CN108169540A - A kind of measuring method of wind power generating set voltage flicker - Google Patents
A kind of measuring method of wind power generating set voltage flicker Download PDFInfo
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/04—Measuring peak values or amplitude or envelope of ac or of pulses
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The present invention relates to wind power generating set power quality field of measuring technique, disclose a kind of measuring method of wind power generating set voltage flicker, include the following steps：S1, the output terminal for measuring wind power generating set, obtain the time series of voltage and current；S2, analog voltage fluctuates in virtual power grid, S3, the output signal progress square to virtual power grid；S4, by Nuttall window functions to square after output signal block；S5, it is filtered using FFT；S6, the highest flicker envelope signal of frequency is screened out by empirical mode decomposition to the signal for only including DC component and low frequency flicker envelope；S7, HHT transformation is carried out to each IMF fluctuation signals；S8, spectrum analysis is carried out to multiple flickering voltages, obtains and include the Short Term Flicker severity of multiple frequency contents, this measuring method can accurately measure the Short Term Flicker severity of the flickering voltage containing multiple frequency contents.
Description
Technical field
The present invention relates to wind power generating set power quality field of measuring technique, more particularly to a kind of wind power generating set electricity
Press the measuring method of flickering.
Background technology
In recent years, increasingly consume and cause today of environment severe exacerbation in fossil energy, wind energy as clean energy resource
Through being widely used, it is increasingly taken seriously, and one of which is exactly effectively wind-power electricity generation using hairdo, and wind-force is sent out
Electricity becomes the research emphasis of various countries.
With the fast development of wind-power electricity generation, more and more high-power blowers are connected to the grid so that the electric energy of power grid
Quality seriously reduces.So as to which the power quality problem of wind-powered electricity generation and its solution be made to be increasingly becoming the hot spot of research.It will be to power grid
Power quality improved, first have to make power quality accurate detection and analysis, measure the power quality water of power grid
The reason of flat, and analysis and judgement cause various power quality problems, the improvement for power quality provides foundation.So to electric energy
The detection and analysis of quality is even more important.
In recent years, increasingly consume and cause today of environment severe exacerbation in fossil energy, wind energy as clean energy resource
Through being widely used, it is increasingly taken seriously, and one of which is exactly effectively wind-power electricity generation using hairdo, and wind-force is sent out
Electricity becomes the research emphasis of various countries.
It is larger that IEC simulates the measurement error of flickermeter, digital flicker and rectification detection method in low frequency and high frequency；Instantaneously
Reactive power method, Teager energy operators method, Hilbert algorithm, the measurement error in low frequency are larger；IEC simulations flickermeter,
Digital flicker, instantaneous detecting method, D-q converter techniques, when can not be carried out to flicker envelope-frequency analysis, it is impossible to flickering is obtained
The time of generation and the frequency of flickering voltage, amplitude.
In order to solve problem above, it is proposed that the unit voltage flicker Measurement Algorithm of the window correction based on FFT and HHT makes
Voltage fluctuation caused by unit is obtained with virtual power grid in order to inhibit spectral leakage, adds an individual character to the signal of squarer output
The excellent window function of energy, filters out the frequency component higher than 35Hz by FFT, reuses empirical mode decomposition and flickering voltage is obtained,
Then the parameters such as time, amplitude, the frequency of flickering voltage are obtained using Hilbert transformation, are finally obtained in short-term using frequency domain method
Flickering severity.
Invention content
The present invention provides a kind of measuring method of wind power generating set voltage flicker, can solve of the prior art above-mentioned
Problem.
