CN104833844A - Alternating-current effective value sampling measurement method - Google Patents
Alternating-current effective value sampling measurement method Download PDFInfo
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- CN104833844A CN104833844A CN201510237666.3A CN201510237666A CN104833844A CN 104833844 A CN104833844 A CN 104833844A CN 201510237666 A CN201510237666 A CN 201510237666A CN 104833844 A CN104833844 A CN 104833844A
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Abstract
The invention provides an alternating-current (AC) effective value sampling measurement method comprising the following steps: step 1, calculating a first amplitude value of each frequency component according to sampling data obtained by performing A/D sampling on an AC electrical signal to be measured; step 2, compensating the first amplitude value of each frequency component to obtain a second amplitude value of each frequency component; and step 3, obtaining the total effective value and the AC/DC total effective value of the AC electrical signal to be measured according to the second amplitude values of the frequency components. According to the invention, the amplitude of each frequency component is calculated according to the AD sampling data, and then the amplitude of each frequency component is compensated, so as to improve the measurement accuracy of the amplitude of each frequency component. The total effective value is calculated by a root-mean-square method according to the amplitude of each frequency component. By adopting the method of the invention, the problem that an A/D converter brings different amplitude attenuation to different frequency signals due to the unavoidable aperture time in the existing method is effectively solved. The method of the invention can be used for precision measurement of the AC effective value and harmonic analysis.
Description
Technical field
The present invention relates to a kind of measuring method, particularly, relate to a kind of sampled measurements method of effective value of alternating current.
Background technology
The measuring method of current effective value of alternating current can be divided into two kinds.
The first common method is: be by thermoelectricity equivalency transform principle, by thermoelectric converter, convert alternating current become direct current.Survey galvanic amplitude and be AC value.Below list the some patents involved by the method:
A kind of real effective A.C. voltmeter disclosed in the utility model patent 201320195662.X that Chengdu Zhangwo Mobile Information Technology Co., Ltd. applied on April 18th, 2013.
The patent 87209290 that Shen Yufeng applied on June 20th, 1987 discloses a kind of Multifunctional true effective value voltagemeter.
A kind of device of the measurement effective value of alternating current for experimental teaching disclosed in the patent 201010170561.8 that Miao Gengping applied on May 12nd, 2010, feature is provided with resistance element R1 at outer casing frontispiece, rheostat R and sinusoidal ac, three couples of output connection stake aa ' of direct current and rectangle alternating current three kinds of power supplys, bb ', cc ', one end of rheostat R is connected with the binding post e of resistance element R1, the other end is connected as the crocodile clip g of binding clip with one, the binding post f of R1 is connected with another crocodile clip g ', the probe of resistance element R1 and thermal effect measurement mechanism faces, the binding post e of R1, f is connected with oscillograph, crocodile clip g and g ' experimentally can require the three butted line stake aa ' clipping to three kinds of power supplys respectively, bb ', on cc ', the reading of thermal effect measurement mechanism can become one-to-one relationship with the effective value of voltage on resistance element R1.
The patent 200410101017.2 that Huawei Tech Co., Ltd applied on Dec 2nd, 2004 discloses a kind of method and apparatus measuring alternating current, in order to measure frequency and the effective value of single-phase alternating current.Described method comprises the following steps: that by tested AC signal rectification be half-wave voltage signal; Described half-wave voltage signal is shaped as the square-wave signal of same frequency; Add up described square-wave signal umber of pulse, the peak value of described half-wave voltage signal of sampling; Frequency and the effective value of described tested AC signal is determined according to statistical value and sampled value.Described measurement mechanism comprises: be the half-wave rectifying circuit of half-wave voltage signal by the AC signal rectification of input; Export the schmidt trigger circuit of a square-wave signal; The peak value of described half-wave voltage signal of sampling, adds up the umber of pulse of described square-wave signal, and determines the frequency of described AC signal and the metering circuit of effective value according to sampled value and statistical value.Application the method for the invention and device can safe ready, the frequency of high-acruracy survey single-phase alternating current and effective values.
