CN106526422A - Method for processing fault traveling wave of flexible DC transmission line - Google Patents

Abstract

The invention provides a method for processing the fault traveling wave of a flexible direct current transmission line, comprising: respectively obtaining the pole-mode current and pole-mode voltage fault transient traveling waves of the flexible direct current transmission line; obtaining the pole-mode reverse voltage fault transient traveling wave ; Obtain the modulus maximum value of the transient traveling wave of the pole-mode reverse voltage fault, and obtain the equivalent pole-mode reverse voltage traveling wave of the transient traveling wave of the pole-mode reverse voltage fault. The technical solution of the present invention can effectively show the difference between fault traveling waves and high-frequency transient interference, making the overall characteristics of flexible direct current transmission line faults more concise and intuitive; it can also eliminate fault transient traveling waves of polar mode reverse voltage The influence of medium-DC and low-frequency signals highlights the high-frequency characteristics of the traveling wave process, reduces the difficulty of analyzing the down-going wave process of the flexible DC system, and makes the protection of ultra-high-speed flexible DC transmission lines possible.

Description

Fault Traveling Wave Treatment Method for Flexible HVDC Transmission Lines

technical field

The invention relates to the technical field of relay protection and fault detection of power systems, in particular to a method for processing fault traveling waves of flexible direct current transmission lines.

Background technique

Compared with traditional DC transmission technology, flexible DC transmission technology has the advantages of low harmonic level, no commutation failure problem, no reactive power compensation problem, power supply for passive systems, and independent adjustment of active power and reactive power at the same time. It has broad application prospects in our country. However, when a short-circuit fault occurs on the flexible DC transmission line, the excessive short-circuit current will permanently damage the power electronic devices of the converter station. Therefore, it is necessary to correctly identify the fault in a very short time after the fault occurs and open the DC circuit breaker to protect the converter. Station power electronics. The relay protection of traditional DC transmission lines cannot meet the requirements of flexible DC transmission lines for fast protection, and the protection technology and fault technology based on traveling wave principle is an ideal choice to solve this problem.

However, the current analysis method of fault traveling wave takes a single fault traveling wave head as the research object, and lacks an in-depth analysis of the characteristics of the entire wave process; and only through a single fault traveling wave head, it is difficult to highlight the overall characteristics of the fault traveling wave concisely and effectively , it is difficult to distinguish fault traveling waves from high-frequency transient disturbances. Therefore, the fault traveling wave processing method based on the wave process is of great significance for understanding the fault traveling wave and improving the reliability of traveling wave protection.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

For this reason, an object of the present invention is to propose a method for processing fault traveling waves of flexible direct current transmission lines.

In order to achieve the above object, according to an embodiment of the present invention, a method for processing the fault traveling wave of a flexible direct current transmission line is proposed, which includes: acquiring the pole-mode current fault transient traveling wave and pole-mode voltage fault transient wave of the flexible direct current transmission line respectively state traveling wave; obtain the pole mode reverse voltage fault transient traveling wave of the flexible DC transmission line; obtain the modulus maximum value of the pole mode reverse voltage fault transient traveling wave, and calculate the pole mode reverse voltage fault Equivalent pole-mode reverse voltage traveling wave of transient traveling wave.

According to the processing method of the fault traveling wave of the flexible direct current transmission line according to the embodiment of the present invention, the pole mode reverse voltage fault obtained by obtaining the pole mode current fault transient traveling wave and the pole mode voltage fault transient traveling wave of the flexible direct current transmission line Transient traveling wave, and the technical scheme of obtaining the equivalent pole-mode reverse voltage traveling wave by obtaining the modulus maximum value of the polar-mode reverse voltage fault transient traveling wave can eliminate the pole-mode reverse voltage fault transient The influence of DC and low-frequency signals in waves makes it possible to protect ultra-high-speed flexible DC transmission lines.

According to an embodiment of the present invention, obtaining the transient traveling wave of the pole-mode current fault and the transient traveling wave of the pole-mode voltage fault of the flexible direct current transmission line may specifically include: when the flexible direct current transmission line fails, the flexible direct current transmission line Sampling and storing the current of the current sampled value sequence; the positive current i _p (n) and the negative current i _n (n) in the current sampling value sequence are subjected to pole-mode conversion, and the positive current and the negative current in the electromagnetic coupling relationship Current decoupling is independent zero-mode current fault transient traveling wave i ₀ (n) and pole-mode current fault transient traveling wave i ₁ (n); for the positive voltage u _p (n) in the voltage sampling value sequence Pole-mode conversion is carried out with the sampling value of the negative pole voltage u _n (n), and the positive pole voltage and the negative pole voltage with electromagnetic coupling relationship are decoupled into independent zero-mode voltage fault transient traveling wave u ₀ (n) and pole-mode voltage fault Transient traveling wave u ₁ (n).

In this embodiment, the way to obtain the transient traveling wave of the pole-mode current fault and the transient traveling wave of the pole-mode voltage fault of the flexible direct current transmission line is specifically to pass the current of the flexible direct current transmission line when the flexible direct current transmission line is faulty The sampling results are carried out by pole-mode transformation, through which the independent zero-mode current fault transient traveling wave i ₀ (n) and pole-mode current fault transient traveling wave i ₁ (n), as well as the independent zero-mode current fault transient traveling wave i 1 (n), are obtained. Mode voltage fault transient traveling wave u ₀ (n) and polar mode voltage fault transient traveling wave u ₁ (n).

According to an embodiment of the present invention, obtaining the transient traveling wave of the pole-mode reverse voltage fault of the flexible DC transmission line specifically includes: using the inductance _L1 of the pole-mode unit length and the capacitance of the pole-mode unit length of the flexible DC transmission line C ₁ , to obtain the pole-mode wave impedance Z _c1 ; using the pole-mode current fault transient traveling wave i ₁ (n), the pole-mode voltage fault transient traveling wave u ₁ (n) and the pole-mode wave Impedance Z _c1 , to obtain the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In this embodiment, the pole-mode wave impedance Z _c1 is obtained through the pole-mode unit length L _l and the pole-mode capacitance C ₁ of the flexible direct current transmission line, and then through the pole-mode wave impedance Z _c1 , the Pole-mode reverse voltage fault transient traveling wave u _r1 (n).