The present invention provides a kind of measuring methods of wind power generating set voltage flicker, include the following steps：
S1, the output terminal for measuring wind power generating set, obtain the time series of voltage and current；
S2, the time series to voltage and current, analog voltage fluctuates in the virtual power grid of other no fluctuation sources,
S3, pass through output signal progress square of the squarer to virtual power grid；
S4, by Nuttall window functions to square after output signal block；
S5, Nuttall window functions are blocked using FFT after signal in be filtered higher than the frequency component of 35Hz, obtain
Obtain the only signal comprising DC component and low frequency flicker envelope；
S6, zero crossing is subtracted by empirical mode decomposition EMD to the signal for only including DC component and low frequency flicker envelope
The method of fluctuation screens out the highest flicker envelope signal of frequency, obtains frequency and is fluctuated by multiple IMF that height is arranged in order on earth
Signal；
S7, HHT transformation is carried out to each IMF fluctuation signals, obtains multiple flickering voltages；
S8, spectrum analysis is carried out to multiple flickering voltages, obtains the sudden strain of a muscle in short-term of the flickering voltage comprising multiple frequency contents
Become severity.
Preferably, the virtual power grid in the step S2 is by ideal voltage source u0(t), current source, inductance and resistance series connection
Composition, wind power generating set electric current source-representation, im(t) the instantaneous value u for line current instantaneous value, wherein analog voltageficFor：
R in formula (1)ficFor the resistance of virtual power grid, LficInductance for virtual power grid；
Ideal voltage source u0(t) the following characteristic of desired voltage should be met：Desired voltage should not have any fluctuation, and voltage
Sudden strain of a muscle becomes zero；u0(t) there should be identical electrical angle α with the fundamental wave for measuring voltagem(t)；
To meet conditions above u0(t) it is defined as：
In formula (2), unFor the virtual value of power grid rated voltage, the electrical angle α of the fundamental wave of voltage is measuredm(t) it is：
In formula (3), f (t) is mains frequency, is changed over time；T is the initial time of start recording；α0During for t=0
Electrical angle；
Unit voltage and current time series obtains voltage fluctuation entirely from wind power generating set by virtual power grid
Analog voltage instantaneous value ufic。
Preferably, the time-domain expression of Nuttall window functions is in the step S4：
Item numbers of the M for four minimum secondary lobe Nuttall windows, b in formula (4)mFormula (5) need to be met
Using four minimum secondary lobe Nuttall windows to u2(t) it is blocked, i.e., time-domain is multiplied, and frequency domain convolution obtains
z(t)
Z (t)=ufic 2WN(n) (6)
Signal z (t) after minimum secondary lobe Nuttall windows block to four carries out Fourier transformation, obtains its frequency spectrum F (ω)
In formula (7) frequency domain remove F (ω) be more than 35Hz high fdrequency components, obtain F1(ω), to F1(ω) asks Fourier
Inverse transformation obtains the only signal z comprising direct current and low frequency flicker envelope1(t)
Z in formula (8)1(t) DC component and flicker envelope are only included.
Preferably, empirical mode decomposition EMD described in the step S6 is screened out by subtracting the method that zero crossing fluctuates
The highest ingredient of frequency, according to the method, IMF is arranged in order from high to low according to frequency, and each IMF represents what signal included
One fluctuation, EMD processes are as follows：
1) the only signal z comprising direct current and low frequency flicker envelope is enabled1(t)=x (t) finds the extreme point of signal x (t), makes
The coenvelope v of signal is obtained with the method for cubic spline difference1(t) and lower envelope v (t)；
2) mean value envelope m (t) can be obtained according to formula (9)：
M (t)=[v1(t)+v(t)]/2 (9)
3) h is obtained by formula (10)1(t)：
h1(t)=x (t)-m (t) (10)
If 4) the h obtained by formula (10)1(t) it is discontented with full measure end condition, then by h1(t) iteration is new x (t), heavy
Multiple 1), 2) He 3) step, until h1(t) when meeting decomposition end condition, iteration stopping, the IMF obtained at this time is denoted as c1(t),
Mean value envelope m (t) and the signal h (t) subtracted after mean value envelope m (t) continue according to formula (11) iteration：
5) first IMF components c is obtained by formula (12)1(t)
Formula (12) r1(t) it is residue signal；By the highest frequency component in x (t), obtained according to formula (13) continuation iteration several
Be free of the r of any frequency contentn(t)
Original signal x (t) can be reconstructed by formula (14)：
R in formula (13)n(t) it is n-th of residual volume, cn(t) it is n-th of IMF component.
