CN103983852B - Harmonic analysis method of power quality harmonic analyzer - Google Patents
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Abstract
The invention discloses a harmonic analysis method of a power quality harmonic analyzer, wherein the harmonic analysis method is achieved based on the improvement on the quasi-synchronization DFT. The harmonic analysis method comprises the steps that an electrical signal X on which the harmonic analysis needs to be carried out is sampled in a power grid, and data of W+2 sampling points are sampled at equal intervals; when the harmonic analysis is carried out according to the quasi-synchronization DFT, the position of frequency domain sampling is changed according to the drifting value, seen in the specification, of the signal frequency and then the frequency domain sampling position confirms to the value in the specification; the amplitude, seen in the specification, of all harmonics of the electrical signal X and the initial phase angles, seen in the specification, of the harmonics of the electrical signals X are worked out; the amplitude percentage, seen in the specification, of the amplitude Pk of the higher harmonics of the voltage signal V and the current signal I to the amplitude of the fundamental harmonic P1 is worked out, and the phase angle difference seen in the specification is worked out, and the amplitude percentage and the phase angle difference are output and displayed.
Description
The application is Application No.：201110322629.4, invention and created name is《A kind of electric energy quality harmonic analyser
Harmonic analysis method》, the applying date is：The divisional application of the application for a patent for invention on October 21st, 2011.
Technical field
The present invention relates to the technical field of electric energy quality harmonic analysis, specifically a kind of high-precision harmonic analysis method.
Background technology
Frequency analyses technology should in various fields such as electric energy quality monitoring, electronic product production testing, electric appliances monitorings
It is the important technical for carrying out power system monitor, quality inspection, monitoring of tools with extensive.
In power supply grid, the generation of harmonic phenomena is mainly due to large-capacity power equipment, with electric rectification or converter
And other nonlinear-loads are caused.Developing rapidly recently as Power Electronic Technique, many industrial undertakings introduce big
The impact load of amount, asymmetric load and nonlinear load, it is dirty that they inevitably occur harmonic wave when electrical network is accessed
Dye phenomenon.Therefore, voltage to power supply grid, current signal carry out frequency analyses, can preferably observe electric network pollution situation,
And then be that power network compensation and purification provide theoretical foundation.
At present the most widely used technology of frequency analyses is discrete Fourier transform（DFT）And fast Fourier transform
（FFT）.The frequency analyses technology that quasi-synchronous sampling technique and DFT technique combine（I.e.：Plesiochronous DFT frequency analyses technology）Energy
The precision of frequency analyses is enough improved, its formula is：
,
In formula：K is the number of times of the harmonic wave for needing to obtain（Such as fundamental wave k=1,3 subharmonic k=3）；Sin and cos is respectively sine
And cosine function；And akAnd bkThe respectively real part and imaginary part of k subharmonic；N is iterationses；W is determined by integration method, adopted
During muiltiple-trapezoid integration method, W=nN；For a weight coefficient；, it is all weight coefficient sums；F (i) is to divide
The ith sample value of analysis waveform；N is sampling number in the cycle.
In engineer applied, frequency analyses always carry out the sampling of finite point and are difficult to the synchronization of stricti jurise adopting
Sample.So, when frequency analyses are carried out using plesiochronous DFT, will exist due to long scope leakage caused by truncation effect and
Due to short scope leakage caused by fence effect so that analysis result precision is not high, or even insincere.
The content of the invention
The technical problem to be solved in the present invention is to provide a kind of harmonic wave point of the higher electric energy quality harmonic analyser of precision
Analysis method, to be efficiently modified the analytical error of plesiochronous DFT frequency analyses technology, obtains high-precision frequency analyses result, from
And improve the reliability and the effectiveness of condition adjudgement based on the theoretical electric energy quality monitoring equipment of frequency analyses.