According to an embodiment of the present invention, obtaining the modulus maximum value of the polar mode reverse voltage fault transient traveling wave, obtaining the equivalent polar mode reverse voltage traveling wave of the polar mode reverse voltage fault transient traveling wave specifically includes: Perform wavelet transform on the polar mode reverse voltage fault transient traveling wave u _r1 (n) to obtain the corresponding wavelet transform coefficients; obtain the modulus maxima of the wavelet transform coefficients respectively; Singularity identification is carried out for a large value, the Lipschitz exponent is calculated, and noise interference is eliminated; the interference of continuous signal discretization on the modulus maximum value of the wavelet transform coefficient is eliminated; the polar mode reverse voltage fault transient traveling wave is The modulus maximum of the wavelet transform coefficient at one place is expressed by the impulse function at this place, and the magnitude of the impulse function is equal to the modulus maximum of the wavelet transform coefficient at this place, and the impulse The impulse function sequence formed by the function is used as the equivalent polar mode reverse voltage traveling wave.

In this embodiment, the noise interference is eliminated by performing wavelet transformation on the polar mode reverse voltage fault transient traveling wave, and performing singularity identification on the modulus maximum value of the wavelet transformation coefficient. Then, by eliminating the interference of the continuous signal discretization on the modulus maxima of the wavelet transform coefficients, the polar-mode reverse voltage fault transient traveling wave is converted into the equivalent polar-mode reverse voltage traveling wave represented by the impulse function sequence, It can eliminate the influence of DC and low-frequency signals in the transient traveling wave of polar mode reverse voltage fault, and highlight the high-frequency characteristics of the traveling wave process.

According to an embodiment of the present invention, the wavelet transform adopts the derivative function of the cubic central B-spline function as the wavelet function, and the wavelet coefficient sequence ﹛h _k ﹜ _k∈z ,﹛g _k ﹜ _k∈z is:

﹛h _k ﹜ _k∈z = (0.125, 0.375, 0.375, 0.125) (k = -1, 0, 1, 2),

﹛g _k ﹜ _k∈z = (-2, 2) (k = 0, 1),

After wavelet transform, the transient traveling wave of polar mode reverse voltage fault is decomposed into the following form:

in, is the wavelet approximation coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n), is the wavelet transform coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In this embodiment, the wavelet transform uses the derivative function of the cubic central B-spline function as the wavelet function, which can effectively extract the wavelet transform coefficients that characterize the transient traveling wave characteristics of polar-mode reverse voltage faults.

According to an embodiment of the present invention, the modulus maximum value of the wavelet transform coefficient is: for any given positive number ε>0, when satisfying |nn ₀ |<ε, for any n≠n ₀ , we have established, where n ₀ is the sampling number of the transient traveling wave of polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sampling number n ₀ of the extreme mode reverse voltage fault transient traveling wave, and j is the scale of the wavelet transform.

In this embodiment, by obtaining the modulus maximum value of the wavelet transform coefficient, the transient traveling wave of the polar mode reverse voltage fault can be reduced on the premise of retaining the characteristics of the transient traveling wave of the polar mode reverse voltage fault as much as possible. noise processing.

According to one embodiment of the present invention, the Lipschitz exponent is:

Among them, α is the Lipschitz exponent, n ₀ is the sampling number of the transient traveling wave of polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sampling number, and j is the scale of the wavelet transform; when α<0, the modulus maximum value at the sampling number is noise interference, and the modulus maximum value at the sampling number is eliminated .

In this embodiment, the Lipschitz exponent can be used to eliminate the modulus maxima formed by noise interference at the sampling sequence number of the polar mode reverse voltage fault transient traveling wave.

According to an embodiment of the present invention, the method further includes: determining a modulus maximum value below 10% of the maximum modulus maximum value as the interference of the continuous signal discretization on the modulus maximum value, and eliminating the interference.

In this embodiment, it is further pointed out that the interference of continuous signal discretization on the modulus maxima can be reduced by eliminating the modulus maxima below 10% of the largest modulus maxima.

According to another aspect of the present invention, a processing device for fault traveling waves of flexible direct current transmission lines is also proposed, including: pole-mode current fault transient traveling waves and pole-mode voltage fault transient traveling wave acquisition units to obtain flexible direct current transmission The pole-mode current fault transient traveling wave and pole-mode voltage fault transient traveling wave of the line; the pole-mode reverse voltage fault transient traveling wave acquisition unit is used to obtain the pole-mode reverse voltage fault transient wave of the flexible direct current transmission line wave; and a calculation unit, which is used to obtain the modulus maximum value of the transient traveling wave of the pole-mode reverse voltage fault, and calculate the equivalent pole-mode reverse voltage line of the transient traveling wave of the pole-mode reverse voltage fault Wave.

According to the processing device for the fault traveling wave of the flexible direct current transmission line according to the embodiment of the present invention, the pole mode reverse voltage fault obtained by obtaining the pole mode current fault transient traveling wave and the pole mode voltage fault transient traveling wave of the flexible direct current transmission line Transient traveling wave, and the technical scheme of obtaining the equivalent pole-mode reverse voltage traveling wave by obtaining the modulus maximum value of the polar-mode reverse voltage fault transient traveling wave can eliminate the pole-mode reverse voltage fault transient The influence of DC and low-frequency signals in waves makes it possible to protect ultra-high-speed flexible DC transmission lines.

According to another embodiment of the present invention, the pole-mode current fault transient traveling wave and pole-mode voltage fault transient traveling wave acquisition unit specifically includes:

The sampling unit is configured to sample and store the current and voltage of the flexible direct current transmission line at a predetermined sampling rate when a fault occurs on the flexible direct current transmission line, and obtain a current sampling value sequence or a voltage sampling value sequence;

Pole-mode conversion unit, used to perform pole-mode conversion on the sampling values of positive current i _p (n) and negative current i _n (n) in the current sampling value sequence, and convert positive current and negative current with electromagnetic coupling relationship Decoupling into independent zero-mode current fault transient traveling wave i ₀ (n) and pole-mode current fault transient traveling wave i ₁ (n); and positive pole voltage u _p (n) in the voltage sampling value sequence Pole-mode conversion is carried out with the sampling value of the negative pole voltage u _n (n), and the positive pole voltage and the negative pole voltage with electromagnetic coupling relationship are decoupled into independent zero-mode voltage fault transient traveling wave u ₀ (n) and pole-mode voltage fault Transient traveling wave u ₁ (n).

