CN102156246A  Wavelet energy entropy detecting method for recognizing faults of ultrahigh voltage directcurrent transmission line  Google Patents
Wavelet energy entropy detecting method for recognizing faults of ultrahigh voltage directcurrent transmission line Download PDFInfo
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 CN102156246A CN102156246A CN2011100714968A CN201110071496A CN102156246A CN 102156246 A CN102156246 A CN 102156246A CN 2011100714968 A CN2011100714968 A CN 2011100714968A CN 201110071496 A CN201110071496 A CN 201110071496A CN 102156246 A CN102156246 A CN 102156246A
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Abstract
Description
Technical field
The present invention relates to the relay protection of power system technical field, specifically a kind of wavelet energy entropy detection method of discerning the extra high voltage direct current transmission line internal fault external fault.
Background technology
The DC power transmission line throughput power is big, behind the line failure, requires the excision fault that line protective devices must be fast as far as possible, otherwise will cause very big impact to total system, and the safe and stable operation of system is constituted a threat to.General power frequency protection responsiveness is slow, and is consuming time longer, is difficult to satisfy the requirement of protection of direct current supply line.At present; extensively adopt the main protection of travelingwave protection in the world as the hvdc transmission line protection; its singleended amount protection is as criterion according to the sudden change amount of voltage traveling wave and rate of change and electric current variable gradient; have the hypervelocity acting characteristic, be not subjected to that current transformer is saturated, advantage such as system oscillation and long line distributed capacitance influence.But related data shows, the DC line travelingwave protection of using at present is existing easy malfunction and being subjected to the problem of noise in various degree all.Or, cause the tripping of existing direct current protecting device sometimes owing to problems such as direction row ripple rate of change are subjected to that transition resistance influences.The security and the reliability that how to improve at present the DC line operation have become urgent problem, and can make accurate judgment to DC line fault be the key of DC line protection.
DC transmission system comprises the smoothing reactor and the DC filter at DC power transmission line, DC line two ends, and wherein smoothing reactor and DC filter have constituted " natural " physical boundary of DC power transmission line high frequency transient amount.The frequencyresponse analysis on border shows that there is notable attribute difference in the high fdrequency component of the inside and outside faultsignal in circuit border, can propose the criterion of internal fault external fault identification in view of the above.
Summary of the invention
The purpose of this invention is to provide a kind of wavelet energy entropy detection method of discerning the extra high voltage direct current transmission line internal fault external fault.
Carry out 8 layers of wavelet transformation among the present invention, choose 15 layer wavelet coefficient energy and constitute parameter sets, calculate the wavelet energy entropy, promptly 1562.5Hz is analyzed with upper frequency, think among the present invention that it is a HFS.For troubles inside the sample space, this moment, 15 layer wavelet coefficient energy distribution was even relatively, and scrambling is less; For external area error, deviation is bigger between this moment 15 layer wavelet coefficient energy, skewness, by accompanying drawing 5 can obviously find out in the district, wavelet coefficient energy distributions difference when the district is outer.Can characterize each layer wavelet coefficient regularity of energy distribution based on the wavelet energy entropy, entropy is big more, illustrates that distribution is even more between each layer wavelet coefficient energy, otherwise illustrates that then distributed pole is inhomogeneous.Therefore draw criterion, when troubles inside the sample space, the wavelet energy entropy is greater than 1, and during external area error, the wavelet energy entropy is less than 1.
The present invention adopts the new method of wavelet energy entropy identification extra high voltage direct current transmission line internal fault external fault to carry out according to the following steps:
(1) after DC line broke down, starting element started immediately, chose the two poles of the earth DC voltage that the protection installation place records, and obtained the line mode voltage of protection installation place according to the Karenbauer transformation matrix U _{1}( k) be:
U _{1}( k) =( U _{ + }?( k) ?U _{}( k))/ (1)
In the formula, U _{+}( k) be the anodal DC voltage of DC power transmission line, U _{}( k) be DC power transmission line negative pole DC voltage, k=1,2,3 .... N, NBe sample sequence length;
(2) sample frequency 100kHz, window length is chosen 5ms, adopts the db4 small echo that the line mode voltage is carried out wavelet transformation and decomposes, and obtains E _{1}, E _{2}..., Ej (j=8) the wavelet coefficient energy coefficient on 8 yardsticks.
