Boundary protection method and system based on waveform difference quantization, medium and equipment

Abstract

The invention discloses a boundary protection method and system based on waveform difference quantization, a medium and equipment. The method comprises the following steps: calculating a 1-mode fault voltage reverse traveling wave; calculating a frequency domain component of a 1-mode fault voltage inverse traveling wave by using numerical Laplace transformation; correcting the frequency domain component of the 1-mode fault voltage reverse traveling wave; calculating the time domain waveform of the corrected 1-mode fault voltage reverse traveling wave; a waveform difference quantitative index is calculated based on the time domain wave of the corrected 1-mode fault voltage reverse traveling wave, and when the waveform difference quantitative index is larger than a setting value of intra-region and intra-region fault judgment, an intra-region fault is judged; and when the waveform difference quantitative index is smaller than or equal to the setting value of the internal and external fault judgment, judging that the fault is an external fault. The problem that the protection performance is reduced due to the fact that low-frequency energy changes along with the fault position is solved, and the adaptive capacity of protection to high transition resistance and a small fault phase angle is improved on the basis that the protection selectivity is guaranteed.

Description

Background Art

[0002] The large-scale access of distributed power sources, energy storage and other equipment 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 are mainly used as one-way power transmission networks to transmit electricity from large power plants to users. Their protection mechanisms mainly rely on classical methods such as overcurrent protection and distance protection, which play an important role in maintaining the stable operation of the power grid. However, with the large-scale integration of renewable energy (such as solar energy and wind energy) and the widespread access to distributed power sources (DG), the distribution network has gradually transformed into a multi-source power supply system that includes multiple energy types, bidirectional power flow, and flexible and changeable topology.

[0004] This transformation poses a severe challenge to the protection strategy of the distribution network. First, the access of distributed power sources changes the power flow distribution of the distribution network, making the original unidirectional current flow complex and changeable, and even reverse current may occur in some cases. This directly leads to the failure or malfunction of the traditional overcurrent protection method based on the unidirectional power flow assumption, because the overcurrent may no longer be caused only by system faults, but may also be caused by the normal operation or switching operation of the distributed power source.

[0005] Secondly, the topology of the distribution network has become 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 a fixed network structure and are difficult to adapt to frequently changing topologies. This may lead to the emergence of protection blind spots or protection overlapping areas, increasing the risk of protection misoperation and refusal to operate.

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

[0007] The core principle of boundary protection is to use the attenuation characteristics of boundary elements for specific high-frequency components to distinguish between internal and external faults. When a fault occurs in the power system, a series of current and voltage signals will be generated at the fault point, including some high-frequency components. These high-frequency components will be affected by the line impedance and the characteristics of the boundary elements during transmission. For external faults, that is, the fault occurs outside the boundary element, the high-frequency components will be effectively attenuated by the boundary element; while for internal faults, that is, the fault occurs within the boundary element, the impact of the high-frequency components is relatively small.

[0008] However, in practical applications, high-frequency energy is not only affected by the fault type, 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). Especially in the case of high transition resistance or small fault phase angle, the high-frequency component method alone has a reduced ability to identify faults, resulting in reduced sensitivity to high-resistance faults.

[0009] In order to improve the accuracy of fault identification, especially in the case of small fault phase angle and high transition resistance, researchers 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 identification. Wavelet transform is a time-frequency analysis tool that can effectively separate different frequency components in the signal, providing convenience for analyzing fault signals.

[0010] Although the wavelet transform-based method shows good performance in theory and experiment, it still has a problem: there is no clear basis for how to select the frequency band corresponding to the low-frequency energy. In fact, the low-frequency energy will also change with the change of the fault location, which may lead to the protection device mistakenly identifying the fault as an internal fault in some cases, especially in the case of an internal fault, thereby triggering unnecessary circuit breaker action and causing false operation.

[0011] Therefore, in order to further improve the reliability and accuracy of boundary protection, it is necessary to conduct in-depth research on the selection criteria of low-frequency energy and how to combine high-frequency energy information to form a more complete fault identification mechanism. This may involve the development of new mathematical models and algorithms, as well as a deep understanding of the operating characteristics of the power system. In addition, it is also necessary to consider how to deal with the challenges brought about by the dynamic characteristics of the power system, 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 of the invention The technical problem to be solved by the present invention is to provide a boundary protection method, system, medium and equipment based on waveform difference quantization in response to the above-mentioned deficiencies in the prior art, utilizing the attenuation of specific frequency components by line boundary elements and utilizing the waveform differences in the time domain to distinguish internal and external faults, thereby solving the technical problem that the existing boundary protection method lacks a theoretical basis for frequency band selection.