In this embodiment, the way to obtain the transient traveling wave of the pole-mode current fault and the transient traveling wave of the pole-mode voltage fault of the flexible direct current transmission line is specifically to pass the current of the flexible direct current transmission line when the flexible direct current transmission line is faulty The sampling results are carried out by pole-mode transformation, through which the independent zero-mode current fault transient traveling wave i ₀ (n) and pole-mode current fault transient traveling wave i ₁ (n), as well as the independent zero-mode current fault transient traveling wave i 1 (n), are obtained. Mode voltage fault transient traveling wave u ₀ (n) and polar mode voltage fault transient traveling wave u ₁ (n).

According to an embodiment of the present invention, the pole-mode reverse voltage fault transient traveling wave acquisition unit is specifically configured to: use the inductance L _l of the pole-mode unit length and the capacitance C ₁ of the pole-mode unit length of the flexible direct current transmission line, Obtaining the pole-mode wave impedance Z _c1 ; using the pole-mode current fault transient traveling wave i ₁ (n), the pole-mode voltage fault transient traveling wave u ₁ (n) and the pole-mode wave impedance Z _c1 , to calculate the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In this embodiment, the pole-mode wave impedance Z _c1 is obtained through the pole-mode unit length L _l and the pole-mode capacitance C ₁ of the flexible direct current transmission line, and then through the pole-mode wave impedance Z _c1 , the Pole-mode reverse voltage fault transient traveling wave u _r1 (n).

According to an embodiment of the present invention, the calculation unit is specifically configured to: perform wavelet transformation on the polar-mode reverse voltage fault transient traveling wave u _r1 (n) to obtain corresponding wavelet transformation coefficients; obtain the wavelet transformation respectively The modulus maximum value of the coefficient; the singularity identification is carried out to the modulus maximum value of the wavelet transform coefficient, the Lipschitz index is calculated, and the noise interference is eliminated; the interference of the continuous signal discretization to the modulus maximum value of the wavelet transform coefficient is eliminated ; The modulus maxima of the wavelet transform coefficients of the polar mode reverse voltage fault transient traveling wave at each place are expressed with the impulse function at this place, and the amplitude of the impulse function is the same as that at this place The modulus maxima of the wavelet transform coefficients are equal, and the impulse function sequence formed by the impulse function is used as the equivalent extreme mode reverse voltage traveling wave.

In this embodiment, the noise interference is eliminated by performing wavelet transformation on the polar mode reverse voltage fault transient traveling wave, and performing singularity identification on the modulus maximum value of the wavelet transformation coefficient. Then, by eliminating the interference of the continuous signal discretization on the modulus maxima of the wavelet transform coefficients, the polar-mode reverse voltage fault transient traveling wave is converted into the equivalent polar-mode reverse voltage traveling wave represented by the impulse function sequence, It can eliminate the influence of DC and low-frequency signals in the transient traveling wave of polar mode reverse voltage fault, and highlight the high-frequency characteristics of the traveling wave process.

According to an embodiment of the present invention, described wavelet transform adopts the derivation function of cubic central B-spline function as wavelet function, and wavelet coefficient sequence﹛h _k ﹜ _k∈z ,﹛ _gk ﹜ _k∈z is:

﹛h _k ﹜ _k∈z = (0.125, 0.375, 0.375, 0.125) (k = -1, 0, 1, 2),

﹛g _k ﹜ _k∈z = (-2, 2) (k = 0, 1),

After the wavelet transform, the polar mode reverse voltage fault transient traveling wave is decomposed into the following forms:

in, is the wavelet approximation coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n), is the wavelet transform coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In this embodiment, the wavelet transform uses the derivative function of the cubic central B-spline function as the wavelet function, which can effectively extract the wavelet transform coefficients that characterize the transient traveling wave characteristics of polar-mode reverse voltage faults.

According to an embodiment of the present invention, the modulus maximum value of the wavelet transform coefficient is: for any given positive number ε>0, when satisfying |nn ₀ |<ε, for any n≠n ₀ , we have established, where n ₀ is the sampling number of the transient traveling wave of polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sampling number n ₀ of the extreme mode reverse voltage fault transient traveling wave, and j is the scale of the wavelet transform.

According to an embodiment of the present invention, the modulus maximum value of the wavelet transform coefficient is:

For any given positive number ε>0, when satisfying |nn ₀ |<ε, for any n≠n ₀ , we have set up,

Wherein, _n0 is the sampling sequence number of the transient traveling wave of the polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sample number n ₀ of the extreme mode reverse voltage fault transient traveling wave, and j is the scale of wavelet transform.

In this embodiment, by obtaining the modulus maximum value of the wavelet transform coefficient, the transient traveling wave of the polar mode reverse voltage fault can be reduced on the premise of retaining the characteristics of the transient traveling wave of the polar mode reverse voltage fault as much as possible. noise processing.

According to one embodiment of the present invention, the Lipschitz exponent is:

Wherein, α is the Lipschitz exponent, _n0 is the sampling sequence number of the transient traveling wave of the polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sampling number, and j is the scale of the wavelet transform; when α<0, the modulus maximum value at the sampling number is the noise interference, and the sampling Modulo maximal value removal at the serial number.

In this embodiment, the Lipschitz exponent can be used to eliminate the modulus maxima formed by noise interference at the sampling sequence number of the polar mode reverse voltage fault transient traveling wave.

According to an embodiment of the present invention, the calculation unit is configured to determine a modulus maximum value below 10% of the maximum modulus maximum value as the interference of the continuous signal discretization on the modulus maximum value, and eliminate the interference.

