Fault phase selection method for wind farm transmission line based on transient waveform-energy multi-feature fusion and application thereof

Abstract

The application relates to the technical field of relay protection, in particular to a fault phase selection method for a wind farm sending-out line based on transient waveform-energy multi-feature fusion and application thereof. Wavelet energy of each-phase current fault component is used as a horizontal axis, and a fractal dimension thereof is used as a vertical axis, so that a two-dimensional plane with two types of minimum enclosing circles is formed; a fault sample is projected onto the two-dimensional plane; and a distance between the fault sample and a two-class minimum enclosing circle region on the two-dimensional plane is used as a fault phase selection criterion; and the fault phase selection is performed when a ground fault is excluded according to the size of zero-mode voltage. The required time window is short, and the problem that fault phase selection is inaccurate when a far-end high resistance is identified by a traditional phase selection method is overcome. The application aims to solve the problem of how to perform fast and accurate fault phase selection for a wind farm sending-out line without relying on power frequency quantities.

Description

Technical Field

[0001] This application relates to the field of relay protection technology, and in particular to a fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion and its application. Background Technology

[0002] When a wind farm's transmission line experiences a fault, if the phase selection element can quickly and accurately identify the faulty phase, it can not only improve the reliability of the power system but also reduce the significant losses caused by power outages. However, since most wind turbines in current wind farms are doubly-fed induction generators (DFIGs), the fault characteristics of these DFIGs differ significantly from the short-circuit current characteristics of traditional synchronous generators after large-scale integration into the system. Therefore, phase selection methods based on the fault characteristics of traditional synchronous generators face serious challenges.

[0003] Traditional fault phase selection primarily relies on power frequency quantities, employing a combination of abrupt and steady-state phase selection methods. However, due to the long transmission distances, the phase selection elements cannot meet the requirements for rapid tripping. Furthermore, for remote high-resistance faults, traditional phase selection methods cannot accurately determine the fault type. Related phase selection methods are essentially improvements upon traditional power frequency quantity phase selection methods. However, power frequency quantity phase selection has limitations: its selection speed cannot meet the rapid tripping requirements of ultra-high-speed protection, resulting in decreased sensitivity and reliability.

[0004] In view of this, this application proposes a new method for fault phase selection of wind farm transmission lines, aiming to provide a fast and accurate fault phase selection method for wind farm transmission lines that does not rely on power frequency quantities. Summary of the Invention

[0005] The main objective of this application is to provide a fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion, aiming to solve the problem of how to perform fast and accurate fault phase selection for wind farm transmission lines without relying on power frequency quantities.

[0006] To achieve the above objectives, this application provides a fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion, the method comprising:

[0007] S10, when a fault signal is detected in the wind farm's transmission line, acquire the zero-mode voltage signal and transient current signal of each phase collected at the wind farm's transmission line end;

[0008] S20, determine the fractal dimension and wavelet energy value of the transient current signal of each phase, and use the fractal dimension and wavelet energy value as the vertical and horizontal coordinates of the transient current signal projected onto a two-dimensional plane, respectively. Each phase corresponds to a two-dimensional plane, and the horizontal axis of the two-dimensional plane is the wavelet energy and the vertical axis is the fractal dimension.

[0009] S30, determine the ordinate and abscissa of each phase, the first Euclidean distance between each phase and the first center of each corresponding preset fractal dimension fault reference circle, and the second Euclidean distance between each phase and the second center of each corresponding preset wavelet energy fault reference circle;

[0010] S40, when the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is greater than the first Euclidean distance, the target phase is determined to be a faulty phase.

[0011] Optionally, the steps for drawing the preset fractal dimension fault reference circle and the preset wavelet energy fault reference circle include:

[0012] S50, input ground faults to each phase of the wind farm's transmission line, collect transient current signals of each phase after the fault on the wind farm side, and calculate the target fractal dimension and target wavelet energy value of the transient current fault component of each phase.

[0013] S60, determine the point coordinates of the target fractal dimension value and the target wavelet energy value of each phase on the two-dimensional plane, and draw two minimum enclosing circles to enclose the point coordinates, respectively obtaining the corresponding preset fractal dimension fault reference circle and preset wavelet energy fault reference circle.