To solve above-mentioned technical problem, the invention provides a kind of harmonic analysis method of electric energy quality harmonic analyser,
The electric energy quality harmonic analyser includes what is be sequentially connected：Sensor, signal conditioning circuit, data acquisition circuit and CPU are mono-
Unit；The harmonic analysis method comprises the steps：
（1）The signal of telecommunication X of frequency analyses, and W+2 sampled point of equal interval sampling are needed in the CPU element sampling electrical network
Data f (i), i=0,1 ..., w+1 }（W is determined that the present invention does not specify a certain kind integration method by selected integration method,
Conventional integration method has muiltiple-trapezoid integration method W=nN, complexification rectangular integration method W=n (N-1), iterative Simpson integration
Method W=n (N-1)/2 etc., can select suitable integration method according to the practical situation of present invention application.Typically with complexification
Trapezoidal integration method effect is more satisfactory）；
（2）CPU element starts using plesiochronous DFT formula from the sampled point i=0 of the signal of telecommunication X：
W+1 data of analysis obtain fundamental informationWith；
Then, CPU element starts using plesiochronous DFT formula from the sampled point i=1 of the signal of telecommunication X：
W+1 data of analysis obtain fundamental information；
Using formulaCalculate the frequency drift of the signal of telecommunication X；
Using formula, the fundamental wave and high order of the signal of telecommunication X are drawn respectively
Harmonic wave；
（3）, CPU element calculate the fundamental wave of the signal of telecommunication X and the amplitude of higher hamonic wave respectivelyWith it is first
Phase angle；
（5）, CPU element calculate respectively the signal of telecommunication X higher hamonic wave amplitude PkWith fundamental wave P1Amplitude percentage ratioAnd phase angle difference, and output display（It is general to be shown using the LCD cell being connected with the CPU element
Show）.
The signal of telecommunication X is generally grid ac voltage signal or electrical network ac current signal.
Plesiochronous DFT frequency analyses can effectively suppress long scope to leak, and the main cause of its spectrum leakage is signal
Short scope leakage caused by frequency drift, and the spectral peak peak value that is mainly characterized by of short scope leakage goes out caused by signal frequency drift
Existing position synchronous change with signal frequency drift, so variable fence frequency domain sample effectively can catch according to signal drift
The position that spectral peak peak value occurs, so as to obtain high-precision harmonic information.
Equal interval sampling is the cycle T and frequency f of the ideal signal according to frequency analyses are carried out（Such as power frequency component frequency f
For 50Hz, the cycle is 20mS）, N points, the i.e. sample frequency of sampling in a cycle is fs=Nf, and N >=64.
Described W+2 sample point data of sampling is to make corresponding selection according to selected integration method, according to multiple
Change trapezoidal integration method, then W=nN；According to complexification rectangular integration method, then W=n (N-1)；According to iterative Simpson integration
Method, then W=n (N-1)/2.Then according to sample frequency fs=Nf, obtains sample point data sequence { f (i), i=0,1 ..., w+
1 }, n >=3, finally carry out frequency analyses to the data sequence.
An iteration coefficientDetermined by integration method, ideal period sampled point N and iterationses n, specific derivation process
Referring to document【Dai Xianzhong. some problem [J] in quasi-synchro sampling application. electrical measurement and instrument, 1988, (2):2-7.】.
For all weight coefficient sums.For the imaginary part and real part of k subharmonic, according toJust
Harmonic amplitude and initial phase angle can be obtained.
The drift of signal frequencyIt is the fixation according to sampling number N in neighbouring sample point fundamental wave phase angle difference and ideal period
Relation and obtain, the drift of signal frequencyCan also be used for correcting frequency f of fundamental wave and higher hamonic wave1With the frequency of higher hamonic wave
Rate fk。
Present invention is mainly applied in the analysis software of electric energy quality harmonic analyser, for improving frequency analyses
Quality, obtain amplitude, phase angle and the frequency of high-precision fundamental wave and higher hamonic wave.The present invention is sampled analyzed signal
And analysis, and analysis result（Amplitude, phase angle and frequency etc.）Requirement according to electric energy quality harmonic analyser is exported.The present invention
Electric energy quality harmonic analyser adopt harmonic analysis method, be, based on the frequency analyses technology of variable fence thought, have
Following technical advantage：
（1）High-precision frequency analyses result.The analysis result that frequency analyses technology of the present invention is obtained is either
Amplitude or phase angle error are improved more than 4 orders of magnitude.
