CN112444673A - Frequency measurement method applied to standard meter of electric energy meter calibrating device - Google Patents
Frequency measurement method applied to standard meter of electric energy meter calibrating device Download PDFInfo
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- CN112444673A CN112444673A CN202011249141.9A CN202011249141A CN112444673A CN 112444673 A CN112444673 A CN 112444673A CN 202011249141 A CN202011249141 A CN 202011249141A CN 112444673 A CN112444673 A CN 112444673A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/10—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into a train of pulses, which are then counted, i.e. converting the signal into a square wave
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
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Abstract
The invention discloses a frequency measurement method applied to a standard meter of an electric energy meter calibrating device, which comprises the steps of sampling input voltage of a power source, carrying out digital direct-current filtering processing on voltage sampling data, caching multi-level sampling filtering data, judging zero crossing points according to zero crossing conditions, repeatedly counting two zero crossing points by using a counter, estimating the positions of the zero crossing points by combining the sampling filtering data on two sides of the two zero points, and carrying out frequency calculation. According to the invention, the frequency measurement of the standard meter of the electric energy meter calibrating device does not need a hardware zero-crossing detection circuit, so that the hardware cost is saved; meanwhile, the frequency measurement precision of the standard meter of the electric energy meter calibrating device is improved by a reliable zero-crossing judgment mechanism and a simple and convenient calculation method.
Description
Technical Field
The invention particularly relates to the technical field of frequency measurement, in particular to a frequency measurement method applied to a standard meter of an electric energy meter calibrating device.
Background
The frequency is an important index for representing the operating characteristics of a power system, plays a critical role in the fields of power quality monitoring, power system protection and the like, and the specific 50Hz periodic sine wave is also used for electricity consumption of residents in China. Meanwhile, in the working process of the standard meter of the electric energy meter calibrating device, strict requirements are placed on the measurement of the power consumption frequency, and the waveform frequency output by the power source needs to be measured in real time.
Common frequency measurement generally comprises hardware zero-crossing period counting, software zero-crossing period counting and Fourier transform difference value calculating methods, but the hardware zero-crossing period counting method needs to use a hardware zero-crossing circuit, occupies hardware resources and has higher cost; the precision of software zero-crossing period counting is low; the fourier transform difference calculation method is complex in calculation mode.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the invention provides the frequency measuring method applied to the standard meter of the electric energy meter calibrating device, which can simply, quickly and accurately measure the frequency of the standard meter in the electric energy meter calibrating device, does not occupy hardware resources and saves the cost.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a frequency measurement method applied to a standard meter of an electric energy meter calibrating device specifically comprises the following steps:
step 1: the power source outputs sine wave voltage to access a standard table;
step 2: the standard table program frequency is F, the standard table controls the A/D converter according to the sampling rate FsSampling the power source voltage;
and step 3: filtering the voltage sampling data by digital direct current filtering;
and 4, step 4: carrying out 2 i-level cache on the filtered voltage sampling data, and every time N appears in the sampled and filtered data1,N2,…N2i-1,N2iWhen outputting the zero-crossing signal, and simultaneously outputting Ni、Ni+1；
And 5: counting by the counter, simultaneously detecting whether a zero-crossing signal exists, if no, continuing counting by the counter, and counting the counter value N when the zero-crossing signal is detectedzcAnd sampling the filtered data Ni、Ni+1Step 6 is transmitted, meanwhile, the counter is reset, step 5 is repeated, and sampling filtering data are continuously output;
step 6: according to the current counter value NzcSampled filtered data Ni、Ni+1Sampled filtered data N from the previous timej、Nj+1(with N)j、Nj+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.
Further, the filtered data N is sampled in the step 41,N2,…N2i-1,N2iSatisfies the following conditions: n is a radical of1,N2,…Ni<0，Ni+1,Ni+2,…N2i≥0；
Further, the sampling filtering data N in the step 6i、Ni+1Satisfies the following conditions: n is a radical ofi<0，Ni+1≥0。
Further, the input waveform frequency of the power source in the step 6 is:
the invention has the beneficial technical effects that:
1. the frequency measurement does not need a hardware zero-crossing detection circuit, so that the hardware cost is saved;
2. the zero crossing point position is accurately estimated, and the frequency measurement precision of the standard meter of the electric energy meter calibrating device is improved;
3. complex operations such as Fourier transform and the like are not needed, and the calculation is simpler and more convenient according to a reliable zero-crossing judgment mechanism and zero-crossing point approximate processing.
Drawings
Fig. 1 is a flow chart of a frequency measurement method applied to a standard meter of an electric energy meter calibration device according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
As shown in fig. 1, in particular, it relates to a frequency measurement method applied to a standard meter of an electric energy meter calibrating apparatus, which includes the following steps:
step 1: the power source outputs sine wave voltage to access a standard table.
Step 2: the standard table program frequency is 25MHz, and the standard table controls the A/D converter to sample the power source voltage according to the sampling rate of 100 kHz.
And step 3: digital dc filtering filters the voltage sample data.
In step 3, digital dc filtering is necessary, because of factors such as an a/D converter, unnecessary dc components are introduced into the sampled value, and zero crossing points are inaccurate, so that frequency measurement is inaccurate, and digital dc filtering needs to be added to preprocess the sampled data.