[0014] Optionally, the fractal dimension of the transient current signal is calculated as follows:

[0015]

[0016] In the formula, N kε Let Y be the grid count of the set Y, where Y is the transient current signal y(i) in n-dimensional Euclidean space R. n The closed set on the scale; k1 and k2 are the start and end points of the scale-free interval, respectively; ε is the minimum size of the box dimension covering the transient current signal; k = 1, 2, ..., n represents the number of sampling points;

[0017] in:

[0018]

[0019]

[0020] In the formula, Indicates sampling point k ( i -1)+1 to sampling point k ( i The set at -1)+k+1 Y The value of .

[0021] Optionally, the wavelet energy of the transient current signal is calculated using the following expression:

[0022]

[0023] In the formula, D j (k) represents the wavelet reconstruction coefficients of the signal; k=1,2,…,n represents the number of sampling points.

[0024] Optionally, the Euclidean distance is calculated as follows:

[0025]

[0026] In the formula, d1 is the first Euclidean distance between the projection of the transient current signal on the two-dimensional plane and the first center O1 of the fractal dimension fault reference circle; d2 is the second Euclidean distance between the projection on the two-dimensional plane and the second center O2 of the preset wavelet energy fault reference circle; R1 and R2 represent the radii of the first center O1 and the second center O2, respectively, and r1 and r2 represent the reliability coefficients, respectively.

[0027] in, The distance (q) represents the distance between the projection of the transient current signal onto the two-dimensional plane and the center O1 of the fractal dimension fault reference circle / the center O2 of the wavelet energy fault reference circle. j1 ,q j2 ) represent the coordinates of the points with center O1 and center O2, respectively.

[0028] Optionally, the wind farm transmission line includes three phases A, B, and C, wherein:

[0029] d1=d a1 =d b1 =d c1 The first Euclidean distance is the projection of the transient current signals of phases A, B, and C onto a two-dimensional plane and the first center of the fault reference circle with a preset fractal dimension.

[0030] O1=O a1 =O b1 =O c1 The first center of the fractal dimension fault reference circle for phases A, B, and C are respectively;

[0031] d2=d a2 =d b2 =d c2 The second Euclidean distance is the projection of the transient current signals of phases A, B, and C onto the two-dimensional plane and the second center of the preset wavelet energy fault reference circle.

[0032] O2=O a2 =O b2 =O c2 The second center of the preset wavelet energy fault reference circle for phases A, B, and C are respectively.

[0033] Optionally, after step S30, the following steps are also included:

[0034] S70, when the amplitude of the zero-mode voltage signal is greater than the preset voltage threshold, it is determined to be a ground short circuit fault.

[0035] Optionally, after step S30, the method further includes:

[0036] S80, when the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is less than the first Euclidean distance, the target phase is determined to be a non-faulty phase.

[0037] In addition, to achieve the above objectives, this application also provides a relay protection system, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in any of the preceding claims.

[0038] In addition, to achieve the above objectives, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in any of the preceding claims.

[0039] This application has at least the following beneficial effects:

[0040] 1. Compared with the traditional phase selection method based on the principle of sudden change in phase current, the phase selection method of the transmission line based on the fusion of transient waveform and energy multi-features has higher reliability.

[0041] 2. Compared with the phase selection method based on the low voltage principle, the phase selection method of the sending line using the fusion of transient waveform and energy multi-features has better sensitivity and overcomes the problem of inaccurate phase selection under fault conditions with high resistance at the far end.

[0042] 3. The phase selection method of this application is less affected by fault location, fault type, initial phase angle, and wind speed. Attached Figure Description

[0043] Figure 1 This is a simulation model diagram of the doubly fed wind farm grid-connected system involved in the embodiments of this application;

[0044] Figure 2 This is a flowchart illustrating the fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion, as described in an embodiment of this application.

