CN104849545A  Power system frequency measuring method and power system frequency measuring device  Google Patents
Power system frequency measuring method and power system frequency measuring device Download PDFInfo
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 CN104849545A CN104849545A CN201510216704.7A CN201510216704A CN104849545A CN 104849545 A CN104849545 A CN 104849545A CN 201510216704 A CN201510216704 A CN 201510216704A CN 104849545 A CN104849545 A CN 104849545A
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 238000005070 sampling Methods 0.000 claims abstract description 48
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 238000000354 decomposition reaction Methods 0.000 claims abstract description 8
 238000005259 measurement Methods 0.000 claims description 25
 230000000694 effects Effects 0.000 claims description 5
 230000000737 periodic Effects 0.000 claims description 4
 238000000691 measurement method Methods 0.000 claims description 2
 230000003252 repetitive Effects 0.000 claims description 2
 230000001131 transforming Effects 0.000 abstract description 5
 230000001934 delay Effects 0.000 description 4
 230000000051 modifying Effects 0.000 description 3
 238000010586 diagram Methods 0.000 description 2
 230000000630 rising Effects 0.000 description 2
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Classifications

 G—PHYSICS
 G01—MEASURING; TESTING
 G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
 G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
 G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
Abstract
The invention relates to a power system frequency measuring method and a power system frequency measuring device. First, a current signal to be measured is sampled, and an obtained sampling signal is made discrete; then, sampling matrixes [In] and [In1] of the current signal to be measured at the time n and at the time n1 are listed based on the discrete sampling signal, a reference frequency f(reference) is set, a reference voltage signal u(t) is constructed based on f(reference), and u(t) is made discrete to obtain a reference matrix; and finally, phase values corresponding to the time n and the time n1 are obtained based on characteristic roots of matrixes [In]+[U] and [In1]+[U], and a calculation frequency f(calculation) is solved. According to the invention, QR decomposition and similarity transformation are performed on the sampling matrixes constructed with a reference signal and the signal to be measured, the phase of the signal to be measured is obtained based on the characteristic roots of the corresponding matrixes, and the frequency of the signal to be measured is worked out based on the phase difference between former and latter moments of time. Compared with the prior art, the calculation process is simplified, the amount of calculation is reduced greatly, and the frequency of a sinusoidal signal can be calculated in a powerfrequency data window quickly and accurately.
Description
Technical field
The present invention relates to a kind of power system frequency measuring method, belong to technical field of power systems.
Background technology
Frequency is one of important electric parameter of electric system, has important meaning to the research of power system frequency Measurement Algorithm in theory and reality.When electric system normally runs, frequency weighs an important indicator of the quality of power supply, and when electric system is broken down, frequency is the important evidence judging the system failure.
At present, power system frequency Measurement Algorithm mainly discrete Fourier transformation method (Discrete FourierTransform, DFT), the method is for observation model (supposing D=0), when sampling rate and data window are selected suitable, correctly can obtain model parameter, but consider that true measurement departs from ideal conditions, DFT algorithm has the inherent characteristic being insensitive to harmonic component, during for the signal slowly changed under dynamic condition, its precision can greatly reduce.In addition, when the frequency departure rated frequency of reality, due to the constraint that potential data window is long, frequency measurement also there will be error.Its innovatory algorithm to a certain degree can reduce measuring error when considering harmonic wave and noise, but there is shortcoming such as increase calculated amount and time lag etc.And in electric system, the transient signal particularly after fault, except containing except power frequency component, also has a large amount of integer harmonic, nonstoichiometric oxide and attenuating dc component, the impact of current algorithm when calculated rate by these components is larger.
Such as, publication No. is the Chinese patent of CN 101852826 A, which disclose a kind of harmonic analysis method of electric system, approach by carrying out three times to electric system fundamental frequency, approach at every turn and Fourier transform complex coefficient is adjusted, and the hits of signal sampling period each in signal sampling series is adjusted, finally obtain the fundamental frequency value after approaching for three times, this value is to be evaluated, although the program can realize highprecision frequency computation part, but its calculated amount of data processing in approximate procedure is larger, comparatively complicated in computation process, in addition, the program is only carried out three times to fundamental frequency and is approached, its precision cannot adjust according to actual conditions.
Summary of the invention
The object of this invention is to provide a kind of power system frequency measuring method and measurement mechanism, in order to solve the complicated problem with more precise frequency result can not be obtained of existing computation process.
