CN104181389B - Phasor measurement method in electric-power system - Google Patents
Phasor measurement method in electric-power system Download PDFInfo
- Publication number
- CN104181389B CN104181389B CN201410313200.2A CN201410313200A CN104181389B CN 104181389 B CN104181389 B CN 104181389B CN 201410313200 A CN201410313200 A CN 201410313200A CN 104181389 B CN104181389 B CN 104181389B
- Authority
- CN
- China
- Prior art keywords
- sampled signal
- aperture
- window
- amplitude
- frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 238000000691 measurement method Methods 0.000 title claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 33
- 230000008569 process Effects 0.000 claims abstract description 17
- 230000009466 transformation Effects 0.000 claims abstract description 17
- 238000005070 sampling Methods 0.000 claims abstract description 7
- 238000001228 spectrum Methods 0.000 abstract description 15
- 239000002131 composite material Substances 0.000 abstract 3
- 230000002401 inhibitory effect Effects 0.000 abstract 1
- 238000005259 measurement Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000010355 oscillation Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000012634 fragment Substances 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
Landscapes
- Measurement Of Resistance Or Impedance (AREA)
Abstract
The invention provides a phasor measurement method in an electric-power system. The method includes the following steps: adopting a composite window used for inhibiting negative frequencies to process sampling signals; and carrying out Fourier transformation on the sampling signals processed by the composite window so that a phasor value is obtained, wherein the amplitudes of sidelobes corresponding to -48 to -52 HZ frequencies in the sampling signals processed by the composite window are smaller than a preset value. The method is capable of solving a problem, which exists in the prior art, that more high-frequency interferences and spectrum energy leakage exist in a rectangular window and Fourier transformation.
Description
Technical field
The present invention relates to power technology, phasor measurement method in more particularly, to a kind of power system.
Background technology
In grid-connected photovoltaic system, phasor value is an important observed quantity, and grid-connected photovoltaic system safety is certainly
Dynamic device needs to measure its value in real time, and makes corresponding control measure according to the change of its value.
In prior art, under power system medium and low frequency oscillating condition, most widely used phasor measurement method is mainly based upon
Discrete Fourier transform (Discrete Fourier Transform, DFT) obtains phasor value.
Existing Fourier transformation is to study the relation of whole time domain and frequency domain.Can not possibly be to unlimited in practical application
Long signal measures and computing, but takes its limited time slice to be analyzed；Thus, intercept one from sampled signal
Individual signal time fragment, then carries out periodic extension process with the signal time fragment intercepting, obtains the letter of virtual endless
Number, endless signal is carried out with Fourier transformation and obtains phasor value.
However, after the signal of the endless of reality is truncated, its frequency spectrum there occurs distortion, originally concentrate on f (0) place
Energy is dispersed in whole frequency band and goes, and this phenomenon is referred to as spectrum energy leakage.
For solving the problems, such as prior art intermediate frequency spectrum energy leakage, to the Fourier transformation using signal in prior art
Before, sampled signal is carried out with the process of window function, is such as processed using rectangular window function, and then by the signal after processing again
Carry out Fourier transformation, obtain phasor value.
However, the secondary lobe after this rectangular window goes out is higher, lead to there is more High-frequency Interference in follow-up Fourier transformation, and frequency
Spectrum energy leaks.
Content of the invention
For defect of the prior art, the present invention provides a kind of phasor measurement method in power system, existing for solving
There is the problem of more High-frequency Interference and spectrum energy leakage in rectangular window and Fourier transformation in technology.
The present invention provides a kind of phasor measurement method in power system, including：
Using the complex-aperture for suppressing negative frequency, sampled signal is processed；
Sampled signal after described complex-aperture is processed carries out Fourier transformation, obtains phasor value；
Wherein, in the sampled signal after described complex-aperture is processed, the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies is less than in advance
If value.
Alternatively, described using the complex-aperture for suppressing negative frequency, sampled signal is processed, specially：Using under
State formula sampled signal is processed；
W (n)=w0(n)sinc(n/N)
N=-2N ... ..., 2N-1
Wherein, w0N ()=0.51327588+0.48672412cos (2 π n/4N), N are the sampling number in a cycle.
Alternatively, in the sampled signal after described complex-aperture is processed, the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies declines
Depreciation is more than 125dB.