[0045] Figure 3 This is a schematic diagram of the projection position of the transient current signal involved in the embodiments of this application onto a two-dimensional plane;

[0046] Figure 4 (a) to Figure 4 (c) are schematic diagrams in a two-dimensional plane of the preset fractal dimension fault reference circle (left) and preset wavelet energy fault reference circle (right) of phases A, B and C involved in the first embodiment of this application;

[0047] Figure 5 This is a logic block diagram of the fault phase selection criterion involved in the embodiments of this application;

[0048] Figure 6 (a) to Figure 6 (c) is a two-dimensional plan view of a two-phase short-circuit fault (BC) according to the first embodiment of this application;

[0049] Figure 7 (a) to Figure 7 (c) is a two-dimensional plan view of a two-phase-to-ground short-circuit fault according to the second embodiment of this application;

[0050] Figure 8 This is a schematic diagram of the hardware operating environment of the relay protection system involved in the embodiments of this application.

[0051] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] To better understand the above technical solutions, exemplary embodiments of this disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0053] First Embodiment

[0054] The simulation model of the doubly fed wind farm grid-connected system involved in this embodiment is attached. Figure 1 As shown, the total installed capacity of the doubly-fed induction generator (DFIG) wind farm is 200 MW. The low-voltage ride-through methods for the wind turbines are either using a skid or continuous excitation by a frequency converter. The transmission line is 200 km long and has a voltage level of 220 kV. The fault is assumed to occur 100 km from the wind farm side, is a two-phase (BC) short-circuit fault, has a transition resistance of 0.1 Ω, and a sampling rate of 10 kHz.

[0055] Reference Figure 2This embodiment provides a fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion, including the following steps:

[0056] S10, when a fault signal is detected in the wind farm's transmission line, acquire the zero-mode voltage signal and transient current signal of each phase collected at the wind farm's transmission line end;

[0057] In this embodiment, when a fault signal is detected in the wind farm's transmission line, the zero-mode voltage signal and the transient current signal of each phase collected at the wind farm's transmission line end are acquired.

[0058] In some optional implementations, faults in the wind farm's transmission line can be detected using the longitudinal current differential protection method. By comparing the amplitude and phase of the current at both ends of the line, during normal operation, the inflow current equals the outflow current, and the differential current is zero; when a fault occurs, the differential current will increase sharply; when the differential current exceeds the preset differential current threshold, a fault signal for the wind farm's transmission line is generated.

[0059] S20, determine the fractal dimension and wavelet energy value of the transient current signal of each phase, and use the fractal dimension and wavelet energy value as the vertical and horizontal coordinates of the transient current signal projected onto a two-dimensional plane, respectively. Each phase corresponds to a two-dimensional plane, and the horizontal axis of the two-dimensional plane is the wavelet energy and the vertical axis is the fractal dimension.

[0060] In this embodiment, transient current signals are first used as one of the fault criteria for processing. The fractal dimension and wavelet energy values ​​of the transient current signals of each phase are calculated respectively.

[0061] Specifically, let the fractal dimensions of the transient current fault components of each phase be D. a D b and D c The calculation of fractal dimension involves the following steps:

[0062] Consider a small box with side length ε, covering the object under study. This is a visual representation of box dimension. Since fractals contain various levels of voids and gaps, some boxes will be empty. Let N(ε) be the number of non-empty boxes. Then, by reducing the size of the boxes by ε, the counted N(ε) will naturally increase. We can plot the curve of lnN(ε) against lnε on logarithmic graph paper; the slope of the straight line portion is the box dimension D of this fractal object. Assume X is an n-dimensional Euclidean space R. n Let N(X, ε) be a non-empty bounded subset of X, and let N(X, ε) represent the minimum grid count that has a maximum diameter of ε and can cover the set X. Then the box dimension of X is defined as follows:

[0063]

[0064] The limit of the above equation is solved using an approximation method. Let the discrete signal y(i) ⊂ Y, where Y is an n-dimensional Euclidean space R. n Closed set on N ε Let N be the grid count of set Y, with the grid of side length ε as the reference. kε Let Y be the grid count, where k∈Z + To satisfy:

[0065]