For achieving the above object, the solution of the present invention comprises:
Not by a power system frequency measuring method for noise effect nonperiodic, step is as follows:
1) to N number of point of sampling in current signal one cycle to be measured, and carry out discrete to the sampled signal obtained;
2) by discrete sampled signal, the sampling matrix [I in current signal n moment to be measured and n1 moment is listed
_{n}] and [I
_{n1}]:
Wherein M≤L≤NM, L, M are setting value;
3) reference frequency f is set
_{reference}, by f
_{reference}with voltage expression structure voltage signal u (t), and obtain Rmatrix to u (t) is discrete:
4) by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}the characteristic root of [U], obtains n moment and phase value θ corresponding to n1
_{n}and θ
_{n1}, and by θ
_{n}and θ
_{n1}obtain calculated rate f
_{calculate}, this f
_{calculate}for frequency to be measured.
Described frequency measurement method also comprises: step 5): calculate f
_{calculate}with f
_{reference}difference; Step 6): judge difference whether in the error range of setting, if so, then this f
_{calculate}be and treat measured frequency actual value; If not, then the calculated rate f will obtained
_{calculate}as new reference frequency, repeat step 3), 4), 5), until the difference of calculated rate and reference frequency is in the error range set.
Step 4 comprises following process: to sampling matrix [I
_{n}] and [I
_{n1}] carry out svd.
Step 4 comprises following process: by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}[U] carries out QR decomposition: [I
_{n}]
^{+}[U]=[Q
_{n}] [Λ
_{n}] [R'
_{n}], [I
_{n1}]
^{+}[U]=[Q
_{n1}] [Λ
_{n1}] [R'
_{n1}], wherein [Λ
_{n}] and [Λ
_{n1}] for the first two diagonal element is not 0, all the other diagonal elements are the diagonal matrix of 0.
Described error range is: be less than 0.000001.
Not by a power system frequency measurement mechanism for noise effect nonperiodic, comprising:
Module one: to N number of point of sampling in current signal one cycle to be measured, and carry out discrete to the sampled signal obtained;
Module two: by discrete sampled signal, lists the sampling matrix [I in current signal n moment to be measured and n1 moment
_{n}] and [I
_{n1}]:
Wherein M≤L≤NM, L, M are setting value;
Module three: setting reference frequency f
_{reference}, by f
_{reference}with voltage expression structure voltage signal u (t), and obtain Rmatrix to u (t) is discrete:
Module four: by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}the characteristic root of [U], obtains n moment and phase value θ corresponding to n1
_{n}and θ
_{n1}, and by θ
_{n}and θ
_{n1}obtain calculated rate f
_{calculate}, this f
_{calculate}for frequency to be measured.
Described frequency measuring equipment also comprises: module five: for calculating f
_{calculate}with f
_{reference}difference; Module six: for judging difference whether in the error range of setting, if so, then this f
_{calculate}be and treat measured frequency actual value; If not, then the calculated rate f will obtained
_{calculate}as new reference frequency, repetitive operation module three, module four and module five, until the difference of calculated rate and reference frequency is in the error range set.
Module four comprises sampling matrix [I
_{n}] and [I
_{n1}] carry out svd.
Module four comprises matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}[U] carries out QR decomposition: [I
_{n}]
^{+}[U]=[Q
_{n}] [Λ
_{n}] [R'
_{n}], [I
_{n1}]
^{+}[U]=[Q
_{n1}] [Λ
_{n1}] [R'
_{n1}], wherein [Λ
_{n}] and [Λ
_{n1}] for the first two diagonal element is not 0, all the other diagonal elements are the diagonal matrix of 0.
The beneficial effect of this programme is: the pencil of matrix analytical approach of the sampling matrix that this programme utilizes reference signal and measured signal to construct and Singular Value Decomposition Using technology, by carrying out QR decomposition and similarity transformation to matrix, and the characteristic root of correlation matrix calculates, obtain the phase place of measured signal, the frequency of measured signal is calculated by the phasometer of front and back sampling instant, this programme is prior art comparatively, simplify computation process, calculated amount is greatly reduced, and the frequency of sinusoidal signal can be calculated fast, accurately in power frequency data window.
Accompanying drawing explanation
Fig. 1 is the process flow diagram of the embodiment of the present invention 1.
The frequency error measurement result that Fig. 2 is modulation frequency when being amplitude modulation and the frequency modulation of 2Hz.
Frequency measurement result figure when Fig. 3 (a) is amplitude Spline smoothing 10%.
Frequency measurement result figure when Fig. 3 (b) is amplitude Spline smoothing10%.
