Waveform difference-based boundary protection method, system, medium, and device

Abstract

The application discloses a boundary protection method and system based on waveform difference quantification, a medium and equipment, calculates a 1-mode fault voltage reverse wave; the frequency domain component of the 1-mode fault voltage reverse wave is calculated by using numerical Laplace transform; the frequency domain component of the 1-mode fault voltage reverse wave is corrected; the time domain waveform of the corrected 1-mode fault voltage reverse wave is calculated; the waveform difference quantification index is calculated based on the time domain wave of the corrected 1-mode fault voltage reverse wave, when the waveform difference quantification index is greater than the setting value of the in-zone and out-zone fault discrimination, it is judged as in-zone fault; when the waveform difference quantification index is less than or equal to the setting value of the in-zone and out-zone fault discrimination, it is judged as out-zone fault. The problem of protection performance decline caused by low-frequency energy change with fault position is avoided, and the adaptive capacity of protection to high transition resistance and small fault phase angle is improved on the basis of ensuring protection selectivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of relay protection, and particularly relates to a boundary protection method and system based on waveform difference quantization, a medium and equipment. BACKGROUND

[0002] The large-scale access of distributed power sources and energy storage devices to distribution networks has become an important trend in the development of distribution networks.

[0003] With the rapid development of energy transformation and smart grid technology, the form and structure of distribution networks are undergoing unprecedented changes. Traditionally, distribution networks mainly serve as one-way power transmission networks that transport electrical energy from large power plants to user terminals, and their protection mechanisms mainly rely on classic methods such as overcurrent protection and distance protection. These methods have played an important role in maintaining the stable operation of power grids. However, with the large-scale integration of renewable energy (such as solar and wind energy) and the widespread access of distributed power sources (DG), distribution networks have gradually evolved into a multi-source power supply system containing various energy types, bidirectional power flow, and flexible and variable topology.

[0004] This transformation poses severe challenges to the protection strategies of distribution networks. First, the access of distributed power sources changes the power flow distribution of distribution networks, making the originally unidirectional current complex and variable, and even in some cases, reverse power flow may occur. This directly leads to the failure or misoperation of traditional overcurrent protection methods based on the assumption of unidirectional power flow, because overcurrent may no longer be caused only by system faults, but also by the normal operation or switching operation of distributed power sources.

[0005] Secondly, the topology of distribution networks becomes more dynamic and complex due to the access of distributed power sources, energy storage devices, and flexible loads. Traditional protection configurations are often based on fixed network structures and are difficult to adapt to frequently changing topologies. This may lead to the emergence of protection blind areas or overlapping areas, increasing the risk of protection misoperation and refusal.

[0006] Boundary protection is a technology used in power systems to achieve fault detection and isolation, which deploys special protection devices, boundary elements, at key nodes in the power system to cooperate with traditional line protection to achieve a wider and more flexible fault coverage range. This protection strategy is particularly suitable for environments where network topology may change frequently, such as the internal network of large power plants or key nodes of power grids connected to multiple transmission lines.

[0007] The core principle of boundary protection is to utilize the attenuation characteristics of boundary elements to distinguish between internal and external faults. When a fault occurs in a power system, the fault point generates a series of current and voltage signals, including some high-frequency components. These high-frequency components are affected by both the line impedance and the characteristics of the boundary elements during transmission. For external faults, i.e., faults occurring outside the boundary elements, the high-frequency components are effectively attenuated by the boundary elements; for internal faults, i.e., faults occurring inside the boundary elements, the influence of high-frequency components is relatively small.

[0008] However, in practical applications, high-frequency energy is not only affected by the type of fault, but also by the transition resistance (i.e., the resistance near the fault point) and the fault phase angle (i.e., the phase difference between the current and voltage at the fault point). In particular, in the case of high transition resistance or small fault phase angle, the pure high-frequency component method has reduced ability to identify faults, resulting in reduced sensitivity to high-resistance faults.

[0009] To improve the accuracy of fault discrimination, especially in the face of small fault phase angles and high transition resistances, researchers have proposed a method based on wavelet transform. This method extracts energy in different frequency bands and uses the ratio of high and low frequency energy to weaken the influence of transition resistance and fault phase angle, thereby improving the robustness of fault discrimination. Wavelet transform is a time-frequency analysis tool that can effectively separate different frequency components in a signal, providing convenience for analyzing fault signals.