[0066] In the formula, i = 1, 2, ..., N / k, where N is the number of sampling points, k = 1, 2, ..., M, M < N. The grid count N... kε for:

[0067]

[0068] Then, calculate ln(kε)-lnN kε And based on this, the segment with better linearity is defined as the scale-free region. Assuming the start and end points of the scale-free region are k1 and k2 respectively, then:

[0069]

[0070] In the formula: α is the slope of the line defined by the scale-free region, and b is a constant term. Finally, the slope of this line is determined using the least squares method, which is the box dimension D that measures the change of the characteristic signal, expressed as:

[0071] )

[0072] In the formula, N kε Let Y be the grid count of the set Y, where Y is the transient current signal y(i) in n-dimensional Euclidean space R. n The closed set on; k1 and k2 are the start and end points of the scale-free interval, respectively; ε is the minimum size of the box dimension covering the transient current signal; k =1, 2, ..., n represent the number of sampling points.

[0073] Therefore, D can be calculated using the above formula. a D b and D c .

[0074] On the other hand, let the wavelet energies of the transient current fault components of each phase be E a E b and E c The energy of orthogonal wavelets at each scale can be obtained by reconstructing the squares of the wavelet coefficients, for the signal x. i The sum of energy (n) at scale j is:

[0075]

[0076] In the formula, D j (k) represents the wavelet reconstruction coefficients of the signal; k = 1, 2, ..., n, where n is the number of sampling points.

[0077] It should be noted that the main characteristics of transient current are concentrated in the frequency band with higher energy. Therefore, selecting the frequency band with concentrated fault characteristics as the characteristic frequency band based on the principle of energy and maximum energy can effectively avoid fault misjudgment caused by measurement and calculation errors when the signal frequency band energy is low. In this embodiment, the db10 wavelet is selected and decomposed into 5 layers.

[0078] Furthermore, the fractal dimension value and the wavelet energy value are respectively used as the vertical and horizontal coordinates of the transient current signal projected onto a two-dimensional plane.

[0079] For example, refer to Figure 3 , Figure 3 The image shown is a projection of the transient current signal onto a two-dimensional plane, with the horizontal axis representing wavelet energy and the vertical axis representing fractal dimension. The horizontal axis of this projection represents the wavelet energy value, and the vertical axis represents the fractal dimension value.

[0080] S30, determine the ordinate and abscissa of each phase, the first Euclidean distance between each phase and the first center of each corresponding preset fractal dimension fault reference circle, and the second Euclidean distance between each phase and the second center of each corresponding preset wavelet energy fault reference circle;

[0081] In this step, we pre-define two circles in a two-dimensional plane: a pre-define fractal dimension fault reference circle and a pre-define wavelet energy fault reference circle. When a fault occurs in the wind farm, the Euclidean distance between the vertical and horizontal coordinates of the projected transient current signal and the centers of these two pre-define circles is calculated and used as the fault phase selection criterion.

[0082] Further and optionally, the steps for drawing the preset fractal dimension fault reference circle and the preset wavelet energy fault reference circle include:

[0083] S50, input ground faults to each phase of the wind farm's transmission line, collect transient current signals of each phase after the fault on the wind farm side, and calculate the target fractal dimension and target wavelet energy value of the transient current fault component of each phase.

[0084] S60, determine the point coordinates of the target fractal dimension value and the target wavelet energy value of each phase on the two-dimensional plane, and draw two minimum enclosing circles to enclose the point coordinates, respectively obtaining the corresponding preset fractal dimension fault reference circle and preset wavelet energy fault reference circle.

[0085] For example, ground faults of phase A, phase B, and phase C are installed every 2 km from near to far along the wind farm's transmission line, with transition resistances of 0 Ω and 50 Ω, respectively, resulting in the following results (see reference). Figure 4 (a) to Figure 4 (c) shows a two-dimensional planar diagram. Taking the centers of the two circles, we obtain the first center and the second center.

