A frequency band range selection method for fast traveling wave protection and related device

Abstract

The application discloses a frequency band range selection method for fast traveling wave protection and a related device, and the method comprises the following steps: collecting positive electrode voltage data and negative electrode voltage data in a preset data window, and determining a fault initial line mode voltage traveling wave based on the positive electrode voltage data and the negative electrode voltage data; analyzing the fault initial line mode voltage traveling wave, and extracting a plurality of wavelet transform modulus maxima of different scales; comparing the plurality of wavelet transform modulus maxima of different scales with preset conditions, and determining a frequency band range of fast traveling wave protection based on a comparison result. The method realizes accurate selection of the frequency band range of fast traveling wave protection, and provides strong support for guaranteeing the reliability of fast traveling wave protection of a flexible direct current power transmission system.

Description

Technical Field

[0001] This invention relates to the field of relay protection technology, specifically to a method and related apparatus for selecting the frequency band range for fast traveling wave protection. Background Technology

[0002] Flexible direct current (DC) transmission systems are an effective solution for the smooth integration and reliable transmission of large-scale renewable and clean energy, and a crucial development direction for supporting the construction of a new power system with stronger new energy absorption capacity, thus fulfilling the grand strategy of "carbon peaking and carbon neutrality." However, due to the low damping of flexible DC transmission systems, once a DC transmission line fault occurs, the fault current will rise rapidly at a rate of thousands of amperes per millisecond, easily causing damage to the power electronic devices of the main system equipment, and even the collapse of the entire DC system. Therefore, to ensure the continuous and reliable operation of flexible DC transmission systems, fast and reliable line protection is particularly important.

[0003] Among all protection principles, traveling wave protection can effectively utilize the earliest fault information propagating to the protection installation point, making it one of the fastest-acting protection principles and highly suitable for protection of flexible DC transmission lines. To fully utilize broadband fault information, traveling wave protection requires accurate fault feature extraction methods. Wavelet transform, as an effective time-frequency analysis tool, creates extremely favorable conditions for comprehensive analysis of fault traveling waves and full extraction of fault information. However, due to the lack of a unified theory for selecting frequency bands, existing fast traveling wave protection based on wavelet transform multi-resolution analysis appears to be inefficient and time-consuming in extracting fault features. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the existing fast traveling wave protection based on wavelet transform multi-resolution analysis, which is blind and time-consuming in extracting fault features due to the lack of a unified frequency band range selection theory. Thus, the present invention provides a frequency band range selection method and related device for fast traveling wave protection.

[0005] This invention provides a method for selecting the frequency band range for fast traveling wave protection, comprising:

[0006] Collect positive and negative voltage data within a preset data window, and determine the initial line-mode voltage traveling wave of the fault based on the positive and negative voltage data;

[0007] The traveling wave of the initial line-mode voltage during a fault is analyzed, and wavelet transform modal maxima at multiple scales are extracted.

[0008] The maximum values ​​of wavelet transform modulus at multiple scales are compared with preset conditions, and the frequency band range of fast traveling wave protection is determined based on the comparison results.

[0009] This invention provides a frequency band selection method for fast traveling wave protection. By calculating and comparing wavelet transform modulus maxima at multiple scales, the wavelet transform modulus maxima are determined, and the frequency band of fast traveling wave protection is selected based on the wavelet transform modulus maxima. This method eliminates noise interference and accurately extracts fault traveling wave characteristics. Compared with existing technologies, the frequency band selection method proposed in this invention is simple and clear in principle, and has high accuracy and speed. It is easy to implement in engineering and has high practical value, providing strong support for ensuring the reliability of fast traveling wave protection in flexible DC transmission systems.

[0010] Optionally, the traveling wave of the initial line-mode voltage during the fault is analyzed, and wavelet transform modal maxima at multiple scales are extracted, including:

[0011] Wavelet transform multi-resolution analysis is performed on the initial line-mode voltage of the fault to generate signal components at multiple scales; among which, the signal components include approximation components and detail components;

[0012] Wavelet transform modulus maxima at multiple scales are extracted based on signal components at multiple scales.

[0013] Optionally, the following calculation formula can be used to perform wavelet transform multi-resolution analysis on the initial line-mode voltage of the fault to generate signal components of multiple scales:

[0014]

[0015] In the above formula, h represents the approximation component of the initial fault line-mode voltage traveling wave U1 at the j-th scale. k This represents the coefficients of the low-pass filter. G represents the detail component of the initial fault-induced line-mode voltage traveling wave U1 at the j-th scale. k Represents the coefficients of the high-pass filter. The value represents the approximation component of the initial line-mode voltage traveling wave U1 at the (j-1)th scale, and n represents the sequence number of the sampling point within the preset data window.

[0016] Optionally, wavelet transform modulus maxima at multiple scales are extracted based on signal components at multiple scales, including:

[0017] Suppose that at the j-th scale, within the neighborhood of sampling point n0, we arbitrarily select sampling point n. If there exists... Then the detail component corresponding to the sampling point n0 is taken as the wavelet transform modulus maxima at the j-th scale.

