AC line protection method and system based on wavefront index coefficient

Abstract

The present invention discloses an AC line protection method and system based on wavefront index coefficient, which uses a traveling wave voltage sensor to collect the three-phase voltages and currents of the transmission line a, b, and c and perform phase-mode conversion to obtain the modulus voltage u m and current i m ; According to the modulus voltage u m The sudden change of the protection starts; according to the modulus voltage u m and current i m The system calculates the voltage reverse traveling wave based on the mutation amount. Using the voltage reverse traveling wave, the wavelet modulus maximum method is used to extract the arrival time of the second traveling wave head within a given time window. Data from the data window between the startup time and the arrival time of the second traveling wave head is then extracted, and the fault direction is determined using the fault direction criterion. When the fault direction is positive, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain the wavefront index coefficient. This wavefront index coefficient is used to identify in- and out-of-zone faults, enabling AC line protection. This system provides fast, reliable, and sensitive protection for AC transmission lines and is suitable for various scenarios involving the integration of new energy and power electronics equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of AC transmission line protection, and in particular relates to an AC line protection method and system based on a wavefront index coefficient. Background Art

[0002] Renewable energy generation is characterized by volatility and randomness. To effectively support the integration and consumption of a high proportion of renewable energy, power conversion equipment based on power electronics is being adopted. Traditional AC power systems, centered around electromagnetic induction power equipment, are gradually transitioning to grids powered by power electronic power supplies. The weak infeed characteristics of power electronic commutation equipment reduce the sensitivity of overcurrent and current differential protection. Furthermore, the post-fault regulation of power electronic equipment can lead to changes in power supply characteristics and operating parameters, impacting the reliability of distance protection.

[0003] To address the inadequacy of traditional protection systems in electronic power systems, domestic and international researchers have conducted research on adaptability and performance improvement technologies for traditional protection systems, such as distance protection and pilot protection. However, these improvements are still based on the power characteristics of traditional synchronous generators and can only address the adaptability issues of some protection systems in specific scenarios. The post-fault wave process reflects the redistribution of energy storage in the line. The characteristics of traveling waves are solely related to line parameters and are independent of the boundaries at either end of the line. Therefore, traveling wave protection is expected to become a key component of power electronic power system protection.

[0004] Existing traveling wave protection methods primarily include traveling wave directional pilot protection (based on the direction of traveling wave propagation), traveling wave differential protection, traveling wave distance protection (based on the arrival time of traveling waves), and power line carrier high-frequency traveling wave protection. Traveling wave directional pilot protection and traveling wave differential protection are two-terminal protection methods. Besides relying on communication and incurring time delays, their reliability is also affected by factors such as the frequency-variable characteristics of line parameters and the busbar outgoing line structure. Traveling wave distance protection requires accurate calibration of the wave head arrival time or extraction of characteristic frequencies. Although many researchers have proposed methods such as wavelet transform and mathematical morphology to calibrate / extract traveling wave features, the impact of high-impedance faults, noise interference, parameter frequency variations, and near-end fault refraction and reflection waves on protection reliability remains unaddressed. High-frequency traveling wave protection utilizes busbar equivalent capacitance and wave traps to form line boundaries, achieving single-ended, full-line fast-acting protection. However, AC transmission lines without boundary elements are more common, so the applicability of these methods is relatively limited. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned prior art and provide an AC line protection method and system based on a wavefront index coefficient, so as to solve the technical problem of poor adaptability of traditional protection in the AC system when new energy is connected to the system.

[0006] The present invention adopts the following technical solutions:

[0007] An AC line protection method based on a wavefront index coefficient comprises the following steps:

[0008] S1. Use the traveling wave voltage sensor to collect the three-phase voltage and current of the transmission line a, b, and c and perform phase-to-mode conversion to obtain the modulus voltage u m and current i m ;

[0009] S2, based on the modulus voltage u obtained in step S1 m Calculate the modulus voltage u m The amount of mutation, according to the modulus voltage u m The amount of mutation that initiates protection;

[0010] S3. After the protection of step S2 is started, the modulus voltage u obtained in step S1 is m and current i m The voltage reverse wave is calculated by the mutation amount;

[0011] S4. Using the voltage reverse traveling wave obtained in step S3, the wavelet modulus maximum method is used to extract the arrival time of the second traveling wave head within a given time window. Then, data from the data window from the start time to the arrival time of the second traveling wave head is extracted, and the fault direction is determined using the fault direction criterion.