Alternatively, during N=64, the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after described complex-aperture process
The pad value of amplitude is in 160 to 250dB；
During N=128 or 32, the width of the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after described complex-aperture process
The pad value of value is in 130 to 150dB.
Alternatively, in the sampled signal after described complex-aperture is processed, the amplitude of the corresponding secondary lobe of -50HZ frequency is less than and presets
Value.
As shown from the above technical solution, phasor measurement method in the power system of the present invention, using for suppressing negative frequency
Complex-aperture sampled signal is processed；And the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after complex-aperture process
Amplitude be less than preset value, thus, to described complex-aperture process after sampled signal carry out Fourier transformation, obtain phasor value,
More High-frequency Interference and spectrum energy leakage in rectangular window and Fourier transformation in prior art can be solved the problems, such as.
Brief description
The schematic flow sheet of phasor measurement method in the power system that Fig. 1 provides for one embodiment of the invention；
The phasor amplitude of CSW method, RCW method and conventional DFT estimation in the power system that Fig. 2 provides for one embodiment of the invention
Schematic diagram；
Fig. 3 is the enlarged schematic partial view of Fig. 2；
Fig. 4 is the phasor amplitude measurement error schematic diagram of CSW method in Fig. 2, RCW method and conventional DFT estimation.
Specific embodiment
With reference to the accompanying drawings and examples, the specific embodiment of the present invention is described in further detail.Hereinafter implement
Example is used for the present invention is described, but is not limited to the scope of the present invention.
Currently, the leakage of sampled signal intermediate frequency spectrum is relevant with the both sides secondary lobe of window function frequency spectrum, if side lobe height is lower,
Main lobe is got over and is concentrated, then spectrum leakage is fewer, is closer to real frequency spectrum.
In prior art, the most frequently used window function is rectangular window, the Chinese peaceful (Hanning) window, Hamming (Hamming) window, cloth
Rec graceful (Blackman) window, raised cosine window (raised cosine window, abbreviation RCW) etc..
The advantage of rectangular window is that main lobe compares concentration, and shortcoming is that secondary lobe is higher, leads to bring into high frequency in Fourier transformation
Interference and leakage.
Currently, Cosine Window expression formula is following formula (1)：
In formula (1), K represents the item number of Cosine Window, akIt is demonstrated by the time-frequency characteristics of Cosine Window, for example, for one
Individual two Cosine Window (P=4, K=2) of four cycles, work as a0=0.5, a1=0.5, then the corresponding window of above-mentioned formula (1) is Hanning window；
Work as a0=0.54, a1=0.46, the corresponding window of above-mentioned formula (1) is Hamming window.
For three Cosine Window (P=4, K=3) of four cycle, work as a0=0.42, a1=0.5, a2When=0.08, above-mentioned
The corresponding window of formula (1) is Blackman window.
It should be noted that item number K is a parameter of Cosine Window, refer to the number of different cosine term in cosine expression formula.?
Number is more, and the main lobe of Cosine Window is wider, and accessible side lobe attenuation is also bigger.
In prior art, Hamming window and Hanning window broadly fall into Cosine Window, and simply weight coefficient is different.Hanning window weighting be
It is less that number can make secondary lobe reach；Blackman window is second order raised cosine window, main lobe width, and secondary lobe ratio is relatively low, but main lobe compares Hanning window
Larger, secondary lobe is smaller.
The corresponding computing formula of RCW is as follows：
W [n]=sinc (n/N) * (sinc (0.7*n/N+0.5)+sinc (0.7*n/N-0.5))
N=-2N ..., 2N-1 (2)
RCW main lobe compared with Cosine Window is relatively concentrated, and secondary lobe is higher.
The amplitude of secondary lobe near the frequency of 100Hz for the above-mentioned window function still compares high it is impossible to meet Fourier's change
The demand changed.
The core of the present invention is to provide a kind of complex-aperture (Cosine-sinc window, CSW) function, this complex-aperture and Cosine Window
Compare and have greater concentration of main lobe and lower secondary lobe, have similar main lobe compared with RCW, but in frequency spectrum, particularly exist
There is lower secondary lobe, thus, the method for the present invention processes sampled signal and can have preferable negative frequency near the frequency of 100Hz
Rejection ability.
