CN101408586B - On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition - Google Patents

On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition Download PDF

Info

Publication number
CN101408586B
CN101408586B CN2008102275431A CN200810227543A CN101408586B CN 101408586 B CN101408586 B CN 101408586B CN 2008102275431 A CN2008102275431 A CN 2008102275431A CN 200810227543 A CN200810227543 A CN 200810227543A CN 101408586 B CN101408586 B CN 101408586B
Authority
CN
China
Prior art keywords
mode
natural mode
oscillation
frequency
curve
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.)
Active
Application number
CN2008102275431A
Other languages
Chinese (zh)
Other versions
CN101408586A (en
Inventor
段刚
林俊杰
吴京涛
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beijing Sifang Automation Co Ltd
Beijing Sifang Engineering Co Ltd
Original Assignee
Beijing Sifang Automation Co Ltd
Beijing Sifang Engineering Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Beijing Sifang Automation Co Ltd, Beijing Sifang Engineering Co Ltd filed Critical Beijing Sifang Automation Co Ltd
Priority to CN2008102275431A priority Critical patent/CN101408586B/en
Publication of CN101408586A publication Critical patent/CN101408586A/en
Application granted granted Critical
Publication of CN101408586B publication Critical patent/CN101408586B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Landscapes

  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

The invention belongs to the technical field of the low-frequency oscillation on-line detection and analysis in an electric power system and provides a low-frequency oscillation modal analysis method, which is based on wide area phasor metrical information and an empirical mode decomposition method and can carry out the on-line detection and node homology grouping toward the complex low-frequency oscillation of the electric power system. The modal analysis method not only has strong adaptability to the complex waveforms of non-linearity, non-stationarity or those containing non-periodic constituents, but also can carry out phase comparison toward nonsine or cosinoidal inherent modal curves which belong to the oscillation mode of the same electric power system but are slightly different in frequency and realize the homology grouping of the nodes participating in each oscillation mode, thus obtaining the power conversion relation among the nodes and the position of an oscillation center or interface.