[0012] S5. When the fault direction in step S4 is a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain a wave front index coefficient, and the internal and external faults are judged according to the wave front index coefficient to implement AC line protection.

[0013] Specifically, in step S1, the modulus voltage u m and current i m Specifically:

[0014]

[0015] in, and is the phase voltage, T is the phase transformation matrix.

[0016] Specifically, in step S2, if the following equation is satisfied, the protection is started, specifically:

[0017]

[0018] Among them, |Δu1(n)| is the absolute value of the voltage mutation at the nth sampling point, Δ u1set The setting can be adjusted according to avoid voltage fluctuations during normal operation.

[0019] Furthermore, the modulus voltage and current mutation Δu at the nth sampling point m (n) and Δi m (n) is calculated as follows:

[0020]

[0021] Among them, u m (n) and i m (n) represents the nth sampling point of the modulus voltage and current, and N represents the number of sampling points corresponding to one cycle of the power frequency.

[0022] Specifically, in step S3, the voltage reverse wave Δu of the 1-mode fault b1 for:

[0023] Δu b1 =0.5(Δu1-Z c1 Δi1)

[0024] Among them, Δu1 and Δi1 represent the voltage and current mutation of the first mode; Z c1 is the 1-mode wave impedance of the line.

[0025] Furthermore, in step S4, the fault direction criterion is as follows:

[0026]

[0027] Where Δu 1k , Δ i1k are the kth sampling points of the 1-mode voltage and current fault components, N w is the number of sampling points in the data window, F T It is the fault direction judgment criterion.

[0028] Specifically, in step S5, the fitting index coefficient p is:

[0029] p≥p set =k rel ×p ser

[0030] Among them, p set is the fixed value of the fitting exponential coefficient, k rel is the reliability coefficient, p ser is the fitting exponential coefficient under line end fault.

[0031] In a second aspect, an embodiment of the present invention provides an AC line protection system based on a wavefront index coefficient, comprising:

[0032] The conversion module uses the traveling wave voltage sensor to collect the three-phase voltage and current of the transmission line a, b, and c and perform phase-to-mode conversion to obtain the modulus voltage u m and current im ;

[0033] Mutation module, based on the modulus voltage u obtained by the transformation module m Calculate the modulus voltage u m The amount of mutation, according to the modulus voltage u m The amount of mutation that initiates protection;

[0034] After the calculation module and the mutation module protection are started, the modulus voltage u obtained by the transformation module is m and current i m The voltage reverse wave is calculated by the mutation amount;

[0035] The discrimination module uses the voltage reverse traveling wave obtained by the calculation module to extract the arrival time of the second traveling wave head within a given time window using the wavelet modulus maximum method. It then extracts the data window from the start time to the arrival time of the second wave head and determines the fault direction using the fault direction judgment criterion.

[0036] When the fault direction of the protection module is determined to be a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain the wave front index coefficient. The internal and external faults are determined based on the wave front index coefficient to achieve AC line protection.

[0037] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned AC line protection method based on wavefront index coefficient when executing the computer program.

[0038] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned AC line protection method based on wavefront index coefficients.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] A wavefront index coefficient-based AC line protection method uses the wavefront information of the fault traveling wave to decouple the fault distance and fault severity information, thereby achieving ultra-high-speed protection of the AC line.

[0041] Furthermore, the line parameters are decoupled in the phase domain through phase mode transformation, which reduces the influence of the coupling effect of the three-phase line on the propagation of the traveling wave after the fault.

[0042] Furthermore, by setting the protection start-up criteria, calculation of the protection under normal operating conditions is avoided, reducing the risk of malfunction of the protection.