[0010] Although the wavelet transform-based method has shown good performance in theory and experiments, it still has a problem: how to choose the frequency band corresponding to low-frequency energy lacks clear basis. In fact, low-frequency energy also changes with the change of fault location, which may lead to the situation that, in some cases, especially in internal faults, the protection device incorrectly identifies the fault as an internal fault, triggering unnecessary breaker actions and causing misoperation.

[0011] Therefore, in order to further improve the reliability and accuracy of boundary protection, it is necessary to further study the selection criteria of low-frequency energy and how to combine high-frequency energy information to form a more perfect fault discrimination mechanism. This may involve developing new mathematical models and algorithms, as well as a deep understanding of the operating characteristics of power systems. In addition, it is also necessary to consider how to handle the challenges brought by the dynamic characteristics of power systems, such as transient changes in voltage and current, and how to implement these algorithms in actual engineering to ensure the real-time and stability of the system SUMMARY

[0012] The technical problems to be solved by the present application are to provide a boundary protection method, system, medium and equipment based on waveform difference quantification, and to utilize the attenuation of a line boundary element to specific frequency components to distinguish internal and external faults in the time domain by using the difference of waveforms, so as to solve the technical problem of lack of theoretical basis for frequency band selection in the prior art boundary protection method.

[0013] The present application adopts the following technical solutions:

[0014] A boundary protection method based on waveform difference quantification comprises the following steps:

[0015] Calculating a 1-mode fault voltage reverse traveling wave;

[0016] Calculating the frequency domain component of the 1-mode fault voltage reverse traveling wave by using numerical Laplace transform;

[0017] Correcting the frequency domain component of the 1-mode fault voltage reverse traveling wave;

[0018] Calculating the time domain waveform of the corrected 1-mode fault voltage reverse traveling wave;

[0019] Calculating the waveform difference quantification index based on the time domain wave of the corrected 1-mode fault voltage reverse traveling wave, and determining that it is an internal fault when the waveform difference quantification index is greater than the setting value of internal and external fault discrimination, and determining that it is an external fault when the waveform difference quantification index is less than or equal to the setting value of internal and external fault discrimination.

[0020] Preferably, the 1-mode fault voltage reverse traveling wave is calculated as follows:

[0021]

[0022] wherein, is the i th sampling point of the 1-mode fault voltage reverse traveling wave, m is the i th sampling point of the 1-mode current abrupt change quantity, is the line 1-mode wave impedance, m is the i th sampling point of the 1-mode voltage abrupt change quantity. m

[0023] Preferably, the frequency domain component of the 1-mode fault voltage reverse traveling wave is calculated as follows:

[0024]

[0025] wherein, is the frequency domain component of the 1-mode fault voltage reverse traveling wave, T is the data window length, N W is the number of sampling points contained in the data window, and σ is the exponential term coefficient of the attenuation exponential window function.​​​

[0026] Preferably, the coefficient σ of the exponential term of the decay exponential window function is:

[0027]

[0028] Preferably, the time-domain wave calculation of the corrected mode 1 voltage inverse traveling wave is as follows:

[0029]

[0030] in, The first step of the corrected 1-mode voltage inverse traveling wave m One sampling point.

[0031] Preferably, the voltage fluctuation of mode 1 within the operating frequency band of the boundary element is set to 0.

[0032] Preferably, the quantitative index of the difference between the corrected modulus 1 voltage inverse traveling wave and the original waveform is... for:

[0033]

[0034] in, This represents the number of sampling points contained within the data window. The first step of the corrected 1-mode voltage inverse traveling wave m One sampling point, The first phase of the inverse traveling wave of the 1-mode voltage m One sampling point.

[0035] Secondly, embodiments of the present invention provide a boundary protection system based on waveform difference quantization, comprising:

[0036] The calculation module calculates the fault voltage reverse traveling wave;

[0037] The transformation module uses numerical Laplace transform to calculate the frequency domain components of the fault voltage backflow.

[0038] The correction module corrects the frequency domain distribution of the mode 1 voltage back traveling wave based on the frequency domain components of the fault voltage back traveling wave.

[0039] The time-domain module calculates the time-domain waveform of the corrected modulus 1 voltage inverse traveling wave;

[0040] The protection module calculates the waveform difference quantization index based on the time-domain waveform of the corrected modulus voltage reverse traveling wave. When the waveform difference quantization index is greater than the set value for distinguishing between faults inside and outside the zone, it is judged as a fault inside the zone; when the waveform difference quantization index is less than or equal to the set value for distinguishing between faults inside and outside the zone, it is judged as a fault outside the zone.