Preferably, formula (15) can be obtained by doing Hilbert transform in the step S7 to each IMF：
In formula (15), P be Cauchy's principal component, Cj(t) it is IMF；
Corresponding plural number analytical function is formula (16)：
It can be obtained by formula (16)：
In formula (17), aj(t) it is instantaneous amplitude；θj(t) it is instantaneous phase；ωj(t) it is instantaneous frequency.
Preferably, it is expressed as in the step S8 according to IEC61000-4-15 standards, instantaneous visual sense degree S (t)：
I.e. instantaneous visual sense degree S (t) is equal to flickering voltage modulation degree mfSquare with visual sense degree coefficient kfSquare be weighted
Operation is obtained multiplied by a constant coefficient h, when the frequency of flickering voltage is 8.8Hz, and modulation degree is m=0.0025, is instantaneously regarded
Sensitivity S (t)=1, at this time kf=1 can acquire h=1/0.00252；
Statistical analysis in 10 minutes is carried out to S (t), Short Term Flicker severity P is can obtain according to formula (19)st
P in formula (19)0.1、P1、P3、P10、P50Surpassed for 0.1%, 1%, 3%, 10%, 50% time in respectively 10 minutes
Perceive unit value.
Compared with prior art, the beneficial effects of the present invention are：
The present invention realizes the accurate measurement that single wind generator group causes voltage flicker, utilizes unit measurement of output end
Obtained voltage, current time sequence analog voltage in the virtual power grid of other no fluctuation sources fluctuates；Pass through Nuttall windows
Spectral leakage is reduced, is filtered using FFT, flicker envelope is obtained with HHT, to improve its measurement accuracy, not by system frequency
Variation, the influence of white noise, harmonic wave, m-Acetyl chlorophosphonazo can also carry out spectrum analysis to flickering voltage.
The error of this method is significantly less than the flickermeter and rectification detection method, instantaneous detecting method, Teager of IEC recommendations
This five kinds common flicker envelope demodulation methods of energy operator method, Hilbert converter techniques, D-q converter techniques, hardly by white noise
The influence of sound, harmonic wave, and the Short Term Flicker severity of the flickering voltage containing multiple frequency contents can be accurately measured,
Simultaneously this method can also directly to flickering voltage carry out spectrum analysis, obtain flickering frequency and flickering occur start-stop when
Between.Further, it is also possible to detect the power quality problems such as harmonic wave caused by unit and voltage swell.
Description of the drawings
Fig. 1 is a kind of flow diagram of the measuring method of wind power generating set voltage flicker provided by the invention.
Fig. 2 is the emulation frame of virtual power grid in a kind of measuring method of wind power generating set voltage flicker provided by the invention
Figure.
Fig. 3 a are the frequency of flickering voltage in a kind of measuring method of wind power generating set voltage flicker provided by the invention
With the relational graph of time.
Fig. 3 c are that wind power generating set is drawn in a kind of measuring method of wind power generating set voltage flicker provided by the invention
The relational graph of Short Term Flicker severity relative error in the flicker measurement result risen.
Fig. 3 b are the amplitude of flickering voltage in a kind of measuring method of wind power generating set voltage flicker provided by the invention
With the relational graph of time.
Fig. 4 a be a kind of measuring method of wind power generating set voltage flicker provided by the invention in the harmonic signal time with
The relational graph of frequency.
Fig. 4 b be a kind of measuring method of wind power generating set voltage flicker provided by the invention in the harmonic signal time with
The relational graph of amplitude.
Fig. 5 a are that wind power generating set is drawn in a kind of measuring method of wind power generating set voltage flicker provided by the invention
Temporal frequency relational graph when the voltage swell risen occurs.
Fig. 5 b are that wind power generating set is drawn in a kind of measuring method of wind power generating set voltage flicker provided by the invention
Time-amplitude relational graph when the voltage swell risen occurs.