[0018] Optionally, the analysis of the initial line-mode voltage traveling wave during the fault, and the extraction of wavelet transform modal maxima at multiple scales, also includes:

[0019] Obtain the initial traveling wave frequency band range, and determine the frequency range corresponding to multiple scales based on the initial traveling wave frequency band range.

[0020] Optionally, the wavelet transform modulus maxima at multiple scales are compared with preset conditions, and the frequency band range of fast traveling wave protection is determined based on the comparison results, including:

[0021] The first ratio between the wavelet transform modulus maxima at the first scale and the wavelet transform modulus maxima at the second scale is compared with a first preset threshold and a second preset threshold, respectively; wherein the first preset threshold is less than the second preset threshold.

[0022] When the first ratio is greater than the first preset threshold and less than the second preset threshold, the second ratio between the wavelet transform modulus maxima at the second scale and the wavelet transform modulus maxima at the third scale is compared with the first preset threshold and the second preset threshold, respectively.

[0023] When the second ratio is greater than the first preset threshold and less than the second preset threshold, the frequency range corresponding to the first scale is taken as the frequency band range of fast traveling wave protection.

[0024] Optionally, the initial line-mode voltage traveling wave of the fault can be determined using the following calculation formula based on the positive and negative voltage data:

[0025]

[0026] In the above formula, U p U represents the positive voltage data. n U0 represents the negative electrode voltage data, U1 represents the initial zero-mode voltage traveling wave of the fault, and U1 represents the initial line-mode voltage traveling wave of the fault.

[0027] In a second aspect of this application, a frequency band selection device for fast traveling wave protection is also provided, comprising:

[0028] The acquisition module is used to acquire positive and negative voltage data within a preset data window, and to determine the initial line-mode voltage traveling wave of the fault based on the positive and negative voltage data.

[0029] The analysis module is used to analyze the traveling wave of the initial line-mode voltage during a fault and extract wavelet transform modal maxima at multiple scales.

[0030] The comparison module is used to compare the wavelet transform modulus maxima at multiple scales with preset conditions, and determine the frequency band range of fast traveling wave protection based on the comparison results.

[0031] Optionally, the analysis module includes:

[0032] The analysis unit is used to perform wavelet transform multi-resolution analysis on the initial line-mode voltage of the fault, generating signal components at multiple scales; among which, the signal components include approximation components and detail components;

[0033] The extraction unit is used to extract wavelet transform modulus maxima at multiple scales based on signal components at multiple scales.

[0034] Optionally, the analysis unit includes:

[0035] The following calculation formula is used to perform wavelet transform multi-resolution analysis on the initial line-mode voltage of the fault, generating signal components at multiple scales:

[0036]

[0037] In the above formula, h represents the approximation component of the initial fault line-mode voltage traveling wave U1 at the j-th scale. k This represents the coefficients of the low-pass filter. G represents the detail component of the initial fault-induced line-mode voltage traveling wave U1 at the j-th scale. k Represents the coefficients of the high-pass filter. The value represents the approximation component of the initial line-mode voltage traveling wave U1 at the (j-1)th scale, and n represents the sequence number of the sampling point within the preset data window.

[0038] Optionally, the extraction unit includes:

[0039] Suppose that at the j-th scale, within the neighborhood of sampling point n0, we arbitrarily select sampling point n. If there exists... Then the detail component corresponding to the sampling point n0 is taken as the wavelet transform modulus maxima at the j-th scale.

[0040] Optionally, the analysis module also includes:

[0041] Obtain the initial traveling wave frequency band range, and determine the frequency range corresponding to multiple scales based on the initial traveling wave frequency band range.

[0042] Optionally, the comparison module includes:

[0043] The first comparison unit is used to compare a first ratio between the wavelet transform modulus maxima at the first scale and the wavelet transform modulus maxima at the second scale with a first preset threshold and a second preset threshold, respectively; wherein the first preset threshold is less than the second preset threshold.

[0044] The second comparison unit compares the second ratio between the wavelet transform modulus maxima at the second scale and the wavelet transform modulus maxima at the third scale with the first preset threshold and the second preset threshold, respectively, when the first ratio is greater than the first preset threshold and less than the second preset threshold.

[0045] The selection unit is used to select the frequency range corresponding to the first scale as the frequency band range of fast traveling wave protection when the second ratio is greater than the first preset threshold and less than the second preset threshold.

[0046] Optionally, the data acquisition module includes:

[0047] The following calculation formula is used to determine the initial line-mode voltage traveling wave during a fault, based on positive and negative voltage data:

[0048]

[0049] In the above formula, U p U represents the positive voltage data. n U0 represents the negative electrode voltage data, U1 represents the initial zero-mode voltage traveling wave of the fault, and U1 represents the initial line-mode voltage traveling wave of the fault.