Description

Online low-frequency oscillation detection and node coherence grouping method based on the empirical modal decomposition
Technical field
The invention belongs to online detection of low-frequency oscillation of electric power system and analysis technical field, relate more specifically to utilize the information of wide area phasor measurement system to carry out the method for online low-frequency oscillation detection of electric system and node coherence grouping.
Background technology
During electric system generation low-frequency oscillation, the operations staff suppresses vibration in order to be familiar with and to take measures, and except needs are known frequency, amplitude and the damping ratio of vibration, also needs to know the modal information of low-frequency oscillation.The modal information of low-frequency oscillation comprises that the coherence grouping relation of the node that vibrates is interactive relation, oscillation center or the interface location of meritorious hunting power between node.For these modal informations, method in the past is to obtain by eigenwert and proper vector based on the little interference analysis program solving system state matrix of mathematical model.The correctness of this class methods analysis result depends on the accuracy of used mathematical model, component parameters, state parameter, and the accuracy of these models and parameter often can not guarantee in practical power systems, therefore causes this class unreliable or insincere based on the methods and results of mathematics model analysis.In addition, calculate, also have the slow problem of computing velocity for these class methods of large scale system owing to need carry out the eigenwert and the proper phasor of matrix.
The frequency of information such as the voltage phasor of each measuring point of electrical network, electric current phasor, power, frequency with per second tens or frames up to a hundred can be sent to the WAMS main website based on the WAMS (WAMS) of phasor measurement unit (PMU), can guarantee the synchronism of whole network data by GPS (GPS).Therefore can realize the Real Time Observation to each measuring point dynamic process of electrical network, this makes that directly carrying out the low-frequency oscillation model analysis according to measurement information becomes possibility.Yet, the low-frequency oscillation detection of WAMS and analytic function were confined to the oscillating curve of each node is carried out frequency, amplitude, the damping ratio information that spectrum analysis obtains vibrating in the past, and in view of the above the danger vibration that takes place is reported to the police, can not provide the modal information of electricity grid oscillating, especially can not correctly provide the phase information of oscillating curve, and correct oscillating curve phase information is the prerequisite of node coherence grouping, also is the prerequisite that the operations staff understands vibration mode and adopts right measures.Below just at present the shortcoming of the existing various low-frequency oscillation analysis methods of WAMS research field do respectively and discuss.
(1) discrete Fourier transform method (DFT): though discrete Fourier transform method speed is very fast, but can only obtain the frequency and the amplitude of mode of oscillation, can not obtain damping ratio and phase information, therefore in the actual WAMS of majority system, only as testing tool and coarse analysis instrument that vibration is taken place.
(2) Prony analytic approach: frequency, amplitude and the damping ratio that can not only calculate oscillating curve based on the frequency spectrum analysis method of Prony, and can obtain the initial phase of oscillating curve, but owing to belong to the frequency of oscillating curve of the different nodes of identical systems mode of oscillation in the reality is discrepant, even therefore the frequency of same node self-oscillation curve is directly carried out node coherence grouping according to initial phase and is tended to obtain wrong result still in variation.And, because the Prony method can not correctly be handled the complicated wave form that non-linear, non-stationary changes, contains composition non-periodic, therefore it is that frequency or initial phase are all unreliable that the spectrum analysis result that this method obtains does not have human relations, and in fact it obtains phase information and can't use in low-frequency oscillation is analyzed.In addition, compare Prony method calculated amount with other frequency spectrum analysis methods very big, and speed is extremely slow, when the measurement amount number of analyzing when needs is a lot (when carrying out the node coherence grouping of large scale electric network low-frequency oscillation, this is essential), be difficult to reach real-time requirement in line computation.(having provided example about Prony method unreliable on frequency computation part and problem that computing velocity is slow in " specific embodiments " part of this document is illustrated).For above-mentioned reasons, although the Prony method has the function of calculating the oscillating curve phase place, to also there not being at present actual WAMS to utilize it to realize the coherence grouping of node.
(3) the autoregression method of moving average (ARMA) and stochastic subspace method (N4SID): these methods are primarily aimed under relative strong white noise environment, signal does not have the data cases of obviously vibration to carry out spectrum analysis, computing time is long, can not provide phase information, not be suitable for fast detecting and warning are carried out in low-frequency oscillation significantly.
(4) Hilbert-Huang converter technique: the Empirical mode decomposition (EMD) that proposed by the yellow Hubei Province of U.S. scientist NASA in 1998 can with non-linear, non-stationary changes, the complicated wave form that contains composition non-periodic is decomposed into some natural mode of vibration oscillating components (promptly satisfy the limit number and zero point number differ 1 or equate, and the mean value of envelope is 0 curve up and down, as seen this component differ be decided to be sine or cosine curve) and non-oscillatory component, and its speed will be far faster than the Prony analytic approach.But, EMD method itself can not provide frequency, amplitude, damping ratio and the phase information of each natural mode of vibration oscillating component, when carrying out spectrum analysis, need solve the instantaneous frequency and the amplitude of modal components with Hilbert-Huang conversion based on the EMD method, yet the Hilbert-Huang conversion does not provide natural mode of vibration component phase information, and its calculated amount is bigger, and is consuming time longer.Therefore, though there has been the scholar to utilize the Hilbert-Huang converter technique to carry out the analysis of low-frequency oscillation under study for action, but its application only limits to detect low-frequency oscillation according to the oscillation frequency and the amplitude that analyze, and can not carry out phase analysis and hive off with point of adjustment.
From top summary as seen, existing low-frequency oscillation analysis method all can not or be unsuitable for the node that participates in low-frequency oscillation is carried out the analysis of relative phase.Because each node is not only relevant with oscillation amplitude to the degree of participation of vibration, and relevant with internodal relative phase, so these methods also all can not be estimated the degree of participation of the associated unit of each node to vibration quantitatively.The problems referred to above at existing low-frequency oscillation analysis method, the method that the present invention proposes realizes utilizing the wide area measurement data to carry out the online model analysis of low-frequency oscillation, correct calculation goes out the common mode internodal phase relation of vibrating, and analyzes these internodal people having the same aspiration and interest relation and Power Exchange relations.
At last, the node coherence grouping that is carried out in the present patent application method is distinguished and clarified at conceptive and existing similar concept.Although a people having the same aspiration and interest group of planes is identified in the stability analysis field of electric system and often uses, and the method for existing many judgement same tones, these methods all are to judge the same tone of curve according to the similarity of original measurement (or emulation) curve shape; And the same tone in the present patent application method is meant the phase place same tone of the mode curve that respectively vibrates in the primary curve, and adopted natural mode of vibration curve decomposition method, avoided non-linear, non-stationary to change and problem and difficulty that aperiodic component causes traditional frequency spectrum analysis methods such as Prony and DFT (traditional frequency spectrum analysis method think that any curve all be made up of some sines or the cosine curve with different fixing frequency that continue the whole period) based on Empirical mode decomposition.For example, in the low-frequency oscillation analysis method based on WAMS of certain famous producer, it is based on the dominant pattern theory of expansion homalographic criterion, measure the original power-angle curve that obtains according to each PMU earlier, and carry out coherence grouping in conjunction with the generator moment of inertia, just carry out spectrum analysis then, thisly hive off that to obtain be the same tone of each generator node overall movement trend, but not be superimposed upon the phase place same tone of the oscillationg component on the trend amount based on Prony.And method of the present invention is to carry out original meritorious or the fast frequency spectrum analysis that frequency measures of each PMU earlier, carry out node oscillation phase coherence grouping about certain system oscillation pattern according to the natural mode of vibration oscillating curve that decomposites again, the node coherence grouping result of each system oscillation pattern does not influence each other.
Summary of the invention
Detect at existing low-frequency oscillation based on WAMS (WAMS) and can not realize online node coherence grouping and may incorrect problem the nonstationary oscillation spectrum analysis.The invention provides a kind ofly based on Empirical mode decomposition, can realize low-frequency oscillation modal analysis method electric system complicated low-frequency oscillation carrying out online detection and node coherence grouping.Realize that the typical flowchart of this method sees Figure of description 1.
Described analytical approach is specifically by the following technical solutions:
A kind of based on Wide-area Measurement Information and Empirical mode decomposition, can realize low-frequency oscillation modal analysis method to electric system complicated low-frequency oscillation carrying out online detection and node coherence grouping, described analytical approach is not only applicable to non-linear, non-stationary changes, the actual complex waveform that contains composition non-periodic, also can be to belonging to same power system oscillation pattern, but the natural mode of vibration curve of non-sinusoidal that frequency is slightly variant or cosine carries out the phase bit comparison, realization is to the coherence grouping of the node that participates in each mode of oscillation, thereby obtains internodal Power Exchange relation and oscillation center or interfacial position; It is characterized in that described analytical approach may further comprise the steps:
(1) at the current time window, the meritorious injecting power of node or the frequency actual measurement oscillating curve that adopt the frequency spectrum analysis method that decomposes based on empirical modal will deliver to the wide area measurement main website in the phasor measurement unit PMU collection are decomposed into the natural mode of vibration curve;
(2) calculate the parameter of oscillation of each natural mode of vibration curve according to the natural mode of vibration parameter of curve computing method of definition;
(3) parameter of oscillation according to each the natural mode of vibration curve that is calculated carries out the dangerous mode of oscillation identification of electric system, and by the dangerous mode of oscillation of the electric system found to the grouping of natural mode of vibration curve, be about to the natural mode of vibration curve frequency natural mode of vibration curve close and belong to same mode of oscillation with system's limit risk frequency;
(4) node that participates in the dangerous mode of oscillation of electric system is carried out coherence grouping according to the phase place difference of corresponding natural mode of vibration curve;
(5) circuit that passes through according to the cutting plane between homology group is determined the oscillation center of each dangerous mode of oscillation of electric system or the sets of lines at interphase place;
(6) according to geographic position or topological relation the node division that does not directly link to each other on electric in the same homology group is become different people having the same aspiration and interest subgroups.
In step (1), in electrical network, there are not electromagnetic looped network or electromagnetic looped network scope very little, and nearly all node injects active power to be had PMU to measure or can be measured extrapolate the time by other PMU, adopts node to inject active power and carries out spectrum analysis and carry out low-frequency oscillation detection and model analysis; When the serious or most of node injection of electromagnetic looped network active power does not have the PMU measurement, adopt nodal frequency to carry out spectrum analysis and carry out low-frequency oscillation detection and model analysis.
In step (2), calculate the parameter of oscillation of each natural mode of vibration curve according to the natural mode of vibration parameter of curve computing method of definition; The natural mode of vibration parameter of curve of definition is as follows:
(a) the data point phase place of natural mode of vibration curve: the phase place of each data point adopts zero-crossing method to obtain, be that curve positive going zeror crossing point place is 0 °, negative sense zero crossing place is ± 180 °, maximum point is 90 °, minimum point position-90 °, the phase place of the data point between the adjacent zeros limit is tried to achieve according to uniformly-spaced dividing 90 parts equally;
(b) relative phase of natural mode of vibration curve phase differential and natural mode of vibration curve: in the frequency phase place of two natural mode of vibration curves relatively under the difference condition slightly, definition natural mode of vibration curve phase differential Φ is the difference φ of each corresponding data point phase place on two curves iArithmetic mean, described φ iSatisfy-180 °＜φ i≤ 180 °.In the low-frequency oscillation model analysis, for one group of natural mode of vibration curve that belongs to same mode frequencey, with the curve of amplitude maximum wherein is reference curve, even its natural mode of vibration curve relative phase is 0, all the other natural mode of vibration curves should be the relative phase of all the other natural mode of vibration curves with reference to the phase differential of natural mode of vibration curve relatively;
(c) the data point frequency of natural mode of vibration curve and natural mode of vibration curve frequency: the frequency of each data point of natural mode of vibration curve is tried to achieve through conversion the angular frequency that time difference obtains by the phase place and the last data point phase place of this data point, in order to compare the frequency of two mode curves under the situation of non-stationary frequency, definition natural mode of vibration curve frequency is the mean value of each data point frequency of this curve; In order to improve computing velocity, the approximate natural mode of vibration curve frequency f of representing with following formula of asking of short-cut method Curve:
f curve = ( n extrm - 1 ) / 2 t last - t first
N wherein ExtrmCount for this natural mode of vibration curve extreme value, described extreme point contains maximum point and minimum point, t LastBe the moment of this last extreme point of natural mode of vibration curve, t FirstBe the moment of this first extreme point of natural mode of vibration curve;
(d) amplitude of natural mode of vibration curve: be defined as each maximal point of natural mode of vibration curve and the mean value of minimal point amplitude;
(e) damping ratio of natural mode of vibration curve data point and natural mode of vibration curve damping ratio: the amplitude that makes natural mode of vibration curve data point i is A i, the amplitude of the data point of corresponding phase is A in the adjacent last cycle I-TReason owing to fixed sampling interval technique, often there is not sampled point in the data point of current data point corresponding phase in last cycle, at this moment, need utilize the amplitude and the phase place of current data point actual samples point before and after the corresponding phase data point in last cycle to obtain amplitude A with the method for interpolation I-T, can be similar to the damping ratio of obtaining the data point i on the natural mode of vibration curve according to following formula:
ζ i = ln ( A i - T / A i ) 2 π
Natural mode of vibration curve damping ratio is defined as the mean value of this each data point damping ratio of natural mode of vibration curve; In order to reduce calculated amount, the mean value of also available each extreme point damping ratio is similar to.
In step (3), parameter of oscillation according to each the natural mode of vibration curve that is calculated carries out the dangerous mode of oscillation identification of electric system, and the natural mode of vibration curve is divided into groups by the dangerous mode of oscillation of the electric system found, be about to the natural mode of vibration curve frequency natural mode of vibration curve close with system's limit risk frequency and belong to same mode of oscillation, its concrete grammar is as follows:
In the natural mode of vibration curve that each node that decomposites measures, select amplitude maximum and amplitude greater than defined threshold A Threshold, damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously ThresholdThe natural mode of vibration curve frequency of a certain node, mode frequencey 1 as current system, close with it as if having in the natural mode of vibration curve frequency of all nodes, promptly the ratio of absolute value of both frequency differences and system oscillation mode frequency 1 is less than the percentage threshold FD that sets Threshold, think that then this node participates in the vibration of mode of oscillation 1, can only have a natural mode of vibration curve to be included into the mode of oscillation 1 of system at most for each node.
The natural mode of vibration curve that is included into mode of oscillation 1 of getting rid of all nodes is selected amplitude maximum and amplitude greater than defined threshold A in remaining natural mode of vibration curve Threshold, damping ratio is less than the damping ratio threshold value D that sets simultaneously ThresholdThe natural mode of vibration curve frequency that measures of a certain node, as the mode frequencey 2 of current system, find out all natural mode of vibration curves and the corresponding node thereof that participates in mode of oscillation 2 in the system according to aforesaid method.
The rest may be inferred find out whole electric system at current period amplitude enough big and maximum amplitude greater than defined threshold A Threshold, damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously ThresholdAll mode of oscillation, promptly dangerous mode of oscillation, and find out node and the corresponding natural mode of vibration curve that participates in corresponding dangerous mode of oscillation.
Defined threshold A for above-mentioned amplitude Threshold, carry out low-frequency oscillation detection and analysis, then A if adopt node to inject active power ThresholdUsually be taken as 30MW, detect and analyze if adopt nodal frequency to carry out low-frequency oscillation, then A ThresholdUsually be taken as 0.02Hz; For above-mentioned damping ratio threshold value D ThresholdUsually be taken as 0.05; Absolute value and system oscillation mode frequency percentage threshold FD for above-mentioned frequency difference ThresholdUsually be taken as 10%.
In step (4), the node that participates in the dangerous mode of oscillation of electric system is carried out coherence grouping according to the phase place difference of corresponding natural mode of vibration curve, its concrete grammar is as follows:
Each the dangerous system oscillation pattern that finds for abovementioned steps, all natural mode of vibration curves that participate in the node correspondence of this mode of oscillation are carried out the phase bit comparison, natural mode of vibration curve with the amplitude maximum is a reference curve, calculate all the other natural mode of vibration curves and this relative phase Φ with reference to the natural mode of vibration curve, wherein-180 °＜Φ≤180 °; If the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is less than 90 °, then the node that this node and reference curve are corresponding belongs to identical homology group; Otherwise if the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is greater than 90 °, then this node belongs to the homology group opposite with reference mode; In view of the above, all nodes that participate in certain mode oscillation are divided into two groups, hunting power mainly back and forth exchanges between these two groups.
When the group is carried out visual expression, the coherence grouping situation of different system mode of oscillation is plotted on different factory's station geographic maps, the vibration of the natural mode of vibration curve of respective nodes correspondence is described with colored vector arrow in each factory's station bus nodes, the different homology group of different colours representative of vector arrow, the length of arrow is represented the amplitude of natural mode of vibration curve, and the direction of arrow is determined by the relative phase of natural mode of vibration curve.
In step (5), when phasor measurement unit PMU is layouted when closeer, be when not having other not hive off substation bus bar between substation bus bar homology group, can determine that accurately oscillation center or interphase which circuit are made of, and promptly determine the oscillation center of system oscillation pattern or the sets of lines at interphase place by the circuit that the cutting plane between homology group is passed through.On group's visual expression figure, use short dash line with the circuit square crossing to indicate circuit on the vibration interphase.
