated voltage harmonic effective value
And phaseBit
Effective value of current harmonics
And phase
Calculating harmonic active power and reactive power; the calculation formula is as follows:
effective value of active power
Effective value of reactive power
，
The high-accuracy three-phase standard meter converts power into standard electric energy pulses, and the standard electric energy pulses are output through a standard meter pulse output circuit 10 and serve as the verification standard of the electric energy meter to be detected, and the standard electric energy pulse output can be selected from full-wave active electric energy pulse output, full-wave reactive electric energy pulse output, fundamental wave active electric energy pulse output, fundamental wave reactive electric energy pulse output, harmonic electric energy pulse output and the like. The high-accuracy three-phase standard meter calculates the electric energy error of the electric energy meter to be detected through the error calculator 8, and can finish the verification of the fundamental wave electric energy and the harmonic wave electric energy of the harmonic wave electric energy meter.
The high-accuracy three-phase standard meter expands the small current range (20 mA) and improves the measurement precision of the small current.
The high-accuracy three-phase standard meter generates fundamental wave or harmonic wave electric energy and can be used as a standard for checking the fundamental wave electric energy or the harmonic wave electric energy by the harmonic wave electric energy meter.
The above-mentioned embodiment is right the utility model discloses an explanation, it is not right the utility model discloses a limited, any right the scheme after the simple transform of the utility model all belongs to the protection scope of the utility model.
Claims (7)
1. The utility model provides a high accuracy three-phase standard electric energy meter with harmonic is measured which characterized in that: the three-phase voltage signal sampling circuit comprises a three-phase voltage signal sampling circuit (1), a three-phase current signal sampling circuit (2), a signal isolation circuit (3), a sampling part CPU (4), a human-computer interface CPU (5), a display unit (6), a keyboard unit (7), an error calculator (8), a detected meter pulse input circuit (9) and a standard meter pulse output circuit (10), wherein the three-phase voltage signal sampling circuit (1) and the three-phase current signal sampling circuit (2) are respectively connected with the input end of the sampling part CPU (4) through the signal isolation circuit (3), the three-phase voltage signal and the three-phase current signal are respectively input into the three-phase voltage signal sampling circuit (1) and the three-phase current signal sampling circuit (2), the three-phase current signal sampling circuit (2) comprises an active compensation current transformer and a program control operational amplifier circuit, and the active compensation current transformer comprises a primary winding N, a, The secondary winding N1 and N2, compensation winding N3 and excitation winding N4, primary winding N links to each other with current input terminal, and secondary winding N1 and N2 are connected with sampling resistance R through the relay switching, and the programme-controlled operational amplifier circuit of sampling signal input is connected with a compensation circuit between compensation winding N3 and the excitation winding N4, the output of sampling part CPU (4) links to each other with error calculator (8), standard table pulse output circuit (10) respectively, human-computer interface CPU (5), error calculator (8) are connected with sampling part CPU (4) through serial ports commentaries on classics RS-485 communication line, human-computer interface CPU (5) and display element (6), keyboard element (7) link to each other, the output of examined table pulse input circuit (9) links to each other with error calculator (8).
2. A high accuracy three-phase standard electric energy meter with harmonic measurement as in claim 1, wherein: the three-phase voltage signal sampling circuit (1) comprises a resistance voltage division circuit, a program control operational amplifier circuit, an ADC conversion circuit and an ADC reference voltage circuit, wherein the divided signals are amplified through the program control operational amplifier circuit so as to adapt to full-scale input of ADC input signals.
3. A high accuracy three-phase standard electric energy meter with harmonic measurement as in claim 2, wherein: the three-phase current signal sampling circuit (2) further comprises an ADC conversion circuit and an ADC reference voltage circuit.
4. The three-phase standard electric energy meter with high accuracy of harmonic measurement according to claim 3, wherein the resistance of the three-phase voltage signal sampling circuit (1) and the sampling resistance R of the three-phase current signal sampling circuit (2) both adopt low temperature floating foil resistance produced by VIHAY company, the temperature coefficient is 0.05 ppm/DEG C, the ADC conversion circuit adopts an 18-bit AD conversion chip AD7634, the data width is 18-bit, the ADC reference voltage circuit adopts L M399H with extremely low temperature drift, and the temperature drift parameter is 0.5 ppm/DEG C.
5. A high accuracy three-phase standard electric energy meter with harmonic measurement as in claim 1, wherein: the number of turns of the secondary winding N1 is 200, and the number of turns of the secondary winding N2 is 1800.
6. A high accuracy three-phase standard electric energy meter with harmonic measurement as in claim 1, wherein: the signal isolation circuit (3) is used for reducing signal interference between the analog circuit and the digital circuit, and the input circuits of three-phase voltage and three-phase current all use independent power supplies to work.
7. A high accuracy three-phase standard electric energy meter with harmonic measurement as in claim 1, wherein: the sampling section CPU (4) has a single-precision floating-point arithmetic unit.
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| CN201921611504.1U CN210982602U (en) | 2019-09-26 | 2019-09-26 | High-accuracy three-phase standard electric energy meter with harmonic measurement function |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110531153A (en) * | 2019-09-26 | 2019-12-03 | 浙江涵普电力科技有限公司 | A kind of high accuracy three-phase standard electric energy meter with harmonic measure |
| CN112763969A (en) * | 2020-12-30 | 2021-05-07 | 深圳供电局有限公司 | Device and method for detecting field harmonic electric energy metering error |
-
2019
- 2019-09-26 CN CN201921611504.1U patent/CN210982602U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110531153A (en) * | 2019-09-26 | 2019-12-03 | 浙江涵普电力科技有限公司 | A kind of high accuracy three-phase standard electric energy meter with harmonic measure |
| CN112763969A (en) * | 2020-12-30 | 2021-05-07 | 深圳供电局有限公司 | Device and method for detecting field harmonic electric energy metering error |
| CN112763969B (en) * | 2020-12-30 | 2023-08-15 | 深圳供电局有限公司 | Device and method for detecting field harmonic electric energy metering error |
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