Specific embodiment
Below in conjunction with the accompanying drawings, the specific embodiment of the present invention is described in detail, it is to be understood that of the invention
Protection domain be not restricted by specific implementation.
As depicted in figs. 1 and 2, the measuring method of a kind of wind power generating set voltage flicker provided in an embodiment of the present invention,
Include the following steps：
S1, the output terminal for measuring wind power generating set, obtain the time series of voltage and current；
S2, the time series to voltage and current, analog voltage fluctuates in the virtual power grid of other no fluctuation sources,
S3, pass through output signal progress square of the squarer to virtual power grid；
S4, by Nuttall window functions to square after output signal block；
S5, Nuttall window functions are blocked using FFT after signal in be filtered higher than the frequency component of 35Hz, obtain
Obtain the only signal comprising DC component and low frequency flicker envelope；
S6, zero crossing is subtracted by empirical mode decomposition EMD to the signal for only including DC component and low frequency flicker envelope
The method of fluctuation screens out the highest flicker envelope signal of frequency, obtains frequency and is fluctuated by multiple IMF that height is arranged in order on earth
Signal；
S7, HHT transformation is carried out to each IMF fluctuation signals, obtains multiple flickering voltages；
S8, spectrum analysis is carried out to multiple flickering voltages, obtains the sudden strain of a muscle in short-term of the flickering voltage comprising multiple frequency contents
Become severity.
Example one：Flickering caused by wind power generating set
According to formula (20) or formula (21) setting emulation signal, to flickering caused by method wind power generating set proposed in this paper
The accuracy of measurement result carries out simulation analysis.This example emulates the sample rate f of signalsFor 2000Hz
In the flickering three times that 3s to 18s difference occurrence frequencies are 6Hz, 8.8Hz, 12Hz, the frequency of flickering voltage, amplitude with
The relationship of time is as shown in Figure 3a and Figure 3b shows.
The standard parameter for choosing S (t)=1 within the 25Hz that IEC standard provides causes wind power generating set the short of flickering
When severity carry out simulation analysis.Based on Short Term Flicker severity error under the different frequency obtained set forth herein method such as
Shown in Fig. 3 c.
In formula (20), A0For power grid fundamental voltage amplitude,For initial phase angle,
M1, m2 and m3 are flickering voltage modulation degree, m1=0.00325, m2=0.0025, m3=0.00314, simulation time 20s.
In formula (21), A0For power grid fundamental voltage amplitude,For initial phase angle, φ0=0；M is flickering voltage
Modulation degree (selects) according to IEC, simulation time 20s.
By Fig. 3 a and Fig. 3 b it is found that in 3s~8s, 8s~13s, 13s~18s, flickering three times occurs, the frequency of flickering is
6Hz, 8.8Hz, 12Hz, the amplitude of flickering is 343.9,264.5,332.2, and amplitude meets flicker envelope amplification value requirement.
By Fig. 3 c it is found that the sudden strain of a muscle that flickering voltage frequency is obtained when below 25Hz changes based on measuring method proposed in this paper
Become severity error in short-term and be no more than 1.6%.
As it can be seen that caused by can accurately obtaining wind power generating set using context of methods multi-frequency voltage flicker occur when
Between and flickering voltage amplitude, frequency, and accurately calculate the severity P in short-term that wind power generating set causes flickeringst。
Example two：Harmonic wave caused by wind power generating set
In order to verify set forth herein the accuracy of harmonic wave caused by method detection wind power generating set, set according to formula (22)
Harmonic signal.This example emulates the sample rate f of signalsFor 4000Hz
The harmonic wave that different numbers occur for different time is arranged on, since fundamental wave energy is far longer than harmonic energy, need
FFT filtering is carried out to the harmonic signal blocked by 4 minimum secondary lobe Nuttall windows, filter out 50Hz fundamental waves.Then pass through HHT
The frequency and amplitude of harmonic wave is obtained.The results are shown in Figure 4 for emulation experiment harmonic measure.Wherein Fig. 4 a are harmonic signal time and frequency
The relationship of rate, Fig. 4 b are the relationship of harmonic signal time and amplitude.