In step (6), the node that does not directly link to each other on electric in the same homology group further is divided into different people having the same aspiration and interest subgroups according to geographic position or topological relation.The knot vector arrow of different people having the same aspiration and interest subgroup adopts the same color of different depth degrees to carry out painted.
Natural mode of vibration curve (differ and be decided to be sine or the cosine curve) phase differential that the present invention proposes and the notion and the computing method of natural mode of vibration curve relative phase are to utilize Empirical mode decomposition to carry out the key that online low-frequency oscillation node hives off, no similar definition and method in traditional Hilbert-Huang conversion Spectral Analysis Method of decomposing based on empirical modal.Utilize this method to can be implemented under the slightly different situation of frequency oscillating curve is carried out reasonably phase bit comparison, non-linear, non-stationary, the oscillationg component that contains in the complicated wave form of composition non-periodic are carried out rational phase bit comparison and analysis thereby this method is applicable to.Overcome frequency spectrum analysis methods such as FFT, Prony at non-linear, non-stationary, contain under the complicated wave form situation of composition non-periodic the shortcoming that can not calculate phase place or can not rationally carry out the phase bit comparison oscillationg component wherein.Carry out in the method for utilizing the present invention to propose on the basis of natural mode of vibration curve phase bit comparison of PMU actual measurement oscillating curve, the present invention has realized the sets of lines of hiving off with point of adjustment and determining oscillation center or interphase place based on the online low-frequency oscillation of PMU measured data first.The above-mentioned low-frequency oscillation modal analysis result that is obtained by this method is compared with the result that traditional little interference analysis program based on mathematical model obtains, advantage with accuracy limitations of the mathematical model of not being subjected to, component parameters, state parameter, so the credibility of its low-frequency oscillation modal analysis result, reliability and accuracy are all very high.
Description of drawings
Fig. 1 is online low-frequency oscillation detection and the node coherence grouping algorithm block diagram that decomposes based on empirical modal;
Fig. 2 is online low-frequency oscillation detection of frequency-division section and a model analysis algorithm block diagram in the real system;
Fig. 3 is the spectrum analysis result based on the empirical modal decomposition that the outer net of A electrical network injects active power;
Fig. 4 is for the natural mode of vibration curve at 4 main factory stations in the 0.7Hz system oscillation pattern and by the relative phase situation of hiving off;
Fig. 5 is that 0.7Hz system oscillation pattern node coherence grouping and amplitude, the visual geography of phase place are schemed.
Embodiment
Also in conjunction with specific embodiments technical scheme of the present invention is made further detailed presentations according to Figure of description below.
The present invention proposes a kind of based on wide area measurement information and Empirical mode decomposition, can realize low-frequency oscillation modal analysis method to non-stationary electric system complicated low-frequency oscillation carrying out on-line quick detection and node coherence grouping, realize that the typical flowchart of this method sees Figure of description 1, its detailed step is as follows:
(1) at the current time window, the meritorious injecting power of node or the frequency actual measurement oscillating curve that adopt the frequency spectrum analysis method that decomposes based on empirical modal will deliver to the wide area measurement main website on PMU gathers are decomposed into the natural mode of vibration curve; In electrical network, there are not electromagnetic looped network or electromagnetic looped network scope very little, and nearly all node injects active power to be had PMU to measure or can be measured extrapolate the time by other PMU, adopts node to inject active power and carries out spectrum analysis and carry out low-frequency oscillation detection and model analysis; When the serious or most of node injection of electromagnetic looped network active power does not have the PMU measurement, adopt nodal frequency to carry out spectrum analysis and carry out low-frequency oscillation detection and model analysis.
(2) calculate the parameter of oscillation of each natural mode of vibration curve according to the natural mode of vibration parameter of curve computing method of definition.The present invention proposes and has defined the notions such as data point phase place, natural mode of vibration curve phase differential and natural mode of vibration curve relative phase of the natural mode of vibration curve (differ and be decided to be sine or cosine curve) that is obtained by Empirical mode decomposition, is used under the slightly different situation of frequency vibration mode curve being carried out the phase bit comparison.These definition are utilize Empirical mode decomposition to vibrate key that node hives off, no similar definition in the Hilbert-Huang converter technique based on EMD.In addition, natural mode of vibration curve data point damping ratio and data point frequency, natural mode of vibration curve damping ratio, natural mode of vibration curve frequency, natural mode of vibration curve amplitude have also been defined.The instantaneous frequency based on the Hilbert conversion that the natural mode of vibration curve that decomposites for EMD carries out in these definition and the Hilbert-Huang conversion is different with the instantaneous amplitude computing method, but simple, fast, and precision satisfies the requirement of low-frequency oscillation of electric power system analysis.The natural mode of vibration parameter of curve and the computing method thereof of the present invention's definition are as follows:
(a) the data point phase place of natural mode of vibration curve: the phase place of each data point adopts zero-crossing method to obtain, be that curve positive going zeror crossing point place is 0 °, negative sense zero crossing place is ± 180 °, maximum point is 90 °, minimum point position-90 °, the phase place of the data point between the adjacent zeros limit is tried to achieve according to uniformly-spaced dividing 90 parts equally.
(b) relative phase of natural mode of vibration curve phase differential and natural mode of vibration curve: in the frequency phase place of two natural mode of vibration curves relatively under the difference condition slightly, definition natural mode of vibration curve phase differential Φ is the difference φ of each corresponding data point phase place on two curves iArithmetic mean, described φ iSatisfy-180 °＜φ i≤ 180 °.In the low-frequency oscillation model analysis, for one group of natural mode of vibration curve that belongs to same mode frequencey, with the curve of amplitude maximum wherein is reference curve, even its natural mode of vibration curve relative phase is 0, all the other natural mode of vibration curves should be the relative phase of all the other natural mode of vibration curves with reference to the phase differential of natural mode of vibration curve relatively.
(c) the data point frequency of natural mode of vibration curve and natural mode of vibration curve frequency: the frequency of each data point of natural mode of vibration curve is tried to achieve through conversion the angular frequency that time difference obtains by the phase place and the last data point phase place of this data point, in order to compare the frequency of two natural mode of vibration curves under the situation of non-stationary frequency, definition natural mode of vibration curve frequency is the mean value of each data point frequency of this curve; In order to improve computing velocity, the approximate natural mode of vibration curve frequency f of representing with following formula of asking of short-cut method Curve:
f curve = ( n extrm - 1 ) / 2 t last - t first
N wherein ExtrmCount for this natural mode of vibration curve extreme value, described extreme point contains maximum point and minimum point, t LastBe the moment of this last extreme point of natural mode of vibration curve, t FirstBe the moment of this first extreme point of natural mode of vibration curve.
(d) amplitude of natural mode of vibration curve: be defined as each maximal point of natural mode of vibration curve and the mean value of minimal point amplitude.
(e) damping ratio of natural mode of vibration curve data point and natural mode of vibration curve damping ratio: the amplitude that makes natural mode of vibration curve data point i is A i, the amplitude of the data point of corresponding phase is A in the adjacent last cycle I-TReason owing to fixed sampling interval technique, often there is not sampled point in the data point of current data point corresponding phase in last cycle, at this moment, need to utilize the amplitude and the phase place of current data point actual samples point before and after the corresponding phase data point in last cycle to obtain amplitude A with the method for interpolation (for example linear interpolation) I-T, can be similar to the damping ratio of obtaining the data point i on the natural mode of vibration curve according to following formula:
ζ i = ln ( A i - T / A i ) 2 π
Natural mode of vibration curve damping ratio is defined as the mean value of this each data point damping ratio of natural mode of vibration curve; In order to reduce calculated amount, the mean value of also available each extreme point damping ratio is similar to.
(3) parameter of oscillation according to each the natural mode of vibration curve that is calculated carries out the dangerous mode of oscillation identification of electric system, and the natural mode of vibration curve is divided into groups by the dangerous mode of oscillation of the electric system found, be about to the natural mode of vibration curve frequency natural mode of vibration curve close with system's limit risk frequency and belong to same mode of oscillation, its concrete grammar is as follows:
In the natural mode of vibration curve that each node that decomposites measures, select amplitude maximum and amplitude greater than defined threshold A Threshold, damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously ThresholdThe natural mode of vibration curve frequency of a certain node, mode frequencey 1 as current system, close with it as if having in the natural mode of vibration curve frequency of all nodes, promptly the ratio of absolute value of both frequency differences and system oscillation mode frequency 1 is less than the percentage threshold FD that sets Threshold, think that then this node participates in the vibration of mode of oscillation 1, can only have a natural mode of vibration curve to be included into the mode of oscillation 1 of system at most for each node.
The natural mode of vibration curve that is included into mode of oscillation 1 of getting rid of all nodes is selected amplitude maximum and amplitude greater than defined threshold A in remaining natural mode of vibration curve Threshold, damping ratio is less than the damping ratio threshold value D that sets simultaneously ThresholdThe natural mode of vibration curve frequency that measures of a certain node, as the mode frequencey 2 of current system, find out all natural mode of vibration curves and the corresponding node thereof that participates in mode of oscillation 2 in the system according to aforesaid method.
