CN109374968A - A kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation - Google Patents
A kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation Download PDFInfo
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- CN109374968A CN109374968A CN201811531707.XA CN201811531707A CN109374968A CN 109374968 A CN109374968 A CN 109374968A CN 201811531707 A CN201811531707 A CN 201811531707A CN 109374968 A CN109374968 A CN 109374968A
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The embodiment of the invention discloses a kind of VFTO frequency spectrum analysis methods based on STFT-WVD transformation, it the described method comprises the following steps: the time domain waveform of VFTO is subjected to STFT time-frequency conversion and WVD time-frequency conversion respectively, obtain the identical STFT matrix of dimension and WVD matrix；Selected threshold, by the element binaryzation of STFT matrix；The cross term that WVD matrix is eliminated using the STFT matrix after binaryzation, obtains the time-frequency spectrum of VFTO；According to the amplitude versus time feature of the Time-frequency Spectrum Analysis VFTO frequency for including and each frequency component.The present invention eliminates the cross term interference in WVD transformation by the STFT of binaryzation, on the basis of keeping WVD transformation highest time-frequency locality, eliminates WVD and converts existing cross-interference terms, have better time frequency analysis performance.
Description
Technical field
The present invention relates to digital signal processing technique field, specifically a kind of VFTO frequency based on STFT-WVD transformation
Spectral analysis method.
Background technique
GIS (Gas Insulated Substation, gas insulated transformer substation) be it is a kind of by disconnecting switch, breaker,
The high voltage electric equipments such as bus and voltage transformer are enclosed in metal-back, are then charged with technology of the SF6 gas as insulation.
In GIS substation, since the movement velocity of isolation switch contact is lower, in the mistake of closing or opening small capacitances electric current
Cheng Zhong, it may occur that tens of times or even hundreds of times arc reignitions, and then generate VFTO (Very Fast Transient
Overvoltage, very fast transient overvoltage).VFTO includes frequency content abundant, when some of them frequency content and winding
When the resonance frequency of class equipment matches, resonance overvoltage can be generated in the turn-to-turn of winding, threaten the insulation safety of equipment.In order to
Targetedly inhibit the specific frequency ingredient for including in VFTO, it is necessary to analyze the spectrum signature of VFTO.
From the point of view of frequency domain, the spectrum signature of VFTO is changed over time, i.e. different moments include different frequency contents.
And Fourier transformation is a kind of integral transformation of time domain, analysis is spectrum signature in a period of time, is not suitable for VFTO's
Spectrum analysis.For the non-stationary characteristic of VFTO, Time-Frequency Analysis Method is suitable for its spectrum analysis.Time-Frequency Analysis Method is from time domain
The shortcomings that VFTO is analyzed, overcomes Fourier transformation well with two aspects of frequency domain.
In all time-frequency conversion methods, WVD transformation possesses highest time-frequency locality, can obtain than Fourier in short-term
The better time frequency analysis result such as transformation, wavelet transformation.But it is directed to this kind of signal comprising multiple frequency components of VFTO, WVD becomes
It changes and there are problems that cross term interference, seriously affected its time frequency analysis performance.
Summary of the invention
A kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation is provided in the embodiment of the present invention, it is existing to solve
The problem of in technology, WVD is converted there are cross term interference, influences VFTO time frequency analysis performance.The present invention passes through binaryzation
STFT eliminates the cross term interference in WVD transformation, can obtain the VFTO time-frequency spectrum with good time-frequency locality.
In order to solve the above-mentioned technical problem, the embodiment of the invention discloses following technical solutions:
The present invention provides a kind of VFTO frequency spectrum analysis methods based on STFT-WVD transformation, and the method includes following steps
It is rapid:
The time domain waveform of VFTO is subjected to STFT time-frequency conversion and WVD time-frequency conversion respectively, obtains the identical STFT of dimension
Matrix and WVD matrix；
Selected threshold, by the element binaryzation of STFT matrix；
The cross term that WVD matrix is eliminated using the STFT matrix after binaryzation, obtains the time-frequency spectrum of VFTO；
According to the amplitude versus time feature of the Time-frequency Spectrum Analysis VFTO frequency for including and each frequency component.