[0050] In a third aspect of this application, a computer device is also provided, comprising a processor and a memory, wherein the memory is used to store a computer program, the computer program including a program, and the processor is configured to invoke the computer program to perform the method described in the first aspect.

[0051] In a fourth aspect of this application, embodiments of the present invention provide a computer-readable storage medium storing a computer program that is executed by a processor to implement the method of the first aspect described above. Attached Figure Description

[0052] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0053] Figure 1 This is a flowchart of a frequency band range selection method for fast traveling wave protection according to Embodiment 1 of the present invention;

[0054] Figure 2 This is a schematic diagram of a frequency band range selection method for fast traveling wave protection according to Embodiment 1 of the present invention;

[0055] Figure 3 This is a flowchart of S102 in Embodiment 1 of the present invention;

[0056] Figure 4 This is a flowchart of S103 in Embodiment 1 of the present invention;

[0057] Figure 5 This is a graph of the line-mode wave impedance in Embodiment 1 of the present invention;

[0058] Figure 6 This is a graph of the zero-mode impedance in Embodiment 1 of the present invention;

[0059] Figure 7 This is a graph of the propagation function of the line mode wave in Embodiment 1 of the present invention;

[0060] Figure 8 This is a graph of the zero-mode wave propagation function in Embodiment 1 of the present invention;

[0061] Figure 9 This is a schematic diagram of the fault area of ​​the flexible DC transmission system in Embodiment 1 of the present invention;

[0062] Figure 10 This is a traveling wave waveform diagram of the voltage at the measurement point on this side in Embodiment 1 of the present invention;

[0063] Figure 11 This is a schematic diagram of wavelet transform multi-resolution analysis in Embodiment 1 of the present invention;

[0064] Figure 12 This is a waveform diagram of the modulus maxima of the traveling wavelet transform of the initial line-mode voltage when j=1 in Embodiment 1 of the present invention.

[0065] Figure 13 This is a waveform diagram of the modulus maxima of the traveling wavelet transform of the initial line-mode voltage when j=2 in Embodiment 1 of the present invention;

[0066] Figure 14 This is a waveform diagram of the modulus maxima of the traveling wavelet transform of the initial line-mode voltage when j=3 in Embodiment 1 of the present invention;

[0067] Figure 15 This is a waveform diagram of the modulus maxima of the traveling wavelet transform of the initial line-mode voltage when j=4 in Embodiment 1 of the present invention.

[0068] Figure 16 This is a schematic diagram of the electromagnetic transient simulation model of the flexible DC power grid in Embodiment 1 of the present invention;

[0069] Figure 17 This is a schematic block diagram of a frequency band range selection device for fast traveling wave protection according to Embodiment 2 of the present invention;

[0070] Figure 18 This is a schematic diagram of a specific example of the processing module 172 in Embodiment 2 of the present invention;

[0071] Figure 19 This is a schematic diagram of the generation module 173 in Embodiment 2 of the present invention. Detailed Implementation

[0072] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0073] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0074] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0075] Example 1

[0076] This embodiment provides a method for selecting the frequency band range for fast traveling wave protection, such as... Figures 1-2 As shown, it includes:

[0077] S101. Collect the positive voltage data and negative voltage data in the preset data window, and determine the fault initial line mode voltage traveling wave based on the positive voltage data and the negative voltage data.

[0078] Specifically, a wideband fast-response measurement device is used to collect a certain amount of positive and negative voltage data before and after the protection start-up moment in real time, constructing a "data window" for fast traveling wave protection. The positive and negative voltage data within the collected "data window" are then subjected to pole mode transformation to construct the initial line-mode voltage traveling wave of the fault. The initial line-mode voltage traveling wave of the fault is determined based on the aforementioned positive and negative voltage data using the following calculation formula:

[0079]

[0080] In the above formula, U p U represents the positive voltage data. n U0 represents the negative electrode voltage data, U1 represents the initial zero-mode voltage traveling wave of the fault, and U1 represents the initial line-mode voltage traveling wave of the fault.

[0081] S102. Analyze the traveling wave of the initial line-mode voltage of the above fault and extract the wavelet transform modal maxima at multiple scales.

[0082] S103. Compare the maximum values ​​of the wavelet transform modulus at the above multiple scales with the preset conditions, and determine the frequency band range of the fast traveling wave protection based on the comparison results.

[0083] Specifically, the wavelet transform modulus maxima at multiple extracted scales are compared, the scale at which the wavelet transform modulus maxima begin to stabilize is marked, and the frequency range corresponding to this scale is selected as the frequency band range for fast traveling wave protection.