(3) choose front 15 layer wavelet coefficient energy and constitute parameter sets, calculate the wavelet energy entropy W _{ EE }For:
(3)
Wherein: , , then
(4) the examination criterion of internal fault external fault, when W _{ EE }≤ 1 o'clock is external area error, when W _{ EE }1 o'clock be troubles inside the sample space.
Design concept of the present invention is as follows:
1. boundary element
The extrahigh voltage DC transmission system structural drawing as shown in Figure 1.Among Fig. 1, power transmission capacity is 5000MW, and the reactive compensation capacity of rectification side and inversion side is respectively 3000Mvar and 3040Mvar; Every utmost point convertor unit is composed in series by 2 12 pulse transverters, and DC power transmission line is a sixmultiple conductor, and total length is 1500km, adopts J.R.Marti frequency dependence model; The smoothing reactor of 400mH is equipped with in the circuit both sides; The M point is the protection installation place.
The present invention has creatively proposed to constitute its physical boundary with smoothing reactor and DC filter, and its amplitude versus frequency characte is analyzed.As shown in Figure 2, wherein U _{1}For distinguishing outer transient voltage, U _{2}For U _{1}Fade to the voltage of DC line protection installation place through flank pass; B _{1}, B _{2}, B _{3}, B _{4}Be DC filter lightning arrester, D _{1}Be smoothing reactor lightning arrester, D _{2}Be DC bus arrester, the present invention is with lightning arrester B _{1}, B _{2}, B _{3}, B _{4}, D _{1}, D _{2}Be referred to as the border lightning arrester.B _{1}, B _{2}Rated voltage is 150kV, B _{3}, B _{4}Rated voltage is 75kV, D _{1}, D _{2}Rated voltage is 824kV.
Among Fig. 2, L=400mH, L _{1}=39.09mH, L _{2}=26.06mH, L _{3}=19.545mH, L _{4}=34.75mH, C _{1}=0.9 μ F, C _{2}=0.9 μ F, C _{3}=1.8 μ F, C _{4}=0.675 μ F.
When breaking down outside the district, the voltage traveling wave of generation arrives the capable ripple of transient voltage of protecting the installation place by refraction; because the filter action on " border " that smoothing reactor and DC filter are formed; frequency range is high more, and it is big more to decay, and causes between the high frequency band wavelet coefficient energy distribution extremely inhomogeneous.When the generating region internal fault, the initial voltage ripple does not have the filter action through " border ", and the full frequency band energy is not decayed, and each layer of high band wavelet coefficient energy distribution is even relatively.
2. the basic theories of wavelet energy entropy
1) continuous wavelet transform
If φ( t) be a quadractically integrable function, if its Fourier transform ψ( ω) satisfy the admissibility condition, that is:
（1）
Then claim φ( t) be basic small echo, perhaps a wavelet mother function.With wavelet mother function φ( t) stretch and translation, can obtain the continuous wavelet basis function φ _{ a, b }( t):
（2）
In the formula: aBe contractionexpansion factor, or be called scale factor; bIt is shift factor.For function arbitrarily f( t) ∈ L ^{2}( R) continuous wavelet transform (Continuous Wavelet Transform CWT) is:
（3）
In the formula: Expression Conjugation.