[0043] Furthermore, calculating the mutation amount by using the modulus voltage and current can eliminate the influence of the slowly changing power frequency amount and improve the reliability of the method.

[0044] Furthermore, the fault voltage reverse wave is calculated by the voltage and current mutation under the modulus, eliminating the influence of the reflected wave caused by the discontinuity of the wave impedance at the line boundary.

[0045] Furthermore, the reverse direction fault is identified by the fault direction criterion, thereby eliminating the interference of the fault outside the reverse direction zone on the protection method.

[0046] Furthermore, by calculating the wavefront exponential coefficient p, the fault distance and fault severity information are decoupled, so that the exponential coefficient p can be used to construct the protection criterion.

[0047] It can be understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0048] In summary, the present invention achieves ultra-high-speed protection of AC transmission lines by decoupling the fault distance and fault severity information in the fault traveling wave front. This method does not rely on power supply characteristics and is applicable to AC systems with renewable energy access. It also has high transient resistance resistance.

[0049] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the process of the present invention;

[0051] Figure 2 This is a schematic diagram of an AC power grid model with access to new energy power sources;

[0052] Figure 3 Figure 1 is a diagram of different fault types and transition resistance faults at the end of the line, where (a) is a phase A grounding fault, (b) is a BC two-phase short circuit fault, (c) is a BC two-phase short circuit grounding fault, and (d) is an ABC three-phase short circuit fault. DETAILED DESCRIPTION

[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] In the description of the present invention, it is to be understood that the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0055] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0056] It should be further understood that the term "and / or" as used in the present specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. For example, A and / or B may represent: A alone, A and B simultaneously, or B alone. Furthermore, the character " / " herein generally indicates that the associated items are in an "or" relationship.

[0057] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0058] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0059] The accompanying drawings illustrate various schematic diagrams of the structures of the disclosed embodiments of the present invention. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes, relative sizes, and positional relationships of the various regions and layers shown in the figures are merely illustrative and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0060] The present invention provides an AC line protection method based on wavefront exponential coefficients. The method uses the voltage and current measured at the protection installation point after the fault to calculate the fault voltage reverse traveling wave, then uses the LM algorithm to fit the fault traveling wavefront to obtain the exponential coefficient, and finally uses the exponential coefficient to distinguish between internal and external faults.

[0061] See also Figure 1 The present invention provides an AC line protection method based on a wavefront index coefficient, comprising the following steps:

[0062] S1. Using a traveling wave voltage sensor to collect the three-phase voltages and currents of the transmission line a, b, and c, and performing phase-mode conversion on the collected phase voltages and phase currents;

[0063] The phase mode transformation is specifically:

[0064]

[0065] Among them, u m and i m is the voltage and current under the modulus after phase transformation, m=0,1,2, and is the phase voltage, where T is the phase transformation matrix, as shown below:

[0066]

[0067] S2. Calculate the modulus voltage u m The amount of mutation is used to determine whether protection is activated;

[0068] The calculation method of voltage mutation is as follows:

[0069]

[0070] Among them, u m (n) and i m (n) represents the nth sampling point of the modulus voltage and current, N represents the number of sampling points corresponding to one cycle of the power frequency, Δu m (n) and Δi m (n) is the nth sampling point of the modulus voltage and current mutation. The following calculations are based on 1 modulus voltage and current, i.e., m = 1.

[0071] The following formula is used to determine whether the protection is activated. If the following formula is satisfied, the protection is activated. The details are as follows:

[0072]

[0073] Among them, |Δu1(n)| is the absolute value of the voltage mutation at the nth sampling point, Δ u1setThe setting can be adjusted according to avoid voltage fluctuations during normal operation.

[0074] S3. After the protection is started, the voltage reverse wave is calculated based on the modulus voltage and current mutation amount;

[0075] The calculation method is as follows:

[0076] Δu b1 =0.5(Δu1-Z c1 Δi1) (5)

[0077] Among them, Δu1 and Δi1 represent the voltage and current mutation of the first mode; Z c1 is the 1st mode wave impedance of the line, Δu b1 It is the reverse traveling wave of the 1-mode fault voltage.