[0084] The aforementioned method for selecting the frequency band range for fast traveling wave protection determines the wavelet transform modulus maxima by calculating and comparing them at multiple scales, and selects the frequency band range for fast traveling wave protection based on these maxima. This method fully utilizes the opposite Lipshitz characteristics of the wavelet transform modulus maxima of traveling wave signals and noise signals, eliminating noise interference and accurately extracting fault traveling wave characteristics. Compared with existing technologies, the frequency band range selection method proposed in this invention is simple and clear in principle, and has high accuracy and speed. It is easy to implement in engineering and has high practical value, providing strong support for ensuring the reliability of fast traveling wave protection in flexible DC transmission systems.

[0085] Preferably, such as Figure 3 As shown, in step S102, the traveling wave of the initial line-mode voltage of the above-mentioned fault is analyzed, and wavelet transform modal maxima at multiple scales are extracted, including:

[0086] S1021. Perform wavelet transform multi-resolution analysis on the initial line-mode voltage of the above fault to generate signal components of multiple scales; wherein, the above signal components include approximation components and detail components.

[0087] Specifically, the initial traveling wave frequency band range is obtained, and based on the initial traveling wave frequency band range, the frequency ranges corresponding to multiple scales are determined. The frequency range corresponding to the j-th scale is shown below:

[0088] f p ∈(f s / 2 j+1 ,f s / 2 j )

[0089] In the above formula, f p For the frequency range, f s This represents the initial traveling wave frequency band range.

[0090] Specifically, the initial line-mode voltage of the above fault is analyzed by wavelet transform multi-resolution analysis using the following calculation formula to generate signal components of multiple scales:

[0091]

[0092] In the above formula, h represents the approximation component of the initial fault line-mode voltage traveling wave U1 at the j-th scale. k This represents the coefficients of the low-pass filter. The details of the initial fault-induced line-mode voltage traveling wave U1 at the j-th scale are represented by the components from the frequency distribution range of 0 to f. s The frequency band decomposed from the initial line-mode voltage U1(n) of the fault is 0~f s / 2 j+1 and f s / 2 j+1 ~f s / 2 j signal components, g k Represents the coefficients of the high-pass filter. The value represents the approximation component of the initial line-mode voltage traveling wave U1 at the (j-1)th scale, and n represents the sequence number of the sampling point within the preset data window.

[0093] Among them, h k and g k The value can be:

[0094]

[0095] S1022. Extract the wavelet transform modulus maxima of the above-mentioned multiple scales based on the signal components of the above-mentioned multiple scales respectively.

[0096] Wherein, suppose that at the j-th scale, within the neighborhood of sampling point n0, i.e., within the range of (n0-δ, n0+δ), we arbitrarily select sampling point n. If there exists The detail components corresponding to the above sampling point n0 are then taken as the wavelet transform modulus maxima at the j-th scale.

[0097] Preferably, such as Figure 4 As shown, in step S103, comparing the wavelet transform modulus maxima at the multiple scales with preset conditions and determining the frequency band range of fast traveling wave protection based on the comparison results includes:

[0098] S1031. The first ratio between the wavelet transform modulus maxima at the first scale and the wavelet transform modulus maxima at the second scale is compared with a first preset threshold and a second preset threshold, respectively; wherein the first preset threshold is less than the second preset threshold.

[0099] S1032. When the first ratio is greater than the first preset threshold and less than the second preset threshold, the second ratio between the wavelet transform modulus maxima at the second scale and the wavelet transform modulus maxima at the third scale is compared with the first preset threshold and the second preset threshold, respectively.

[0100] Specifically, such as Figure 2 As shown, the maximum value of the wavelet transform modulus at the j-th scale is determined. The maximum wavelet transform modulus at the (j+1)th scale is WTMM2. j+1The maximum value of the wavelet transform modulus at the (j+2)th scale is WTMM2. j+2 To determine whether they are approximately equal, the formula is as follows:

[0101] and

[0102] Wherein, TH1 represents the first preset threshold and TH2 represents the second preset threshold.

[0103] S1033. When the second ratio is greater than the first preset threshold and less than the second preset threshold, the frequency range corresponding to the first scale is taken as the frequency band range of the fast traveling wave protection.

[0104] Specifically, if the above comparison results are valid, then the frequency range f corresponding to the j-th scale is determined. s / 2 j+1 ~f s / 2 j The frequency band range for fast traveling wave protection.

[0105] Furthermore, if the above comparison results are not valid, let j = j+1, and continue to calculate and compare the wavelet transform modulus maxima at the (j+1)th, (j+2)th, and (j+3)th scales, repeating this process until the condition is met.

[0106] The following specific embodiment illustrates a method for selecting the frequency band range for fast traveling wave protection.

[0107] Based on the boundary conditions at the fault point, the initial modulus voltage traveling wave characteristics of a bipolar flexible DC transmission system under positive ground fault, negative ground fault, and bipolar short-circuit fault can be obtained, as follows:

[0108] 1) During a positive ground fault, the traveling wave of the line-mode voltage and the traveling wave of the zero-mode voltage are as follows:

[0109] Among them, U dc R is the rated DC voltage. f Z1 and Z0 are the fault transition resistances, respectively, and the line-mode impedance and zero-mode impedance of the DC transmission line.

