CN104569738A - Method for selecting line by utilizing wavelet packet energy relative entropy of zero sequence current - Google Patents

Abstract

The invention discloses a method for selecting a line by utilizing the wavelet packet energy relative entropy of zero sequence currents. The method comprises the following steps: (1) performing four layers of decomposition on the zero sequence currents of all lines by utilizing db 10 wavelet packets, obtaining the total energy of the zero sequence currents of the lines, and further obtaining the relative wavelet packet energy of each line; (2) calculating the matrix of wavelet packet energy relative entropy (WPERE); (3) judging the matrix of wavelet packet energy relative entropy (WPERE), wherein when i of ij is equal to k, the WPERE exists, when kj is larger than 1, and k is not equal to j, the judgment is that a line fails, the step (4) is performed, else the judgment is that a bus fails; (4) calculating the comprehensive wavelet packet energy relative entropy of the zero sequence currents of the lines, if the comprehensive wavelet packet energy relative entropy of the zero sequence current of the line Li is larger than the sum of the comprehensive wavelet packet energy relative entropy of the zero sequence currents of the other lines, the judgment is that the line Li fails. Through the adoption of the method, a frequency band can be self-adaptively selected, so that the frequency band is matched with a signal frequency spectrum, and the time-frequency resolution is improved.

Description

A kind of selection method utilizing zero-sequence current wavelet-packet energy relative entropy

Technical field

The present invention relates to a kind of selection method utilizing zero-sequence current wavelet-packet energy relative entropy, belong to faulty line selection method technical field in electric system.

Background technology

In prior art, in electric system, the selection method of faulty line extracts signal mainly through signal processing methods such as wavelet transformation, S-transformation, Prony algorithm, Hough transform, then adopts artificial neural network, support vector machine etc. to set up route selection criterion.Wherein, adopt small wave converting method processing signals to have good time domain, frequency localization characteristic, the feature of transient signal at different scale can be extracted, but wavelet transformation is easily affected by noise; In addition, different wavelet basis functions extracts result by causing different transient characteristic.

Summary of the invention

The present invention for the deficiency that prior art exists, provides a kind of selection method utilizing zero-sequence current wavelet-packet energy relative entropy, meets actual operation requirements just.

For solving the problem, the technical solution used in the present invention is as follows:

Utilize a selection method for zero-sequence current wavelet-packet energy relative entropy, comprise the following steps:

Step one: utilize db10 wavelet packet to do 4 layers of decomposition to each circuit zero-sequence current, according to formula:

$E=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{D}_j\left(k\right)$

Ask for the gross energy of circuit zero-sequence current, and then try to achieve the relative wavelet-packet energy of each circuit;

Step 2: according to formula:

${\mathrm{WP}}_{\mathrm{EREj}}=\underset{j=1}{\overset{l}{\mathrm{\Σ}}}\left|p_j\ln (p_j/q_j)\right|$

Calculate wavelet-packet energy relative entropy matrix W P _eRE;

Step 3: judge wavelet-packet energy relative entropy matrix W P _eREif, WP _{eRE, ij}wP is there is as i=k _{eRE, kj}> 1, and k ≠ j, be then judged to be line fault, transfers step 4 to; Otherwise be judged to be bus-bar fault;

Step 4: the comprehensive wavelet-packet energy relative entropy calculating each circuit zero-sequence current, if the zero-sequence current of circuit Li comprehensive wavelet-packet energy relative entropy is greater than other all circuit zero-sequence currents comprehensive wavelet-packet energy relative entropy sum, that is:

${\mathrm{ZWP}}_{\mathrm{ERE}}\left(L_i\right)>\underset{j\≠i}{\mathrm{\Σ}}{\mathrm{ZWP}}_{\mathrm{ERE}}\left(L_j\right),$

Then can be judged to be circuit Li fault.

Compared with prior art, implementation result of the present invention is as follows in the present invention:

A kind of selection method utilizing zero-sequence current wavelet-packet energy relative entropy of the present invention, compared with wavelet analysis, for signal provides a kind of meticulousr analytical approach, frequency band divides by many levels, decomposes further the HFS that multiresolution analysis does not segment, and can according to the feature of analyzed signal, select frequency band adaptively, make it to match with signal spectrum, thus improve time frequency resolution, therefore wavelet packet analysis has and is applied even more extensively value.

Accompanying drawing explanation

Fig. 1 is a kind of process flow diagram utilizing the selection method of zero-sequence current wavelet-packet energy relative entropy of the present invention;

Fig. 2 is WAVELET PACKET DECOMPOSITION tree construction schematic diagram of the present invention;

The oscillogram of circuit and zero-sequence current when Fig. 3 is singlephase earth fault;

Fig. 4 is the schematic diagram of faulty line zero-sequence current paraphase process.

Embodiment

Below in conjunction with specific embodiments content of the present invention is described.