Frequency measurement result figure when Fig. 3 (c) is phase step change 10 degree.
Fig. 3 (d) is the frequency measurement result figure of phase step change10 when spending.
Frequency measurement result figure when Fig. 3 (e) is frequency step change 1Hz.
Frequency measurement result figure when Fig. 3 (f) is frequency step change1Hz.
Fig. 4 (a) is that frequency delays the frequency measurement result figure rising initial period.
Fig. 4 (b) is that frequency delays the frequency measurement result figure rising ending phase.
Fig. 4 (c) is that frequency delays the frequency measurement result figure falling initial period.
Fig. 4 (d) is that frequency delays the frequency measurement result figure falling ending phase.
Fig. 5 is the process flow diagram of embodiment of the method 2.
Embodiment
Below in conjunction with accompanying drawing, the present invention will be further described in detail.
Embodiment of the method 1:
As shown in Figure 1, the substance of this method is as follows:
1) to N point of sampling in current signal oneperiod to be measured, and carry out discrete to the sampled signal obtained, obtain the discrete expression of sampled signal;
2) according to the discrete expression of sampled signal, the sampling matrix [I in current signal n moment to be measured and n1 moment is listed
_{n}] and [I
_{n1}]:
Wherein M≤L≤NM;
3) reference frequency f is set
_{reference}, by f
_{reference}structure reference signal u (t), discrete and obtain Rmatrix to u (t):
4) by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}the characteristic root of [U], obtains n moment and phase value θ corresponding to n1
_{n}and θ
_{n1}, by θ
_{n}and θ
_{n1}obtain calculated rate f
_{calculate}.
Below for current signal 100 [1+0.1cos (4 π t)] cos [100 π t+0.1 (4 π tπ)], abovementioned technological means is specifically described:
The present embodiment is the electric system of power frequency 50Hz, first samples to current signal to be measured, and each cycle sampling N point, then sampling interval is
and carry out discrete to the sampled signal obtained, obtain the discrete expression of sampled signal.
According to the discrete expression of sampled signal, list the sampling matrix [I in current signal n moment to be measured and n1 moment
_{n}] and [I
_{n1}]:
Wherein M≤L≤NM, L, M are setting value, can according to treating that examining system itself and measuring accuracy set.
Utilize generalized circular matrix, sampling matrix can be expressed as:
[I
_{n}]＝[Z
_{1}][P]
_{n}[Z
_{2}]，[I
_{n1}]＝[Z
_{1}][P]
_{n1}[Z
_{2}]，
Wherein
Can by comparatively complicated sampling matrix [I by this step
_{n}] and [I
_{n1}] carry out abbreviation, to the process of sampling matrix after being convenient to, if certainly do not consider the impact of computation complexity, also abovementioned conversion can not be carried out to sampling matrix.
Setting reference frequency is electric system power frequency, i.e. f
_{reference}=50Hz, obtaining reference voltage signal by reference frequency is u (t
_{1})=cos ω
_{1}t
_{1}, 0≤t
_{1}≤ 0.02, construct a comparatively simple and reference voltage signal for rule here, object is for the ease of process computing afterwards, as other embodiment, reference frequency also can be utilized to construct other u (t) expression formula.
Carry out discrete to reference signal again, obtain the sampling matrix that reference signal is corresponding:
Similarly, generalized circular matrix reference signal matrix is utilized also can be expressed as: [U]=[Z
_{1}] [P '] [Z
_{2}], wherein
here identical with the processing mode of sampling matrix to the processing mode of Rmatrix, no longer repeat to introduce.
Can be obtained by above sampling matrix and Rmatrix:
[I
_{n}]
^{+}[U]＝[Z
_{2}]
^{+}[P]
_{n} ^{}[Z
_{1}]
^{+}[Z
_{1}][P′][Z
_{2}]
＝[Z
_{2}]
^{+}[P]
_{n} ^{}[P′][Z
_{2}]
In like manner
QR is utilized to decompose and similarity transformation, can by high level matrix [I
_{n}]
^{+}the characteristic root of [U] is asked for the characteristic root transferring 2 rank matrixes to and is calculated, greatly simplify computation process, but, when not considering computation complexity, also matrix transformation method Sum decomposition mode otherwise can be made, high level matrix is simplified, or directly the characteristic root of a matrix is solved.