[0110] 2) During a negative ground fault, the traveling wave of the line-mode voltage and the traveling wave of the zero-mode voltage are as follows:

[0111] 3) During a bipolar short-circuit fault, the traveling waves of the line-mode voltage and the zero-mode voltage are as follows:

[0112] In summary, it can be seen that under different fault types, the initial line-mode traveling wave voltage is always negative. The initial zero-mode traveling wave is negative when the positive-to-ground fault occurs, positive when the negative-to-ground fault occurs, and zero when the bipolar short-circuit fault occurs.

[0113] Secondly, such as Figures 5-8 Based on the frequency-varying characteristics of the modulus wave impedance and modulus propagation function of the overhead transmission line in the flexible DC transmission system shown, the following conclusions can be drawn:

[0114] 1) In the frequency range of 1Hz (Hertz) to 1MHz (Megahertz), the line mode impedance of DC transmission lines is approximately constant, while its zero-mode impedance varies over a large range.

[0115] 2) At the same propagation distance, the higher the frequency, the more severe the attenuation of the fault traveling wave; at the same frequency, the longer the propagation distance, the more severe the attenuation of the fault traveling wave; when the fault traveling waves of the same frequency propagate the same distance, the zero-mode traveling wave attenuates more severely.

[0116] Based on the above conclusions, the frequency band range for fast traveling wave protection of flexible DC transmission systems can be determined by taking the initial line-mode voltage traveling wave of the fault as the object.

[0117] like Figure 9 As shown, L dc This indicates a DC reactor, and f indicates the location of the fault point on the DC transmission line Line. m A metallic positive electrode grounding short-circuit fault is set up, with the fault point and measurement point m being... p1 300km away, and the distance from the measurement point m p2 When the distance is 500km and the sampling rate is 1MHz, the measurement point m p1 The measured voltage traveling wave waveform propagating from the DC line to the DC bus is as follows: Figure 10 As shown, the time unit is ms (milliseconds), and the voltage traveling wave unit is kV (kilovolts), where u b1 For the initial voltage traveling wave from the fault point, u b2 The initial voltage traveling wave of the fault passes successively through the measurement point m. p1 The DC reactor on the side, after being reflected from the fault point, reaches the measuring point m. p1 The traveling wave component, u b3 To measure point m p2 The side-propagating fault initial voltage traveling wave successively passes through the measurement point m p2 The DC reactor on the side reflects and refracts through the fault point to reach the measuring point m. p1 The traveling wave component.

[0118] Using measurement point m p1 and m n1The measured positive and negative voltage data are the objects of this study. The method for selecting the fast traveling wave protection frequency band range specifically includes the following steps:

[0119] Step 1: Use a wideband fast response measurement device to collect positive and negative voltage data at 64 points before and 192 points after the protection start time in real time, forming a "data window" of fast traveling wave protection algorithm containing a total of 256 points;

[0120] Step 2: Calculate the initial line-mode voltage traveling wave of the fault using the following formula based on the positive and negative voltage data in the "Data Window".

[0121] Among them, U p and U n These are the positive and negative voltage data collected at the protection installation location, respectively. U0 and U1 are the constructed initial zero-mode and line-mode voltage traveling waves of the fault, respectively.

[0122] Step 3: Using the derivative of the cubic central B-spline function as the mother wavelet function, extract the wavelet transform modulus maxima at different scales using wavelet transform multi-resolution analysis.

[0123] The schematic diagram of wavelet transform multiresolution analysis is shown below. Figure 11 As shown, the approximation coefficient at the j-th scale is calculated according to the following formula. and detail coefficient

[0124] In the formula, h k For the low-pass filter coefficients, g k These are the coefficients of the high-pass filter, and their values ​​are:

[0125] Wavelet transform modulus maxima at scale j Defined as: In the δ-neighborhood (x0-δ, x0+δ) of x0, for any x, if there exists

[0126] The wavelet transform result at x0 is then called This represents the maximum value of the wavelet transform modulus at this scale.

[0127] Wherein, the wavelet transform modulus maxima at j=1 are as follows: Figure 12 As shown, the wavelet transform modulus maxima at j=2 are as follows: Figure 13 As shown, the wavelet transform modulus maxima at j=3 are as follows: Figure 14 As shown, the wavelet transform modulus maxima at j=4 are as follows: Figure 15 As shown above, Figures 12-15It can be seen that the wavelet transform modulus maxima correspond one-to-one with the signal abrupt change points, accurately reflecting the abrupt change time and polarity of the signal. The wavelet transform modulus maxima of the initial line-mode voltage at different scales and their corresponding frequency ranges are shown in Table 1 below:

[0128] Table 1:

[0129]

[0130]

[0131] Step 4: Extract the wavelet transform modulus maxima at different scales, and compare and determine whether the wavelet transform modulus maxima at scale j has become stable according to the following formula.