In this embodiment, it is further pointed out that the interference of continuous signal discretization on the modulus maxima can be reduced by eliminating the modulus maxima below 10% of the largest modulus maxima.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

Fig. 1 shows a schematic flowchart of a method for processing fault traveling waves of a flexible direct current transmission line according to an embodiment of the present invention;

Fig. 2 shows a schematic flowchart of an implementation manner of the processing procedure of step 102 in the embodiment in Fig. 1;

FIG. 3 shows a schematic flowchart of an implementation manner of the processing procedure of step 104 in the embodiment in FIG. 1;

FIG. 4 shows a schematic flowchart of an implementation manner of the processing procedure of step 106 in the embodiment in FIG. 1;

Fig. 5 shows a schematic diagram of a processing device for a fault traveling wave of a flexible direct current transmission line according to an embodiment of the present invention.

detailed description

In order to understand the above-mentioned purpose, features and advantages of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described here. Therefore, the protection scope of the present invention is not limited by the specific details disclosed below. EXAMPLE LIMITATIONS.

As shown in Figure 1, an embodiment of the present invention provides a method for processing fault traveling waves of flexible direct current transmission lines, including: step 102, respectively obtaining pole-mode current fault transient traveling waves and pole-mode current fault traveling waves of flexible direct current transmission lines Mode voltage fault transient traveling wave; step 104, obtain the pole mode reverse voltage fault transient traveling wave of the flexible direct current transmission line; step 106, obtain the modulus maximum value of the pole mode reverse voltage fault transient traveling wave, The equivalent polar mode reverse voltage traveling wave of the polar mode reverse voltage fault transient traveling wave is calculated.

In the above-mentioned embodiment, the processing method of the fault traveling wave of the flexible DC transmission line is to obtain the pole-mode reverse voltage fault transient state obtained by obtaining the pole-mode current fault transient traveling wave and the pole-mode voltage fault transient traveling wave of the flexible DC transmission line Traveling waves can effectively show the difference between fault traveling waves and high-frequency transient interference, making the overall characteristics of flexible DC transmission line faults more concise and intuitive. By obtaining the modulus maximum value of the polar mode reverse voltage fault transient traveling wave, the equivalent polar mode reverse voltage traveling wave obtained can eliminate the influence of DC and low frequency signals in the polar mode reverse voltage fault transient traveling wave , which highlights the high-frequency characteristics of the traveling wave process, reduces the difficulty of analyzing the down-going wave process of the flexible DC system, and makes the protection of ultra-high-speed flexible DC transmission lines possible.

In the above embodiment, preferably, step 102 in FIG. 1 includes, as shown in FIG. 2: step 202, when the flexible direct current transmission line fails, the current (or voltage) of the flexible direct current transmission line Sampling and storage, the sampling rate is 1MHz, obtain the sampling value sequence of current (or voltage); step 204, to the collected bipolar current value i _p (n), i _n (n) (or voltage value u _p (n ), u _n (n)) to perform pole-mode transformation, decoupling the positive and negative currents (or positive and negative voltages) with electromagnetic coupling relationship into independent zero-mode current fault transient traveling wave i ₀ (n) and pole Mode current fault transient traveling wave i ₁ (n) and zero-mode voltage fault transient traveling wave u ₀ (n) and pole-mode voltage fault transient traveling wave u ₁ (n)).

In this embodiment, when the flexible direct current transmission line fails, the waveform of the current or voltage in the flexible direct current transmission line will change abruptly, and it is difficult to judge whether the flexible direct current transmission line is faulty directly through the current or voltage. However, the pole-mode transformation of the positive and negative currents or positive and negative pole voltages with electromagnetic coupling relationship in the sampled current or voltage can obtain the pole-mode current fault transient traveling wave and pole-mode Voltage fault transient traveling wave.

_In the above embodiment, preferably, step 104 in FIG. ₁ includes, step 302 shown in FIG. , to obtain the pole-mode wave impedance Z _c1 ; Step 304, using the pole-mode current fault transient traveling wave i ₁ (n), the pole-mode voltage fault transient traveling wave u ₁ (n) and the pole-mode wave impedance Z _c1 , to obtain Take the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In the above embodiment, preferably, in step 302, the pole-mode wave impedance Z _c1 is:

Among them, L ₁ is the inductance per unit length of the pole mode of the flexible DC transmission line, and C ₁ is the capacitance per unit length of the pole mode of the flexible DC transmission line.

In the above embodiment, preferably, in step 304, the pole mode reverse voltage fault transient traveling wave u _r1 (n) is:

u _r1 (n)＝u ₁ (n)-Z _c1 i ₁ (n)

Among them, u ₁ (n) is the transient traveling wave of pole-mode voltage fault; i ₁ (n) is the transient traveling wave of pole-mode current fault; Z _c1 is the impedance of pole-mode wave.

In this embodiment, it specifically shows that the electrical parameters in the flexible direct current transmission line (the inductance per unit length of the pole mode, the capacitance per unit length of the pole mode, and the wave impedance of the pole mode) in the flexible direct current transmission line can be obtained and combined with the electrical parameters in the flexible direct current transmission line parameters (polar-mode current fault transient traveling wave and pole-mode voltage fault transient traveling wave) to obtain the polar-mode reverse voltage fault transient traveling wave.

In the above-mentioned embodiment, preferably, step 106 in Fig. 1 includes step 402 shown in Fig. 4 , performing wavelet transformation on the pole-mode reverse voltage fault transient traveling wave u _r1 (n) to obtain Corresponding wavelet transform coefficient; Step 404, seek respectively the modulus maxima of wavelet transform coefficient; Step 406, carry out singularity identification to the modulus maxima of wavelet transform coefficient, calculate Lipschitz (Lipschitz) exponent, remove noise interference; Step 408, eliminate the interference of continuous signal discretization on the modulus maxima of wavelet transform coefficients; The impulse function is expressed by the impulse function, the magnitude of the impulse function is equal to the modulus maximum value of the wavelet transform coefficient at this place, and the impulse function sequence formed by the impulse function is the equivalent extreme mode reverse voltage traveling wave.