In theory, with signal a (t) to prime power signal cos (2 π f0T+ θ) carry out Modulation and Amplitude Modulation, then signal model
For：
S (t)=a (t) cos (2 π f0T+ θ) formula (3)
In formula (3), a (t) is amplitude-modulated signal, f0It is fundamental frequency, θ is phase angle.
Directly carrying out Fourier transformation to signal model is：
Formula (4)
In formula (4), W (f) is the conversion of spectral window w (t) of fundamental frequency, and A (f) is the spectrum envelope function of a (t),
And Aw=W (0).In addition, the Section 1 in formula (4) corresponds to the output of required Fourier filtering, Section 2 is to be not required to
The negative frequency infiltration wanted.
Negative frequency infiltration in actual applications is unwanted content, suppression negative frequency preferably, needs the window function can
There is special low sidelobe near the frequency of 100Hz.
In the present invention, as shown in figure 1, in the power system of the present embodiment phasor measurement method as described below.
101st, using the complex-aperture for suppressing negative frequency, sampled signal is processed；
102nd, Fourier transformation is carried out to the sampled signal after the process of described complex-aperture, obtain phasor value；
Wherein, in the sampled signal after described complex-aperture is processed, the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies is less than in advance
If value.
Preferably, in the sampled signal after described complex-aperture is processed, the amplitude of the corresponding secondary lobe of -50HZ frequency is less than and presets
Value.
It will be appreciated that in the present embodiment complex-aperture process after sampled signal in the corresponding secondary lobe of -48 to -52HZ frequencies
Amplitude pad value be more than 125dB, and at present commonly use window decay be both less than 120dB.
For example, the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after above-mentioned complex-aperture is processed
Pad value is bigger than conventional window (such as Hanning, Hamming, Blackamn, RCW window), for example：During N=64 (that is, every
When primitive period sampled point is 64 sampled points), in the sampled signal after described complex-aperture process, -48 to -52HZ frequencies correspond to
The amplitude of secondary lobe pad value in 160 to 250dB；
During N=128 or 32, the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after described complex-aperture process
The pad value of amplitude is in 130 to 150dB.
Thus, (sampled signal after alignment processing exists in 100Hz for Hamming window, Hanning window, Blackman window, RCW window
Near frequency 50Hz), the amplitude attenuation of secondary lobe is less than 120dB, and the complex-aperture proposing in the application is near the frequency of 100Hz
The amplitude attenuation of secondary lobe is more than 125dB.
Phasor measurement method in the power system of the present embodiment, using the complex-aperture for suppressing negative frequency to sampled signal
Processed；Sampled signal after described complex-aperture is processed carries out Fourier transformation, obtains phasor value, it is possible to resolve prior art
The problem of more High-frequency Interference and spectrum energy leakage in middle rectangular window and Fourier transformation.
In actual applications, described using the complex-aperture for suppressing negative frequency, sampled signal is processed, specially：
Using following formula, sampled signal is processed；
W (n)=w0(n)sinc(n/N)
N=-2N ... ..., 2N-1 formula (5)
Wherein, w0N ()=0.51327588+0.48672412cos (2 π n/4N), N are the sampling number of a cycle, and
Above-mentioned w0N () is two Cosine Window.
In a particular application, the sampling electricity in 4 cycles is generally selected to carry out phasor calculation.
In formula (5), corresponding complex-aperture, in frequency spectrum, has relatively low secondary lobe near particularly 100Hz in window, this
It is a preferable negative frequency rejection characteristic in vibration phasor measurement.Can answering for a Cosine Window and sinusoidal windows by this complex-aperture
Close.
Specifically, above-mentioned formula (5) is applied in the vibration phasor measurement of power system under the conditions of low-frequency oscillation, sample
Frequency configuration is 3200Hz, and nominal frequency is set to 50Hz.The DFT of length of window size is calculated as four cycles, in experiment is
256 sampled points.
One typical low frequency modulations is as follows：
X (t)=(1+0.1cos (2 π fmt))sin(2πft)
Wherein, f=50.2Hz, fm=1Hz.
In the present embodiment, the phasor amplitude estimated respectively using CSW method, RCW method and conventional DFT, as shown in Fig. 2 Fig. 3 is
The schematic diagram that the part of Fig. 2 is amplified, Fig. 4 shows the schematic diagram of amplitude measurement error.
Shown in Fig. 2, CSW method, RCW method and conventional DFT can follow the tracks of low-frequency oscillation, can be obtained by traditional DFT
Significantly distortion curve, this is mainly to be permeated by negative frequency and is determined.