[0132] and Among them, TH1 and TH2 are two threshold values, with values ​​of 0.98 and 1.02 respectively.

[0133] Comparison revealed that starting from the 4th scale, the wavelet transform modulus maxima at each scale already satisfy the above formula, indicating that the wavelet transform modulus maxima have begun to stabilize. Therefore, the fast traveling wave protection frequency band selection range can be determined to be 31.25kHz-62.5kHz.

[0134] In addition, since the wavelet transform multiresolution analysis has reached the fourth scale at this time, and considering that the wavelet transform modulus maxima of the traveling wave signal and the noise signal have opposite Lipschitz exponent characteristics, the extracted fault traveling wave features have eliminated the influence of noise interference.

[0135] The verification process for the above frequency band selection method is as follows:

[0136] like Figure 16 As shown, an electromagnetic transient simulation model of a ±500kV flexible DC power grid was built using a simulation platform (e.g., PSCAD / EMTDC simulation platform). MMC represents the converter station, and four converter stations, S1, S2, S3, and S4, were set up. ab Let a = 1, 2, 3, 4, b = 1, 2, 3, 4, and DL be the measurement points. 12 DL 13 DL 42 and DL 34 DB represents the DC lines between different converter stations. ab B1, B2, B3, and B4 represent resistors, and L represents transistors. abThe DC reactor is represented by f, and the location of the fault point is represented by f. A frequency response model is used for the DC line, with a sampling frequency of 1MHz. Faults of different types, distances, and transition resistances are set up on the DC line DL34. The m value is calculated when a metallic fault occurs at different fault distances. 34 The wavelet transform modulus maxima of the initial line-mode voltage measured at the fault location are shown in Table 2 below:

[0137] Table 2:

[0138]

[0139] When different transition resistances occur 150km away from the S3 converter station, m 34 The wavelet transform modulus maxima of the initial line-mode voltage measured at the fault location are shown in Table 3 below:

[0140] Table 3:

[0141]

[0142] As can be seen from the table above, the extracted wavelet transform modulus maxima vary greatly below the third scale. However, regardless of the fault condition, the wavelet transform modulus maxima begin to stabilize after the fourth scale. Therefore, selecting wavelet transform modulus maxima at the third scale or below will reduce the accuracy of the extracted fault features.

[0143] Furthermore, although the extracted fault features become more accurate as the wavelet transform scale increases, the wavelet transform modulus maxima change almost little at higher scales, which can actually increase the time burden on the protection algorithm. Therefore, selecting the frequency range where the wavelet transform modulus maxima begin to stabilize as the frequency band for fast traveling wave protection has advantages in both accuracy and speed, and can effectively improve the reliability of the fast traveling wave protection algorithm for flexible DC transmission systems.

[0144] Example 2

[0145] This embodiment provides a frequency band range selection device for fast traveling wave protection, such as... Figure 17 As shown, it includes:

[0146] The acquisition module 171 is used to acquire positive voltage data and negative voltage data within a preset data window, and to determine the initial line-mode voltage traveling wave of the fault based on the positive voltage data and the negative voltage data.

[0147] Specifically, a wideband fast-response measurement device is used to collect a certain amount of positive and negative voltage data before and after the protection start-up moment in real time, constructing a "data window" for fast traveling wave protection. The positive and negative voltage data within the collected "data window" are then subjected to pole mode transformation to construct the initial line-mode voltage traveling wave of the fault. The initial line-mode voltage traveling wave of the fault is determined based on the aforementioned positive and negative voltage data using the following calculation formula:

[0148]

[0149] In the above formula, U p U represents the positive voltage data. n U0 represents the negative electrode voltage data, U1 represents the initial zero-mode voltage traveling wave of the fault, and U1 represents the initial line-mode voltage traveling wave of the fault.

[0150] Analysis module 172 is used to analyze the traveling wave of the initial line-mode voltage of the above-mentioned fault and extract the wavelet transform modulus maxima at multiple scales.

[0151] The comparison module 173 is used to compare the wavelet transform modulus maxima of the above multiple scales with preset conditions, and determine the frequency band range of fast traveling wave protection based on the comparison results.

[0152] Specifically, the wavelet transform modulus maxima at multiple extracted scales are compared, the scale at which the wavelet transform modulus maxima begin to stabilize is marked, and the frequency range corresponding to this scale is selected as the frequency band range for fast traveling wave protection.

[0153] The aforementioned frequency band selection device for fast traveling wave protection determines the wavelet transform modulus maxima by calculating and comparing them at multiple scales, and selects the frequency band for fast traveling wave protection based on these maxima. This fully utilizes the opposite Lipshitz characteristics of the wavelet transform modulus maxima of traveling wave signals and noise signals, eliminating noise interference and accurately extracting fault traveling wave characteristics. Compared with existing technologies, the frequency band selection method proposed in this invention is simple and clear in principle, and exhibits high accuracy and speed, making it easy to implement in engineering and possessing high practical value. It provides strong support for ensuring the reliability of fast traveling wave protection in flexible DC transmission systems.