The rest may be inferred find out whole electric system at current period amplitude enough big and maximum amplitude greater than defined threshold A Threshold, damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously ThresholdAll mode of oscillation, promptly dangerous mode of oscillation, and find out node and the corresponding natural mode of vibration curve that participates in corresponding dangerous mode of oscillation.
Defined threshold A for above-mentioned amplitude Threshold, carry out low-frequency oscillation detection and analysis, then A if adopt node to inject active power ThresholdUsually be taken as 30MW, detect and analyze if adopt nodal frequency to carry out low-frequency oscillation, then A ThresholdUsually be taken as 0.02Hz; For above-mentioned damping ratio threshold value D ThresholdUsually be taken as 0.05; Absolute value and system oscillation mode frequency percentage threshold FD for above-mentioned frequency difference ThresholdUsually be taken as 10%.
(4) node that participates in the dangerous mode of oscillation of electric system is carried out coherence grouping according to the phase place difference of corresponding natural mode of vibration curve, its concrete grammar is as follows:
Each the dangerous system oscillation pattern that finds for abovementioned steps, all natural mode of vibration curves that participate in the node correspondence of this mode of oscillation are carried out the phase bit comparison, natural mode of vibration curve with the amplitude maximum is a reference curve, calculate all the other natural mode of vibration curves and this relative phase Φ with reference to the natural mode of vibration curve, wherein-180 °＜Φ≤180 °; If the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is less than 90 °, then the node that this node and reference curve are corresponding belongs to identical homology group; Otherwise if the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is greater than 90 °, then this node belongs to the homology group opposite with reference mode; In view of the above, all nodes that participate in certain mode oscillation are divided into two groups, hunting power mainly back and forth exchanges between these two groups.
When the group was carried out visual expression, the coherence grouping situation of different system mode of oscillation was plotted on different factory's station geographic maps.The vibration of the natural mode of vibration curve of respective nodes correspondence is described with colored vector arrow in each factory's station bus nodes, the homology group (for example distinguishing two homology groups) that the different colours representative of vector arrow is different with red and blueness, the length of arrow is represented the amplitude of natural mode of vibration curve, and the direction of arrow is determined by the relative phase of natural mode of vibration curve.
(5) determine the oscillation center of system oscillation pattern or the sets of lines at interphase place.Because the oscillation center of power system oscillation pattern or interphase are on the circuit between the two opposite homology groups, therefore layout when closeer when phasor measurement unit PMU, be when not having other not hive off substation bus bar between substation bus bar homology group, can determine accurately oscillation center or interphase which circuit are made of by the circuit that the cutting plane between homology group is passed through.On group's visual expression figure, use short dash line with the circuit square crossing to indicate circuit on the vibration interphase.
(6) according to geographic position or topological relation the node that does not directly link to each other on electric in the same homology group further is divided into different people having the same aspiration and interest subgroups.When visual, the knot vector arrow of different people having the same aspiration and interest subgroup adopts the same color of different depth degrees to carry out painted.For example, northeast electrical network and Shandong Power are vibrated with respect to North China electrical network (not containing Shandong), though the node of northeast electrical network and Shandong Power belongs to same homology group from the natural mode of vibration curve, but directly do not link to each other on electric, therefore they can be subdivided into again two people having the same aspiration and interest subgroups, its same tone is respectively with blue and light blue the expression, and the same tone of North China grid nodes is all unified to represent with redness.
Be combined in the application example of certain actual 500kV regional power grid (below be called the A electrical network) here, specific embodiments of the present invention is described.
Based on the low-frequency oscillation check and analysis software on-line operation of principle of the invention exploitation on the senior application server of the WAMS main website of grid dispatching center.Deliver to the wide area measurement main website of grid dispatching center when the phasor measurement unit PMU that is distributed in each transformer station in the electrical network or generating plant will have accurate GPS in real time on the speed (for example 100 frame/seconds or 50 frame/seconds) of information with per second tens frames or frames up to a hundred such as target voltage phasor, electric current phasor, power, frequency, handle depositing real time data server in through preposition communication equipment.Run on online low-frequency oscillation detection on the senior application server and analysis software obtain each PMU substation of the whole network from real time data server real-time measurement result, through online check and analysis, provide and report to the police or analysis result, and analysis result is stored in the historic data server of main website.The PMU substation mainly is installed on the 500kV transformer station of each province's net or regional power grid and main 220kV generating plant at present, can realize that by these data the low-frequency oscillation on the 500kV trunk rack detects, and analyze the related down contribution of power plant of main power plant and each 500kV transformer station vibrating.
Based on above-mentioned hardware environment, the low-frequency oscillation routine analyzer that runs on the present invention's proposition on the senior application server carries out online low-frequency oscillation and detects, analyzes and report to the police.Because the transformer high-voltage side at the most of 500kV of A electrical network factory station is meritorious and outer net injects and meritoriously has PMU and measure or can be calculated by other PMU measuration meter, promptly each injects to gain merit to have the PMU measurement or can be measured by other PMU and extrapolate, though and there is electromagnetic looped network in A electrical network regional area, but its various mode of oscillation on the 500kV rack, usually can with the equivalence of looped network part a node, therefore electromagnetic looped network is very little or do not have influence to the analyzing influence of vibration mode, and therefore the method that can adopt analysis node to inject active power is carried out the detection and the analysis of low-frequency oscillation.(, the serious or most of node of electromagnetic looped network do not have the PMU measurement if injecting active power, can adopt the method for analysis frequency to carry out low-frequency oscillation detection and analysis, but because the work frequency variation range is limited, therefore the numerical resolution relative power is lower, is unfavorable for the detection and the analysis of low-frequency oscillation by a small margin).In addition, in real system, realize alarm in time and improve the analysis speed of low-frequency oscillation that suggestion is adopted frequency-division section, become the frequency spectrum analysis method of time window, variable sampling rate, change moving step length for low-frequency oscillation to various frequency ranges with different alarm time requirements.Under above-mentioned prerequisite, as follows based on the step of online quick low-frequency oscillation detection of frequency-division section of the present invention and node coherence grouping model analysis, overall algorithm block diagram is seen Fig. 2:
(1) the PMU measured curve being carried out empirical modal decomposes: obtain the on high-tension side injection active power of all substation transformers from the real-time data base of WAMS main website, its speed was 100 frame/seconds.Low-frequency oscillation check and analysis program is divided into 3 frequency ranges with whole low-frequency oscillation frequency range, i.e. 0.1～0.5Hz, and 0.5 ~ 1.0Hz and 1.0～2.5Hz use 3 empirical modals to decompose the EMD threads and respectively these 3 frequency ranges are carried out low-frequency oscillation and detect and analyze.Adopt 2Hz respectively at above-mentioned 3 frequency ranges, the data sampling rate of 5Hz and 10Hz measures all meritorious PMU that inject and samples.When accumulation data length in the meritorious metric data window of each PMU reaches 30 seconds respectively, when 10 seconds and 5 seconds, adopt Empirical mode decomposition EMD that the data point curve in each data window is carried out the empirical modal decomposition and obtain each natural mode of vibration curve, when the natural mode of vibration curve frequency that decomposites respectively less than 0.1Hz, 0.5Hz, 1.0Hz the time, the empirical modal that stops the respective window current curves decomposes, and carries out the mode of oscillation and the vibration model analysis of this window this frequency range in the time then according to follow-up step.The step-length of the each reach of the data window of each frequency range was respectively 2 seconds, 1 second and 0.4 second, began new PMU data accumulation, empirical modal decomposition and mode of oscillation and model analysis then.For the imperial scale system, if the whole network spectrum analysis duration surpasses the window moving step length, then getting with the current time is that data in the time window of terminal point are proceeded spectrum analysis and model analysis.
(2) calculate the parameter of oscillation of each natural mode of vibration curve: each the natural mode of vibration curve that decomposites is calculated information such as natural mode of vibration curve frequency, natural mode of vibration curve amplitude, each data point phase place of natural mode of vibration curve, each extreme point damping ratio of natural mode of vibration curve, natural mode of vibration curve damping ratio respectively, and can calculate the signal energy and the signal power of corresponding natural mode of vibration curve according to the generic definition of oscillating curve energy and power.The computing method of main vibration characterising parameter are as follows:
A) the data point phase place of natural mode of vibration curve: the phase place of each data point adopts zero-crossing method to obtain, be that curve positive going zeror crossing point place is 0 °, negative sense zero crossing place is ± 180 °, maximum point is 90 °, minimum point position-90 °, the phase place of the data point between the adjacent zeros limit is tried to achieve according to uniformly-spaced dividing 90 parts equally.
B) natural mode of vibration curve frequency: the short-cut method that adopts following formula to represent is asked natural mode of vibration curve frequency f Curve:
f curve = ( n extrm - 1 ) / 2 t last - t first
N wherein ExtrmFor this natural mode of vibration curve extreme value is counted (containing maximum point and minimum point) t LastBe the moment of this last extreme point of natural mode of vibration curve, t FirstBe the moment of this first extreme point of natural mode of vibration curve.