In this embodiment, the pole-mode reverse voltage fault transient traveling wave is transformed into an equivalent pole-mode reverse voltage traveling wave represented by the impulse function sequence by performing wavelet transformation on the pole-mode reverse voltage fault transient traveling wave . It can eliminate the influence of DC and low-frequency signals in the transient traveling wave of polar mode reverse voltage fault, and highlight the high-frequency characteristics of the traveling wave process.

In the above embodiment, preferably, in step 402, the wavelet transform uses the derivative function of the cubic central B-spline function as the wavelet function, and the wavelet coefficient sequence ﹛h _k ﹜ k ∈ _z , ﹛ g _k ﹜ k ∈ _z is:

﹛h _k ﹜ _k∈z = (0.125, 0.375, 0.375, 0.125) (k = -1, 0, 1, 2),

﹛g _k ﹜ _k∈z = (-2, 2) (k = 0, 1),

After wavelet transform, the polar mode reverse voltage fault transient traveling wave u _r1 (n) is decomposed into the following form:

in, is the wavelet approximation coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n), is the wavelet transform coefficient of transient traveling wave u _r1 (n) of extreme mode reverse voltage fault.

In this embodiment, the wavelet transform uses the derivative function of the cubic central B-spline function as the wavelet function, which can effectively extract the wavelet transform coefficients that characterize the transient traveling wave characteristics of polar-mode reverse voltage faults.

In the above embodiment, preferably, in step 404, the modulus maximum value of the wavelet transform coefficient is:

For any given positive number ε>0, when satisfying |nn ₀ |<ε, for any n≠n ₀ , we have set up, It is called the modulus maximum value of the wavelet transform coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n) at the sampling number n ₀ , and j is the scale of the wavelet transform.

In this embodiment, by obtaining the modulus maximum value of the wavelet transform coefficient, the transient traveling wave of the polar mode reverse voltage fault can be reduced on the premise of retaining the characteristics of the transient traveling wave of the polar mode reverse voltage fault as much as possible. noise processing.

In the above embodiment, preferably, in step 406, the Lipschitz index is:

in is the modulus maximum value of the wavelet transform coefficient at sampling number n ₀ , and j is the scale of wavelet transform;

When α<0, the modulus maximum value at sampling number n ₀ is noise interference, and the modulus maximum value at sampling number n ₀ is eliminated.

In this embodiment, the Lipschitz exponent can be used to eliminate the modulus maxima formed by noise interference at the sampling sequence number of the polar mode reverse voltage fault transient traveling wave.

In the above embodiment, preferably, in step 408, modulus maxima below 10% of the maximum modulus maxima interfere with the discretization of the continuous signal to the modulus maxima, and need to be eliminated.

In this embodiment, it is further pointed out that the interference of continuous signal discretization on the modulus maxima can be reduced by eliminating the modulus maxima below 10% of the largest modulus maxima.

Fig. 5 shows a schematic diagram of a processing device for a fault traveling wave of a flexible direct current transmission line according to an embodiment of the present invention.

As shown in FIG. 5 , a processing device 500 for fault traveling waves of flexible direct current transmission lines according to an embodiment of the present invention includes:

Pole-mode current fault transient traveling wave and pole-mode voltage fault transient traveling wave acquisition unit 502, to obtain the pole-mode current fault transient traveling wave and pole-mode voltage fault transient traveling wave of the flexible direct current transmission line; pole-mode reverse voltage The fault transient traveling wave acquisition unit 504 is used to obtain the polar mode reverse voltage fault transient traveling wave of the flexible direct current transmission line; and the calculation unit 506 is used to obtain the mode of the pole mode reverse voltage fault transient traveling wave The maximum value is calculated to obtain the equivalent pole-mode reverse voltage traveling wave of the transient traveling wave of the pole-mode reverse voltage fault.

According to the processing device for the fault traveling wave of the flexible direct current transmission line according to the embodiment of the present invention, the pole mode reverse voltage fault obtained by obtaining the pole mode current fault transient traveling wave and the pole mode voltage fault transient traveling wave of the flexible direct current transmission line Transient traveling wave, and the technical scheme of obtaining the equivalent pole-mode reverse voltage traveling wave by obtaining the modulus maximum value of the polar-mode reverse voltage fault transient traveling wave can eliminate the pole-mode reverse voltage fault transient The influence of DC and low-frequency signals in waves makes it possible to protect ultra-high-speed flexible DC transmission lines.

According to an embodiment of the present invention, the pole-mode current fault transient traveling wave and pole-mode voltage fault transient traveling wave acquisition unit 502 may include:

The sampling unit 5022 is configured to sample and store the current and voltage of the flexible direct current transmission line at a predetermined sampling rate when a fault occurs on the flexible direct current transmission line, and obtain a current sampling value sequence or a voltage sampling value sequence;

Pole-mode conversion unit 5024, configured to perform pole-mode conversion on the sampling values of the positive current i _p (n) and the negative current i _n (n) in the current sampling value sequence, and convert the positive current and the negative current in the electromagnetic coupling relationship Current decoupling is independent zero-mode current fault transient traveling wave i ₀ (n) and pole-mode current fault transient traveling wave i ₁ (n); and the positive voltage u _p (n ) and negative pole voltage u _n (n) are subjected to pole-mode conversion, and the positive pole voltage and negative pole voltage with electromagnetic coupling relationship are decoupled into independent zero-mode voltage fault transient traveling wave u ₀ (n) and pole-mode voltage Fault transient traveling wave u ₁ (n).

In this embodiment, the way to obtain the transient traveling wave of the pole-mode current fault and the transient traveling wave of the pole-mode voltage fault of the flexible direct current transmission line is specifically to pass the current of the flexible direct current transmission line when the flexible direct current transmission line is faulty The sampling results are carried out by pole-mode transformation, through which the independent zero-mode current fault transient traveling wave i ₀ (n) and pole-mode current fault transient traveling wave i ₁ (n), as well as the independent zero-mode current fault transient traveling wave i 1 (n), are obtained. Mode voltage fault transient traveling wave u ₀ (n) and polar mode voltage fault transient traveling wave u ₁ (n).