[0086] Furthermore, and optionally, the expression for calculating Euclidean distance is:

[0087]

[0088] In the formula, d1 is the Euclidean distance between the projection of the transient current signal on the two-dimensional plane and the first center O1 of the fractal dimension fault reference circle; d2 is the Euclidean distance between the projection on the two-dimensional plane and the second center O2 of the preset wavelet energy fault reference circle; R1 and R2 represent the radii of the center O1 and center O2, respectively, and r1 and r2 represent the reliability coefficients. In this example, r1=1.5 and r2=1.75 are taken as empirical values ​​and can be adjusted according to the actual situation.

[0089] in, The distance (q) represents the distance between the projection of the transient current signal onto the two-dimensional plane and the center O1 of the fractal dimension fault reference circle / the center O2 of the wavelet energy fault reference circle. j1 ,q j2 ) represent the coordinates of the points with center O1 and center O2, respectively.

[0090] S40, when the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is greater than the first Euclidean distance, the target phase is determined to be a faulty phase.

[0091] In this step, another criterion, the zero-mode voltage signal, is used to determine its magnitude. When the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is greater than the first Euclidean distance, the target phase is determined to be a faulty phase.

[0092] Furthermore, and optionally, in this embodiment, when the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is less than the first Euclidean distance, the target phase is determined to be a non-faulty phase.

[0093] For example, taking a wind farm comprising phases A, B, and C, the following expression can be obtained:

[0094] ;

[0095] ;

[0096] ;

[0097] Furthermore, and optionally, in this embodiment, when the amplitude of the zero-mode voltage signal is greater than a preset voltage threshold, it is determined to be a ground short-circuit fault.

[0098] For example, refer to Figure 5 The logic block diagram shown indicates that G represents a ground fault, U0 is the zero-mode voltage signal, and U... set To preset the voltage threshold, the method involved in this embodiment can determine which phase is the faulty phase and whether it is a ground fault.

[0099] For example, refer to Figure 6 (a) to Figure 6 (c) shows a two-dimensional plan view of phases A, B, and C with a two-phase ground fault (BC) occurring 100 km from the wind farm and a transition resistance of 300 Ω. It can be seen that the fault data of phase A (i.e., the vertical and horizontal coordinates of the transient current signal projected onto the two-dimensional plane) is closer to the center of the preset fractal dimension fault reference circle on the left, meaning the second Euclidean distance is greater than the first Euclidean distance, indicating that phase A is not faulty.

[0100] The fault data of phase B is closer to the preset wavelet energy fault reference circle on the right, meaning the second Euclidean distance is less than the first Euclidean distance. Therefore, phase B is determined to be a non-faulty phase. The same logic applies to phase C, which is also a faulty phase.

[0101] In the technical solution provided in this embodiment, the wavelet energy of each phase current fault component is used as the horizontal axis, and its fractal dimension is used as the vertical axis to form a two-dimensional plane with two types of minimum enclosing circles. The fault sample is projected onto this two-dimensional plane, and the distance between the fault sample and the two types of minimum enclosing circle regions on the two-dimensional plane is used as the fault phase selection criterion. Fault phase selection is performed when determining whether to eliminate a ground fault based on the magnitude of the zero-mode voltage. The required time window is short, and it overcomes the problem of inaccurate fault phase selection when identifying high resistance at a distant end using traditional phase selection methods.

[0102] Second Embodiment

[0103] Based on the first embodiment, the simulation model of the doubly fed wind farm grid-connected system in this embodiment is also as attached. Figure 1 As shown, the total installed capacity of the doubly-fed wind farm is 200 MW. The low-voltage ride-through methods for the wind turbines are divided into two types: using a crowbar and continuous excitation by a frequency converter. The total length of the transmission line is 200 km, and the voltage level is 220 kV. The fault is set to occur 190 km from the wind farm side of the line. The fault is a two-phase-to-ground short circuit fault (A and B phases), with a transition resistance of 300Ω and a sampling rate of 10 kHz. The rest of the settings are the same as in the first embodiment.