[0012] The present invention adopts the following technical solutions: A boundary protection method based on waveform difference quantization includes the following steps: Calculate the reverse traveling wave of the 1-mode fault voltage; The frequency domain component of the reverse traveling wave of the 1-mode fault voltage is calculated using numerical Laplace transform; Correct the frequency domain component of the reverse traveling wave of the 1-mode fault voltage; Calculate the time domain waveform of the corrected 1-mode fault voltage reverse wave; The waveform difference quantification index is calculated based on the time domain wave of the modified 1-mode fault voltage reverse wave. When the waveform difference quantification index is greater than the setting value for distinguishing between internal and external faults, it is judged as an internal fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between internal and external faults, it is judged as an external fault.

[0013] Preferably, the 1-mode fault voltage reverse traveling wave is calculated as follows:

[0014] in, is the reverse wave of the 1-mode fault voltage m sampling points, is the magnitude of the 1st mode current mutation m sampling points, is the line 1 mode wave impedance, is the voltage mutation amount of the first mode m sampling points.

[0015] Preferably, the frequency domain component of the 1-mode fault voltage reverse traveling wave is calculated as follows:

[0016] in, is the frequency domain component of the reverse traveling wave of the 1-mode fault voltage, 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 attenuated exponential window function.

[0017] Preferably, the exponential term coefficient σ of the attenuated exponential window function is: .

[0019] Preferably, the time domain wave of the modified 1-mode voltage reverse traveling wave is calculated as follows:

[0020] in, is the first phase of the corrected 1-mode voltage reverse wave m sampling points.

[0021] Preferably, the 1-mode voltage mutation amount within the action frequency band of the boundary element is set to zero.

[0022] Preferably, the quantitative index of the difference between the corrected 1-mode voltage reverse wave and the original waveform is for:

[0023] in, is the number of sampling points contained in the data window, is the first phase of the corrected 1-mode voltage reverse wave m sampling points, is the first reverse wave of the 1st mode voltage m sampling points.

[0024] In a second aspect, an embodiment of the present invention provides a boundary protection system based on waveform difference quantization, including: A calculation module, for calculating the fault voltage reverse wave; A transformation module calculates the frequency domain component of the fault voltage reverse wave using numerical Laplace transformation; A correction module, which corrects the frequency domain distribution of the 1-mode voltage reverse traveling wave based on the frequency domain component of the fault voltage reverse traveling wave; The time domain module calculates the time domain waveform of the corrected 1-mode voltage reverse wave; The protection module calculates the waveform difference quantification index based on the time domain wave of the modified 1-mode voltage reverse wave. When the waveform difference quantification index is greater than the setting value for distinguishing between internal and external faults, it is judged as an internal fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between internal and external faults, it is judged as an external fault.

[0025] In a third aspect, a computer device comprises 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 boundary protection method based on waveform difference quantization when executing the computer program.

[0026] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned boundary protection method based on waveform difference quantization.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects: A boundary protection method based on waveform difference quantization. When a fault (such as a short circuit) occurs in the power system, the voltage and current waveforms will be distorted. A 1-mode fault refers to a single-phase ground short circuit. In this case, a special waveform called a reverse wave will be generated, which is opposite to the waveform under normal operating conditions. The frequency domain component of the 1-mode fault voltage reverse wave is calculated 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 the time domain signal to the frequency domain; The frequency domain component of the 1-mode fault voltage reverse 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 diagnostic results. Therefore, it is necessary to correct the frequency domain data to improve the accuracy of fault diagnosis; calculate the time domain waveform of the corrected 1-mode fault voltage reverse wave: convert the corrected frequency domain data back to the time domain to obtain the corrected 1-mode fault voltage reverse wave time domain waveform; calculate the waveform difference quantification index based on the time domain wave of the corrected 1-mode fault voltage reverse wave: calculate a quantitative index (such as root mean square error) by comparing the waveform at the time of the fault with the waveform at the time of normal operation. This index can reflect the degree of change of the waveform before and after the fault; when the waveform difference quantification 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 quantification index is less than or equal to the setting value of the internal and external fault discrimination, it is judged as an external fault. The ability of the boundary protection to withstand high transition resistance faults and handle small fault phase angles is improved, avoiding the selection of low-frequency energy by the protection method based on the principle of high-low frequency energy ratio, and improving the selectivity of protection.

[0028] Furthermore, the reverse traveling wave of the 1-mode fault voltage is calculated, which strengthens the electrical quantity characteristics of the protection measuring point at the local end under the protection of the opposite end of the line, and is conducive to the identification of faults inside and outside the zone.