（2）Frequency analyses technology of the present invention fundamentally solves the problems, such as that plesiochronous DFT analysis precisions are low, and
The inverting and amendment of complexity need not be carried out, algorithm is simple.
（3）Relative to plesiochronous DFT, frequency analyses technology of the present invention only needs to one sampled point of increase and just solves
Plesiochronous DFT analytical errors big problems, it is easy to accomplish.
（4）Existing instrument and equipment is improved using the present invention, is technically feasible, and need not increase any hard
Part expense can be such that analysis result improves more than 4 orders of magnitude.
（5）Variable fence thought is similarly also applied for carrying out the frequency analyses process of successive ignition rather than an iteration,
Now only needing to an iteration to resolve into that successive ignition realizes just can be with.As an iteration is substantially with successive ignition
, simply when calculating, successive ignition carries out decoupled method, and an iteration is that the process of successive ignition is merged into iteration system
NumberIn once calculate complete, so the present disclosure applies equally to successive ignition process.
（6）The present invention carries out the drift of the position according to signal frequency of frequency analyses time-frequency domain sampling using plesiochronous DFT
And change, i.e., described frequency domain sampling position is 2 π of μ/N, wherein：For the drift of signal frequency, without during driftFor 1.The present invention
Thought of the harmonic analysis method based on variable fence, be to be realized by 5 analytical procedures.The thought of variable fence：It is accurate same
The main cause of step DFT analytical errors is that the drift of signal frequency causes the position that spectrum peak occurs to occur partially with ideal position
Difference, if the analysis result obtained with being sampled in a frequency domain still according to 2 π/N it is extremely incorrect.What variable fence referred to
It is：The position of frequency domain sampling is not fixed 2 π/N, but is changed according to the drift of signal frequency, i.e. frequency sampling position
It is set to 2 π of μ/N（μ is the drift of signal frequency）.Frequency domain sampling fence changes with the drift of signal frequency and can accurately estimate
Go out the position of higher hamonic wave peak value appearance, and then obtain high-precision amplitude and phase angle information.
Specific embodiment
Electric energy quality harmonic analyser is mainly by sensor, signal conditioning circuit, data acquisition circuit, CPU, LCD cell
And corresponding analysis software composition.Sensor typically adopts voltage transformer and current transformer, the high voltage of tested electrical network
Changed by a certain percentage with high current signal；Voltage that signal conditioning circuit sends sensor, current signal are transformed to
The voltage signal of suitable data acquisition circuit sampling；The signal after conditioning is sampled by data acquisition circuit, then is led to by CPU
Cross analysis software to complete the analysis to harmonic wave with detection.
The harmonic analysis method of the electric energy quality harmonic analyser of the present invention, comprises the following steps：
First, the signal of telecommunication X of frequency analyses, and W+2 sampled point of equal interval sampling are needed in CPU element sampling electrical network,
To obtain the discrete serieses { f (k), k=0,1 ..., w+1 } of the signal of telecommunication X.W is by integration method, iterationses n and ideal week
Sampling number N is together decided in phase.Equal interval sampling refers to frequency f according to the ideal signal for carrying out frequency analyses（Such as work
Frequency signal frequency is 50Hz, and the cycle is 20mS）Determine sample frequency fs=Nf, in sample frequency fsIn the presence of in a cycle
Equably sample N points.Usually, periodic sampling point N=64 or more can just obtain preferable frequency analyses result, and iteration is secondary
Number n=3-5 just can obtain comparatively ideal frequency analyses result.Integration method has muiltiple-trapezoid integration method W=nN, complexification rectangle product
Divide method W=n (N-1), Simpson's integration method W=n (N-1)/2 etc. various, can be selected according to practical situation.
Secondly, CPU element starts using plesiochronous DFT formula from the sampled point i=0 of the signal of telecommunication X：W+1 data of analysis obtain fundamental informationWith.Wherein,
An iteration coefficientDetermined by integration method, ideal period sampled point N and iterationses n, andFor all weightings
Coefficient sum.