In formula (22), A0For power grid fundamental voltage amplitude,M3, m5 are flickering voltage modulation degree, m3=
9%, m5=4%；Simulation time is 5s.
By Fig. 4 a and Fig. 4 b it is found that the frequency in 0s~2s is 150Hz, the fundamental frequency in China is 50Hz, therefore in 0s
There is the 150/50=3 subharmonic that amplitude is 2.93 in~2s, is 250Hz, therefore width occur in 2s~5s in the frequency of 2s~5s
It is worth the 250/50=5 subharmonic for 1.3.150Hz corresponds to triple-frequency harmonics in figure, 250Hz correspond to the harmonic amplitude of quintuple harmonics with
mA0It coincide.As it can be seen that using set forth herein method can accurately measure wind power generating set cause the number of harmonic wave, amplitude, when
Between.
Example three：Voltage swell caused by wind power generating set
The uncertainty of wind speed causes wind power generator incorporated in power network group output current, power unstable, network voltage is caused to be sent out
Raw voltage swell.According to formula (23), emulation signal, voltage caused by detecting wind power generating set to algorithm proposed in this paper are set
The accuracy temporarily risen carries out simulating, verifying.This example emulates the sample rate f of signalsFor 2000Hz
Twice 5% voltage swell occurs in different time for network voltage.Voltage swell caused by wind power generating set
Measurement result is as shown in Figure 5.Fig. 5 a are the relationship of Time And Frequency, and Fig. 5 b are the relationship of time and amplitude.
In formula (23), fs=2KHz；A0For power grid fundamental voltage amplitude,For initial phase angle, φ0=0；It is imitative
The true time is 10s.
As shown in Figure 5, the voltage swell that amplitude twice is 341.5 occurs in 2s~3s and 7s~8s, amplitude meets
1.05A0.It can be seen that algorithm proposed in this paper can accurately measure wind power generating set caused by voltage swell generation time
And amplitude.
The mathematical model of flickering voltage
In order to accurately demodulate voltage flicker ingredient, usually regard voltage flicker as am signals.Its mathematical expression
Formula is：
In formula (24), A0Amplitude for work frequency carrier；f0Frequency for work frequency carrier；Initial phase angle for work frequency carrier；mi
Modulation degree for i-th flicker envelope；fiFor the frequency for i-th flicker envelope；φiInitial phase angle for i-th flicker envelope.Represent flicker envelope.
The extraction of flicker envelope
Flickering voltage u (t) is exported and is by squarer：
The m in formula (25)i<<1, so being included in formula (25)Or mimjItem it is very small, can ignore.Therefore u2
(t) about：
In formula (26),For flicker envelope；For direct current；Other two are high frequency divisions
Amount.
The unit voltage flicker measuring method of the window correction based on FFT and HHT is proposed, unit is obtained using virtual power grid
Caused voltage fluctuation in order to inhibit spectral leakage, adds the signal of squarer output the window function of one function admirable, passes through
FFT filters out the frequency component higher than 35Hz, reuses empirical mode decomposition and flickering voltage is obtained, then converted using Hilbert
The parameters such as time, amplitude, the frequency of flickering voltage are obtained, Short Term Flicker severity finally is obtained using frequency domain method.
The measurement result that tested person place grid conditions do not influence in order to obtain excludes shadow caused by power grid exports unit
Sound, the voltage obtained using unit measurement of output end, current time sequence are simulated in the virtual power grid of other no fluctuation sources
Voltage fluctuation；Spectral leakage is reduced by Nuttall windows, is filtered using FFT, flicker envelope is obtained with HHT, to improve it
Measurement accuracy, is not changed, white noise, harmonic wave, m-Acetyl chlorophosphonazo are influenced by system frequency, can also carry out frequency spectrum point to flickering voltage
Analysis.