Further, the time domain waveform of VFTO is subjected to the STFT matrix that STFT time-frequency conversion obtains are as follows:
In formula, x (τ) is the time domain waveform of VFTO, and h (t) is window function.
Further, the time domain waveform of VFTO is subjected to the WVD matrix that WVD time-frequency conversion obtains are as follows:
Further, the choosing method of the threshold value are as follows:
According to research purpose or field experience, the amplitude that the frequency of harm is generated to equipment is determined, selected threshold value is less than should
Amplitude.
Further, the detailed process by STFT matrix element binaryzation are as follows:
In formula, λ is threshold value.
Further, the STFT matrix using after binaryzation eliminates the detailed process of the cross term of WVD matrix are as follows:
By the element multiplication of STFT matrix and WVD matrix same position after binaryzation.
Further, the time-frequency spectrum of the VFTO are as follows:
STFT-WVDx(w, t)=STFT2(w,t)·WVDx(w,t)；
In formula, same position element multiplication in representing matrix.
The effect provided in summary of the invention is only the effect of embodiment, rather than invents all whole effects, above-mentioned
A technical solution in technical solution have the following advantages that or the utility model has the advantages that
1, the time domain waveform of VFTO is subjected to STFT time-frequency conversion and WVD time-frequency conversion respectively, and using after binaryzation
STFT matrix eliminates the cross term in WVD matrix, on the basis of keeping WVD transformation highest time-frequency locality, eliminates WVD change
Existing cross-interference terms are changed, there is better time frequency analysis performance.
2, suitable threshold value is chosen by STFT matrix binaryzation, when threshold value is chosen, it is contemplated that the major frequency components of VFTO
With frequency content of concern, the STFT matrix after binaryzation is multiplied with the respective items of WVD matrix: when the STFT square of binaryzation
When a certain element of battle array is 1, the corresponding frequency content necessary being of the element, by being multiplied with WVD matrix corresponding element, WVD square
Battle array same position element remains unchanged, then the actual frequency ingredient in WVD transformation remains unchanged；When the STFT matrix of binaryzation
When one element is 0, the corresponding frequency content of the element is not present or is not the frequency content being concerned about, by corresponding with WVD matrix
Element multiplication, WVD matrix same position element set 0, then eliminate false frequency content that may be present in WVD transformation.It is ingenious
The WVD that eliminates convert existing cross-interference terms.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, for those of ordinary skill in the art
Speech, without creative efforts, is also possible to obtain other drawings based on these drawings.
Fig. 1 is the flow diagram of the method for the invention embodiment.
Specific embodiment
In order to clarify the technical characteristics of the invention, below by specific embodiment, and its attached drawing is combined, to this hair
It is bright to be described in detail.Following disclosure provides many different embodiments or example is used to realize different knots of the invention
Structure.In order to simplify disclosure of the invention, hereinafter the component of specific examples and setting are described.In addition, the present invention can be with
Repeat reference numerals and/or letter in different examples.This repetition is that for purposes of simplicity and clarity, itself is not indicated
Relationship between various embodiments and/or setting is discussed.It should be noted that illustrated component is not necessarily to scale in the accompanying drawings
It draws.Present invention omits the descriptions to known assemblies and treatment technology and process to avoid the present invention is unnecessarily limiting.
VFTO is a kind of non-stationary signal, needs to carry out spectrum analysis using Time-Frequency Analysis Method.In all time-frequency conversions
In method, WVD transformation possesses highest time-frequency locality.The embodiment of the present invention is keeping WVD transformation highest time-frequency locality
On the basis of, it eliminates WVD and converts existing cross term interference, possess time frequency analysis performance more better than STFT and wavelet transformation.
The embodiment of the present invention can satisfy the requirement of VFTO spectrum analysis, to help the frequency of GIS design and operations staff's understanding VFTO
Spectrum signature, and targetedly inhibit the harmful frequency content of VFTO.
As shown in Figure 1, a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation of the invention, including following step
It is rapid:
The time domain waveform of VFTO is carried out STFT time-frequency conversion and WVD time-frequency conversion respectively, it is identical to obtain dimension by S1
STFT matrix and WVD matrix.
Assuming that the time domain waveform of VFTO is x (t), VFTO time domain waveform is subjected to STFT time-frequency conversion, obtained STFT square
Battle array are as follows:
In formula, h (t) is window function.