[0104] Reference Figure 7 (a)- Figure 7 (c) shows a two-dimensional plan view of phases A, B, and C with a two-phase ground fault (AB) occurring 190 km from the wind farm side and a transition resistance of 300 Ω. It can be seen that the fault data of phase A (i.e., the vertical and horizontal coordinates of the transient current signal projected onto the two-dimensional plane) is closer to the center of the preset wavelet energy fault reference circle on the right, meaning the second Euclidean distance is less than the first Euclidean distance, thus indicating a fault in phase A; the same applies to phase B, which is also a faulty phase.

[0105] The fault data of phase C is closer to the preset fractal dimension fault reference circle on the left, that is, the second Euclidean distance is greater than the first Euclidean distance, so phase C is judged to be a non-faulty phase.

[0106] As one implementation scheme, Figure 8 This is a schematic diagram of the hardware operating environment of the relay protection system involved in the embodiments of this application.

[0107] like Figure 8 As shown, the relay protection system may include: a processor 1001, such as a CPU; a memory 1005; a user interface 1003; a network interface 1004; and a communication bus 1002. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be a high-speed RAM or a stable, non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001.

[0108] Those skilled in the art will understand that Figure 8 The relay protection system architecture shown does not constitute a limitation on the relay protection system and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0109] like Figure 8 As shown, the memory 1005, which serves as a storage medium, may include an operating system, a network communication module, a user interface module, and computer programs. The operating system is a program that manages and controls the hardware and software resources of the relay protection system, while the computer programs and other software or programs run.

[0110] exist Figure 8In the relay protection system shown, the user interface 1003 is mainly used to connect to the terminal and communicate with the terminal; the network interface 1004 is mainly used to communicate with the back-end server; and the processor 1001 can be used to call the computer program stored in the memory 1005.

[0111] In this embodiment, the relay protection system includes: a memory 1005, a processor 1001, and a computer program stored in the memory and executable on the processor, wherein:

[0112] When processor 1001 calls a computer program stored in memory 1005, it performs the following operations:

[0113] S10, when a fault signal is detected in the wind farm's transmission line, acquire the zero-mode voltage signal and transient current signal of each phase collected at the wind farm's transmission line end;

[0114] S20, determine the fractal dimension and wavelet energy value of the transient current signal of each phase, and use the fractal dimension and wavelet energy value as the vertical and horizontal coordinates of the transient current signal projected onto a two-dimensional plane, respectively. Each phase corresponds to a two-dimensional plane, and the horizontal axis of the two-dimensional plane is the wavelet energy and the vertical axis is the fractal dimension.

[0115] S30, determine the ordinate and abscissa of each phase, the first Euclidean distance between each phase and the first center of each corresponding preset fractal dimension fault reference circle, and the second Euclidean distance between each phase and the second center of each corresponding preset wavelet energy fault reference circle;

[0116] S40, when the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is greater than the first Euclidean distance, the target phase is determined to be a faulty phase.

[0117] Furthermore, those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program includes program instructions and can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in the relay protection system to implement the process steps of the embodiments of the above methods.

[0118] Therefore, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the various steps of the fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in the above embodiments.

[0119] The computer-readable storage medium can be any computer-readable storage medium capable of storing program code, such as a USB flash drive, portable hard drive, read-only memory (ROM), magnetic disk, or optical disk.

[0120] It should be noted that, since the storage medium provided in the embodiments of this application is the storage medium used to implement the methods of the embodiments of this application, those skilled in the art can understand the specific structure and variations of the storage medium based on the methods described in the embodiments of this application, and therefore will not be repeated here. All storage media used in the methods of the embodiments of this application fall within the scope of protection of this application.

[0121] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application 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.

[0122] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. 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... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0123] 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.

[0124] 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.