[0078] S4. Using the wavelet modulus maximum algorithm to extract the arrival time of the second traveling wave head within a given time window, extract the data window from the start time to the arrival time of the second traveling wave head, extract the first traveling waves of voltage and current, and then determine the fault direction using the fault direction criterion;

[0079] If the arrival of the second wave head is not detected within the entire data window, the data of the entire data window is extracted, and the fault direction criterion is calculated as follows:

[0080]

[0081] Where Δu 1k , Δ i1k are the kth sampling points of the 1-mode voltage and current fault components, N w is the number of sampling points in the data window, F T It is the fault direction judgment criterion.

[0082] When the fault direction criterion determines that the fault is in the positive direction, the calculation of step S5 is performed.

[0083] S5. Use the Levenberg-Marquardt algorithm to fit the first fault voltage traveling wavefront to obtain the wavefront index coefficient and distinguish the fault inside and outside the zone.

[0084] The formula to be fitted is as follows:

[0085] u(t)=C1 sin(ω0t+θ)+C2e -pt (7)

[0086] Where u(t) is the fitting function of the fault voltage traveling wave front, C1 is the amplitude of the sine term of the fitting function, C2 is the amplitude of the attenuation exponential term, ω0 is the power frequency angular frequency, θ is the phase angle of the sine term of the fitting function, and p is the fitting exponential coefficient.

[0087] p≥p set =k rel ×p ser (8)

[0088] Among them, p set is the setting value of the fitting index coefficient, which is set according to the most serious fault at the end of the area, k rel is the reliability coefficient, its value is greater than 1, p ser is the fitting exponential coefficient under line end fault.

[0089] When formula (8) is satisfied, it is determined to be an internal fault.

[0090] In another embodiment of the present invention, an AC line protection system based on a wavefront index coefficient is provided. The system can be used to implement the above-mentioned AC line protection method based on a wavefront index coefficient. Specifically, the AC line protection system based on a wavefront index coefficient includes a module, a module, a module, a module, and a module.

[0091] The conversion module uses a traveling wave voltage sensor to collect the three-phase voltages and currents of the transmission line a, b, and c and performs phase-to-mode conversion to obtain the modulus voltage u m and current i m ;

[0092] Mutation module, based on the modulus voltage u obtained by the transformation module m Calculate the modulus voltage u m The amount of mutation, according to the modulus voltage u m The amount of mutation that initiates protection;

[0093] After the calculation module and the mutation module protection are started, the modulus voltage u obtained by the transformation module is m and current i m The voltage reverse wave is calculated by the mutation amount;

[0094] The discrimination module uses the voltage reverse traveling wave obtained by the calculation module to extract the arrival time of the second traveling wave head within a given time window using the wavelet modulus maximum method. It then extracts the data window from the start time to the arrival time of the second wave head and determines the fault direction using the fault direction judgment criterion.

[0095] When the fault direction of the protection module is determined to be a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain the wave front index coefficient. The internal and external faults are determined based on the wave front index coefficient to achieve AC line protection.

[0096] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the AC line protection method based on the wavefront index coefficient, including:

[0097] The traveling wave voltage sensor is used to collect the three-phase voltage and current of the transmission line a, b, and c and perform phase-to-mode conversion to obtain the modulus voltage u m and current i m ; Based on the modulus voltage u m Calculate the modulus voltage u m The amount of mutation, according to the modulus voltage u m The sudden change of the protection starts; after the protection starts, according to the modulus voltage u m and current i m The voltage reverse traveling wave is calculated based on the mutation amount. The voltage reverse traveling wave is used to extract the arrival time of the second traveling wave head within a given time window using the wavelet modulus maximum method. Then, the data window from the start time to the arrival time of the second traveling wave head is extracted, and the fault direction is determined using the fault direction judgment criterion. When the fault direction is a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain the wavefront index coefficient. The wavefront index coefficient is used to distinguish between internal and external faults and realize AC line protection.