The accurate measurement that single wind generator group causes voltage flicker is realized, is obtained using unit measurement of output end
Voltage, current time the sequence analog voltage in the virtual power grid of other no fluctuation sources fluctuate；Frequency is reduced by Nuttall windows
Spectrum leakage, is filtered using FFT, flicker envelope is obtained with HHT, to improve its measurement accuracy, do not changed by system frequency, in vain
The influence of noise, harmonic wave, m-Acetyl chlorophosphonazo can also carry out spectrum analysis to flickering voltage.
The error of this method is significantly less than the flickermeter and rectification detection method, instantaneous detecting method, Teager of IEC recommendations
This five kinds common flicker envelope demodulation methods of energy operator method, Hilbert converter techniques, D-q converter techniques, hardly by white noise
The influence of sound, harmonic wave, and the Short Term Flicker severity of the flickering voltage containing multiple frequency contents can be accurately measured,
Simultaneously this method can also directly to flickering voltage carry out spectrum analysis, obtain flickering frequency and flickering occur start-stop when
Between.Further, it is also possible to detect the power quality problems such as harmonic wave caused by unit and voltage swell.
Disclosed above is only several specific embodiments of the present invention, and still, the embodiment of the present invention is not limited to this, is appointed
What what those skilled in the art can think variation should all fall into protection scope of the present invention.
Claims (6)
1. a kind of measuring method of wind power generating set voltage flicker, which is characterized in that include the following steps：
S1, the output terminal for measuring wind power generating set, obtain the time series of voltage and current；
S2, the time series to voltage and current, analog voltage fluctuates in the virtual power grid of other no fluctuation sources；
S3, pass through output signal progress square of the squarer to virtual power grid；
S4, by Nuttall window functions to square after output signal block；
S5, Nuttall window functions are blocked using FFT after signal in be filtered higher than the frequency component of 35Hz, obtain only
Signal comprising DC component and low frequency flicker envelope；
S6, zero crossing fluctuation is subtracted by empirical mode decomposition EMD to the signal for only including DC component and low frequency flicker envelope
Method screen out the highest flicker envelope signal of frequency, obtain multiple IMF fluctuation signals that frequency is arranged in order on earth by height；
S7, HHT transformation is carried out to each IMF fluctuation signals, obtains multiple flickering voltages；
S8, spectrum analysis is carried out to multiple flickering voltages, the Short Term Flicker for obtaining the flickering voltage comprising multiple frequency contents is tight
Weight degree.
2. the measuring method of wind power generating set voltage flicker as described in claim 1, which is characterized in that in the step S2
Virtual power grid by ideal voltage source u0(t), current source, inductance and resistance are composed in series, wind power generating set current source table
Show, im(t) the instantaneous value u for line current instantaneous value, wherein analog voltageficFor：
R in formula (1)ficFor the resistance of virtual power grid, LficInductance for virtual power grid；
Ideal voltage source u0(t) the following characteristic of desired voltage should be met：Desired voltage should not have any fluctuation, and voltage flicker
It is zero；u0(t) there should be identical electrical angle α with the fundamental wave for measuring voltagem(t)；
To meet conditions above u0(t) it is defined as：
In formula (2), unFor the virtual value of power grid rated voltage, the electrical angle α of the fundamental wave of voltage is measuredm(t) it is：
In formula (3), f (t) is mains frequency, is changed over time；T is the initial time of start recording；α0It is electrical during for t=0
Angle；
Unit voltage and current time series obtains mould of the voltage fluctuation entirely from wind power generating set by virtual power grid
Intend the instantaneous value u of voltagefic。
3. the measuring method of wind power generating set voltage flicker as described in claim 1, which is characterized in that in the step S4
The time-domain expression of Nuttall window functions is：
Item numbers of the M for four minimum secondary lobe Nuttall windows, b in formula (4)mFormula (5) need to be met
Using four minimum secondary lobe Nuttall windows to u2(t) it is blocked, i.e., time-domain is multiplied, and frequency domain convolution obtains z (t)
Z (t)=ufic 2WN(n) (6)
Signal z (t) after minimum secondary lobe Nuttall windows block to four carries out Fourier transformation, obtains its frequency spectrum F (ω)
In formula (7) frequency domain remove F (ω) be more than 35Hz high fdrequency components, obtain F1(ω), to F1(ω) asks Fourier's inversion
Get the only signal z comprising direct current and low frequency flicker envelope in return1(t)
Z in formula (8)1(t) DC component and flicker envelope are only included.