[0125] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0126] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion, characterized in that, Applied to wind farm transmission lines comprising at least two phases, the method includes the following steps: S10, when a fault signal is detected in the wind farm's transmission line, acquire the zero-mode voltage signal and transient current signal of each phase collected at the wind farm's transmission line end; S20, determine the fractal dimension and wavelet energy value of the transient current signal of each phase, and use the fractal dimension and wavelet energy value as the vertical and horizontal coordinates of the transient current signal projected onto a two-dimensional plane, respectively. Each phase corresponds to a two-dimensional plane, and the horizontal axis of the two-dimensional plane is the wavelet energy and the vertical axis is the fractal dimension. S30, determine the ordinate and abscissa of each phase, the first Euclidean distance between each phase and the first center of each corresponding preset fractal dimension fault reference circle, and the second Euclidean distance between each phase and the second center of each corresponding preset wavelet energy fault reference circle; S40, when the amplitude of the zero-mode voltage signal is greater than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is less than the first Euclidean distance, the target phase is determined to be a faulty phase; The steps for drawing the preset fractal dimension fault reference circle and the preset wavelet energy fault reference circle include: S50, input ground faults to each phase of the wind farm's transmission line, collect transient current signals of each phase after the fault on the wind farm side, and calculate the target fractal dimension and target wavelet energy value of the transient current fault component of each phase. S60, determine the point coordinates of the target fractal dimension value and the target wavelet energy value of each phase on the two-dimensional plane, and draw two minimum enclosing circles to enclose the point coordinates, respectively obtaining the corresponding preset fractal dimension fault reference circle and preset wavelet energy fault reference circle; The expression for calculating the fractal dimension of the transient current signal is as follows: ； In the formula, N kε Let Y be the grid count of the set Y, where Y is the transient current signal y(i) in n-dimensional Euclidean space R. n The closed set on the scale; k1 and k2 are the start and end points of the scale-free interval, respectively; ε is the minimum size of the box dimension covering the transient current signal; k = 1, 2, ..., n represents the number of sampling points; in: ； ； In the formula, Indicates sampling point k ( i -1)+1 to sampling point k ( i The set at -1)+k+1 Y The possible values ​​of ; The expression for calculating the wavelet energy of the transient current signal is as follows: ； In the formula, D j (k) represents the wavelet reconstruction coefficients of the signal; k=1,2,…,n represents the number of sampling points.

2. The fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in claim 1, characterized in that, The Euclidean distance is calculated as follows: ； In the formula, d1 is the first Euclidean distance between the projection of the transient current signal on the two-dimensional plane and the first center O1 of the fractal dimension fault reference circle; d2 is the second Euclidean distance between the projection on the two-dimensional plane and the second center O2 of the preset wavelet energy fault reference circle; R1 and R2 represent the radii of the first center O1 and the second center O2, respectively, and r1 and r2 represent the reliability coefficients, respectively. in, This represents the distance (q) between the projection of the transient current signal onto the two-dimensional plane and the first center O1 of the fractal dimension fault reference circle / the second center O2 of the wavelet energy fault reference circle. j1 ,q j2 ) represent the coordinates of the points O1 and O2 of the first circle, respectively.

3. The fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in claim 2, characterized in that, The wind farm's transmission line includes three phases: A, B, and C. d1=d a1 =d b1 =d c1 The first Euclidean distance is the projection of the transient current signals of phases A, B, and C onto a two-dimensional plane and the first center of the fault reference circle with a preset fractal dimension. O1=O a1 =O b1 =O c1 The first center of the fractal dimension fault reference circle for phases A, B, and C are respectively; d2=d a2 =d b2 =d c2 The second Euclidean distance is the projection of the transient current signals of phases A, B, and C onto the two-dimensional plane and the second center of the preset wavelet energy fault reference circle. O2=O a2 =O b2 =O c2 The second center of the preset wavelet energy fault reference circle for phases A, B, and C are respectively.

4. The fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in claim 1, characterized in that, After step S30, the following is also included: S70, when the amplitude of the zero-mode voltage signal is greater than the preset voltage threshold, it is determined to be a ground short circuit fault.

5. The fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in claim 1, characterized in that, After step S30, the method further includes: S80, when the amplitude of the zero-mode voltage signal is less than or equal to a preset voltage threshold, if the second Euclidean distance of the target phase is less than the first Euclidean distance, the target phase is determined to be a non-faulty phase.

6. A relay protection system, characterized in that, The relay protection system includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the fault phase selection method for wind farm transmission lines based on transient waveform-energy multi-feature fusion as described in any one of claims 1 to 5.

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