[0041] 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, and the processor implements the steps of the above waveform difference quantification-based boundary protection method when executing the computer program.

[0042] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium including a computer program, and the computer program implements the steps of the above waveform difference quantification-based boundary protection method when executed by a processor.

[0043] Compared with the prior art, the present application has at least the following beneficial effects:

[0044] A waveform difference quantification-based boundary protection method, when a fault (such as a short circuit) occurs in a power system, the voltage and current waveforms will be distorted; 1-mode fault refers to single-phase ground short circuit, and in this case a special waveform called anti-traveling wave is generated, which is opposite to the waveform under normal operating conditions; the frequency domain component of the 1-mode fault voltage anti-traveling wave is calculated by using numerical Laplace transform: by converting the time domain signal to the frequency domain, the frequency characteristics of the signal can be more conveniently analyzed. Numerical Laplace transform is a method of converting time domain signals to frequency domain; the frequency domain component of the 1-mode fault voltage anti-traveling wave is corrected: due to the complexity and uncertainty of the actual power system, directly using the original frequency domain data may lead to inaccurate diagnosis results. Therefore, the frequency domain data needs to be corrected to improve the accuracy of fault diagnosis; the time domain waveform of the corrected 1-mode fault voltage anti-traveling wave is calculated: the corrected frequency domain data is converted back to the time domain to obtain the time domain waveform of the corrected 1-mode fault voltage anti-traveling wave; a waveform difference quantification index is calculated based on the time domain wave of the corrected 1-mode fault voltage anti-traveling wave: by comparing the waveform at the time of the fault with the waveform under normal operation, a quantification index (such as root mean square error) is calculated. This index can reflect the degree of change in the waveform before and after the fault; when the waveform difference quantification index is greater than the setting value of the intra-zone and extra-zone fault discrimination, it is judged as an intra-zone fault; when the waveform difference quantification index is less than or equal to the setting value of the intra-zone and extra-zone fault discrimination, it is judged as an extra-zone fault. The ability of boundary protection to withstand high transient resistance faults and handle small fault phase angles is improved, and the selectivity of the protection is improved, which avoids the selection of low-frequency energy based on the principle of high-low frequency energy ratio.

[0045] Further, the 1-mode fault voltage anti-traveling wave is calculated, which strengthens the electrical quantity characteristics of the protection measurement point at the local end under the protection of the line opposite end, and is beneficial to the identification of intra-zone and extra-zone faults.

[0046] Further, by calculating the frequency domain component of the 1-mode fault voltage anti-traveling wave, the complex characteristics that are difficult to describe in the time domain are converted into simple and direct characteristics in the frequency domain, which is beneficial to the construction of the criterion.

[0047] Further, by transforming the 1-mode fault voltage traveling wave corrected in the frequency domain to the time domain, it is beneficial to realize the criterion in the time domain.

[0048] Further, by setting the 1-mode fault voltage traveling wave in the frequency band range of the boundary element to 0, the characteristics of the 1-mode fault voltage traveling wave of the faults inside and outside the region under the action of the boundary element are strengthened.

[0049] Further, by calculating the waveform difference quantization index in the time domain, the faults inside and outside the region are distinguished, and the selection of the low-frequency energy band based on the high-low frequency energy ratio method is avoided, and the performance of the protection is improved.

[0050] It can be understood that the beneficial effects of the above-mentioned second aspect to the fourth aspect can be referred to the related description in the first aspect, which will not be repeated here.

[0051] In summary, by constructing the waveform difference criterion in the time domain, the selection of the low-frequency energy in the high-low frequency energy ratio method is avoided, thereby avoiding the problem of performance degradation of the protection due to the change of the low-frequency energy with the fault position, and improving the adaptability of the protection to high transition resistance and small fault phase angle on the basis of ensuring the selectivity of the protection.

[0052] The technical solutions of the present application will be further described in detail below by means of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the accompanying drawings used in the relative example description will be briefly introduced, and obviously, the accompanying drawings in the following description can only be some embodiments of the present application, and those skilled in the art can also obtain other accompanying drawings according to these accompanying drawings without creating any creative labor.