Fig. 3 illustrates, the distortion degree of traditional DFT curve is greatly weakened on RCW curve and CSW curve
?.However, still having certain distortion on RCW curve, and such distortion substantially be there is no on CSW curve.
Fig. 4 shows that the error of RCW method is higher than the error of the CSW method that the present embodiment is proposed.
It will be appreciated that the error of CSW is essentially from pass band damping, or the main lobe decay of window.Typical low-frequency oscillation
Scope is 0.1 to 2Hz, and the amplitude of the main lobe of CSW decays to 99.72% from 99.98%, and therefore, CSW main lobe amplitude is led to
Error is less than 0.28%, this be far below ieee standard c37.118.1-2011 limit it is often more important that, main lobe decay is with the later stage
Process can compensate.
Thus, the phasor measurement method of the present embodiment has the ability of good suppression harmonic wave/m-Acetyl chlorophosphonazo and noise, can be relatively
It is applied to well in the vibration phasor measurement of power system under the conditions of low-frequency oscillation.
Finally it should be noted that：Various embodiments above only in order to technical scheme to be described, is not intended to limit；To the greatest extent
Pipe has been described in detail to the present invention with reference to foregoing embodiments, it will be understood by those within the art that：Its according to
So the technical scheme described in foregoing embodiments can be modified, or wherein some or all of technical characteristic is entered
Row equivalent；And these modifications or replacement, do not make the essence of appropriate technical solution depart from the claims in the present invention and limited
Fixed scope.
Claims (4)
1. in a kind of power system phasor measurement method it is characterised in that include：
Using the complex-aperture for suppressing negative frequency, sampled signal is processed；
Sampled signal after described complex-aperture is processed carries out Fourier transformation, obtains phasor value；
Wherein, in the sampled signal after described complex-aperture is processed, the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies is less than and presets
Value；
Wherein, described using the complex-aperture for suppressing negative frequency, sampled signal is processed, specially：
Using following formula, sampled signal is processed；
W (n)=w0(n)sinc(n/N)
N=-2N ... ..., 2N-1
Wherein, w0N ()=0.51327588+0.48672412cos (2 π n/4N), N are the sampling number in a cycle.
2. method according to claim 1 it is characterised in that
In sampled signal after described complex-aperture process, the pad value of the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies is more than
125dB.
3. method according to claim 1 it is characterised in that
During N=64, the decay of the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after described complex-aperture process
Value is in 160 to 250dB；
During N=128 or 32, the amplitude of the corresponding secondary lobe of -48 to -52HZ frequencies in the sampled signal after described complex-aperture process
Pad value is in 130 to 150dB.
4. method according to claim 1 it is characterised in that
In sampled signal after described complex-aperture process, the amplitude of the corresponding secondary lobe of -50HZ frequency is less than preset value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410313200.2A CN104181389B (en) | 2014-07-02 | 2014-07-02 | Phasor measurement method in electric-power system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410313200.2A CN104181389B (en) | 2014-07-02 | 2014-07-02 | Phasor measurement method in electric-power system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN104181389A CN104181389A (en) | 2014-12-03 |
| CN104181389B true CN104181389B (en) | 2017-02-15 |
Family
ID=51962606
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410313200.2A Expired - Fee Related CN104181389B (en) | 2014-07-02 | 2014-07-02 | Phasor measurement method in electric-power system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN104181389B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104655965B (en) * | 2015-02-13 | 2017-07-07 | 中国农业大学 | A kind of phasor measurement method in power system |
| CN105871767B (en) * | 2016-03-25 | 2019-05-14 | 广东顺德中山大学卡内基梅隆大学国际联合研究院 | A kind of inhibition cosine combination window design method of the ofdm system with outward leakage |
| CN108627694B (en) * | 2018-04-17 | 2020-02-11 | 中国农业大学 | Method, device and equipment for detecting voltage frequency of power grid |