[0154] Preferably, such as Figure 18 As shown, the analysis module 172 includes:

[0155] Analysis unit 1721 is used to perform wavelet transform multi-resolution analysis on the initial line-mode voltage of the above-mentioned fault to generate signal components of multiple scales; wherein, the above-mentioned signal components include approximation components and detail components.

[0156] Specifically, the initial traveling wave frequency band range is obtained, and based on the initial traveling wave frequency band range, the frequency ranges corresponding to multiple scales are determined. The frequency range corresponding to the j-th scale is shown below:

[0157] f p ∈(f s / 2 j+1 ,f s / 2 j )

[0158] In the above formula, f p For the frequency range, f s This represents the initial traveling wave frequency band range.

[0159] Specifically, the initial line-mode voltage of the above fault is analyzed by wavelet transform multi-resolution analysis using the following calculation formula to generate signal components of multiple scales:

[0160]

[0161] In the above formula, h represents the approximation component of the initial fault line-mode voltage traveling wave U1 at the j-th scale. k This represents the coefficients of the low-pass filter. The details of the initial fault-induced line-mode voltage traveling wave U1 at the j-th scale are represented by the components from the frequency distribution range of 0 to f. s The frequency band decomposed from the initial line-mode voltage U1(n) of the fault is 0~f s / 2 j+1 and f s / 2 j+1 ~f s / 2 j signal components, g k Represents the coefficients of the high-pass filter. The value represents the approximation component of the initial line-mode voltage traveling wave U1 at the (j-1)th scale, and n represents the sequence number of the sampling point within the preset data window.

[0162] Among them, h k and g k The value can be:

[0163]

[0164] Extraction unit 1722 is used to extract wavelet transform modulus maxima at the above-mentioned multiple scales based on the signal components at the above-mentioned multiple scales respectively.

[0165] Wherein, suppose that at the j-th scale, within the neighborhood of sampling point n0, i.e., within the range of (n0-δ, n0+δ), we arbitrarily select sampling point n. If there exists The detail components corresponding to the above sampling point n0 are then taken as the wavelet transform modulus maxima at the j-th scale.

[0166] Preferably, such as Figure 19 As shown, the comparison module 173 includes:

[0167] The first comparison unit 1731 is used to compare a first ratio between the wavelet transform modulus maxima at the first scale and the wavelet transform modulus maxima at the second scale with a first preset threshold and a second preset threshold, respectively; wherein the first preset threshold is less than the second preset threshold.

[0168] The second comparison unit 1732 compares the second ratio between the wavelet transform modulus maxima at the second scale and the wavelet transform modulus maxima at the third scale with the first preset threshold and the second preset threshold, respectively, when the first ratio is greater than the first preset threshold and less than the second preset threshold.

[0169] Specifically, determine the maximum value of the wavelet transform modulus at the j-th scale. The maximum wavelet transform modulus at the (j+1)th scale is WTMM2. j+1 The maximum value of the wavelet transform modulus at the (j+2)th scale is WTMM2. j+2 To determine whether they are approximately equal, the formula is as follows:

[0170] and

[0171] Wherein, TH1 represents the first preset threshold and TH2 represents the second preset threshold.

[0172] The selection unit 1733 is used to select the frequency range corresponding to the first scale as the frequency band range of the fast traveling wave protection when the second ratio is greater than the first preset threshold and less than the second preset threshold.

[0173] Specifically, if the above comparison results are valid, then the frequency range f corresponding to the j-th scale is determined. s / 2 j+1 ~f s / 2 j The frequency band range for fast traveling wave protection.

[0174] Furthermore, if the above comparison results are not valid, let j = j+1, and continue to calculate and compare the wavelet transform modulus maxima at the (j+1)th, (j+2)th, and (j+3)th scales, repeating this process until the condition is met.

[0175] Example 3

[0176] This embodiment provides a computer device, including a memory and a processor. The processor is used to read instructions stored in the memory to execute a frequency band selection method for fast traveling wave protection in any of the above method embodiments.

[0177] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0178] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0179] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0180] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0181] Example 4

[0182] This embodiment provides a computer-readable storage medium storing computer-executable instructions that can execute a frequency band selection method for fast traveling wave protection in any of the above-described method embodiments. The storage medium may be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium may also include combinations of the above types of memory.