C) natural mode of vibration curve amplitude: be defined as each maximal point of natural mode of vibration curve and the mean value of minimal point amplitude.
D) damping ratio of natural mode of vibration curve extreme point and natural mode of vibration curve damping ratio: making the amplitude of very big (little) the value point i of natural mode of vibration curve is A i, the amplitude of very big (little) value point is A in the adjacent last cycle I-TCan be similar to the damping ratio of obtaining very big (little) the value point i on the natural mode of vibration curve according to following formula:
ζ i = ln ( A i - T / A i ) 2 π .
Further obtain natural mode of vibration curve damping ratio with the mean value of each extreme point damping ratio.
E) energy of discrete signal oscillating curve is the quadratic sum of each data point amplitude, and the power of discrete signal oscillating curve is the ratio of oscillating curve energy and sampling number.
For the example of A electrical network, external power grid is to the meritorious injection P of this electrical network SysExpression is to P SysOne section PMU measure curve and carry out above-mentioned analysis of decomposing based on empirical modal, main result is (about phase place relatively see Fig. 4) as shown in Figure 3, obtain 3 built-in oscillation patterns altogether, be respectively 0.70Hz, 0.32Hz and 0.18Hz, this result and A power system operating mode department match to the analysis result of this electrical network mode of oscillation: wherein 0.70Hz is the interval mode of oscillation of A electrical network inside, 0.32Hz be the mode of oscillation between A electrical network and external electrical network, and 0.18Hz has the A electrical network to participate in, the wider interval mode of oscillation between two external electrical network.
Carry out spectrum analysis for primary curve shown in Figure 3, under same computing environment, during with 75 sampled points, be 2.8ms the computing time of EMD method, and obtain above-mentioned correct result; And be 37.8ms the computing time of Prony method, and can not get above-mentioned correct result, preceding 3 mode of oscillation of the residual maximum that it obtains are respectively 0.64Hz, and 1.37Hz and 1.38Hz differ greatly to the analysis result of this electrical network mode of oscillation with method of operation department.When sampled point was brought up to 150, (preceding 3 patterns of residual maximum were 0.32Hz, and 0.70Hz 0.19Hz), reaches 115ms computing time though the Prony method can find approximate correct result.Can find out thus based on the spectrum analysis of EMD method than the superiority of spectrum analysis on computing velocity and order of accuarcy based on the Prony method.
(3) dangerous mode of oscillation identification and carry out the grouping of natural mode of vibration curve:, in the natural mode of vibration curve of each node that decomposites by abovementioned steps, select amplitude maximum and amplitude greater than defined threshold A at the current time window by mode of oscillation Threshold(for example, 30MW), damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously Threshold(the natural mode of vibration curve frequency of) a certain node for example, 0.05 is as the mode frequencey 1 of this frequency range of current system; Close with it as if having in the natural mode of vibration curve frequency of all nodes, promptly the ratio of both frequency difference absolute values and system oscillation mode frequency 1 is less than the percentage threshold FD that sets Threshold(for example, 10%) thinks that then this node participates in the vibration of mode of oscillation 1, can only have a natural mode of vibration curve to be included into the mode of oscillation 1 of this frequency range of system at most for each node.So also just can find out the node of this frequency range mode of oscillation 1 of all participation systems.Get rid of the natural mode of vibration curve that is included into this frequency range mode of oscillation 1 in all nodes, in remaining natural mode of vibration curve, select amplitude maximum and amplitude greater than defined threshold, the natural mode of vibration curve frequency that a certain node that the while damping ratio is enough little measures, as the mode frequencey 2 of this frequency range of current system, find out all natural mode of vibration curves and the corresponding node thereof that participates in this frequency range mode of oscillation 2 in the system according to aforesaid method.The rest may be inferred finds out this frequency range amplitude enough greatly (in this example, the amplitude of the curve of amplitude maximum is greater than 30MW in the relevant natural mode of vibration curve) and damping ratio enough little (in this example, the damping ratio of the curve of amplitude maximum is less than 0.05 in the relevant natural mode of vibration curve) all mode of oscillation, and node of participating and corresponding natural mode of vibration curve.Each frequency range looks for 2-3 such mode of oscillation to get final product at most in practical power systems.Each frequency range Using such method is handled, thereby found out the dangerous mode of oscillation of current all frequency ranges of system, and the node and the corresponding natural mode of vibration curve that participate in corresponding dangerous mode of oscillation.
The enough big and enough little mode of oscillation of damping ratio is 0.7Hz at current period amplitude to find out whole A electrical network by said method.In addition, can also find two mode of oscillation of 0.32Hz and 0.18Hz, but the amplitude of the curve of amplitude maximum does not surpass threshold value 30MW in the natural mode of vibration curve relevant with them, therefore not as the dangerous mode of oscillation of current system, do not carry out analysis and alarms such as further coherence grouping yet.The meritorious injection of bus nodes that has provided 4 the main factory stations (respectively getting two factory stations of amplitude maximum from two opposite groups) that participate in 0.7Hz system oscillation pattern among Fig. 4 measures natural mode of vibration curve and the natural mode of vibration parameter of curve that belongs to 0.7Hz system oscillation pattern.In real system, to information such as the frequency of the natural mode of vibration curve relevant with non-dangerous mode of oscillation, amplitude, damping ratio, beginning and ending times, program also records it database, uses when the running status of system is carried out statistical study.
(4) each dangerous mode of oscillation of electric system is carried out node coherence grouping:, all natural mode of vibration curves that participate in the node correspondence of this mode of oscillation are carried out the phase bit comparison for each dangerous system oscillation pattern that abovementioned steps finds.Natural mode of vibration curve with the amplitude maximum is a reference curve, calculate all the other natural mode of vibration curves and this relative phase Φ with reference to the natural mode of vibration curve (180 °＜Φ≤180 °), relative phase Φ is defined as the difference φ of each corresponding data point phase place on two natural mode of vibration curves i(make φ iSatisfy-180 °＜φ i≤ 180 °) arithmetic mean.If the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is less than 90 °, then the node that this node and reference curve are corresponding belongs to identical homology group; Otherwise if the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is greater than 90 °, then this node belongs to the homology group opposite with reference mode.In view of the above, the node of all participation system mode of oscillation is divided into two groups, hunting power mainly back and forth exchanges between these two groups.Adopt said method respectively each dangerous system oscillation pattern to be carried out node coherence grouping, and on different geographic maps, carry out visable representation.
Fig. 4 provides the corresponding natural mode of vibration curve at 4 main factory stations in the 0.7Hz system oscillation pattern and the situation of hiving off by relative phase thereof.The meritorious 0.7Hz natural mode of vibration curve amplitude maximum of injecting of ZX factory among Fig. 4, so it is chosen as reference curve; WS station 0.7Hz natural mode of vibration curve is 4.7 ° with respect to the relative phase of this reference curve, and less than 90 °, so the WS station belongs to same homology group G1 with ZX factory in 0.7Hz system oscillation pattern; And the relative phase of the 0.7Hz natural mode of vibration curve of the meritorious injection of LY station and outer net is respectively 133.0 ° and 121.3 °, so they belong to and the anti-homology group G2 of ZX factory place faciation.Fig. 5 provides 0.7Hz system oscillation pattern node coherence grouping and amplitude, the visual geography of phase place are schemed.The length of each factory's station vector arrow is represented the amplitude of corresponding natural mode of vibration curve among the figure, the direction of arrow is determined by the relative phase of natural mode of vibration curve, the different colours of vector arrow (being respectively red and blue among Fig. 5) the different homology group of representative, the amplitude of arrow representative natural mode of vibration curve and the concrete numerical value of phase place are also corresponding factory other the marking in station.The amplitude of vector arrow is big more in two homology group, angle more near 0 ° or ± 180 °, the genset of respective nodes association is big more to the degree of participation of vibration, may be the crucial unit of this mode oscillation more.In real system, when detecting dangerous low-frequency oscillation, eject this picture, thereby help yardman's understanding and handle low-frequency oscillation problem.
(5) determine the oscillation center of system oscillation pattern or the sets of lines at interphase place: the oscillation center of system oscillation pattern or interphase are on the circuit between the two opposite homology groups.When phasor measurement unit PMU is layouted when closeer, when promptly not having other not hive off substation bus bar between substation bus bar homology group, can determine accurately oscillation center or interphase which circuit are made of by the circuit that the cutting plane between homology group is passed through.As seen from Figure 5, the sets of lines at the interphase place of A electrical network 0.7Hz mode of oscillation is made of the some circuits that indicate vertical short dash line between two opposite homology group.
(6) homology group segmentation: can the node division that does not directly link to each other on electric in the same homology group be become different people having the same aspiration and interest subgroups according to geographic position or topological relation.When visual, the knot vector arrow of different people having the same aspiration and interest subgroup adopts the same color of different depth degrees to carry out painted.For example northeast electrical network and Shandong Power are vibrated with respect to North China electrical network (not containing Shandong), though the node of northeast electrical network and Shandong Power belongs to same homology group from the natural mode of vibration curve, but directly do not link to each other on electric, therefore they can be subdivided into again two people having the same aspiration and interest subgroups, its same tone is respectively with blue and light blue the expression, and the same tone of North China grid nodes is all unified to represent with redness.