As shown in Figure 1, be a kind of selection method structural representation utilizing zero-sequence current wavelet-packet energy relative entropy of the present invention.A kind of selection method utilizing zero-sequence current wavelet-packet energy relative entropy of the present invention, comprises the following steps:

Step one: utilize db10 wavelet packet to do 4 layers of decomposition to each circuit zero-sequence current, according to formula:

$E=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{D}_j\left(k\right)$

Ask for the gross energy of circuit zero-sequence current, and then try to achieve the relative wavelet-packet energy of each circuit;

Step 2: according to formula:

${\mathrm{WP}}_{\mathrm{EREj}}=\underset{j=1}{\overset{l}{\mathrm{\Σ}}}\left|p_j\ln (p_j/q_j)\right|$

Calculate wavelet-packet energy relative entropy matrix W P _eRE;

Step 3: judge wavelet-packet energy relative entropy matrix W P _eREif, WP _{eRE, ij}wP is there is as i=k _{eRE, kj}> 1, and k ≠ j, be then judged to be line fault, transfers step 4 to; Otherwise be judged to be bus-bar fault;

Step 4: the comprehensive wavelet-packet energy relative entropy calculating each circuit zero-sequence current, if the zero-sequence current of circuit Li comprehensive wavelet-packet energy relative entropy is greater than other all circuit zero-sequence currents comprehensive wavelet-packet energy relative entropy sum, that is:

${\mathrm{ZWP}}_{\mathrm{ERE}}\left(L_i\right)>\underset{j\≠i}{\mathrm{\Σ}}{\mathrm{ZWP}}_{\mathrm{ERE}}\left(L_j\right),$

Then can be judged to be circuit Li fault.

In WAVELET PACKET DECOMPOSITION, each layer WAVELET PACKET DECOMPOSITION is exactly that band leads to or low-pass filter from the angle of frequency.The bandwidth of each wave filter is: [f _s(k-1)/2j, fsk/2j], (wherein j is the number of plies of wavelet decomposition, and k is a kth contact of wavelet decomposition, and fs is the frequency of input signal).

As shown in Figure 2, in Fig. 2, A represents low frequency to WAVELET PACKET DECOMPOSITION tree, and D represents high frequency, and the sequence number number at end represents the level of WAVELET PACKET DECOMPOSITION (being also scale parameter).

Decompose and there is following relation:

S＝AAA3+DAA3+ADA3+DDA3+AAD3+DAD3+ADD3+DDD (1)

The integrated correlation coefficient of the wavelet packet coefficient of zero-sequence current feature band shown in calculating chart 3 can obtain:

ρ＝[-0.9642 -0.0419 -0.0177] (2)

Obviously, the integrated correlation coefficient failure line selection algorithm application based on WAVELET PACKET DECOMPOSITION also will lose efficacy in the situation shown in Fig. 3.

Entropy is a pervasive amount of characterization information amount, Wavelet Packet Entropy is the combination of wavelet packet analysis and entropy, it makes full use of the two advantage, the characteristic quantity of signal is described, namely the matrix of coefficients of WAVELET PACKET DECOMPOSITION is processed into a probability distribution sequence, the entropy calculated thus, reflects the sparse degree of this matrix of coefficients, i.e. the order degree of signal probability distribution.

From the angle of energy distribution, define wavelet-packet energy relative entropy as follows:

The value obtained after being added up by the wavelet packet coefficient that each circuit zero sequence current transformation obtains is called the gross energy E of circuit zero-sequence current, that is:

$E=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{D}_j\left(k\right)---\left(3\right)$

In formula, j is WAVELET PACKET DECOMPOSITION yardstick, and k is the sampled point under classification yardstick, k=1,2 ..., n.

Order $E_j=\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{D}_{\mathrm{jk}},$

Represent a certain circuit L _mthe signal energy of zero-sequence current n sampled point under yardstick j and, then wavelet-packet energy p relatively _j=E _j/ E.Thus, then set the relative wavelet-packet energy of another circuit Ln zero-sequence current as q _j, circuit L can be obtained _mand L _nthe wavelet-packet energy relative entropy WP of zero-sequence current _eRE(Wavelet Packet Energy Relative Entropy):

${\mathrm{WP}}_{\mathrm{EREj}}=\underset{j=1}{\overset{l}{\mathrm{\Σ}}}\left|p_j\ln (p_j/q_j)\right|---\left(4\right)$

As can be seen from the above equation, if two circuits are perfect circuit, p _jand q _jdifference less, it is relatively little for gross energy, and wavelet-packet energy is less relative to entropy; Otherwise, if supposition L _mfor faulty line, p _jcomparatively large relative to gross energy, p _jand q _jdifference also comparatively large, wavelet-packet energy relative entropy is also comparatively large, the difference can distinguished faulty line thus and perfect between circuit zero-sequence current.Circuit L _mwith circuit L _nthe wavelet-packet energy relative entropy of zero-sequence current is different from circuit L _nwith circuit L _mthe wavelet-packet energy relative entropy of zero-sequence current, as supposition circuit L _mduring for faulty line, generally can only use circuit L _mwith circuit L _nthe wavelet-packet energy relative entropy of zero-sequence current represents difference between the two.