Second method is: directly carry out quick sampling to interchange with analog to digital converter, then calculates AC value by the data of sampling.The patent that the method relates to has:
Hao Yushan discloses a kind of alternating current physical quantity telemetering device in the patent 201110161132.9 that on June 9th, 2011 applies for, comprising: analog sampling passage, for input AC electricity, carries out analog sampling to export analog sampling value; Sampling switch, for double sampling, to obtain the telemetry frequency that receiver side needs; Register, for storing the double sampling value from sampling switch; Bus, for outputting to receiver side by the double sampling value in described register; With timing controller for controlling the double sampling frequency of described analog sampling passage and sampling switch; It is characterized in that: also comprise wave digital lowpass filter, input connect analog sampling passage export analog sampling value, export connect sampling switch, for the high fdrequency component in filtering sampled value, its cutoff frequency should be less than the double sampling frequency of the sampling switch of 0.5 times.The present invention gives corresponding method.
Wherein, the shortcoming of existence:
The shortcoming of first method is that response speed is slow, and measured result, for exchanging total effective value, cannot analyze the effective value of each harmonic component in signal.
Second method can draw the effective value of AC signal, if but AC signal is broadband signal time, its result is by the more difficult improve of restriction accuracy of A/D converter.Adopting A/D converter directly to carry out analog-to-digital process to AC signal is not fluid shock response.There is an inevitable aperture time in the internal electron switch of A/D sampling holder control inputs signal and holding capacitor break-make.
Summary of the invention
For defect of the prior art, the object of this invention is to provide a kind of method of sampled measurements effective value of alternating current.The existence of aperture time can cause the amplitude attenuation of tested AC signal, and tested AC signal frequency differential declines ratio is also different.Therefore, find out attenuation function relation and just can carry out effective compensation, to improve accuracy of measurement.
According to the method for a kind of sampled measurements effective value of alternating current provided by the invention, comprising:
Step 1, surveys ac signal and carries out the sampled data that A/D sampling obtains according to treating and calculate the first range value of each frequency component;
Step 2, compensates the second range value obtaining each frequency component respectively to the first range value of each frequency component;
Step 3, obtains total effective value and the total effective value of alternating current-direct current of described ac signal to be measured according to the second range value of each frequency component.
As a kind of embodiment, described step 1 comprises further: carry out to described sampled data the first range value that keystone frequency analysis obtains described each frequency component; Described frequency component comprises DC component, first-harmonic angular frequency component and each harmonic angular frequency component.
As a kind of embodiment, between described step 1 and step 2, also comprise Δ t aperture time obtaining A/D sampling holder; Described acquisition A/D sampling holder Δ aperture time t process comprise: the input signal of sampling as A/D with the periodic signal that the bipolarity mean value that function generator produces is 0, in the cycle of adjustment signal, signal period when making A/D sampled value be always 0 is Δ t described aperture time.
As a kind of embodiment, described step 2 comprises further: according to penalty function G (ω
n) to described each frequency component ω
nthe first range value compensate, described penalty function
described ω
nfor described frequency component, described Δ t is aperture time;
First range value of described each frequency component comprises DC component first amplitude A
0, first-harmonic first amplitude A
1with each harmonic first amplitude A
namplitude;
The second range value carrying out the described each frequency component after described compensation comprises: DC component second amplitude A
0', first-harmonic second amplitude A
1' and each harmonic second amplitude A
n';
Wherein, A
0'=A
0,
As a kind of embodiment, described step 3 comprises further: the total effective value A obtaining described ac signal to be measured according to the second amplitude of each frequency component
aC:
wherein n is the maximum times of frequency analysis;
And the total effective value A of alternating current-direct current:
wherein n is the maximum times of frequency analysis.
Compared with prior art, the present invention has following beneficial effect:
The present invention calculates the amplitude of each frequency component by A/D sampled data, then compensates respectively each frequency component amplitudes, improves the accuracy of each frequency component amplitudes.According to frequency component amplitudes, calculate total effective value by root mean square method.The method effectively solves the different amplitude attenuations brought different frequency signals that A/D converter in second method causes inevitable aperture time.