VFTO time domain waveform is subjected to WVD time-frequency conversion, obtained WVD matrix are as follows:
S2 chooses appropriate threshold, by the element binaryzation of STFT matrix.
The principle that selected threshold follows: it according to research purpose or field experience, determines and the frequency endangered is generated to equipment
Amplitude, selected threshold value are slightly less than the amplitude.
The element for being less than threshold value in STFT matrix is set 0, sets 1 above or equal to the element of threshold value.Two are carried out to STFT
The mathematic(al) representation of value are as follows:
(3) in formula, λ is threshold value.STFT2(w, t) is the STFT matrix after binaryzation.
The element multiplication of STFT matrix and WVD matrix same position after binaryzation is obtained VFTO time domain waveform by S3
The result of STFT-WVD transformation:
STFT-WVDx(w, t)=STFT2(w,t)·WVDx(w,t)
In formula, same position element multiplication in representing matrix.
By the element multiplication of the STFT matrix of binaryzation and WVD matrix same position, the meaning of the step is:
1) cross term interference is not present in STFT, and all frequency contents are all actual frequency ingredients in time frequency analysis result；
2) when a certain element of STFT matrix of binaryzation be 1 when, the corresponding frequency content necessary being of the element, by with
WVD matrix corresponding element is multiplied, and WVD matrix same position element remains unchanged, then the actual frequency ingredient in WVD transformation is kept
It is constant；
3) when a certain element of STFT matrix of binaryzation is 0, the corresponding frequency content of the element is not present or is not to close
The frequency content of the heart, by being multiplied with WVD matrix corresponding element, WVD matrix same position element sets 0, then eliminates WVD transformation
In false frequency content that may be present.
S4, the STFT-WVD transformation results obtained according to step S3, the frequency and each frequency component that analysis VFTO includes
Amplitude versus time feature.
STFT-WVDxIn (w, t) matrix, row and column respective frequencies and time, the value of element represents amplitude in matrix.Pass through
STFT-WVDxThe three-dimensional time-frequency spectrum that (w, t) matrix is drawn, can clearly show that the frequency and each frequency component that VFTO includes
Amplitude versus time feature.
The above is the preferred embodiment of the present invention, for those skilled in the art,
Without departing from the principles of the invention, several improvements and modifications can also be made, these improvements and modifications are also regarded as this hair
Bright protection scope.
Claims (7)
1. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation, characterized in that the following steps are included:
The time domain waveform of VFTO is subjected to STFT time-frequency conversion and WVD time-frequency conversion respectively, obtains the identical STFT matrix of dimension
With WVD matrix；
Selected threshold, by the element binaryzation of STFT matrix；
The cross term that WVD matrix is eliminated using the STFT matrix after binaryzation, obtains the time-frequency spectrum of VFTO；
According to the amplitude versus time feature of the Time-frequency Spectrum Analysis VFTO frequency for including and each frequency component.
2. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation according to claim 1, characterized in that will
The time domain waveform of VFTO carries out the STFT matrix that STFT time-frequency conversion obtains are as follows:
In formula, x (τ) is the time domain waveform of VFTO, and h (t) is window function.
3. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation according to claim 2, characterized in that will
The time domain waveform of VFTO carries out the WVD matrix that WVD time-frequency conversion obtains are as follows:
4. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation according to claim 3, characterized in that described
The time-frequency spectrum of VFTO are as follows:
STFT-WVDx(w, t)=STFT2(w,t)·WVDx(w,t)；
In formula, same position element multiplication in representing matrix.
5. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation according to claim 1, characterized in that described
The choosing method of threshold value are as follows:
According to research purpose or field experience, determine that the amplitude that the frequency of harm is generated to equipment, selected threshold value are less than the amplitude.
6. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation according to claim 1, characterized in that described
By the detailed process of STFT matrix element binaryzation are as follows:
In formula, λ is threshold value.
7. a kind of VFTO frequency spectrum analysis method based on STFT-WVD transformation according to claim 1, characterized in that described
The detailed process of the cross term of WVD matrix is eliminated using the STFT matrix after binaryzation are as follows:
By the element multiplication of STFT matrix and WVD matrix same position after binaryzation.
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