According to an embodiment of the present invention, the pole-mode reverse voltage fault transient traveling wave acquisition unit is specifically configured to: use the inductance L _l of the pole-mode unit length and the capacitance C ₁ of the pole-mode unit length of the flexible direct current transmission line, Obtaining the pole-mode wave impedance Z _c1 ; using the pole-mode current fault transient traveling wave i ₁ (n), the pole-mode voltage fault transient traveling wave u ₁ (n) and the pole-mode wave impedance Z _c1 , to calculate the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In this embodiment, the pole-mode wave impedance Z _c1 is obtained through the pole-mode unit length L _l and the pole-mode capacitance C ₁ of the flexible direct current transmission line, and then through the pole-mode wave impedance Z _c1 , the Pole-mode reverse voltage fault transient traveling wave u _r1 (n).

According to an embodiment of the present invention, the calculation unit 506 is specifically configured to: perform wavelet transformation on the polar mode reverse voltage fault transient traveling wave u _r1 (n) to obtain corresponding wavelet transformation coefficients; obtain the wavelet transformation coefficients respectively The modulus maximum value of the transform coefficient; the singularity identification is carried out to the modulus maximum value of the wavelet transform coefficient, the Lipschitz exponent is calculated, and the noise interference is eliminated; Interference; the modulus maximum value of the wavelet transform coefficient at each place of the polar mode reverse voltage fault transient traveling wave is expressed by the impulse function at this place, and the amplitude of the impulse function is the same as that at this place The modulus maxima of the wavelet transform coefficients are equal, and the impulse function sequence formed by the impulse functions is used as the equivalent extreme mode reverse voltage traveling wave.

In this embodiment, the noise interference is eliminated by performing wavelet transformation on the polar mode reverse voltage fault transient traveling wave, and performing singularity identification on the modulus maximum value of the wavelet transformation coefficient. Then, by eliminating the interference of the continuous signal discretization on the modulus maxima of the wavelet transform coefficients, the polar-mode reverse voltage fault transient traveling wave is converted into the equivalent polar-mode reverse voltage traveling wave represented by the impulse function sequence, It can eliminate the influence of DC and low-frequency signals in the transient traveling wave of polar mode reverse voltage fault, and highlight the high-frequency characteristics of the traveling wave process.

According to an embodiment of the present invention, described wavelet transform adopts the derivation function of cubic central B-spline function as wavelet function, and wavelet coefficient sequence﹛h _k ﹜ _k∈z ,﹛ _gk ﹜ _k∈z is:

﹛h _k ﹜ _k∈z = (0.125, 0.375, 0.375, 0.125) (k = -1, 0, 1, 2),

﹛g _k ﹜ _k∈z = (-2, 2) (k = 0, 1),

After the wavelet transform, the polar mode reverse voltage fault transient traveling wave is decomposed into the following forms:

in, is the wavelet approximation coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n), is the wavelet transform coefficient of the polar mode reverse voltage fault transient traveling wave u _r1 (n).

In this embodiment, the wavelet transform uses the derivative function of the cubic central B-spline function as the wavelet function, which can effectively extract the wavelet transform coefficients that characterize the transient traveling wave characteristics of polar-mode reverse voltage faults.

According to an embodiment of the present invention, the modulus maximum value of the wavelet transform coefficient is: for any given positive number ε>0, when satisfying |nn ₀ |<ε, for any n≠n ₀ , we have established, where n ₀ is the sampling number of the transient traveling wave of polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sampling number n ₀ of the extreme mode reverse voltage fault transient traveling wave, and j is the scale of the wavelet transform.

According to an embodiment of the present invention, the modulus maximum value of the wavelet transform coefficient is:

For any given positive number ε>0, when satisfying |nn ₀ |<ε, for any n≠n ₀ , we have set up,

Wherein, _n0 is the sampling sequence number of the transient traveling wave of the polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sample number n ₀ of the extreme mode reverse voltage fault transient traveling wave, and j is the scale of wavelet transform.

In this embodiment, by obtaining the modulus maximum value of the wavelet transform coefficient, the transient traveling wave of the polar mode reverse voltage fault can be reduced on the premise of retaining the characteristics of the transient traveling wave of the polar mode reverse voltage fault as much as possible. noise processing.

According to one embodiment of the present invention, the Lipschitz exponent is:

Wherein, α is the Lipschitz exponent, _n0 is the sampling sequence number of the transient traveling wave of the polar mode reverse voltage fault, is the modulus maximum value of the wavelet transform coefficient at the sampling number, and j is the scale of the wavelet transform; when α<0, the modulus maximum value at the sampling number is the noise interference, and the sampling Modulo maximal value removal at the serial number.

In this embodiment, the Lipschitz exponent can be used to eliminate the modulus maxima formed by noise interference at the sampling sequence number of the polar mode reverse voltage fault transient traveling wave.

According to an embodiment of the present invention, the calculation unit is configured to determine a modulus maximum value below 10% of the maximum modulus maximum value as the interference of the continuous signal discretization on the modulus maximum value, and eliminate the interference.

In this embodiment, it is further pointed out that the interference of continuous signal discretization on the modulus maxima can be reduced by eliminating the modulus maxima below 10% of the largest modulus maxima.

The technical scheme of the present invention has been described in detail above in conjunction with the accompanying drawings. The present invention proposes a new processing method for the fault traveling wave of the flexible direct current transmission line, by obtaining the pole mode current fault transient traveling wave and pole mode of the flexible direct current transmission line The pole-mode reverse voltage fault transient traveling wave obtained from the voltage fault transient traveling wave can effectively show the difference between the fault traveling wave and the high-frequency transient interference, making the overall characteristics of the fault of the flexible direct current transmission line more concise and intuitive.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (16)

1. A method for processing fault traveling waves of a flexible direct current transmission line is characterized by comprising the following steps:

respectively acquiring a polar mode current fault transient traveling wave and a polar mode voltage fault transient traveling wave of the flexible direct current transmission line;

acquiring a polar mode reverse voltage fault transient traveling wave of the flexible direct current transmission line;

and obtaining a mode maximum value of the pole mode reverse voltage fault transient state traveling wave, and calculating to obtain an equivalent pole mode reverse voltage traveling wave of the pole mode reverse voltage fault transient state traveling wave.

