CN106597100B - A kind of interpolation FFT estimation method of the Wide Area Power dynamic frequency - Google Patents
A kind of interpolation FFT estimation method of the Wide Area Power dynamic frequency Download PDFInfo
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- CN106597100B CN106597100B CN201710043594.8A CN201710043594A CN106597100B CN 106597100 B CN106597100 B CN 106597100B CN 201710043594 A CN201710043594 A CN 201710043594A CN 106597100 B CN106597100 B CN 106597100B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
- G01R23/163—Spectrum analysis; Fourier analysis adapted for measuring in circuits having distributed constants
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Abstract
The invention discloses a kind of interpolation FFT estimation methods of the Wide Area Power dynamic frequency, first, power network signal sample and be weighted using second order maximum side lobe attenuation window to sampled signal, then FFT is done to the signal after weighting and obtains discrete spectrum, the frequency of the window is obtained using three spectral line interpolation algorithms, the frequency of next window is calculated finally by mobile window function, and then calculates frequency change rate, realizes the dynamic frequency estimation of power network signal.This method can realize accurate grid frequency measurement when mains frequency fluctuates, and calculation amount is small.
Description
Technical field
The present invention relates to signal measurement field, the interpolation FFT estimation method of specifically a kind of the Wide Area Power dynamic frequency.
Background technique
With various types of nonlinear loads (high-power rectifying equipment, converter, electric arc furnaces, electric railway with
And home electric etc.) be continuously increased, voltage, current sinusoidal waveform wave phenomenon are on the rise in electric system.In practical feelings
In condition, mains frequency is difficult to keep expected standard frequency, but there are certain fluctuation ranges.Therefore, dynamic sinusoidal signal
The accurate estimation of frequency components is crucial problem urgently to be solved.
Dynamic sinusoidal signal intermediate frequency rate estimation method is gradually turned to from the analog detecting method of early stage with Digital Signal Processing
Russian Market based on technology, as wavelet transformation, Short Time Fourier Transform, artificial neural network, support vector machines and
FFT etc..Spectrum analysis, matched filtering, digital communication, image are widely used in because it is realized simply based on the method for FFT
The various fields such as processing.And be exactly effect of the FFT in terms of spectrum analysis used by this patent, however work as measured signal frequency
When transformation, which occurs, to be led to non-synchronous sampling or carry out non-integer truncation to signal, there are fence effects and spectral leakage by FFT
Phenomenon is unable to satisfy the requirement accurately measured so that calculated signal frequency is inaccurate.For this purpose, the window of function admirable can be selected
Function and the caused error of non-integer truncation for reducing non-synchronous sampling or data to calculated result progress interpolation amendment.
Summary of the invention
The purpose of the invention is in view of the deficienciess of the prior art, provide one kind is easily understood, precision is higher,
The faster frequency estimating methods of calculating speed.
Solution proposed by the present invention are as follows: firstly, sample to power network signal and utilizing second order maximum side lobe attenuation
Window is weighted sampled signal；Then FFT is done to the signal after weighting and obtains discrete spectrum, obtained using three spectral line interpolation algorithms
To the frequency of the window, the frequency of next window is calculated finally by mobile window function, and then calculates frequency change rate, realizes electricity
The dynamic frequency of net signal is estimated.
The interpolation FFT estimation method of the Wide Area Power dynamic frequency proposed by the present invention the following steps are included:
With sample frequency fsPower network signal is sampled, the discrete sampling sequence x (n) that length is N is obtained；Utilize length
Truncation is weighted to x (n) for the second order maximum side lobe attenuation window w (m) of M, obtains the weighting sequence x that length is Mw(m)=x
(m)w(m)；Then to weighting sequence xw(m) it is FFT and obtains discrete spectrum | Xw(m)|；When obtaining this by three spectral line interpolation algorithms
Between power network signal in window frequency；The frequency of future time window is calculated by mobile window function, so that frequency be calculated
Rate change rate realizes power grid Dynamic Frequency Measurement.
The frequency spectrum function of the method, the second order maximum side lobe attenuation window that length is M is
The method, it is by searching for amplitude near fundamental frequency in discrete spectrum that three spectral line interpolation algorithms, which calculate frequency,
Maximum spectral line remembers that its position is l, then its two adjacent position of spectral line is respectively l-1 and l+1, thus can calculate interpolation coefficient
η:Frequency is calculated using interpolation coefficient η are as follows:
The method is calculated the power network signal frequency of future time window by mobile window function, calculates and obtain frequency
Change rate is that the second order maximum side lobe attenuation window that length is M is moved backward M/2 point, is calculated using three spectral line interpolation algorithms
The power network signal frequency of future time window, to calculate frequency change rate are as follows:
L in formulak, ηkRespectively indicate k-th of time window power network signal spectral magnitude maximum spectral line position and three spectral lines
Interpolation coefficient, wherein It indicates to be rounded downwards.