[0054] Figure 1 The flowchart of the method of the present application is shown in the figure;

[0055] Figure 2 The model of the AC distribution network containing distributed power supply is shown in the figure;

[0056] Figure 3 The waveform difference quantization value under different fault types at the end of the region and the bus outside the region is shown in the figure;

[0057] Figure 4 The waveform difference quantization value under different fault types at the end of the region and the bus outside the region is shown in the figure;

[0058] Figure 5 The waveform difference quantization value under different fault types at the end of the region and the bus outside the region is shown in the figure;

[0059] Figure 6 The waveform difference quantization value under different fault types at the end of the region and the bus outside the region is shown in the figure;

[0060] Figure 7 a schematic diagram of a computer device according to an embodiment of the present application;

[0061] Figure 8 a block diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort should fall within the protection scope of the present application.

[0063] In the description of the present application, it should be understood that the terms “including” and “comprising” indicate the presence of the described features, integers, steps, operations, elements, and / or components but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0064] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. As used in the specification and the appended claims of the present application, the singular forms “a”, “an” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0065] It should be further understood that the term “and / or” used in the specification and the appended claims of the present application means any combination of one or more of the associated listed items and all possible combinations thereof, and includes these combinations, for example, A and / or B can represent the three cases of A alone, A and B together, and B alone. In addition, the character “ / ” in the present application generally represents an “or” relationship between the front and rear associated objects.

[0066] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present application to describe the preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from each other. For example, the first preset range can also be referred to as the second preset range, and similarly, the second preset range can also be referred to as the first preset range without departing from the scope of the embodiments of the present application.

[0067] Depending on context, the word "if" as used herein can be interpreted to mean "when" or "while" or "in response to determining" or "in response to detecting." Similarly, the phrase "if it is determined" or "if [a stated condition or event] is detected" can be interpreted to mean "when it is determined" or "in response to determining" or "when [a stated condition or event] is detected" or "in response to detecting [a stated condition or event]."

[0068] The various structural diagrams according to the disclosed embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity and others omitted. The shapes and relative sizes of the various regions, layers, and the relative positions of these regions / layers shown in the drawings are merely examples and can deviate in practice due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed according to actual needs by those skilled in the art.

[0069] In power systems, accurately and quickly identifying faults on transmission lines is crucial to ensuring stable operation of the power grid and timely restoration of power supply. Traditional fault identification methods often rely on complex algorithms and a large amount of computing resources, especially when distinguishing between internal and external faults, more sophisticated and efficient technical means are needed. Using voltage waveform differences, combined with the characteristics of boundary elements, through numerical Laplace transform (NLT) and frequency domain processing technology, an innovative solution is provided for this difficult problem.

[0070] The present application provides a boundary protection method based on waveform difference quantization, which only uses voltage waveform differences to distinguish internal and external faults, and the premise is that the line has a boundary element. First, use numerical Laplace transform to extract the components corresponding to different frequencies of the voltage, second, set the high-frequency components affected by the boundary element to 0 in the frequency domain, and finally, inverse transform the corrected frequency spectrum to the time domain, and compare it with the original waveform in the time domain to distinguish internal and external faults.

[0071] When a fault occurs on a transmission line, the voltage waveform generated at the fault point will be significantly different from that during normal operation, and this difference is different when the fault is internal or external. In particular, due to the presence of boundary elements (such as transformers, reactors, etc.), their attenuation effect on high-frequency signals makes the voltage waveform characteristics of internal and external faults in the high-frequency band significantly different.

[0072] Referring to Figure 1 The present application provides a boundary protection method based on waveform difference quantization, which only uses voltage waveform differences to distinguish internal and external faults, and the premise is that the line has a boundary element. First, use numerical Laplace transform to extract the components corresponding to different frequencies of the voltage, second, set the high-frequency components affected by the boundary element to 0 in the frequency domain, and finally, inverse transform the corrected frequency spectrum to the time domain, and compare it with the original waveform in the time domain to distinguish internal and external faults.

[0073] S1, calculate the fault voltage counter-traveling wave;

[0074] The fault voltage backward traveling wave is calculated as follows:

[0075] (1)

[0076] wherein, is the i th sampling point of the 1-modulus voltage backward traveling wave, m is the i th sampling point of the 1-modulus current sudden change, is the 1-modulus wave impedance of the line, m is the i th sampling point of the 1-modulus voltage sudden change. m

[0077] S2, calculating the frequency domain component of the fault voltage backward traveling wave by using the numerical Laplace transform;

[0078] The frequency domain component of the voltage backward traveling wave is calculated as follows:

[0079] (2)

[0080] wherein, is the frequency domain component of the 1-modulus voltage sudden change, T is the data window length, N W is the number of sampling points contained in the data window, and σ is the exponential term coefficient of the attenuation exponential window function, corresponding to the real part of the complex frequency, and the calculation formula thereof is as follows:

[0081] (3)

[0082] S3, correcting the frequency domain distribution of the 1-modulus voltage backward traveling wave;

[0083] The 1-modulus voltage sudden change in the frequency band range of the boundary element is set to 0, and the frequency domain distribution of the corrected 1-modulus voltage sudden change is denoted by V (f).