Accompanying drawing explanation
In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, accompanying drawing in the following describes is only some embodiments of the present invention, for those skilled in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.In accompanying drawing:
Fig. 1 is the principle schematic produced aperture time;
Fig. 2 be △ t constant time the amplitude attenuation of input signal and input signal angular frequency between relation;
Fig. 3 be frequency input signal ω constant time the amplitude attenuation of input signal and aperture time △ t between relation;
Fig. 4 is the comparison test mesoporous time when being 30us, and the first amplitude before actual measurement compensates and the second amplitude after compensating are relative to the result curve of high precision thermoelectricity conversion transposition 792A standard value;
Fig. 5 is the method flow diagram of a kind of sampled measurements effective value of alternating current in embodiment.
Embodiment
Hereafter in the mode of specific embodiment, the present invention is described in detail by reference to the accompanying drawings.Following examples will contribute to those skilled in the art and understand the present invention further, but not limit the present invention in any form.It should be pointed out that the embodiment that can also use other, or the amendment on 26S Proteasome Structure and Function is carried out to the embodiment enumerated herein, and can not depart from the scope and spirit of the present invention.
One, the aperture time of sampling holder (SHA)
As shown in Figure 1, in this patent, Δ t aperture time of sampling holder (SHA) is that sample-hold switch K becomes the time interval of high impedance from Low ESR.Within aperture time, voltage in keeping capacitor continues to follow input signal f (t) change, at the end of aperture time, virtual voltage f ' (t+ Δ t) in keeping capacitor depends on the slew rate of input signal and the integration time constant RC of sampling holder, wherein, C is the equivalent output resistance of holding capacitor, the input channel be connected with electric capacity when R is sample-hold switch low-resistance.
Two, aperture time is to the impact analysis of measurement result:
Suppose that input signal is
When t is sampled to it, ideal state down-sampled values is f (t), due to the existence of Δ t aperture time, supposes that sampled value becomes the mean value f ' of input signal within the Δ t time (t+ Δ t), that is:
Can be obtained by (1) and (3):
From (4), f ' (t+ Δ t) amplitude compared with f (t) exists
decay, phase place exist
time delay.Right
mould take the logarithm:
By formula (5) can input the amplitude attenuation of periodic signal and signal frequency ω and aperture time Δ t jointly determine.Relation when having illustrated in Fig. 2 that △ t is constant between the amplitude attenuation of input signal and input signal angular frequency, in Fig. 2, ordinate is the amplitude attenuation of input signal, horizontal ordinate is the amplitude attenuation value that the amplitude attenuation of angular frequency/(the 2* π * 50Hz) of input signal, ω/(2* π * 50Hz)=11 correspondences is obviously greater than ω/(2* π * 50Hz)=41 correspondences.From formula (5):
1., when fixing Δ t aperture time, the decay of the measured signal amplitude that sampling obtains increases along with the increase of its signal frequency ω.The aperture time of same sampling hardware system is generally constant, if survey input exchange signal containing multiple frequency component time, the amplitude attenuation that different frequency is corresponding is not identical, compensates according to the relation of this patent (5) formula respectively and can improve measurement accuracy varying input signal frequency.Suppose that Δ t=30us is constant, ω=2 π * 50Hz*n (n=1 ~ 60), then can obtain Fig. 2 curve according to (5) formula.
2. and when detected input signals frequencies omega one timing, amplitude attenuation by along with aperture time Δ t reduction and reduce, the bandwidth of sampling hardware system will increase thereupon, also will be more responsive to noise.So, suitable aperture time can be selected according to actual signal frequency content during sampling.Suppose that ω=2 π * 50Hz is constant, Δ t=10us*n (n=1 ~ 100), then can obtain Fig. 3 curve according to (5) formula.