By formula (4), system shown in Figure 3 generation singlephase earth fault is analyzed, obtain bus-bar fault and circuit L ₁the wavelet-packet energy relative entropy matrix of fault is such as formula shown in (5), formula (6).

${\mathrm{WP}}_{\mathrm{EREm}}=\left[\begin{array}{cccccc}0& 0.009& 0.0007& 0.008& 0.003& 0.009\\ & 0& 1.320& 0.084& 0.988& 0.158\\ & & 0& 0.011& 0.003& 0.014\\ & & & 0& 0.679& 0.179\\ & & & & 0& 0.034\\ & & & & & 0\end{array}\right]---\left(5\right)$

${\mathrm{WP}}_{\mathrm{ERE}1}=\left[\begin{array}{cccccc}0& 1.804& 5.137& 2.130& 4.406& 1.400\\ & 0& 0.326& 0.035& 0.257& 0.039\\ & & 0& 0.003& 0.0008& 0.004\\ & & & 0& 0.147& 0.045\\ & & & & 0& 0.009\\ & & & & & 0\end{array}\right]---\left(6\right)$

In formula: WP _eREmfor wavelet-packet energy relative entropy upper triangular matrix during bus-bar fault, WP _eRE1for circuit L ₁wavelet-packet energy relative entropy upper triangular matrix during fault, wherein principal diagonal represents each circuit and self the relative entropy of zero-sequence current energy.As can be seen from above two formulas, existence one returns back out line entropy relative to the wavelet-packet energy of all the other outlet zero-sequence currents and is all greater than 1; Then without this characteristic during bus-bar fault, thus, can distinguish line fault and bus-bar fault.

In order to more adequately distinguish faulty line when line fault, define comprehensive wavelet-packet energy relative entropy (ZWP _eRE) as follows:

One superposition returning back out the relative entropy of wavelet-packet energy between line with other outlet zero-sequence currents.

Obviously, comprehensive wavelet-packet energy relative entropy can power spectrum difference between amplifying signal.

Zero-sequence current as shown in Figure 3, when relevant function method lost efficacy, utilized comprehensive wavelet-packet energy Relative Entropy Analysis to obtain:

ZWP _ERE＝[6.65 2.28 0.002]

Visible, utilize comprehensive wavelet-packet energy relative entropy correctly can identify faulty line.

Based on above-mentioned analysis, during resonant earthed system generation singlephase earth fault, faulty line ground capacitance discharges, and perfects line mutual-ground capacitor charging; Faulty line from perfect circuit there is different charging and discharging circuit, flow through faulty line, from the transient state capacitance current perfecting circuit, there is different amplitudes and the rate of decay, utilize this feature can realize perfect line selection algorithm.

Above content is detailed description made for the present invention in conjunction with specific embodiments, can not assert that the present invention specifically implements to be only limitted to these explanations.For those skilled in the art, without departing from the inventive concept of the premise, some simple deduction or replace can also be made, all should be considered as belonging to the scope of protection of the invention.

Claims (1)

1. utilize a selection method for zero-sequence current wavelet-packet energy relative entropy, it is characterized in that, comprise the following steps:

Step one: utilize db10 wavelet packet to do 4 layers of decomposition to each circuit zero-sequence current, according to formula:

$E=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{D}_j\left(k\right)$

Ask for the gross energy of circuit zero-sequence current, and then try to achieve the relative wavelet-packet energy of each circuit;

Step 2: according to formula:

${\mathrm{WP}}_{\mathrm{EREj}}=\underset{j=1}{\overset{l}{\mathrm{\Σ}}}\left|p_j\ln (p_j/q_j)\right|$

Calculate wavelet-packet energy relative entropy matrix W P _eRE;

Step 3: judge wavelet-packet energy relative entropy matrix W P _eREif, WP _{eRE, ij}wP is there is as i=k _{eRE, kj}> 1, and k ≠ j, be then judged to be line fault, transfers step 4 to; Otherwise be judged to be bus-bar fault;

Step 4: the comprehensive wavelet-packet energy relative entropy calculating each circuit zero-sequence current, if the zero-sequence current of circuit Li comprehensive wavelet-packet energy relative entropy is greater than other all circuit zero-sequence currents comprehensive wavelet-packet energy relative entropy sum, that is:

${\mathrm{ZWP}}_{\mathrm{ERE}}\left(L_i\right)>{\mathrm{ZWP}}_{\mathrm{ERE}}\left(L_j\right),$

Then can be judged to be circuit Li fault.