The characteristic root obtained is utilized to solve amplitude and the phase place of measured signal.Detailed process is: phase place corresponding to n moment is
phase place corresponding to n1 moment is
then due to θ
_{n}θ
_{n1}=ω
_{1}h, can obtain frequency computation part value is:
As shown in Figure 2, be the frequency measurement result figure obtained, as can be seen from the figure, this programme can obtain the calculated rate of measured signal accurately.
In addition, Fig. 3 give the amplitude of signal, phase place and frequency discontinuity time frequency measurement result, method as can be seen from the figure proposed by the invention is by the impact of amplitude, phase place and frequency discontinuity, and the response time of frequency is no more than 20ms.
The frequency that gives Fig. 4 slowly rise (1Hz/s) and slowly decline (1Hz/s) time frequency measurement result, method as can be seen from the figure proposed by the invention can the change of tracking frequencies fast.
Embodiment of the method 2:
As shown in Figure 5, the present embodiment is substantially identical with the implementation process of embodiment 1, and the part distinguished with it is: in the present embodiment, after the frequency computation part value obtained, also has the process of a verification computation result.Detailed process is as follows:
The frequency reference of the frequency computation part value obtained and setting is subtracted each other, obtains difference ε=f
_{calculate}f
_{reference}, when ε is less than 0.000001, then the frequency computation part value obtained is the actual frequency values of measured signal; When ε is more than or equal to 0.000001, then make the frequency computation part value that frequency reference equals to obtain, i.e. f
_{reference}=f
_{calculate}, reconstruct Rmatrix with this frequency reference
repeat above computation process, successive iteration asks for the frequency of measured signal, the frequency that each iteration gets reference signal is the frequency of last computation, reconstruct Rmatrix, until the frequency computation part value obtained is less than 0.000001 with the difference of corresponding frequency reference, the frequency computation part value now obtained is the actual frequency values of measured signal.
As other embodiment, choosing of abovementioned difference can require corresponding setting according to actual conditions and error precision.
Device embodiment
About the embodiment of frequency measuring equipment of the present invention, be the software frame that the flow process with embodiment 1 is completely corresponding, repeat no more here.
Be presented above concrete embodiment, but the present invention is not limited to described embodiment.Basic ideas of the present invention are abovementioned basic scheme, and for those of ordinary skill in the art, according to instruction of the present invention, designing the model of various distortion, formula, parameter does not need to spend creative work.The change carried out embodiment without departing from the principles and spirit of the present invention, amendment, replacement and modification still fall within the scope of protection of the present invention.
Claims (9)
1., not by a power system frequency measuring method for noise effect nonperiodic, it is characterized in that, step is as follows:
1) to N number of point of sampling in current signal one cycle to be measured, and carry out discrete to the sampled signal obtained;
2) by discrete sampled signal, the sampling matrix [I in current signal n moment to be measured and n1 moment is listed
_{n}] and [I
_{n1}]:
Wherein M≤L≤NM, L, M are setting value;
3) reference frequency f is set
_{reference}, by f
_{reference}with voltage expression structure voltage signal u (t), and obtain Rmatrix to u (t) is discrete:
4) by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}the characteristic root of [U], obtains n moment and phase value θ corresponding to n1
_{n}and θ
_{n1}, and by θ
_{n}and θ
_{n1}obtain calculated rate f
_{calculate}, this f
_{calculate}for frequency to be measured.
2. power system frequency measuring method according to claim 1, is characterized in that, described frequency measurement method also comprises: step 5): calculate f
_{calculate}with f
_{reference}difference; Step 6): judge difference whether in the error range of setting, if so, then this f
_{calculate}be and treat measured frequency actual value; If not, then the calculated rate f will obtained
_{calculate}as new reference frequency, repeat step 3), 4), 5), until the difference of calculated rate and reference frequency is in the error range set.
3. power system frequency measuring method according to claim 1 and 2, is characterized in that, step 4 comprises following process: to sampling matrix [I
_{n}] and [I
_{n1}] carry out svd.
4. power system frequency measuring method according to claim 3, is characterized in that, step 4 comprises following process: by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}[U] carries out QR decomposition: [I
_{n}]
^{+}[U]=[Q
_{n}] [Λ
_{n}] [R'
_{n}], [I
_{n1}]
^{+}[U]=[Q
_{n1}] [Λ
_{n1}] [R'
_{n1}], wherein [Λ
_{n}] and [Λ
_{n1}] for the first two diagonal element is not 0, all the other diagonal elements are the diagonal matrix of 0.
5. power system frequency measuring method according to claim 2, is characterized in that, described error range is: be less than 0.000001.