[0098] In another embodiment of the present invention, the present invention further provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and, of course, the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory (Non-Volatile Memory), such as at least one disk memory.

[0099] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the AC line protection method based on the wavefront index coefficient in the above embodiment. The processor may load and execute the following steps:

[0100] The traveling wave voltage sensor is used to collect the three-phase voltage and current of the transmission line a, b, and c and perform phase-to-mode conversion to obtain the modulus voltage u m and current i m ; Based on the modulus voltage u m Calculate the modulus voltage u m The amount of mutation, according to the modulus voltage u m The sudden change of the protection starts; after the protection is started, the voltage u m and current i m The voltage reverse traveling wave is calculated based on the mutation amount. The voltage reverse traveling wave is used to extract the arrival time of the second traveling wave head within a given time window using the wavelet modulus maximum method. Then, the data window from the start time to the arrival time of the second traveling wave head is extracted, and the fault direction is determined using the fault direction judgment criterion. When the fault direction is a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain the wavefront index coefficient. The wavefront index coefficient is used to distinguish between internal and external faults and realize AC line protection.

[0101] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0102] In order to verify the correctness of the protection method proposed in this invention, the following Figure 2 The simulation model for connecting wind and solar power generation to an AC system is shown. The PV array is converted to AC by a boost circuit, then by a two-level VSC. The voltage is then stepped up by transformer T1 before being connected to the AC system. The boost circuit uses an MPPT control strategy, and the grid-connected VSC converter utilizes constant DC voltage and AC voltage control. The wind turbine is a direct-drive wind turbine connected to the AC system via a back-to-back VSC and step-up transformer T2. The generator-side VSC uses a constant active power and turbine-side AC voltage control strategy, while the grid-side VSC uses a constant DC voltage and reactive power control strategy. The transmission lines all use a frequency-variable parameter model. The simulation system parameters are shown in Table 1.

[0103] Table 1 Simulation model parameters

[0104]

[0105] exist Figure 2 Photovoltaic side protection K of China-Israel photovoltaic transmission line L1 1m Take this as an example to verify, where Q set is the protection boundary after setting. Fault f1 is a fault in the forward zone, f2 is a reverse fault, and f3 is a fault outside the forward zone. 3-1 Located at the busbar, the fault f 3-2 Located on line L2, 100km away from the busbar, fault f 3-3 Located on line L3, 50km from the busbar.

[0106] When the fault 3-1 K is the protection value for metallic and 300Ω transition resistance faults under different fault types. 1m The voltage waveform measured at and the fitting results are shown in Figure 2. Figure 3 As shown. Figure 3It can be seen that the voltage wavefront index coefficient p is basically unchanged when the fault location is the same. When the fault type is a single-phase metallic grounding fault, K 1m The exponential coefficient is the largest at p ser =1.39×10 5 , take k rel is 1.2, then the protection setting value is 1.2×1.39×10 5 =1.67×10 5 At this setting value, the protection method can protect 85% of the line length. This setting value can be obtained by simulation or calculation, and the results are consistent.

[0107] Figure 2 The fault direction judgment results, voltage wave front index coefficients, and protection tripping conditions for single-phase grounding faults and three-phase short circuit faults occurring at different fault locations and with different transition resistances in the system shown are shown in the following table.

[0108] Table 2 Protection action under different fault conditions

[0109]

[0110]

[0111] Table 2 shows that the fault direction criterion can correctly identify the reverse direction fault. For the fault within the zone, the voltage wave front index coefficient is greater than the setting value, and for the fault outside the zone, the voltage wave front index coefficient is less than the setting value. Therefore, the protection can operate correctly.

[0112] In summary, the AC line protection method and system based on the wavefront index coefficient of the present invention can quickly, reliably and sensitively protect AC transmission lines, and is not affected by the fault time, fault type and transition resistance. It is suitable for different new energy and power electronic equipment access scenarios, and is beneficial to the operational stability and power supply reliability of the new power system. The simulation results verify the effectiveness of this method.

[0113] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0114] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0115] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0116] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical functional division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, and can be electrical, mechanical, or other forms.