2. The method for processing the fault traveling wave of the flexible direct-current transmission line according to claim 1, wherein the respectively obtaining the pole mode current fault transient traveling wave and the pole mode voltage fault transient traveling wave specifically comprises:

when the flexible direct current transmission line breaks down, sampling and storing the current and the voltage of the flexible direct current transmission line at a preset sampling rate to obtain a current sampling value sequence or a voltage sampling value sequence;

for the anode current i in the current sampling value sequence_p(n) and a negative electrode current i_n(n) carrying out polar-mode conversion on the sampling value, and decoupling the positive current and the negative current with electromagnetic coupling relation into independent zero-mode current fault transient traveling wave i₀(n) sum-mode current fault transient traveling wave i₁(n)；

For positive voltage u in the voltage sampling value sequence_p(n) and negative electrode voltage u_nCarrying out polar-mode conversion on the sampling value of (n), and decoupling the positive voltage and the negative voltage which have the electromagnetic coupling relation into independent zero-mode voltage fault transient traveling wave u₀(n) sum pole mode voltage fault transient traveling wave u₁(n)。

3. The method for processing the fault traveling wave of the flexible direct-current transmission line according to claim 2, wherein the obtaining of the pole mode reverse voltage fault transient traveling wave of the flexible direct-current transmission line specifically comprises:

inductance L of pole mode unit length using the flexible DC transmission line_lCapacitance C of unit length of sum pole mode₁Calculating polar mode wave impedance Z_c1；

Utilizing the polar mode current fault transient traveling wave i₁(n) the pole mode voltage fault transient state traveling wave u₁(n) and the polar mode wave impedance Z_c1And calculating the pole mode reverse voltage fault transient state traveling wave u_r1(n)。

4. The method for processing the fault traveling wave of the flexible direct-current transmission line according to claim 3, wherein the obtaining of the mode maximum value of the pole mode reverse voltage fault transient traveling wave and the obtaining of the equivalent pole mode reverse voltage traveling wave of the pole mode reverse voltage fault transient traveling wave specifically includes:

for the pole mode reverse voltage fault transient state traveling wave u_r1(n) performing wavelet transform to obtain corresponding wavelet transform coefficients;

respectively calculating the modulus maximum value of the wavelet transform coefficient;

performing singular identification on the modulus maximum value of the wavelet transform coefficient, calculating the Lipschitz index, and eliminating noise interference;

eliminating the interference of continuous signal discretization on the modulus maximum of the wavelet transformation coefficient;

and expressing the modulus maximum value of the wavelet transformation coefficient of the polar mode reverse voltage fault transient traveling wave at each position by using an impulse function at the position, wherein the amplitude of the impulse function is equal to the modulus maximum value of the wavelet transformation coefficient at the position, and taking an impulse function sequence formed by the impulse function as the equivalent polar mode reverse voltage traveling wave.

5. The method for processing the fault traveling wave of the flexible direct current transmission line according to claim 4, wherein the wavelet transform adopts a derivative function of a cubic center B spline function as a wavelet function, and a wavelet coefficient sequence (h) is adopted_k﹜_k∈z，﹛g_k﹜_k∈zComprises the following steps:

﹛h_k﹜_k∈z＝(0.125，0.375，0.375，0.125)(k＝-1，0，1，2)，

﹛g_k﹜_k∈z＝(-2，2)(k＝0，1)，

after the wavelet transformation, decomposing the polar mode reverse voltage fault transient traveling wave into the following forms:

$\left\{\begin{array}{c}{A}_{2^j}{u}_{r1}\left(n\right)=\underset{k}{\mathrm{\&Sigma;}}{h}_k{A}_{2^{j-1}}{u}_{r1}(n-2^{j-1}k)\\ W_{2^j}{u}_{r1}\left(n\right)=\underset{k}{\mathrm{\&Sigma;}}{g}_k{A}_{2^{j-1}}{u}_{r1}(n-2^{j-1}k)\end{array}\right.$

wherein A is_2ju_r1(n) is the pole mode reverse voltage fault transient state traveling wave u_r1(n) wavelet approximation coefficient, W_2ju_r1(n) is the pole mode reverse voltage fault transient state traveling wave u_r1(n) wavelet transform coefficients.

6. The method for processing the fault traveling wave of the flexible direct current transmission line according to claim 4, wherein the modulus maximum of the wavelet transform coefficient is as follows:

for any given positive number>0, when | n-n is satisfied₀|<In time, for arbitrary n ≠ n₀Is provided withIt is true that the first and second sensors,

wherein n is₀The sampling serial number of the pole mode reverse voltage fault transient state traveling wave is the sampling serial number of the pole mode reverse voltage fault transient state traveling wave,is a stand forSampling sequence number n of the pole mode reverse voltage fault transient state traveling wave₀The modulus maximum of the wavelet transform coefficient, j is the scale of the wavelet transform.

7. The method for processing the fault traveling wave of the flexible direct current transmission line according to claim 4, wherein the Lipschitz index is:

$\mathrm{\&alpha;}={\log }_2\frac{W_{2^{j+1}}f\left(n_0\right)}{W_{2^j}f\left(n_0\right)}$

wherein α is the Lipschitz index, n₀The sampling serial number of the pole mode reverse voltage fault transient state traveling wave is the sampling serial number of the pole mode reverse voltage fault transient state traveling wave,is the modulus maximum of the wavelet transform coefficient at the sampling number, j is the scale of the wavelet transform;

and when the alpha is less than 0, the modulus maximum value at the sampling sequence number is the noise interference, and the modulus maximum value at the sampling sequence number is removed.

8. The method for processing the fault traveling wave of the flexible direct current transmission line according to claim 4, wherein a mode maximum value with a maximum mode maximum value of less than 10% is determined as the interference of the continuous signal discretization on the mode maximum value, and the interference is eliminated.