[0029] Furthermore, by calculating the frequency domain component of the reverse traveling wave of the 1-mode fault voltage, the complex features that are difficult to describe in the time domain are transformed into simple and direct features in the frequency domain, which is beneficial to the construction of the judgment criteria.

[0030] Furthermore, by transforming the corrected 1-mode fault voltage inverse traveling wave in the frequency domain to the time domain, it is beneficial to realize the judgment criterion in the time domain.

[0031] Furthermore, by setting the 1-mode fault voltage reverse traveling wave within the boundary element action frequency band to 0, the 1-mode fault voltage reverse traveling wave characteristics of the fault inside and outside the zone under the action of the boundary element are strengthened.

[0032] Furthermore, by calculating the waveform difference quantitative index in the time domain, the distinction between internal and external faults is achieved, and the selection of low-frequency energy bands based on the method of high-low frequency energy ratio is avoided, thereby improving the protection performance.

[0033] 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.

[0034] In summary, the present invention avoids the selection of low-frequency energy in the method based on the high-to-low frequency energy ratio by constructing a waveform difference criterion in the time domain, thereby avoiding the problem of protection performance degradation caused by the change of low-frequency energy with the fault position, and improves the adaptability of protection to high transition resistance and small fault phase angle on the basis of ensuring protection selectivity.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings to be used in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 It is an AC distribution network model containing distributed generation; Figure 3 It is a three-phase metallic short circuit at the end of the zone; Figure 4 It is a three-phase metallic short circuit at the export outside the area; Figure 5 It is the quantified value of waveform difference under different fault types at the end of the area and the bus outside the area; Figure 6 It is the quantified value of the waveform difference under different transition resistances at the end of the zone and the bus outside the zone; Figure 7 A schematic diagram of a computer device provided by an embodiment of the present invention; Figure 8 The present invention is a block diagram of an electronic device provided according to an embodiment. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of 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.

[0040] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0041] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0042] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the 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.

[0043] 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 determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0044] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0045] In the power system, accurate and rapid identification of faults on transmission lines is the key 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 faults inside and outside the processing area, which requires more sophisticated and efficient technical means. By utilizing the difference in voltage waveforms, combined with the characteristics of boundary elements, through Numerical Laplace Transform (NLT) and frequency domain processing technology, an innovative solution to this problem is provided.

[0046] The present invention provides a boundary protection method based on waveform difference quantization, which only uses the voltage waveform difference to distinguish the faults inside and outside the zone. The premise for implementation is that the line has boundary elements. First, the components corresponding to different frequencies of the voltage are extracted by numerical Laplace transform. Secondly, the high-frequency components of the boundary elements are set to 0 in the frequency domain. Finally, the corrected spectrum is inversely transformed to the time domain, and compared with the original waveform in the time domain to distinguish the faults inside and outside the zone.

[0047] When a transmission line fails, the voltage waveform generated at the fault point will be significantly different from the waveform during normal operation, and this difference will be different when the fault occurs inside or outside the area. In particular, due to the presence of boundary elements (such as transformers, reactors, etc.), their attenuation of high-frequency signals makes the voltage waveform characteristics of the fault inside and outside the area in the high-frequency band significantly different.

[0048] See also Figure 1 The present invention provides a boundary protection method based on waveform difference quantization, comprising the following steps: S1. Calculate the fault voltage reverse wave; The fault voltage reverse wave is calculated as follows: (1) in, is the first reverse wave of the 1st mode voltage m sampling points, is the magnitude of the 1st mode current mutation m sampling points, is the line 1 mode wave impedance, is the voltage mutation amount of the first mode m sampling points.

[0049] S2, using numerical Laplace transform to calculate the frequency domain component of the fault voltage reverse wave; The frequency domain component of the voltage reverse traveling wave is calculated as follows: (2) in, is the frequency domain component of the 1-mode voltage mutation, T is the data window length, NW is the number of sampling points contained in the data window, σ is the exponential term coefficient of the attenuated exponential window function, corresponding to the real part of the complex frequency, and its calculation formula is as follows: (3) S3, modify the frequency domain distribution of the 1-mode voltage reverse traveling wave; The 1-mode voltage mutation within the frequency band of the boundary element is set to 0, and the frequency domain distribution of the corrected 1-mode voltage mutation is used express.

[0050] S4, calculating and correcting the time domain waveform of the 1-mode voltage reverse traveling wave; The time domain wave calculation of the modified 1-mode voltage reverse traveling wave is as follows: (4) in, is the first phase of the corrected 1-mode voltage reverse wave m sampling points.