Three, solution provided by the invention
In order to the problem that the resolving aperture time impacts measurement result, the invention provides a kind of embodiment of method of sampled measurements effective value of alternating current, comprising:
Step 1, surveys ac signal and carries out the sampled data that A/D sampling obtains according to treating and calculate the first range value of each frequency component;
Step 2, compensates the second range value obtaining each frequency component respectively to the first range value of each frequency component;
Step 3, obtains total effective value and the total effective value of alternating current-direct current of described ac signal to be measured according to the second range value of each frequency component.
As a kind of embodiment, described step 1 comprises further: carry out to described sampled data the first range value that keystone frequency analysis obtains described each frequency component; Described frequency component comprises DC component, first-harmonic angular frequency component and each harmonic angular frequency component.
The present invention carries out A/D sampling and fft algorithm can also be adopted to carry out frequency analysis calculating.But the frequency analysis of the present embodiment keystone can avoid spectral leakage limitation during fft algorithm non-synchronous sampling.
As a kind of embodiment, between described step 1 and step 2, also comprise Δ t aperture time obtaining A/D sampling holder; Described acquisition A/D sampling holder Δ aperture time t process comprise: the input signal of sampling as A/D with the periodic signal that the bipolarity mean value that function generator produces is 0, in the cycle of adjustment signal, signal period when making A/D sampled value be always 0 is Δ t described aperture time.
Periodic signal described in the present embodiment can be as square wave, sinusoidal wave, triangular wave etc.
As a kind of embodiment, described step 2 comprises further: according to penalty function G (ω
n) to described each frequency component ω
nthe first range value compensate, described penalty function
described ω
nfor described frequency component, described Δ t is aperture time;
First range value of described each frequency component comprises DC component first amplitude A
0, first-harmonic first amplitude A
1with each harmonic first amplitude A
namplitude;
The second range value carrying out the described each frequency component after described compensation comprises: DC component second amplitude A
0', first-harmonic second amplitude A
1' and each harmonic second amplitude A
n';
Wherein, A
0'=A
0,
As a kind of embodiment, described step 3 comprises further: the total effective value A obtaining described ac signal to be measured according to the second amplitude of each frequency component
aC:
wherein n is the maximum times of frequency analysis;
And the total effective value A of alternating current-direct current:
wherein n is the maximum times of frequency analysis.
Be applied in the embodiment of electric energy quality harmonic analyser in a kind of sampled measurements effective value of alternating current method provided by the invention, as shown in Figure 1, comprise:
Step 1, sample to the input signal containing multiple harmonic with sigma-delta type A/D converter, sample frequency is undertaken by software the aperture time of 25kHz. A/D converter used, is set to 30us in present case.The first range value A of direct current, first-harmonic and (2 ~ 60) secondary frequency components is calculated according to the DFT algorithm of surveyed sampled data application keystone
0, A
1... A
n(n=2 ~ 60).Described DFT refers to discrete Fourier transformation (Discrete Fourier Transform, is abbreviated as DFT)
Step 2, adjusts the square-wave signal cycle near 30us, and using this signal as input, square-wave signal cycle when making A/D converter sampled value be always 0 is actual measurement Δ t aperture time.The actual measurement of the present embodiment mesoporous time is 30.04 microseconds.
Step 3, according to the fundamental frequency ω of surveyed input signal
1with Δ t aperture time, by formula
calculate penalty coefficient G (ω during n=1 ~ 60
n).Again by penalty coefficient G (ω
n) the first range value of each frequency component is compensated respectively to the second range value obtaining each frequency component.
Step 4, obtains total effective value and the total effective value of alternating current-direct current of described ac signal to be measured according to the second range value of each frequency component.
Four, contrast experiment
The more accurate AC-DC conversion standard of generally acknowledging at present is realized by thermoelectric converter, and thermoelectric converter can compare the Joule heat that AC and DC produces, and uncertainty reaches 10
-7.Contrast, with the value of 792A for standard value with this method and high precision thermoelectric conversion arrangement 792A.In contrast experiment, the aperture time of A/D converter is 30 μ s, by the AC signal of survey frequency from 50Hz to 3kHz, the first amplitude obtained increases decay with signal frequency and obviously becomes large, but the second amplitude after the compensation method that this patent proposes compensates differs within 10ppm with the result of 792A.See Fig. 4.The method effectively solves the different amplitude attenuations brought different frequency signals that A/D converter in existing method causes inevitable aperture time.Can be used in the precision measurement of AC value and frequency analysis.
