CN102156246A - Wavelet energy entropy detecting method for recognizing faults of ultra-high voltage direct-current transmission line - Google Patents

Wavelet energy entropy detecting method for recognizing faults of ultra-high voltage direct-current transmission line Download PDF

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Publication number
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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China
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wavelet
voltage
energy entropy
line
transmission line
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CN2011100714968A
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Chinese (zh)
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束洪春
王雄彪
田鑫萃
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昆明理工大学
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Abstract

The invention relates to a wavelet energy entropy detecting method for recognizing internal and external faults of an ultra-high voltage direct-current transmission line. The method comprises the steps of: when the direct-current line goes wrong, starting a starting element, carrying out electromagnetic decoupling on the obtained two-electrode direct voltage transient signals through measurement at a relay installed place of a rectification side by utilizing Karenbauer transformation to obtain line-mode voltage; carrying out eight-layer wavelet transformation on disperse line-mode voltage signals within 5ms after faults occur; constituting a parameter set by utilizing the transformed energy of 1-5 layers wavelet coefficients to calculate the wavelet energy entropy; and distinguishing the internal and the external faults according to the size of the wavelet energy entropy. The method has very strong performance of tolerating transition resistance, is insensitive to noise and has stronger practicality. The calculation of the wavelet energy entropy is simple, the real-time performance is better and the situation of energy distribution among high-frequency bands can be accurately characterized. Proved by vast simulation results, the method provided by the invention is right.

Description

The wavelet energy entropy detection method of identification extra high voltage direct current transmission line fault

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 through-put 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 traveling-wave protection in the world as the hvdc transmission line protection; its single-ended 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 traveling-wave 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 frequency-response analysis on border shows that there is notable attribute difference in the high fdrequency component of the inside and outside fault-signal 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 1-5 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, 1-5 layer wavelet coefficient energy distribution was even relatively, and scrambling is less; For external area error, deviation is bigger between this moment 1-5 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 1-5 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 extra-high 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 six-multiple 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 1For distinguishing outer transient voltage, U 2For U 1Fade to the voltage of DC line protection installation place through flank pass; B 1, B 2, B 3, B 4Be DC filter lightning arrester, D 1Be smoothing reactor lightning arrester, D 2Be DC bus arrester, the present invention is with lightning arrester B 1, B 2, B 3, B 4, D 1, D 2Be referred to as the border lightning arrester.B 1, B 2Rated voltage is 150kV, B 3, B 4Rated voltage is 75kV, D 1, D 2Rated 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 contraction-expansion 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 mBe 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 1-5 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 real-time 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 3Be external area error, F 1, F 4Be 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 1Be the transient voltage outside distinguishing, U 2For U 1Fade to the voltage of DC line protection installation place through flank pass; B 1, B 2, B 3, B 4Be the DC filter lightning arrester; D 1Be smoothing reactor lightning arrester, D 2Be DC bus arrester; L 1, L 2, L 3, L 4Be inductance element; C 1, C 2, C 3, C 4Be 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 1-5 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 contraction-expansion factor, or be called scale factor; bBe shift factor, Expression Conjugation.

(3) establish E 1, E 2..., E mBe 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 1-5 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.

Claims (1)

1. wavelet energy entropy detection method of discerning the extra high voltage direct current transmission line internal fault external fault is characterized in that carrying out according to the following steps:
(1) after DC line broke down, starting element started immediately, the two poles of the earth DC voltage that gather the fetch protection installation place U +( k) and U -( k), obtain the line mode voltage of protecting the installation place according to the electromagnetic connection between the Karenbauer transformation matrix decoupling zero circuit 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, N=500 is 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, jWavelet coefficient energy coefficient on=8,8 yardsticks
(3) choose front 1-5 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.
CN2011100714968A 2011-03-24 2011-03-24 Wavelet energy entropy detecting method for recognizing faults of ultra-high voltage direct-current transmission line CN102156246A (en)

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CN103163420A (en) * 2011-12-08 2013-06-19 沈阳工业大学 Intelligent power transformer on-line state judgment method
CN103529332A (en) * 2013-10-28 2014-01-22 昆明理工大学 Ultra-high voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics
CN104065597A (en) * 2014-07-04 2014-09-24 哈尔滨工程大学 BPSK/QPSK signal identification method based on wavelet energy distribution entropy
CN104393581A (en) * 2014-11-05 2015-03-04 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) * 2016-03-11 2016-05-18 西南交通大学 High-voltage DC power transmission line single-end protecting method based on wavelet energy relative entropy
CN106199480A (en) * 2016-07-16 2016-12-07 太原理工大学 CT saturation detection method based on B-spline wavelet transformation
CN110350492A (en) * 2019-06-19 2019-10-18 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)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103163420A (en) * 2011-12-08 2013-06-19 沈阳工业大学 Intelligent power transformer on-line state judgment method
CN103163420B (en) * 2011-12-08 2016-01-20 沈阳工业大学 Power transformer intelligent online state judgment method
CN103529332A (en) * 2013-10-28 2014-01-22 昆明理工大学 Ultra-high voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics
CN103529332B (en) * 2013-10-28 2016-11-09 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) * 2014-07-04 2014-09-24 哈尔滨工程大学 BPSK/QPSK signal identification method based on wavelet energy distribution entropy
CN104393581A (en) * 2014-11-05 2015-03-04 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) * 2014-11-05 2018-03-06 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) * 2016-03-11 2016-05-18 西南交通大学 High-voltage DC power transmission line single-end protecting method based on wavelet energy relative entropy
CN106199480A (en) * 2016-07-16 2016-12-07 太原理工大学 CT saturation detection method based on B-spline wavelet transformation
CN106199480B (en) * 2016-07-16 2018-11-13 太原理工大学 CT saturation detection method based on B-spline wavelet transformation
CN110350492A (en) * 2019-06-19 2019-10-18 华北电力大学 Direction pilot transient based protection method suitable for the transmission line of electricity containing UPFC
CN110350492B (en) * 2019-06-19 2020-08-04 华北电力大学 Direction pilot transient state quantity protection method suitable for UPFC-containing power transmission line

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