Claims (7)

1. one kind based on Wide-area Measurement Information and Empirical mode decomposition, can realize low-frequency oscillation modal analysis method to electric system complicated low-frequency oscillation carrying out online detection and node coherence grouping, described analytical approach is not only applicable to non-linear, non-stationary changes, the actual complex waveform that contains composition non-periodic, also can be to belonging to same power system oscillation pattern, but the natural mode of vibration curve of non-sinusoidal that frequency is slightly variant or cosine carries out the phase bit comparison, realization is to the coherence grouping of the node that participates in each mode of oscillation, thereby obtains internodal Power Exchange relation and oscillation center or interfacial position; It is characterized in that described analytical approach may further comprise the steps:
(1) at the current time window, the meritorious injecting power of node or the frequency actual measurement oscillating curve that adopt the frequency spectrum analysis method that decomposes based on empirical modal will deliver to the wide area measurement main website in the phasor measurement unit PMU collection are decomposed into the natural mode of vibration curve;
(2) calculate the parameter of oscillation of each natural mode of vibration curve according to natural mode of vibration parameter of curve computing method;
(3) parameter of oscillation according to each the natural mode of vibration curve that is calculated carries out the dangerous mode of oscillation identification of electric system, and by the dangerous mode of oscillation of the electric system found to the grouping of natural mode of vibration curve, be about to the natural mode of vibration curve frequency natural mode of vibration curve close and belong to same mode of oscillation with system's limit risk frequency;
(4) node that participates in the dangerous mode of oscillation of electric system is carried out coherence grouping according to the phase place difference of corresponding natural mode of vibration curve;
(5) circuit that passes through according to the cutting plane between homology group is determined the oscillation center of each dangerous mode of oscillation of electric system or the sets of lines at interphase place;
(6) according to geographic position or topological relation the node division that does not directly link to each other on electric in the same homology group is become different people having the same aspiration and interest subgroups.
2. low-frequency oscillation modal analysis method according to claim 1, it is characterized in that: when in step (1), phasor measurement unit PMU actual measurement oscillating curve being carried out spectrum analysis, in electrical network, there are not electromagnetic looped network or electromagnetic looped network scope very little, and nearly all node injects active power to be had PMU to measure or can be measured extrapolate the time by other PMU, adopts node to inject active power and carries out spectrum analysis and carry out low-frequency oscillation detection and model analysis; When the serious or most of node injection of electromagnetic looped network in electrical network active power does not have the PMU measurement, adopt nodal frequency to carry out spectrum analysis and carry out low-frequency oscillation detection and model analysis.
3. low-frequency oscillation modal analysis method according to claim 1 is characterized in that: comprise in natural mode of vibration parameter of curve described in the step (2): the amplitude of the relative phase of natural mode of vibration curve data point phase place, natural mode of vibration curve phase differential and natural mode of vibration curve, natural mode of vibration curve data dot frequency and natural mode of vibration curve frequency, natural mode of vibration curve, the damping ratio of natural mode of vibration curve data point and natural mode of vibration curve damping ratio; These parameters are provided as giving a definition and computing method:
(a) the data point phase place of natural mode of vibration curve: the phase place of each data point adopts zero-crossing method to obtain, be that curve positive going zeror crossing point place is 0 °, negative sense zero crossing place is ± 180 °, maximum point is 90 °, minimum point is-90 °, and the phase place of the data point between the adjacent zeros limit is tried to achieve according to uniformly-spaced dividing 90 parts equally;
(b) relative phase of natural mode of vibration curve phase differential and natural mode of vibration curve: in the frequency phase place of two natural mode of vibration curves relatively under the difference condition slightly, definition natural mode of vibration curve phase differential Φ is the difference φ of each corresponding data point phase place on two curves iArithmetic mean, described φ iSatisfy-180 °＜φ i≤ 180 °, in the low-frequency oscillation model analysis, for one group of natural mode of vibration curve that belongs to same mode frequencey, with the curve of amplitude maximum wherein is reference curve, even its natural mode of vibration curve relative phase is 0, all the other natural mode of vibration curves should be the relative phase of all the other natural mode of vibration curves with reference to the phase differential of natural mode of vibration curve relatively;
(c) the data point frequency of natural mode of vibration curve and natural mode of vibration curve frequency: the frequency of each data point of natural mode of vibration curve is tried to achieve through conversion the angular frequency that time difference obtains by the phase place and the last data point phase place of this data point, in order to compare the frequency of two natural mode of vibration curves under the situation of non-stationary frequency, definition natural mode of vibration curve frequency is the mean value of each data point frequency of this curve; In order to improve computing velocity, the approximate natural mode of vibration curve frequency f of representing with following formula of asking of short-cut method Curve:
Figure RE-FSB00000112418600021
N wherein ExtrmCount for this natural mode of vibration curve extreme value, described extreme point contains maximum point and minimum point, t LastBe the moment of this last extreme point of natural mode of vibration curve, t FirstBe the moment of this first extreme point of natural mode of vibration curve;
(d) amplitude of natural mode of vibration curve: be defined as each maximum point of natural mode of vibration curve and the mean value of minimum point amplitude;
(e) damping ratio of natural mode of vibration curve data point and natural mode of vibration curve damping ratio: the amplitude that makes natural mode of vibration curve data point i is A i, the amplitude of the data point of corresponding phase is A in the adjacent last cycle I-TReason owing to fixed sampling interval technique, often there is not sampled point in the data point of current data point corresponding phase in last cycle, at this moment, need utilize the amplitude and the phase place of current data point actual samples point before and after the corresponding phase data point in last cycle to obtain amplitude A with the method for interpolation I-T, can be similar to the damping ratio of obtaining the data point i on the natural mode of vibration curve according to following formula:
Figure RE-FSB00000112418600022
Natural mode of vibration curve damping ratio is defined as the mean value of this each data point damping ratio of natural mode of vibration curve; In order to reduce calculated amount, the mean value of also available each extreme point damping ratio is similar to.
4. low-frequency oscillation modal analysis method according to claim 1, it is characterized in that: the parameter of oscillation according to each the natural mode of vibration curve that is calculated in step (3) carries out the dangerous mode of oscillation identification of electric system, and by the dangerous mode of oscillation of the electric system found to the grouping of natural mode of vibration curve, its concrete grammar is as follows:
In the natural mode of vibration curve that each node that decomposites measures, select amplitude maximum and amplitude greater than regulation amplitude threshold A Threshold, damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously ThresholdThe natural mode of vibration curve frequency of a certain node, mode frequencey 1 as current system, close with it as if having in the natural mode of vibration curve frequency of all nodes, promptly the ratio of absolute value of both frequency differences and system oscillation mode frequency 1 is less than the percentage threshold FD that sets Threshold, think that then this node participates in the vibration of mode of oscillation 1, can only have a natural mode of vibration curve to be included into the mode of oscillation 1 of system at most for each node;
The natural mode of vibration curve that is included into mode of oscillation 1 of getting rid of all nodes is selected amplitude maximum and amplitude greater than regulation amplitude threshold A in remaining natural mode of vibration curve Threshold, damping ratio is less than the damping ratio threshold value D that sets simultaneously ThresholdThe natural mode of vibration curve frequency that measures of a certain node, as the mode frequencey 2 of current system, find out all natural mode of vibration curves and the corresponding node thereof that participates in mode of oscillation 2 in the system according to aforesaid method;
The rest may be inferred find out whole electric system at current period amplitude enough big and maximum amplitude greater than regulation amplitude threshold A Threshold, damping ratio is enough little promptly less than the damping ratio threshold value D that sets simultaneously ThresholdAll mode of oscillation, promptly dangerous mode of oscillation, and find out node and the corresponding natural mode of vibration curve that participates in corresponding dangerous mode of oscillation.
5. low-frequency oscillation modal analysis method according to claim 1 is characterized in that: in step (4) node that participates in the dangerous mode of oscillation of electric system is carried out coherence grouping according to the phase place difference of corresponding natural mode of vibration curve, its concrete grammar is as follows:
On the basis of claim 1 step (3) for each the dangerous system oscillation pattern that finds, all natural mode of vibration curves that participate in the node correspondence of this mode of oscillation are carried out the phase bit comparison, natural mode of vibration curve with the amplitude maximum is a reference curve, calculate all the other natural mode of vibration curves and this relative phase Φ with reference to the natural mode of vibration curve, wherein-180 °＜Φ≤180 °; If the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is less than 90 °, then the node that this node and reference curve are corresponding belongs to identical homology group; Otherwise if the absolute value of the relative phase of the natural mode of vibration curve that certain node measures is greater than 90 °, then this node belongs to the homology group opposite with reference mode; In view of the above, all nodes that participate in certain mode oscillation are divided into two groups, hunting power mainly back and forth exchanges between these two groups.
6. low-frequency oscillation modal analysis method according to claim 4 is characterized in that: for the regulation amplitude threshold A of described amplitude Threshold, carry out low-frequency oscillation detection and analysis, then amplitude threshold A if adopt node to inject active power ThresholdUsually be taken as 30MW, detect and analyze if adopt nodal frequency to carry out low-frequency oscillation, then amplitude threshold A ThresholdUsually be taken as 0.02Hz; For described damping ratio threshold value D ThresholdUsually be taken as 0.05; For the absolute value of described frequency difference and the percentage threshold FD of system oscillation mode frequency ThresholdUsually be taken as 10%.
7. low-frequency oscillation modal analysis method according to claim 1, it is characterized in that: when the grouping result of will vibrating is carried out visual expression, the coherence grouping situation of different system mode of oscillation is plotted on different factory's station geographic maps, the vibration of the natural mode of vibration curve of respective nodes correspondence is described with colored vector arrow in each factory's station bus nodes, the different homology group of different colours representative of vector arrow, the length of arrow is represented the amplitude of natural mode of vibration curve, and the direction of arrow is determined by the relative phase of natural mode of vibration curve; Indicate the circuit of vibration on the interphase with short dash line with the circuit square crossing; The knot vector arrow of different people having the same aspiration and interest subgroup adopts the same color of different depth degrees to carry out painted.
CN2008102275431A 2008-11-28 2008-11-28 On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition Active CN101408586B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN2008102275431A CN101408586B (en) 2008-11-28 2008-11-28 On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN2008102275431A CN101408586B (en) 2008-11-28 2008-11-28 On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition

Publications (2)

Publication Number Publication Date
CN101408586A CN101408586A (en) 2009-04-15
CN101408586B true CN101408586B (en) 2011-05-04

Family

ID=40571682

Family Applications (1)

Application Number Title Priority Date Filing Date
CN2008102275431A Active CN101408586B (en) 2008-11-28 2008-11-28 On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition

Country Status (1)

Country Link
CN (1) CN101408586B (en)

Families Citing this family (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101814739B (en) * 2010-04-08 2013-04-10 国网电力科学研究院 Low-frequency oscillation real-time control method for power system
CN102288280B (en) * 2011-05-09 2012-08-22 华北电力大学（保定） Shafting torsional vibration extraction method
CN102305891B (en) * 2011-07-04 2013-09-11 武汉大学 On-line monitoring method of low-frequency oscillation of power system
CN102288876A (en) * 2011-07-25 2011-12-21 重庆大学 On-line early warning method for low-frequency oscillation of electric power system
CN102508111B (en) * 2011-10-19 2014-06-04 国家电网华中电力调控分中心 Large disturbance fault positioning visualization system of power system
CN102545245B (en) * 2012-01-16 2013-12-04 清华大学 Method for positioning oscillating source of power system on basis of energy supplied to port
CN102680784B (en) * 2012-05-24 2014-07-02 国家电网华中电力调控分中心 United low-frequency oscillation online monitoring method of wide area measurement systems of multiple dispatching centers
CN102916439B (en) * 2012-09-10 2014-10-22 清华大学 Power system oscillation source positioning method based on side bus measurement of generator
CN103913632B (en) * 2013-12-26 2016-10-05 南方电网科学研究院有限责任公司 Low-frequency synchronous oscillation source identification method based on oscillation component power direction
CN103941091A (en) * 2014-04-25 2014-07-23 福州大学 Power system HHT harmonious wave detection method based on improved EMD end point effect
CN104753075A (en) * 2015-03-19 2015-07-01 中国农业大学 Identifying method and device of leading oscillating mode of interconnected electric power system
CN105510710B (en) * 2015-12-23 2018-06-26 国家电网公司 Divide group's net source Oscillatory mode shape discrimination method rendered based on phasor
CN105867353B (en) * 2016-05-25 2018-06-05 广东电网有限责任公司电力科学研究院 A kind of vibration monitoring method and system
CN109342883A (en) * 2018-11-08 2019-02-15 国网天津市电力公司 A kind of local ageing fault detecting and positioning method for cable
CN109787250B (en) * 2018-12-30 2022-08-30 国网辽宁省电力有限公司电力科学研究院 Power system low-frequency oscillation mode identification method based on multivariate empirical mode decomposition
CN111244940B (en) * 2020-01-19 2022-12-09 中国电力科学研究院有限公司 Identification method and system for dynamic stable oscillation center of complex power grid
CN113238117B (en) * 2021-04-25 2023-04-14 北京四方继保工程技术有限公司 Sub-band monitoring and imaging method for complex oscillation process
CN113471960B (en) * 2021-05-31 2024-02-23 国网江苏省电力有限公司 Low-frequency oscillation type judging method and device based on multi-source data fusion

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101046497A (en) * 2006-03-29 2007-10-03 宝山钢铁股份有限公司 Method of detecting local discharge signal in electric power equipment

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101046497A (en) * 2006-03-29 2007-10-03 宝山钢铁股份有限公司 Method of detecting local discharge signal in electric power equipment

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
史坤鹏.基于信号能量分析的电力系统低频振荡模式识别.《华北电力大学工学硕士学位论文》.2008, *

Also Published As

Publication number Publication date
CN101408586A (en) 2009-04-15

Similar Documents

Publication Publication Date Title
CN101408586B (en) On-line low-frequency oscillation detection and node coherence grouping method based on experience modal decomposition
CN101408577B (en) Analysis method of low-frequency oscillation node contribution factor based on wide field measuring information
CN101408567B (en) Large scale electric network low-frequency oscillation frequency division section detection method based on empirical mode decomposition
CN102122823B (en) Method for positioning oscillation disturbance source of power system
CN101944776B (en) Low-frequency oscillation monitoring system of electrical network
CN108257044A (en) A kind of non-intrusion type load decomposition method based on steady-state current model
CN109767054A (en) Efficiency cloud appraisal procedure and edge efficiency gateway based on deep neural network algorithm
CN106443285A (en) Multi-harmonic-source harmonic contribution quantitative analysis method based on total-least square method
Gao et al. Short-term traffic flow forecasting model based on wavelet neural network
CN106526317A (en) Phasor measurement accuracy assessment method and assessment apparatus for synchronized phasor measurement unit
CN100554976C (en) Area voltage stability monitoring method based on synchronous phasor measurement
CN108896944B (en) Laboratory calibrator of synchronous measuring device and synchronous phasor measuring method thereof
CN112510688B (en) Transient voltage stability monitoring method based on phase correction Lyapunov exponent
CN103176108A (en) Double-terminal fault location method and double-terminal fault location system for transmission line
CN100381830C (en) Method for checking out phase handling unit (PHU) in site
CN117610779B (en) Mapping geographic information quality supervision method and system based on CORS big data
CN103995948A (en) Polynomial model-based oscillation center voltage prediction method
CN105488335A (en) Lyapunov exponent based power system load prediction method and apparatus
CN107482778A (en) A kind of method and system of improved power system health status monitoring
CN103941093B (en) A kind of two-way DFT symmetrical compensations Method for Phase Difference Measurement and its device
CN110533548A (en) A method of phantom error evaluation index is established based on track characteristic
CN109387806B (en) Digital electric energy meter traceability system error influence analysis method based on simulink simulation
CN112904083B (en) Power balance verification method and device based on broadband measurement
CN107271814B (en) A method of obtaining load nonlinear function
Messina et al. Wide-area PMU data monitoring using spatio-temporal statistical models

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