[0051] S5, calculating the waveform difference quantitative index; The quantitative index of the difference between the corrected 1-mode voltage reverse wave and the original waveform is calculated using formula (5): (5) in, F P It is a quantitative indicator of the difference between the corresponding waveforms before and after the 1-mode voltage reverse wave correction.

[0052] S6. Identify faults inside and outside the zone.

[0053] Using formula (6) to judge the faults inside and outside the area, the judgment result of the faults inside and outside the area is obtained: (6) in, F set It is the setting value for distinguishing faults inside and outside the zone.

[0054] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0055] In another embodiment of the present invention, 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 includes a calculation module, a transformation module, a correction module, a time domain module and a protection module.

[0056] Among them, the calculation module calculates the reverse traveling wave of the 1-mode fault voltage; A transformation module calculates the frequency domain component of the reverse traveling wave of the 1-mode fault voltage by using numerical Laplace transformation; A correction module is used to correct the frequency domain component of the reverse traveling wave of the 1-mode fault voltage; The time domain module calculates the time domain waveform of the corrected 1-mode fault voltage reverse wave; The protection module calculates the waveform difference quantification index based on the time domain wave of the modified 1-mode fault voltage reverse wave. When the waveform difference quantification index is greater than the setting value for distinguishing between internal and external faults, it is judged as an internal fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between internal and external faults, it is judged as an external fault.

[0057] In another embodiment of the present invention, a terminal device is provided, the terminal device includes a processor and a memory, 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 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., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding functions; the processor described in the embodiment of the present invention can be used for the operation of the boundary protection method based on waveform difference quantization, including: Calculate the 1-mode fault voltage reverse wave; calculate the frequency domain component of the 1-mode fault voltage reverse wave using numerical Laplace transform; correct the frequency domain component of the 1-mode fault voltage reverse wave; calculate the time domain waveform of the corrected 1-mode fault voltage reverse wave; calculate the waveform difference quantification index 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 for distinguishing between inside and outside the zone faults, it is judged as an inside-zone fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between inside and outside the zone faults, it is judged as an outside-zone fault.

[0058] In another embodiment of the present invention, the present invention also 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 is understandable that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device, and can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. 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, and these 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 here include: an electrical connection with 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.

[0059] Computer readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program codes. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0060] Program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0061] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the boundary protection method based on waveform difference quantization in the above embodiment; the processor may load and execute the following steps: Calculate the 1-mode fault voltage reverse wave; calculate the frequency domain component of the 1-mode fault voltage reverse wave using numerical Laplace transform; correct the frequency domain component of the 1-mode fault voltage reverse wave; calculate the time domain waveform of the corrected 1-mode fault voltage reverse wave; calculate the waveform difference quantification index 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 for distinguishing between inside and outside the zone faults, it is judged as an inside-zone fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between inside and outside the zone faults, it is judged as an outside-zone fault.

[0062] See also Figure 7 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the boundary protection method based on waveform difference quantization in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the boundary protection system based on waveform difference quantization in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0063] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 7This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0064] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, central processing units, graphics 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, data processing logic based on quantum computing, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0065] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may 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., equipped on the computer device 60.

[0066] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0067] Any reference to a memory, database or other medium used in the embodiments provided in the present application may include at least one of a non-volatile and a volatile memory. Non-volatile memory may include a read-only memory (ROM), a magnetic tape, a floppy disk, a flash memory, an optical memory, a high-density embedded non-volatile memory, a resistive random access memory (ReRAM), a magnetic random access memory (MRAM), a ferroelectric random access memory (FRAM), a phase change memory (PCM), a graphene memory, etc. Volatile memory may include a random access memory (RAM) or an external cache memory, etc. As an illustration and not limitation, RAM may be in various forms, such as a static random access memory (SRAM) or a dynamic random access memory (DRAM), etc.

[0068] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0069] See also Figure 8 The terminal device 600 is an electronic device, and the electronic device is in the form of a general computing device. The components of the electronic device may 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, etc.

[0070] 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 invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0071] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0072] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0073] Bus 630 may represent one or more of several types of bus structures, including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0074] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output (I / O) interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms, etc.

[0075] 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, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually 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 in 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.

[0076] Simulation Verification The method proposed in the present invention is further verified by combining specific simulation cases.