2) wavelet transform
By the notion of continuous wavelet transform as can be known, the scale factor in the continuous wavelet transform aAnd shift factor bIt is continuous variable.In actual applications, usually will φ _{ a, b }( t) in continuous variable aWith bGet and do the integer discrete form, will φ _{ a, b }( t) be expressed as:
（4）
Corresponding function f( t) wavelet transform (Discrete Wavelet Transform DWT) can be expressed as:
（5）
Because this discrete wavelet φ _{ j, k }( t) be by wavelet function φ( t) through 2 ^{ j }Integral multiple is put, is contracted and through integer kThe family of functions that translation generated φ _{ j, k }( t), j, k∈ Z.Therefore, the little wave train after this disperses is commonly referred to as discrete dyadic wavelet sequence.
(3) establish E _{1}, E _{2}..., E _{m}Be signal X (t) mWavelet coefficient energy on the individual yardstick then can form a kind of division to signal energy on scale domain.By the characteristic of orthogonal wavelet transformation as can be known, (window width in window sometime ω N) signal energy EEqual each layer energy behind the wavelet transformation E _{ j }Sum, wherein , If , then , the wavelet energy entropy of calculating line mode voltage W _{ EE }(Wavelet Energy Entropy) is:
(6)
3. in the district based on the wavelet energy entropy, the examination of external area error
System shown in Figure 1 is at 200km place, distance protection installation place, and the plus earth fault takes place 0.205s, and line mode voltage waveform is shown in Fig. 4 (a); The fault transition resistance is 10 Ω, and time window length is chosen 5ms after the fault, and sample frequency is 100kHz.
Among the present invention, line mode voltage signal is carried out 8 layers of wavelet transformation, chooses front 15 floor height wavelet coefficient energy calculating frequently wavelet energy entropy:
(7)
Therefore, propose to distinguish interior, external area error criterion:
W _{ EE }≤ 1, be external area error (8a)
W _{ EE }1, be troubles inside the sample space (8b)
The present invention compared with prior art has following advantage:
1. the performance of this method tolerance transition resistance is very strong, to insensitive for noise, stronger practicality is arranged.
2. the wavelet energy entropy calculates simply, and realtime is better, can accurately characterize the energy distribution situation between the high frequency band.
3, a large amount of simulation results show that the inventive method is correct.
Description of drawings
Fig. 1 be cloud wide ± 800kV DC transmission system structural drawing, F among the figure _{2}, F _{3}Be external area error, F _{1}, F _{4}Be troubles inside the sample space, M is the protection installation place;
Fig. 2 is the boundary element that smoothing reactor and DC filter constitute, U _{1}Be the transient voltage outside distinguishing, U _{2}For U _{1}Fade to the voltage of DC line protection installation place through flank pass; B _{1}, B _{2}, B _{3}, B _{4}Be the DC filter lightning arrester; D _{1}Be smoothing reactor lightning arrester, D _{2}Be DC bus arrester; L _{1}, L _{2}, L _{3}, L _{4}Be inductance element; C _{1}, C _{2}, C _{3}, C _{4}Be capacity cell;
Fig. 3 is the boundary element transport function Amplitude versus frequency characte figure;
Fig. 4 is a line mode voltage oscillogram, (a) is the line mode voltage during the plus earth fault in the district; Line mode voltage during (b) for the outer plus earth fault in district (rectification side);
Fig. 5 is a 15 layer wavelet coefficient energy distribution histogram behind the line mode voltage wavelet transformation, and wherein (a) is in the district during plus earth fault; During (b) for the outer plus earth fault in district (rectification side);
During Fig. 6 troubles inside the sample space different grounding resistance total track length is traveled through (for the present invention), wherein (a) (b) (c) (d) be respectively the plus earth fault, minus earth fault, the two poles of the earth short trouble, the two poles of the earth ground short circuit fault.
Embodiment
Realistic model as shown in Figure 1, the plus earth fault takes place in 200km place, distance protection installation place, the fault transition resistance is 10 Ω, time window length is got 5ms, sample frequency is 100kHz.