[0117] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0118] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0119] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above-mentioned various method embodiments. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0120] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0121] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0122] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0123] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An AC line protection method based on wavefront index coefficient, characterized in that: The following steps are involved: S1. Use the traveling wave voltage sensor to collect the three-phase voltage and current of the transmission line a, b, and c and perform phase-to-mode conversion to obtain the modulus voltage and current ; S2, based on the modulus voltage obtained in step S1 Calculating the modulus voltage The amount of mutation, according to the modulus voltage The mutation amount starts protection if the following formula is satisfied: in, The voltage mutation amount n The absolute value of the sampling points, The setting can be adjusted according to the voltage fluctuation during normal operation. n The modulus voltage and current mutation of the sampling point and The calculation is as follows: in, and The modulus voltage and current n sampling points, N Indicates the number of sampling points corresponding to one cycle of the power frequency; S3. After the protection of step S2 is started, the modulus voltage obtained in step S1 is and current The voltage reverse wave is calculated by the mutation amount; S4. Using the voltage reverse traveling wave obtained in step S3, the wavelet modulus maximum method is used to extract the arrival time of the second traveling wave head within a given time window. Then, data from the data window from the start time to the arrival time of the second traveling wave head is extracted, and the fault direction is determined using the fault direction criterion. S5. When the fault direction in step S4 is a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain a wave front index coefficient, and the internal and external faults are judged according to the wave front index coefficient to implement AC line protection.

2. The AC line protection method based on wavefront index coefficient according to claim 1, characterized in that: In step S1, the modulus voltage and current Specifically: in, and is the phase voltage, , T is the phase transformation matrix.

3. The AC line protection method based on wavefront index coefficient according to claim 1, characterized in that: In step S3, the voltage reverse wave of the 1-mode fault for: in, 、 Indicates the magnitude of the voltage and current mutation of the 1-mode; is the 1-mode wave impedance of the line.

4. The AC line protection method based on wavefront index coefficient according to claim 3, characterized in that: In step S4, the fault direction criterion is as follows: in, 、 The first and second fault components of the voltage and current modes are k sampling points, N w is the number of sampling points in the data window, F T It is the fault direction judgment criterion.

5. The AC line protection method based on wavefront index coefficient according to claim 1, characterized in that: In step S5, the fitting index coefficient Specifically: in, is the tuning value of the fitting exponential coefficient, is the reliability coefficient, is the fitting exponential coefficient under line end fault.

6. An AC line protection system based on wavefront index coefficient, characterized in that: include: The conversion module uses the traveling wave voltage sensor to collect the three-phase voltage and current of the transmission line a, b, and c and perform phase-to-mode conversion to obtain the modulus voltage and current ; Mutation module, based on the modulus voltage obtained by the transformation module Calculating the modulus voltage The amount of mutation, according to the modulus voltage The mutation amount starts protection if the following formula is satisfied: in, The voltage mutation amount n The absolute value of the sampling points, The setting can be adjusted according to the voltage fluctuation during normal operation. n The modulus voltage and current mutation of the sampling point and The calculation is as follows: in, and The modulus voltage and current n sampling points, N Indicates the number of sampling points corresponding to one cycle of the power frequency; After the calculation module and the mutation module protection are started, the modulus voltage obtained by the conversion module is and current The voltage reverse wave is calculated by the mutation amount; The discrimination module uses the voltage reverse traveling wave obtained by the calculation module to extract the arrival time of the second traveling wave head within a given time window using the wavelet modulus maximum method. It then extracts the data window from the start time to the arrival time of the second wave head and determines the fault direction using the fault direction judgment criterion. When the fault direction of the protection module is determined to be a positive fault, the Levenberg-Marquardt algorithm is used to fit the first fault voltage traveling wave front to obtain the wave front index coefficient. The internal and external faults are determined based on the wave front index coefficient to achieve AC line protection.

7. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the method of any one of claims 1 to 5.

8. A computing device, characterized in that include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include steps for executing the method according to any one of claims 1 to 5.

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