4. the measuring method of wind power generating set voltage flicker as described in claim 1, which is characterized in that in the step S6
The empirical mode decomposition EMD screens out the highest ingredient of frequency by subtracting the method that zero crossing fluctuates, according to the method,
IMF is arranged in order from high to low according to frequency, and each IMF represents the fluctuation that signal includes, and EMD processes are as follows：
1) the only signal z comprising direct current and low frequency flicker envelope is enabled1(t)=x (t) finds the extreme point of signal x (t), uses three
The method of secondary batten difference obtains the coenvelope v of signal1(t) and lower envelope v (t)；
2) mean value envelope m (t) can be obtained according to formula (9)：
M (t)=[v1(t)+v(t)]/2 (9)
3) h is obtained by formula (10)1(t)：
h1(t)=x (t)-m (t) (10)
If 4) the h obtained by formula (10)1(t) it is discontented with full measure end condition, then by h1(t) iteration is new x (t), is repeated
1), 2) He 3) step, until h1(t) when meeting decomposition end condition, iteration stopping, the IMF obtained at this time is denoted as c1(t),
Value envelope m (t) and the signal h (t) subtracted after mean value envelope m (t) continue according to formula (11) iteration：
5) first IMF components c is obtained by formula (12)1(t)
Formula (12) r1(t) it is residue signal；By the highest frequency component in x (t), continue iteration according to formula (13) and obtain hardly
R containing any frequency contentn(t)
Original signal x (t) can be reconstructed by formula (14)：
R in formula (13)n(t) it is n-th of residual volume, cn(t) it is n-th of IMF component.
5. the measuring method of wind power generating set voltage flicker as described in claim 1, which is characterized in that in the step S7
Hilbert transform is done to each IMF can obtain formula (15)：
In formula (15), P be Cauchy's principal component, Cj(t) it is IMF；
Corresponding plural number analytical function is formula (16)：
It can be obtained by formula (16)：
In formula (17), aj(t) it is instantaneous amplitude；θj(t) it is instantaneous phase；ωj(t) it is instantaneous frequency.
6. the measuring method of wind power generating set voltage flicker as described in claim 1, which is characterized in that in the step S8
According to IEC61000-4-15 standards, instantaneous visual sense degree S (t) is expressed as：
I.e. instantaneous visual sense degree S (t) is equal to flickering voltage modulation degree mfSquare with visual sense degree coefficient kfSquare be weighted fortune
It calculates, is obtained multiplied by a constant coefficient h, when the frequency of flickering voltage is 8.8Hz, and modulation degree is m=0.0025, instantaneous visual sense
S (t)=1 is spent, at this time kf=1 can acquire h=1/0.00252；
Statistical analysis in 10 minutes is carried out to S (t), Short Term Flicker severity P is can obtain according to formula (19)st
P in formula (19)0.1、P1、P3、P10、P50Surpass perceiving for 0.1%, 1%, 3%, 10%, 50% time in respectively 10 minutes
Unit value.
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| CN113447701A (en) * | 2021-05-18 | 2021-09-28 | 熊秀 | Lightning current peak value calibration method and device |
| CN113447701B (en) * | 2021-05-18 | 2023-09-01 | 熊秀 | Lightning current peak value calibration method and device |
| CN113569449A (en) * | 2021-07-13 | 2021-10-29 | 内蒙古工业大学 | Method, equipment and medium for optimizing finite element model of motor for flywheel energy storage |
| CN113569449B (en) * | 2021-07-13 | 2023-06-20 | 内蒙古工业大学 | Method, equipment and medium for optimizing finite element model of motor for flywheel energy storage |
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