(1) after DC line broke down, starting element started immediately, according to formula:
U _{ 1 }( k) =( U _{ + }?( k) ?U _{}( k))/ (1)
Obtain the line mode voltage, its waveform is shown in figure (3);
(2) sample frequency 100kHz, window length is chosen 5ms, and the line mode voltage is carried out wavelet transformation:
(2)
In the formula, φ (t)Be a basic small echo, perhaps wavelet mother function, aBe contractionexpansion factor, or be called scale factor; bBe shift factor, Expression Conjugation.
(3) establish E _{1}, E _{2}..., E _{m}Be signal X (t) mWavelet coefficient energy on the individual yardstick, wherein , If , then , the wavelet energy entropy of calculating line mode voltage W _{ EE }(Wavelet Energy Entropy) is:
(3)
Carry out 8 layers of wavelet transformation among the present invention, choose front 15 layer wavelet coefficient energy and constitute parameter sets, calculate the wavelet energy entropy.According to the wavelet energy entropy of being asked for W _{ EE }1, be judged as troubles inside the sample space.
Among the present invention different external area error types, different stake resistances are carried out simulating, verifying, obtained the wavelet energy entropy W _{ EE }, the result is as shown in the table.
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Cited By (7)
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CN103163420A (en) *  20111208  20130619  沈阳工业大学  Intelligent power transformer online state judgment method 
CN103529332A (en) *  20131028  20140122  昆明理工大学  Ultrahigh voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics 
CN104065597A (en) *  20140704  20140924  哈尔滨工程大学  BPSK/QPSK signal identification method based on wavelet energy distribution entropy 
CN104393581A (en) *  20141105  20150304  昆明理工大学  Triangle looped network transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis 
CN105591372A (en) *  20160311  20160518  西南交通大学  Highvoltage DC power transmission line singleend protecting method based on wavelet energy relative entropy 
CN106199480A (en) *  20160716  20161207  太原理工大学  CT saturation detection method based on Bspline wavelet transformation 
CN110350492A (en) *  20190619  20191018  华北电力大学  Direction pilot transient based protection method suitable for the transmission line of electricity containing UPFC 
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Cited By (12)
Publication number  Priority date  Publication date  Assignee  Title 

CN103163420A (en) *  20111208  20130619  沈阳工业大学  Intelligent power transformer online state judgment method 
CN103163420B (en) *  20111208  20160120  沈阳工业大学  Power transformer intelligent online state judgment method 
CN103529332A (en) *  20131028  20140122  昆明理工大学  Ultrahigh voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics 
CN103529332B (en) *  20131028  20161109  昆明理工大学  A kind of extra high voltage direct current transmission line based on voltage degree of association and wavelet transformation transient state energy distribution character thunderbolt interference identification method 
CN104065597A (en) *  20140704  20140924  哈尔滨工程大学  BPSK/QPSK signal identification method based on wavelet energy distribution entropy 
CN104393581A (en) *  20141105  20150304  昆明理工大学  Triangle looped network transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis 
CN104393581B (en) *  20141105  20180306  昆明理工大学  A kind of triangle looped network transient cell protection method using voltage x current Sudden Changing Rate wavelet coefficient correlation analysis 
CN105591372A (en) *  20160311  20160518  西南交通大学  Highvoltage DC power transmission line singleend protecting method based on wavelet energy relative entropy 
CN106199480A (en) *  20160716  20161207  太原理工大学  CT saturation detection method based on Bspline wavelet transformation 
CN106199480B (en) *  20160716  20181113  太原理工大学  CT saturation detection method based on Bspline wavelet transformation 
CN110350492A (en) *  20190619  20191018  华北电力大学  Direction pilot transient based protection method suitable for the transmission line of electricity containing UPFC 
CN110350492B (en) *  20190619  20200804  华北电力大学  Direction pilot transient state quantity protection method suitable for UPFCcontaining power transmission line 
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