And 4, step 4: carrying out 2 i-level cache on the filtered voltage sampling data, and every time N appears in the sampled and filtered data1,N2,…N2i-1,N2iWhen outputting the zero-crossing signal, and simultaneously outputting Ni、Ni+1。
Wherein in step 4, setting i to be 4, namely when N is1,N2,N3,N4<0 and N5,N6,N7,N8When the voltage is more than or equal to 0, outputting a zero-crossing signal and simultaneously outputting N5、N6. The zero crossing point judged by the embodiment is the zero crossing of the waveform from negative to positive, and if the zero crossing from positive to negative needs to be judged, the judgment condition can be reversely processed; the value of i is not limited to 4, and the value of i can be properly selected according to the harmonic component of the waveform to be measured and the condition of judging the stability of the zero crossing point.
And 5: counting by the counter, simultaneously detecting whether a zero-crossing signal exists, if no, continuing counting by the counter, and counting the counter value N when the zero-crossing signal is detectedzcAnd sampling the filtered data Ni、Ni+1Step 6 is transmitted, meanwhile, the counter is reset, step 5 is repeated, and sampling filtering data are continuously output;
wherein in step 5, the frequency of the input waveform of the power source calculated according to the general calculation method is
The maximum error of the frequency compared with the actual power source input waveform is
For this embodiment, the maximum error ε generated by a general method is used for a 50Hz sine wave to be measured0＝0.05％。
Step 6: according to the current counter value NzcAnd sampling the filtered data Ni、Ni+1And the previous sampled filtered data Ni、Ni+1(previous application of Nj、Nj+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.
Step 6: according to the current counter value NzcSampled filtered data Ni、Ni+1Sampled filtered data N from the previous timej、Nj+1(with N)j、Nj+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.
In summary, the invention discloses a frequency measurement method applied to a standard meter of an electric energy meter calibrating device, so that a hardware zero-crossing detection circuit is not needed in frequency measurement, and the hardware cost is saved; the zero crossing point position is accurately estimated, and the frequency measurement precision of the standard meter of the electric energy meter calibrating device is improved; complex operations such as Fourier transform and the like are not needed, and the calculation is simpler and more convenient according to a reliable zero-crossing judgment mechanism and zero-crossing point approximate processing.
The above-mentioned embodiments are illustrative of the specific embodiments of the present invention, and are not restrictive, and those skilled in the relevant art can make various changes and modifications to the corresponding equivalent technical solutions without departing from the spirit and scope of the present invention, so that all equivalent technical solutions should be included in the scope of the present invention.
Claims (4)
1. A frequency measurement method applied to a standard meter of an electric energy meter calibrating device is characterized by comprising the following steps:
step 1: the power source outputs sine wave voltage to access a standard table;
step 2: the standard table program frequency is F, the standard table controls the A/D converter according to the sampling rate FsSampling the power source voltage;
and step 3: filtering the voltage sampling data by digital direct current filtering;
and 4, step 4: carrying out 2 i-level cache on the filtered voltage sampling data, and every time N appears in the sampled and filtered data1,N2,…N2i-1,N2iWhen the sampling filtering data N is output, the zero-crossing signal is output, and the sampling filtering data N is output at the same timei、Ni+1；
And 5: counting by the counter, simultaneously detecting whether a zero-crossing signal exists, if no, continuing counting by the counter, and counting the counter value N when the zero-crossing signal is detectedzcAnd sampling the filtered data Ni、Ni+1Step 6 is transmitted, meanwhile, the counter is reset, step 5 is repeated, and sampling filtering data are continuously output;
step 6: according to the current counter value NzcSampled filtered data Ni、Ni+1Sampled filtered data N from the previous timej、Nj+1(with N)j、Nj+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.
2. The method for measuring the frequency of the standard meter of the electric energy meter calibrating device according to claim 1, wherein the filtered data N is sampled in the step 41,N2,…N2i-1,N2iSatisfies the following conditions: n is a radical of1,N2,…Ni<0，Ni+1,Ni+2,…N2i≥0。
3. The method for measuring the frequency of the standard meter of the electric energy meter calibrating device according to claim 1, wherein the step 6Sampling the filtered data Ni、Ni+1Satisfies the following conditions: n is a radical ofi<0，Ni+1≥0。
4. The method as claimed in claim 1, wherein the power source input waveform frequency in step 6 is:
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2020
- 2020-11-10 CN CN202011249141.9A patent/CN112444673A/en active Pending
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| CN102116798A (en) * | 2011-03-07 | 2011-07-06 | 深圳市锐能微科技有限公司 | Power grid frequency measurement method and device |
| CN202305785U (en) * | 2011-09-21 | 2012-07-04 | 广东电网公司电力科学研究院 | Calibrating device based on tracing technology for 0.05-level DC electric energy meter |
| CN103634263A (en) * | 2013-12-07 | 2014-03-12 | 天津光电通信技术有限公司 | Continuous-phase frequency-shift keying digital demodulation device and demodulation method implemented by same |
| CN103954924A (en) * | 2014-05-04 | 2014-07-30 | 国家电网公司 | Measuring device and method for measurement errors of electric measurement meter in frequency fluctuation process |
| CN104345294A (en) * | 2014-11-04 | 2015-02-11 | 国家电网公司 | Electric energy meter dynamic performance test device |
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