[0084] S4, calculating the time domain waveform of the corrected 1-modulus voltage backward traveling wave;

[0085] The time domain wave of the corrected 1-modulus voltage backward traveling wave is calculated as follows:

[0086] (4)

[0087] wherein, is the i th sampling point of the corrected 1-modulus voltage backward traveling wave. m

[0088] S5, calculating the waveform difference quantization index;

[0089] The quantization index of the difference between the corrected 1-modulus voltage backward traveling wave and the original waveform is calculated by using formula (5):​​​​​

[0090] (5)

[0091] wherein, F P is the difference quantization index of the corresponding waveforms before and after the 1-mod voltage reverse wave correction.

[0092] S6, discriminating the internal and external faults.

[0093] The formula (6) is used to judge the internal and external faults, and the internal and external fault discrimination results are obtained:

[0094] (6)

[0095] wherein, F set is the setting value of the internal and external fault discrimination.

[0096] Those skilled in the art can understand that various aspects of the present application can be implemented as a system, a method or a program product. Therefore, various aspects of the present application can be specifically implemented in the following forms, namely: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or an implementation combining hardware and software aspects, which can be collectively referred to as "circuitry", "module" or "platform" here.

[0097] In another embodiment of the present application, a boundary protection system based on waveform difference quantization is provided, which can be used to implement the above-mentioned boundary protection method based on waveform difference quantization. Specifically, the boundary protection system based on waveform difference quantization comprises a calculation module, a transformation module, a correction module, a time domain module and a protection module.

[0098] The calculation module calculates the 1-mod fault voltage reverse wave.

[0099] The transformation module calculates the frequency domain component of the 1-mod fault voltage reverse wave by using numerical Laplace transformation.

[0100] The correction module corrects the frequency domain component of the 1-mod fault voltage reverse wave.

[0101] The time domain module calculates the time domain waveform of the corrected 1-mod fault voltage reverse wave.

[0102] The protection module calculates the waveform difference quantization index based on the time domain wave of the corrected 1-mod fault voltage reverse wave. When the waveform difference quantization index is greater than the setting value of the internal and external fault discrimination, it is judged as an internal fault. When the waveform difference quantization index is less than or equal to the setting value of the internal and external fault discrimination, it is judged as an external fault.

[0103] In still another embodiment of the present application, a terminal device is provided, which comprises a processor and a memory, the memory is configured to store a computer program, the computer program comprises program instructions, and the processor is configured to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also 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 gate or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are particularly suitable for loading and executing one or more instructions to implement corresponding method processes or corresponding functions; the processor in the embodiments of the present application can be used for the operation of the boundary protection method based on waveform difference quantization, which comprises:

[0104] calculating a 1-mod fault voltage reverse traveling wave; calculating a frequency domain component of the 1-mod fault voltage reverse traveling wave by using a numerical Laplace transform; correcting the frequency domain component of the 1-mod fault voltage reverse traveling wave; calculating a time domain waveform of the corrected 1-mod fault voltage reverse traveling wave; calculating a waveform difference quantization index based on the time domain waveform of the corrected 1-mod fault voltage reverse traveling wave, and when the waveform difference quantization index is greater than a setting value of in-zone and out-zone fault discrimination, judging as an in-zone fault; and when the waveform difference quantization index is less than or equal to the setting value of in-zone and out-zone fault discrimination, judging as an out-zone fault.