9. A processing apparatus of flexible direct current transmission line trouble travelling wave, characterized by includes:

a pole mode current fault transient traveling wave and pole mode voltage fault transient traveling wave acquisition unit for acquiring a pole mode current fault transient traveling wave and a pole mode voltage fault transient traveling wave of the flexible direct current transmission line;

the pole mode reverse voltage fault transient traveling wave acquisition unit is used for acquiring a pole mode reverse voltage fault transient traveling wave of the flexible direct current transmission line; and

and the calculation unit is used for acquiring a mode maximum value of the pole mode reverse voltage fault transient traveling wave and calculating to obtain an equivalent pole mode reverse voltage traveling wave of the pole mode reverse voltage fault transient traveling wave.

10. The apparatus for processing the fault traveling wave of the flexible direct-current transmission line according to claim 9, wherein the polar-mode current fault transient traveling wave and polar-mode voltage fault transient traveling wave acquiring unit specifically includes:

the sampling unit is used for sampling and storing the current and the voltage of the flexible direct current transmission line at a preset sampling rate when the flexible direct current transmission line fails to obtain a current sampling value sequence or a voltage sampling value sequence;

a polar-mode conversion unit for converting the positive electrode current i in the current sampling value sequence_p(n) and a negative electrode current i_n(n) carrying out polar-mode conversion on the sampling value, and decoupling the positive current and the negative current with electromagnetic coupling relation into independent zero-mode current fault transient traveling wave i₀(n) sum-mode current fault transient traveling wave i₁(n); and

for positive voltage u in the voltage sampling value sequence_p(n) and negative electrode voltage u_n(n) the sampled values are converted in polar mode so that there will be electromagnetic couplingPositive pole voltage and negative pole voltage decoupling of relation become independent zero mode voltage fault transient state travelling wave u₀(n) sum pole mode voltage fault transient traveling wave u₁(n)。

11. The apparatus for processing the fault traveling wave of the flexible direct-current transmission line according to claim 10, wherein the pole-mode reverse voltage fault transient traveling wave obtaining unit is specifically configured to:

inductance L of pole mode unit length using the flexible DC transmission line_lCapacitance C of unit length of sum pole mode₁Calculating polar mode wave impedance Z_c1；

Utilizing the polar mode current fault transient traveling wave i₁(n) the pole mode voltage fault transient state traveling wave u₁(n) and the polar mode wave impedance Z_c1And calculating the pole mode reverse voltage fault transient state traveling wave u_r1(n)。

12. The apparatus for processing the fault traveling wave of the flexible direct-current transmission line according to claim 11, wherein the computing unit is specifically configured to:

for the pole mode reverse voltage fault transient state traveling wave u_r1(n) performing wavelet transform to obtain corresponding wavelet transform coefficients;

respectively calculating the modulus maximum value of the wavelet transform coefficient;

performing singular identification on the modulus maximum value of the wavelet transform coefficient, calculating the Lipschitz index, and eliminating noise interference;

eliminating the interference of continuous signal discretization on the modulus maximum of the wavelet transformation coefficient;

and expressing the modulus maximum value of the wavelet transformation coefficient of the polar mode reverse voltage fault transient traveling wave at each position by using an impulse function at the position, wherein the amplitude of the impulse function is equal to the modulus maximum value of the wavelet transformation coefficient at the position, and taking an impulse function sequence formed by the impulse function as the equivalent polar mode reverse voltage traveling wave.

13. The apparatus according to claim 12, wherein the wavelet transform employs a derivative function of a cubic center B-spline function as the wavelet function, and the wavelet coefficient sequence (h) is the same as the wavelet function_k﹜_k∈z，﹛g_k﹜_k∈zComprises the following steps:

﹛h_k﹜_k∈z＝(0.125，0.375，0.375，0.125)(k＝-1，0，1，2)，

﹛g_k﹜_k∈z＝(-2，2)(k＝0，1)，

after the wavelet transformation, decomposing the polar mode reverse voltage fault transient traveling wave into the following forms:

$\left\{\begin{array}{c}{A}_{2^j}{u}_{r1}\left(n\right)=\underset{k}{\mathrm{\&Sigma;}}{h}_k{A}_{2^{j-1}}{u}_{r1}(n-2^{j-1}k)\\ W_{2^j}{u}_{r1}\left(n\right)=\underset{k}{\mathrm{\&Sigma;}}{g}_k{A}_{2^{j-1}}{u}_{r1}(n-2^{j-1}k)\end{array}\right.$

wherein,for reverse voltage failure of said polar modeTransient traveling wave u_r1(n) the wavelet approximation coefficients of (n),for said pole mode reverse voltage fault transient state travelling wave u_r1(n) wavelet transform coefficients.

14. The apparatus for processing the fault traveling wave of the flexible direct current transmission line according to claim 12, wherein a modulus maximum of the wavelet transform coefficient is:

for any given positive number>0, when | n-n is satisfied₀|<In time, for arbitrary n ≠ n₀Is provided withIt is true that the first and second sensors,

wherein n is₀The sampling serial number of the pole mode reverse voltage fault transient state traveling wave is the sampling serial number of the pole mode reverse voltage fault transient state traveling wave,sampling sequence number n for the pole mode reverse voltage fault transient state traveling wave₀The modulus maximum of the wavelet transform coefficient, j is the scale of the wavelet transform.

15. The apparatus for processing the fault traveling wave of the flexible direct current transmission line according to claim 12, wherein the lipschitz index is:

$\mathrm{\&alpha;}={\log }_2\frac{W_{2^{j+1}}f\left(n_0\right)}{W_{2^j}f\left(n_0\right)}$

wherein α is the Lipschitz index, n₀The sampling serial number of the pole mode reverse voltage fault transient state traveling wave is the sampling serial number of the pole mode reverse voltage fault transient state traveling wave,is the modulus maximum of the wavelet transform coefficient at the sampling number, j is the scale of the wavelet transform;

and when the alpha is less than 0, the modulus maximum value at the sampling sequence number is the noise interference, and the modulus maximum value at the sampling sequence number is removed.

16. The method for processing the fault traveling wave of the flexible direct current transmission line according to claim 12, wherein the computing unit is configured to determine a mode maximum value of 10% or less of a maximum mode maximum value as the interference of the discretization of the continuous signal on the mode maximum value, and reject the interference.