The interpolation FFT estimation method of the Wide Area Power dynamic frequency of the present invention, have be easily understood, calculating speed faster, essence
The features such as higher is spent, the frequency of signal is calculated using windowed interpolation method, to reduce fence effect and spectral leakage to frequency
The influence of calculating calculates frequency change rate by mobile window function, and accurate power grid frequency is realized when mains frequency fluctuates
Rate measurement.
Detailed description of the invention
Fig. 1 is the flow chart for the interpolation FFT estimation method that the present invention realizes the Wide Area Power dynamic frequency；
Fig. 2 is the schematic diagram that the present invention realizes window function mobile computing frequency change rate.
Specific embodiment
The invention proposes a kind of interpolation FFT estimation methods of the Wide Area Power dynamic frequency.Make below in conjunction with attached drawing detailed
Illustrate:
In the present embodiment, the signal of input is provided using the signal generator Agilent 33120A of Agilent company of the U.S.
And it is connected to data collecting card.Data collecting card selects the NI USB-6210 of National Instruments, sample frequency setting
For 4KHz, data conversion digit is 16 and includes 16 signal input channels, and one of input channel and input is selected to believe
Number be connected, NI USB-6210 is connect with computer by USB.Computer uses association's Thinkpad X220 laptop,
National Instruments LabVIEW software, version number 12.0 are installed, computer is connected by USB with NI USB-6210
Afterwards, operation LabVIEW software can receive the discrete sampling sequence x (m) that collected length is N=10240.
As shown in Figure 1, determining sample frequency fs=4kHz, length be M=1024 second order maximum side lobe attenuation window to from
Scattered sample sequence is weighted, and obtains the weighting sequence x that length is Mw(m).Then FFT is carried out to weighting sequence and obtains discrete frequency
Rate | Xw(m) |, by searching for the spectral line of amplitude maximum near fundamental frequency in discrete spectrum, remember that its position is l, then its is adjacent
Two position of spectral line are respectively l-1 and l+1, thus calculate interpolation coefficient η, specific formula for calculation are as follows:Thus the frequency of the time-ofday signals, specific formula for calculation are obtained are as follows:
Such as Fig. 2, window function central instant is tk, moment interpolation coefficient η is calculated by above-mentioned three spectral line interpolations algorithmk
=0.574, frequency fk=52.2250, by the mobile M/2 point of window function, obtain tk+1The interpolation coefficient η at momentk+1=0.580,
Frequency fk+1=52.2391, it is ν=(f by the definition of frequency change ratek+1-fk)/(tk+1-tk), arrangement obtains
Then ν=0.11.
Claims (3)
1. a kind of interpolation FFT estimation method of the Wide Area Power dynamic frequency, it is characterised in that: use sample frequency fsTo power network signal
It is sampled, obtains the discrete sampling sequence x (n) that length is N；Using the second order maximum side lobe attenuation window w (m) that length is M to x
(n) it is weighted truncation, obtains the weighting sequence x that length is Mw(m)=x (m) w (m), then to weighting sequence xw(m) it is FFT
Obtain discrete spectrum | Xw(m)|；The frequency of the power network signal in the time window is obtained by three spectral line interpolation algorithms；Pass through shifting
Dynamic window function calculates the frequency of future time window, so that frequency change rate be calculated, realizes power grid Dynamic Frequency Measurement；
The three spectral line interpolation algorithms calculate frequency be by searching for amplitude maximum spectral line near fundamental frequency in discrete spectrum,
Remember that its position is l, then its two adjacent position of spectral line is respectively l-1 and l+1, it thus can calculate interpolation coefficient η:Frequency is calculated using interpolation coefficient η are as follows:
2. according to the method described in claim 1, it is characterized in that the length is the frequency spectrum of the second order maximum side lobe attenuation window of M
Function is
3. according to the method described in claim 1, it is characterized in that described calculate future time window by mobile window function
Power network signal frequency, calculate obtain frequency change rate, be by length be M second order maximum side lobe attenuation window move backward M/2
It is a, the power network signal frequency of future time window is calculated using three spectral line interpolation algorithms, to calculate frequency change rate are as follows:
Wherein lk, ηkRespectively indicate k-th of time window power network signal spectral magnitude maximum spectral line position and three spectral line interpolations
Coefficient, wherein k=1,2 ..., It indicates to be rounded downwards.
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| CN102680948A (en) * | 2012-05-15 | 2012-09-19 | 东南大学 | Method for estimating modulation frequency and starting frequency of linear frequency-modulated signal |
| CN103675758A (en) * | 2013-12-05 | 2014-03-26 | 东南大学 | Method for estimating cycle slope and starting frequency of hyperbolic frequency modulated signals |
| CN104897961A (en) * | 2015-06-17 | 2015-09-09 | 中南民族大学 | Three spectral line interpolation FFT harmonic wave analysis method and system based on multiplication window function |
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