[0105] In still another embodiment of the present application, a computer readable storage medium, specifically a Memory, is also provided. The Memory is a memory device in the terminal device, and is configured to store programs and data. It should be understood that the computer readable storage medium can include an internal storage medium in the terminal device, and of course can include an expansion storage medium supported by the terminal device, and can be any tangible medium that contains or stores a program for use by or in connection with an instruction execution system, apparatus, or device. The computer readable storage medium provides a storage space, and the storage space stores an operating system of the terminal device. In addition, one or more instructions adapted to be loaded and executed by the processor are also stored in the storage space, and the instructions can be one or more computer programs (including program codes). It should be noted that more specific examples (non-exhaustive list) of the computer readable storage medium include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0106] The computer readable storage medium also includes a data signal carried in a baseband or as a part of a carrier wave, in which the readable program code is carried. Such a propagated data signal can take any of a variety of forms, including but not limited to electro-magnetic, optical, or any suitable combination thereof. The readable storage medium can also be any readable medium that can be used to carry, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained in the readable storage medium can be transmitted using any suitable medium, including but not limited to wireless, wired, optical, RF, or any suitable combination thereof.

[0107] The program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C++, or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device and partly on a remote computing device or entirely on the remote computing device or server. In the latter scenario, the remote computing device can be connected to the user's computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computing device, such as through the Internet using an Internet Service Provider.

[0108] The one or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the boundary protection method based on waveform difference quantification in the above embodiments; the one or more instructions stored in the computer-readable storage medium are loaded and executed by the processor to implement the following steps:

[0109] calculating a 1-modulus fault voltage backward wave; calculating a frequency domain component of the 1-modulus fault voltage backward wave by using a numerical Laplace transform; correcting the frequency domain component of the 1-modulus fault voltage backward wave; calculating a time domain waveform of the corrected 1-modulus fault voltage backward wave; calculating a waveform difference quantification index based on the time domain waveform of the corrected 1-modulus fault voltage backward wave, and determining that the fault is an internal fault when the waveform difference quantification index is greater than a setting value of internal and external fault discrimination, and determining that the fault is an external fault when the waveform difference quantification index is less than or equal to the setting value of internal and external fault discrimination.

[0110] Please refer to Figure 7 , the terminal device is a computer device, and the computer device 60 of the embodiment includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. The computer program 63 implements the boundary protection method based on waveform difference quantification in the embodiment when executed by the processor 61. To avoid repetition, details are not described herein. Alternatively, the computer program 63 implements the functions of each model / unit in the boundary protection system based on waveform difference quantification in the embodiment when executed by the processor 61. To avoid repetition, details are not described herein.

[0111] The computer device 60 can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The computer device 60 can include, but is not limited to, the processor 61 and the memory 62. Those skilled in the art can understand that Figure 7 The computer device 60 is only an example and does not constitute a limitation on the computer device 60, and can include more or fewer components than those shown, or combine certain components, or different components, for example, the computer device can also include an input / output device, a network access device, a bus, and the like.

[0112] The processor 61 can be a central processing unit (CPU), and can also be other general-purpose processors, central processing units, graphics processing units, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic components, quantum computing-based data processing logic components, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0113] The memory 62 can be an internal storage unit of the computer device 60, such as a hard disk or a memory of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc.

[0114] Further, the memory 62 can include both an internal storage unit and an external storage device of the computer device 60. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 can also be used to temporarily store data that has been output or will be output.

[0115] Any reference to storage, databases or other media used to store data in the embodiments provided herein is intended to include at least one of volatile and non-volatile storage. Non-volatile storage can include, for example, optical, floppy disks, hard disks, or solid state drives. Volatile storage can include, for example, random access memory (RAM). A basic input / output system (BIOS), containing the basic routines that help to transfer information between elements within the electronic device, such as during startup, can typically be stored in non-volatile memory. By way of illustration, and not limitation, a basic input / output system based on the BIOS, can include a BIOS, a unified extensible firmware interface (UEFI), or the like, including open firmware, firmware option ROM, flash BIOS, or the like. RAM typically contains data and / or program modules that are immediately accessible to and / or being operated on by the processing unit(s) and can include, for example, operating system, application programs, other program modules, and program data.

[0116] The database referred to in the embodiments provided herein can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a blockchain, and the like, but is not limited thereto. The processor referred to in the embodiments provided herein can be a general processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, and the like, but is not limited thereto.

[0117] Referring to Figure 8 , the terminal device 600 is an electronic device, which is manifested in the form of a general computing device. The components of the electronic device can include, but are not limited to, at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components including the storage unit 620 and the processing unit 610, a display unit 640, and the like.

[0118] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present application described in the method part of the present specification. For example, the processing unit 610 can perform the steps as shown in Figure 1 .

[0119] The storage unit 620 can include a readable medium in the form of volatile storage such as random access memory (RAM) 6201 and / or cache memory 6202, and also can include a non-volatile storage such as read only memory (ROM) 6203.