| CN109557367B (en) * | 2018-10-23 | 2020-09-08 | 中国农业大学 | High-frequency resolution harmonic and inter-harmonic Prony method and device |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101510687A (en) * | 2009-03-18 | 2009-08-19 | 天津大学 | Frequency conversion method for implementing multi-sampling rate signal using window function in electric network |
| CN102128975A (en) * | 2010-12-22 | 2011-07-20 | 四川省电力公司 | Voltage stabilization online monitoring phasor data measurement device and phasor measurement method |
| CN102495281A (en) * | 2011-12-14 | 2012-06-13 | 北京易事特电源有限公司 | Method for measuring phasor frequency of power system |
| JP2014081352A (en) * | 2012-09-27 | 2014-05-08 | Daihen Corp | Frequency analysis device, signal processing apparatus using the device, and high-frequency measurement instrument using the apparatus |
| CN103869162A (en) * | 2014-03-05 | 2014-06-18 | 湖南大学 | Dynamic signal phasor measurement method based on time domain quasi-synchronization |
-
2014
- 2014-07-02 CN CN201410313200.2A patent/CN104181389B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101510687A (en) * | 2009-03-18 | 2009-08-19 | 天津大学 | Frequency conversion method for implementing multi-sampling rate signal using window function in electric network |
| CN102128975A (en) * | 2010-12-22 | 2011-07-20 | 四川省电力公司 | Voltage stabilization online monitoring phasor data measurement device and phasor measurement method |
| CN102495281A (en) * | 2011-12-14 | 2012-06-13 | 北京易事特电源有限公司 | Method for measuring phasor frequency of power system |
| JP2014081352A (en) * | 2012-09-27 | 2014-05-08 | Daihen Corp | Frequency analysis device, signal processing apparatus using the device, and high-frequency measurement instrument using the apparatus |
| CN103869162A (en) * | 2014-03-05 | 2014-06-18 | 湖南大学 | Dynamic signal phasor measurement method based on time domain quasi-synchronization |
Non-Patent Citations (1)
| Title |
|---|
| 电力***相量测量方法研究;林达斌;《中国优秀硕士学位论文全文数据库 工程科技II辑》;20130615(第06期);第34-36页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN104181389A (en) | 2014-12-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN104181389B (en) | Phasor measurement method in electric-power system | |
| CN103869162B (en) | Dynamic signal phasor measurement method based on time domain quasi-synchronization | |
| Xu et al. | An enhanced bearing fault diagnosis method based on TVF-EMD and a high-order energy operator | |
| Qin et al. | Weak transient fault feature extraction based on an optimized Morlet wavelet and kurtosis | |
| CN105158740B (en) | Amplitude modulated jamming suppressing method based on high-precision Frequency Estimation | |
| CN109782063A (en) | A kind of dynamic m-Acetyl chlorophosphonazo analysis method based on three spectral line interpolation FFT of Nuttall self-convolution window | |
| CN107085140B (en) | Nonequilibrium system frequency estimating methods based on improved SmartDFT algorithm | |
| WO2016138764A1 (en) | Method for improving pmu synchronous phasor measurement precision | |
| CN110967599A (en) | Electric energy quality disturbance detection and positioning algorithm | |
| US20160274155A1 (en) | Method for acquiring parameters of dynamic signal | |
| CN108764073B (en) | Acceleration noise filtering and integrating method combined with spectrum energy form fitting | |
| Zeng et al. | Parameter estimation of power system signals based on cosine self-convolution window with desirable side-lobe behaviors | |
| CN108535613B (en) | Voltage flicker parameter detection method based on combined window function | |
| CN110221116A (en) | Voltage flicker envelope detection method based on windowed interpolation and parsing Mode Decomposition | |
| Yao et al. | Fast S-transform for time-varying voltage flicker analysis | |
| CN103699513B (en) | A kind of stochastic resonance method adjusted based on multiple dimensioned noise | |
| Qin | Multicomponent AM–FM demodulation based on energy separation and adaptive filtering | |
| NO20056036L (en) | Noise reduction in seismic signals by frequency-dependent weighing | |
| CN105137180B (en) | High-precision harmonic analysis method based on six four spectral line interpolations of Cosine Window | |
| CN110095650A (en) | The complicated harmonic detecting analysis method of four spectral line interpolation FFTs based on five Rife-Vincent (I) windows | |
| Wang | The tutorial: S transform | |
| CN106771592A (en) | A kind of trend of harmonic detection method of power | |
| Langella et al. | Amplitude and phase modulation effects of waveform distortion in power systems | |
| CN116047163A (en) | Method and device for detecting harmonic waves among power systems | |
| CN108252753B (en) | Method, device and equipment for filtering interference signals |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20170215 |