The foregoing is only preferred embodiment of the present invention, those skilled in the art know, without departing from the spirit and scope of the present invention, can carry out various change or equivalent replacement to these characteristic sum embodiments.In addition, under the teachings of the present invention, can modify to adapt to concrete situation and material to these characteristic sum embodiments and can not the spirit and scope of the present invention be departed from.Therefore, the present invention is not by the restriction of specific embodiment disclosed herein, and the embodiment in the right of all the application of falling into all belongs to protection scope of the present invention.
Claims (5)
1. a method for sampled measurements AC value, is characterized in that, comprising:
Step 1, surveys ac signal and carries out the sampled data that A/D sampling obtains according to treating and calculate the first range value of each frequency component;
Step 2, compensates the second range value obtaining each frequency component respectively to the first range value of each frequency component;
Step 3, obtains total effective value and the total effective value of alternating current-direct current of described ac signal to be measured according to the second range value of each frequency component.
2. the method for a kind of sampled measurements AC value according to claim 1, it is characterized in that, described step 1 comprises further: carry out to described sampled data the first range value that keystone frequency analysis obtains described each frequency component; Described frequency component comprises DC component, first-harmonic angular frequency component and each harmonic angular frequency component.
3. the method for a kind of sampled measurements AC value according to claim 1, is characterized in that, also comprises Δ t aperture time obtaining A/D sampling holder between described step 1 and step 2; Described acquisition A/D sampling holder Δ aperture time t process comprise: the input signal of sampling as A/D with the periodic signal that the bipolarity mean value that function generator produces is 0, in the cycle of adjustment signal, signal period when making A/D sampled value be always 0 is Δ t described aperture time.
4. the method for a kind of sampled measurements AC value according to claim 1, it is characterized in that, described step 2 comprises further: according to penalty function G (ω
n) to described each frequency component ω
nthe first range value compensate, described penalty function
described ω
nfor described frequency component, described Δ t is aperture time;
First range value of described each frequency component comprises DC component first amplitude A
0, first-harmonic first amplitude A
1with each harmonic first amplitude A
namplitude;
The second range value carrying out the described each frequency component after described compensation comprises: DC component second amplitude A
0', first-harmonic second amplitude A
1' and each harmonic second amplitude A
n';
Wherein, A
0'=A
0,
5. the method for a kind of sampled measurements AC value according to claim 4, it is characterized in that, described step 3 comprises further: the total effective value A obtaining described ac signal to be measured according to the second amplitude of each frequency component
aC:
wherein n is the maximum times of frequency analysis;
And the total effective value A of alternating current-direct current:
wherein n is the maximum times of frequency analysis.
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Cited By (3)
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| CN105699738A (en) * | 2016-03-07 | 2016-06-22 | 温州大学 | PWM-based AC signal effective value measurement method |
| CN109975598A (en) * | 2019-02-13 | 2019-07-05 | 温州大学 | A kind of periodic signal effective value measurement circuit |
| CN110320405A (en) * | 2019-07-05 | 2019-10-11 | 厦门高瑞特电气自动化有限公司 | A kind of method of sampling and sampling system of super width power frequency analog signals |
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| CN109975598A (en) * | 2019-02-13 | 2019-07-05 | 温州大学 | A kind of periodic signal effective value measurement circuit |
| CN110320405A (en) * | 2019-07-05 | 2019-10-11 | 厦门高瑞特电气自动化有限公司 | A kind of method of sampling and sampling system of super width power frequency analog signals |
| CN110320405B (en) * | 2019-07-05 | 2021-07-09 | 厦门高瑞特电气自动化有限公司 | Sampling method and sampling system for ultra-amplitude power frequency analog quantity signal |
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