[0120] The storage unit 620 also can include a program / utility 6204 having a set of programs / modules 6205, including an operating system, one or more application programs, other program modules, and program data, each of which can implement aspects of a network environment, as each of these example or some combination thereof.

[0121] The bus 630 can represent one or more of several types of bus structures, including a storage bus or bus controller, a peripheral bus, a graphics bus, a processor or local bus using any of a variety of bus architectures.

[0122] The electronic device 600 also can communicate with one or more external devices 700 such as a keyboard or pointing device, a Bluetooth device, etc.; other devices that enable a user to interact with the electronic device 600; and / or one or more devices that enable the electronic device 600 to communicate with one or more other computing devices. Such communication can occur via an input / output (I / O) interface 650. Still yet, the electronic device 600 can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and / or a public network such as the Internet, via a network adapter 660. The network adapter 660 can be communicatively coupled to the other components of the electronic device 600 via the bus 630. It should be appreciated that the electronic device 600 can be a part of one or more networks, such as virtual networks, which further can include more than one network.

[0123] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application but not all embodiments of the present application. The components of the embodiments of the present application 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 application provided in the drawings is not intended to limit the scope of the claimed present application but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application belong to the scope of protection of the present application.

[0124] Simulation verification

[0125] The method proposed in this invention will be further verified below with specific simulation examples.

[0126] Establishing a simulation in the electromagnetic transient simulation software PSCAD, such as Figure 2 The diagram shows a 10kV distribution network model. DG1 and DG2 are both distributed wind turbines connected to the distribution network, with DG1 having a rated power of 1.2MW and DG2 a rated power of 1.4MW. Wave traps are used as boundary elements, with a hysteresis band of 90kHz to 110kHz. The lengths of different lines are shown in the figure, and the model uses overhead lines with frequency-varying parameters. The simulation sampling rate is 1MHz. (The diagram shows the line lengths.) l Example 1 is used to verify the effectiveness of the proposed method, and the protection at the beginning is represented by R1. f 1 indicates a fault within the zone. f 2-1 This indicates a malfunction at the exit outside the zone. f 2-2 Indicates lines outside the area l 7. A malfunction occurred.

[0127] The steps described in this method are used to distinguish between faults inside and outside the forward zone. A data window of 200μs is used, and the first 100μs of data is used for calculating the waveform difference index. When a three-phase metallic short circuit occurs at the end of the line or at the busbar outside the zone, the 1-mode voltage and its corrected voltage are as follows: Figure 3 and Figure 4 As shown, the fault-corrected voltage waveform within the fault zone differs significantly from the original waveform, and the frequency of the error corresponds to the frequency of the boundary element. Conversely, the fault-corrected voltage waveform outside the fault zone differs less from the original waveform.

[0128] against Figure 2 The system shown has the following setpoints for fault criteria within and outside the zone: F set It should be greater than the maximum waveform difference quantization value of faults outside the zone, which can be determined using simulation. F set The figure is 1.6%. When different types of metallic faults occur at the end of the line and at the busbar outside the zone, F P like Figure 5 As shown. It can be seen that when there is a malfunction at the exit outside the area... F P All are less than the set value, while different types of faults within the area F P All are greater than the set value. When a two-phase BC short-circuit fault with different transition resistances occurs at the end of the zone and the busbar outside the zone, F P likeFigure 6 as shown.

[0129] Table 1 Protection action under different fault conditions

[0130]

[0131] The waveform difference quantization values when different fault types and transition resistances occur in different positions are shown in Table 1. It can be seen that the zone fault F P is greater than the setting value, and the zone-out fault F P is less than the setting value, so the proposed method can accurately distinguish zone-in and zone-out faults.

[0132] In summary, the boundary protection method, system, medium and equipment based on waveform difference quantization provided by the application amplify the difference between zone-in and zone-out faults through frequency domain processing, improve the accuracy of discrimination, the numerical Laplace transform and inverse transform have high calculation efficiency and can meet the needs of real-time fault discrimination, are suitable for different types of boundary elements and transmission lines, have strong universality and scalability, have broad application prospects in the field of power system fault detection and protection, and are expected to provide more reliable technical support for the safe and stable operation of power systems.

[0133] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or software. In addition, the specific names of the functional units and modules are only for easy distinction, and do not limit the protection scope of the application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0134] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0135] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized in electronic hardware or in combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0136] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / terminal and method can be implemented in other ways. For example, the apparatus / terminal embodiments described above are merely schematic. The division of the modules or units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between the units can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or in other forms.