[0183] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for selecting the frequency band range for fast traveling wave protection, characterized in that, include: Collect positive and negative voltage data within a preset data window, and determine the initial line-mode voltage traveling wave of the fault based on the positive and negative voltage data; The initial line-mode voltage traveling wave of the fault is analyzed, and wavelet transform modal maxima at multiple scales are extracted; The wavelet transform modulus maxima at the multiple scales are compared with preset conditions, and the frequency band range of fast traveling wave protection is determined based on the comparison results. The initial line-mode voltage traveling wave of the fault is analyzed, and wavelet transform modal maxima at multiple scales are extracted, including: Wavelet transform multi-resolution analysis is performed on the initial line-mode voltage of the fault to generate signal components at multiple scales; wherein, the signal components include approximation components and detail components; The wavelet transform modulus maxima at the multiple scales are extracted based on the signal components at the multiple scales, respectively. The analysis of the initial line-mode voltage traveling wave of the fault, extracting wavelet transform modal maxima at multiple scales, also includes: Obtain the initial traveling wave frequency band range, and determine the frequency range corresponding to multiple scales based on the initial traveling wave frequency band range; The wavelet transform modulus maxima at the multiple scales are compared with preset conditions, and the frequency band range of fast traveling wave protection is determined based on the comparison results, including: The first ratio between the wavelet transform modulus maxima at the first scale and the wavelet transform modulus maxima at the second scale is compared with a first preset threshold and a second preset threshold, respectively; wherein the first preset threshold is less than the second preset threshold. When the first ratio is greater than the first preset threshold and less than the second preset threshold, the second ratio between the wavelet transform modulus maxima at the second scale and the wavelet transform modulus maxima at the third scale is compared with the first preset threshold and the second preset threshold, respectively. When the second ratio is greater than the first preset threshold and less than the second preset threshold, the frequency range corresponding to the first scale is taken as the frequency band range of the fast traveling wave protection.

2. The method for selecting the frequency band range for fast traveling wave protection according to claim 1, characterized in that, The initial line-mode voltage of the fault is analyzed using wavelet transform multi-resolution analysis using the following formula to generate signal components at multiple scales: In the above formula, Indicates the initial line-mode voltage traveling wave during a fault. In the Approximation components at the scale, This represents the coefficients of the low-pass filter. Indicates the initial line-mode voltage traveling wave during a fault. In the Detail weight at scale Represents the coefficients of the high-pass filter. Indicates the initial line-mode voltage traveling wave during a fault. In the Approximation components at the scale, This indicates the sequence number of the sampling point within the preset data window.

3. The method for selecting the frequency band range for fast traveling wave protection according to claim 2, characterized in that, The step of extracting the wavelet transform modulus maxima at the multiple scales based on the signal components at the multiple scales includes: Let the first At the scale, at the sampling point Within the neighborhood of, arbitrarily select sampling points If it exists Then the sampling points The corresponding detail components are used as the first Maximum value of wavelet transform modulus at the scale.

4. The method for selecting the frequency band range for fast traveling wave protection according to claim 1, characterized in that, The initial line-mode voltage traveling wave of the fault is determined using the following formula based on the positive and negative voltage data: In the above formula, This represents the positive electrode voltage data. This represents the negative electrode voltage data. This represents the initial zero-mode voltage traveling wave during a fault. This represents the initial line-mode voltage traveling wave during a fault.

5. A frequency band range selection device for fast traveling wave protection, characterized in that, include: The acquisition module is used to acquire positive and negative voltage data within a preset data window, and determine the initial line-mode voltage traveling wave of the fault based on the positive and negative voltage data. The analysis module is used to analyze the traveling wave of the initial line-mode voltage of the fault and extract wavelet transform modal maxima at multiple scales. The comparison module is used to compare the wavelet transform modulus maxima of the multiple scales with preset conditions, and determine the frequency band range of fast traveling wave protection based on the comparison results; The analysis module includes: The analysis unit is used to perform wavelet transform multi-resolution analysis on the initial line-mode voltage of the fault, generating signal components at multiple scales; among which, the signal components include approximation components and detail components; The extraction unit is used to extract wavelet transform modulus maxima at multiple scales based on signal components at multiple scales. The analysis module also includes: Obtain the initial traveling wave frequency band range, and determine the frequency range corresponding to multiple scales based on the initial traveling wave frequency band range; The comparison module includes: The first comparison unit is used to compare a first ratio between the wavelet transform modulus maxima at the first scale and the wavelet transform modulus maxima at the second scale with a first preset threshold and a second preset threshold, respectively; wherein the first preset threshold is less than the second preset threshold. The second comparison unit compares the second ratio between the wavelet transform modulus maxima at the second scale and the wavelet transform modulus maxima at the third scale with the first preset threshold and the second preset threshold, respectively, when the first ratio is greater than the first preset threshold and less than the second preset threshold. The selection unit is used to select the frequency range corresponding to the first scale as the frequency band range of fast traveling wave protection when the second ratio is greater than the first preset threshold and less than the second preset threshold.

6. A computer device, characterized in that, It includes a processor and a memory, wherein the memory is used to store a computer program, and the processor is configured to invoke the computer program to perform the steps of the method as described in any one of claims 1-4.

7. A computer-readable storage medium storing computer instructions thereon, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method as described in any one of claims 1-4.

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