Then, CPU element starts using plesiochronous DFT formula from the sampled point i=1 of the signal of telecommunication X：
W+1 data of analysis obtain fundamental information。
Then, using formulaCalculate the frequency drift of the signal of telecommunication X
Move.Obtain frequency driftAfterwards, can be according to sample frequency fsCalculate with sampling number N in ideal period and obtain analyzed letter
Number fundamental wave and higher hamonic wave frequency f.
Then, using formula, the fundamental wave of the signal of telecommunication X is calculated respectively
With the real part of higher hamonic waveAnd imaginary part；
CPU element is further according to formula：The fundamental wave and high order for calculating the signal of telecommunication X respectively is humorous
The amplitude of rippleAnd initial phase angle：。
Finally, CPU element calculates respectively amplitude P of the higher hamonic wave of the signal of telecommunication XkWith fundamental wave P1Amplitude percentage
ThanAnd phase angle difference, and output display（It is general to be shown using the LCD cell being connected with the CPU element
Show）.
Those skilled in the art it should be appreciated that the embodiment of the above be intended merely to explanation the present invention, and
Limitation of the invention is not intended as, the present invention can also be changing into more modes, as long as in the connotation model of the present invention
In enclosing, the change, modification to embodiment described above all will fall in the range of claims of the present invention.
Claims (1)
1. a kind of harmonic analysis method of electric energy quality harmonic analyser, it is characterised in that comprise the following steps：
(1), the signal of telecommunication X of frequency analyses is needed in the CPU element sampling electrical network of electric energy quality harmonic analyser, and is adopted at equal intervals
W+2 sample point data of sample：F (i), i=0,1 ..., w+1 }；
(2), CPU element starts using plesiochronous DFT formula from the sampled point i=0 of the signal of telecommunication X：
W+1 data of analysis obtain fundamental informationWith
Then, CPU element starts using plesiochronous DFT formula from the sampled point i=1 of the signal of telecommunication X：
W+1 data of analysis obtain fundamental informationWith
Using formula：
Frequency drift μ of the signal of telecommunication X is calculated, frequency drift μ is according to neighbouring sample point fundamental wave phase angle difference and ideal period
The fixed relationship of interior sampling number N and obtain, frequency drift μ is used to correct frequency f of fundamental wave1With frequency f of higher hamonic wavek；
Using formula：Show that the fundamental wave and high order of the signal of telecommunication X are humorous respectively
The real part a of ripplekWith imaginary part bk；
(3), CPU element calculates respectively the fundamental wave of the signal of telecommunication X and the amplitude of higher hamonic waveAnd initial phase angle
(4), CPU element calculates respectively amplitude P of the higher hamonic wave of the signal of telecommunication XkWith fundamental wave P1Amplitude percentage ratioAnd phase angle differenceAnd output display, shown using the LCD cell being connected with the CPU element；
The signal of telecommunication X is grid ac voltage signal or electrical network ac current signal.
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| CN101900761A (en) * | 2009-11-05 | 2010-12-01 | 中国航天科技集团公司第五研究院第五一四研究所 | High-accuracy non-integer-period sampled harmonic analysis and measurement method |
| CN102128982A (en) * | 2010-12-23 | 2011-07-20 | 东莞市创锐电子技术有限公司 | Harmonic analysis method based on windowed interpolation FFT (Fast Fourier Transform) base frequency tracking technology |
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| JP2006276006A (en) * | 2005-03-01 | 2006-10-12 | Nagoya Institute Of Technology | Harmonic analysis method in power system |
| CN101900761A (en) * | 2009-11-05 | 2010-12-01 | 中国航天科技集团公司第五研究院第五一四研究所 | High-accuracy non-integer-period sampled harmonic analysis and measurement method |
| CN102128982A (en) * | 2010-12-23 | 2011-07-20 | 东莞市创锐电子技术有限公司 | Harmonic analysis method based on windowed interpolation FFT (Fast Fourier Transform) base frequency tracking technology |
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