[0137] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0138] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0139] The integrated module / unit, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer-readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the computer-readable medium can include or exclude contents according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0140] The present application is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as combinations of flows and / or blocks in the flowcharts 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, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one or more blocks or multiple blocks.

[0141] These computer program instructions can also be stored in a computer-readable memory that can direct the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one or more blocks or multiple blocks.

[0142] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable data processing devices to generate a computer implemented process, so that the instructions executed on the computer or other programmable data processing devices provide a process for implementing the functions specified in the flowchart Figure 1 one flow or a plurality of flows and / or the functions specified in the block Figure 1 one block or a plurality of blocks.

[0143] The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A boundary protection method based on waveform difference quantization, characterized in that, Includes the following steps: Calculate the reverse traveling wave of the mode 1 fault voltage; The frequency domain components of the back-traveling wave of a mode 1 fault voltage are calculated using the numerical Laplace transform. Correct the frequency domain components of the reverse traveling wave of the mode 1 fault voltage; Calculate the time-domain waveform of the corrected modulus 1 fault voltage reverse traveling wave; Based on the time-domain waveform of the modified 1-mode fault voltage reverse traveling wave, the waveform difference quantization index is calculated. When the waveform difference quantization index is greater than the set value for distinguishing between faults inside and outside the zone, it is judged as an internal fault; when the waveform difference quantization index is less than or equal to the set value for distinguishing between faults inside and outside the zone, it is judged as an external fault. The time-domain waveform calculation for the corrected modulus 1 voltage inverse traveling wave is as follows: in, The first step of the corrected 1-mode voltage inverse traveling wave m One sampling point; Quantitative index of the difference between the corrected modulus 1 voltage inverse traveling waveform and the original waveform for: in, This represents the number of sampling points contained within the data window. The first step of the corrected 1-mode voltage inverse traveling wave m One sampling point, The first phase of the inverse traveling wave of the 1-mode voltage m One sampling point.

2. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that, The reverse traveling wave of the fault voltage in Mode 1 is calculated as follows: in, It is the first of the mode 1 fault voltage reverse traveling wave m One sampling point, It is the first of the modulus current mutations. m One sampling point, It is the mode impedance of the line. The first of the voltage mutations in mode 1 m One sampling point.

3. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that, The frequency domain components of the reverse traveling wave of the mode 1 fault voltage are calculated as follows: in, It is the frequency domain component of the reverse traveling wave of the mode 1 fault voltage. T It is the length of the data window. N W σ is the number of sampling points contained within the data window, and σ is the coefficient of the exponential term of the decay exponential window function.

4. The boundary protection method based on waveform difference quantization according to claim 3, characterized in that, The coefficient σ of the exponential term of the decaying exponential window function is: 。 5. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that, The voltage fluctuation of the 1-mode voltage within the operating frequency band of the boundary element is set to 0.

6. A boundary protection system based on waveform difference quantization, characterized in that, include: The calculation module calculates the reverse traveling wave of the mode 1 fault voltage; The transformation module uses numerical Laplace transform to calculate the frequency domain components of the back-traveling wave of the mode 1 fault voltage; The correction module corrects the frequency domain components of the reverse traveling wave of the mode 1 fault voltage. The time-domain module calculates the time-domain waveform of the corrected modulus 1 fault voltage reverse traveling wave; The protection module calculates the waveform difference quantization index based on the time-domain waveform of the reverse traveling wave of the modified 1-mode fault voltage. When the waveform difference quantization index is greater than the setting value for distinguishing between faults inside and outside the zone, it is judged as an internal fault; when the waveform difference quantization index is less than or equal to the setting value for distinguishing between faults inside and outside the zone, it is judged as an external fault. The time-domain waveform calculation for the corrected modulus 1 voltage inverse traveling wave is as follows: in, The first step of the corrected 1-mode voltage inverse traveling wave m One sampling point; Quantitative index of the difference between the corrected modulus 1 voltage inverse traveling waveform and the original waveform for: in, This represents the number of sampling points contained within the data window. The first step of the corrected 1-mode voltage inverse traveling wave m One sampling point, The first phase of the inverse traveling wave of the 1-mode voltage m One sampling point.

7. A computer-readable storage medium for 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, the one or more programs including steps for performing the method of any one of claims 1 to 5.

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