6., not by a power system frequency measurement mechanism for noise effect nonperiodic, it is characterized in that, comprising:
Module one: to N number of point of sampling in current signal one cycle to be measured, and carry out discrete to the sampled signal obtained;
Module two: by discrete sampled signal, lists the sampling matrix [I in current signal n moment to be measured and n1 moment
_{n}] and [I
_{n1}]:
Wherein M≤L≤NM, L, M are setting value;
Module three: setting reference frequency f
_{reference}, by f
_{reference}with voltage expression structure voltage signal u (t), and obtain Rmatrix to u (t) is discrete:
Module four: by matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}the characteristic root of [U], obtains n moment and phase value θ corresponding to n1
_{n}and θ
_{n1}, and by θ
_{n}and θ
_{n1}obtain calculated rate f
_{calculate}, this f
_{calculate}for frequency to be measured.
7. power system frequency measurement mechanism according to claim 6, is characterized in that, described frequency measuring equipment also comprises:
Module five: for calculating f
_{calculate}with f
_{reference}difference;
Module six: for judging difference whether in the error range of setting, if so, then this f
_{calculate}be and treat measured frequency actual value; If not, then the calculated rate f will obtained
_{calculate}as new reference frequency, repetitive operation module three, module four and module five, until the difference of calculated rate and reference frequency is in the error range set.
8. the power system frequency measurement mechanism according to claim 6 or 7, is characterized in that, module four comprises sampling matrix [I
_{n}] and [I
_{n1}] carry out svd.
9. power system frequency measurement mechanism according to claim 8, is characterized in that, module four comprises matrix [I
_{n}]
^{+}[U] and [I
_{n1}]
^{+}[U] carries out QR decomposition: [I
_{n}]
^{+}[U]=[Q
_{n}] [Λ
_{n}] [R'
_{n}], [I
_{n1}]
^{+}[U]=[Q
_{n1}] [Λ
_{n1}] [R'
_{n1}], wherein [Λ
_{n}] and [Λ
_{n1}] for the first two diagonal element is not 0, all the other diagonal elements are the diagonal matrix of 0.
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CN106018956A (en) *  20160810  20161012  北京妙微科技有限公司  Power system frequency calculation method of windowing spectral line interpolation 
CN107255749A (en) *  20170524  20171017  中国矿业大学(北京)  The quick determination method of Harmonious Waves in Power Systems based on difference equation 
EP3287795A1 (en) *  20160824  20180228  Schneider Electric Industries SAS  Method for determining the frequency of an ac signal 
CN109142862A (en) *  20180906  20190104  中国人民解放军海军工程大学  A kind of intelligent electrically engineering survey system and its measurement method 
CN110703137A (en) *  20191022  20200117  山东科技大学  Intelligent electrical engineering measurement system 
CN110988465A (en) *  20191205  20200410  深圳市兆驰数码科技股份有限公司  Frequency detection method and device for specific frequency sine wave signal and computer equipment 
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CN101603984A (en) *  20090701  20091216  湖南大学  The digitizing realtime detection method of electric signal frequency 
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2016
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CN101603984A (en) *  20090701  20091216  湖南大学  The digitizing realtime detection method of electric signal frequency 
CN101626266A (en) *  20090727  20100113  北京天碁科技有限公司  Method and device for estimating rank indication and precoding matrix indication in precoding system 
CN102520246A (en) *  20111205  20120627  西安交通大学  Constant frequency phasor extraction method 
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Cited By (9)
Publication number  Priority date  Publication date  Assignee  Title 

CN106018956A (en) *  20160810  20161012  北京妙微科技有限公司  Power system frequency calculation method of windowing spectral line interpolation 
CN106018956B (en) *  20160810  20181016  北京妙微科技有限公司  A kind of power system frequency computational methods of adding window spectral line interpolation 
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EP3287795A1 (en) *  20160824  20180228  Schneider Electric Industries SAS  Method for determining the frequency of an ac signal 
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CN107255749A (en) *  20170524  20171017  中国矿业大学(北京)  The quick determination method of Harmonious Waves in Power Systems based on difference equation 
CN109142862A (en) *  20180906  20190104  中国人民解放军海军工程大学  A kind of intelligent electrically engineering survey system and its measurement method 
CN110703137A (en) *  20191022  20200117  山东科技大学  Intelligent electrical engineering measurement system 
CN110988465A (en) *  20191205  20200410  深圳市兆驰数码科技股份有限公司  Frequency detection method and device for specific frequency sine wave signal and computer equipment 
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