[0077] In the electromagnetic transient simulation software PSCAD, the following is established: Figure 2 The 10kV distribution network model shown in the figure. In the figure, DG1 and DG2 are distributed wind turbines connected to the distribution network, of which DG1 has a rated power of 1.2MW and DG2 has a rated power of 1.4MW. The boundary element uses a wave arrester with a blocking frequency band of 90kHz to 110kHz. The lengths of different lines are shown in the figure. The model uses overhead lines with frequency-variable parameters. The sampling rate of the simulation is 1MHz. l 1 is taken as an example to verify the effectiveness of the proposed method, and the protection of the head end is represented by R1. f 1 indicates a fault within the zone. f 2-1 Indicates a fault at the exit outside the zone. f 2-2 Indicates out-of-area lines l 7A failure occurred.

[0078] The steps described in this method are used to distinguish the faults inside and outside the forward zone. The data window is 200μs, and the data of the first 100μs are used to calculate the waveform difference index. When a three-phase metallic short circuit occurs at the end of the line and the bus outside the zone, the 1-mode voltage and its corrected voltage are as follows Figure 3 and Figure 4 As shown in the figure, it can be seen that the voltage waveform corrected for the fault in the zone is quite different from the original waveform, and the frequency of the error is the frequency corresponding to the boundary element. However, the voltage waveform corrected for the fault outside the zone is slightly different from the original waveform.

[0079] against Figure 2 For the system shown, the setting values ​​of the fault judgment criteria inside and outside the zone F set It should be greater than the maximum waveform difference quantization value of the out-of-zone fault. It can be determined by simulation. F set When metallic faults of different fault types occur at the end of the line and at the busbar outside the area, F P like Figure 5 As shown. It can be seen that when there is a fault at the exit outside the area F P are all less than the set value, and different types of faults in the area F P When a BC two-phase short circuit fault with different transition resistance occurs at the end of the zone and the bus outside the zone, F P like Figure 6 shown.

[0080] Table 1 Protection action under different fault conditions

[0081] When faults of different fault types and transition resistance occur at different locations, the quantified values ​​of waveform differences are shown in Table 1. It can be seen that the faults within the area F P are greater than the set value, and the fault outside the zone F P are all smaller than the set value, so the proposed method can accurately identify faults inside and outside the zone.

[0082] In summary, the present invention provides a boundary protection method, system, medium and device based on waveform difference quantization, which amplifies the difference between faults inside and outside the area through frequency domain processing and improves the accuracy of judgment; the computational efficiency of numerical Laplace transform and inverse transform is high, which can meet the needs of real-time fault judgment; it is suitable for different types of boundary elements and transmission lines, and has strong versatility and scalability; it has broad application prospects in the field of power system fault detection and protection, and is expected to provide more reliable technical support for the safe and stable operation of the power system.

[0083] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be 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 in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in 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, which will not be repeated here.

[0084] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0085] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention 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. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0086] 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 only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0087] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0088] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0089] 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 processes 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, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. 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, U disk, mobile hard disk, 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.

[0090] 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 generate 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.

[0091] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate 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 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0092] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0093] The above contents are 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. A boundary protection method based on waveform difference quantization, characterized in that: The following steps are involved: Calculate the reverse traveling wave of the 1-mode fault voltage; The frequency domain component of the reverse traveling wave of the 1-mode fault voltage is calculated using numerical Laplace transform; Correct the frequency domain component of the reverse traveling wave of the 1-mode fault voltage; Calculate the time domain waveform of the corrected 1-mode fault voltage reverse wave; The waveform difference quantification index is calculated based on the time domain wave of the modified 1-mode fault voltage reverse wave. When the waveform difference quantification index is greater than the setting value for distinguishing between internal and external faults, it is judged as an internal fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between internal and external faults, it is judged as an external fault.

2. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that: The reverse traveling wave of the 1-mode fault voltage is calculated as follows: in, is the reverse wave of the 1-mode fault voltage m sampling points, is the magnitude of the 1st mode current mutation m sampling points, is the line 1 mode wave impedance, is the voltage mutation amount of the first mode m sampling points.

3. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that: The frequency domain component of the reverse traveling wave of the 1-mode fault voltage is calculated as follows: in, is the frequency domain component of the reverse traveling wave of the 1-mode fault voltage, 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 attenuated exponential window function.

4. The boundary protection method based on waveform difference quantization according to claim 3 is characterized in that: The exponential term coefficient σ of the attenuated exponential window function is: 。 5. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that: The time domain wave calculation of the modified 1-mode voltage reverse traveling wave is as follows: in, is the first phase of the corrected 1-mode voltage reverse wave m sampling points.

6. The boundary protection method based on waveform difference quantization according to claim 5, characterized in that: The 1-mode voltage mutation within the action frequency band of the boundary element is set to 0.

7. The boundary protection method based on waveform difference quantization according to claim 1, characterized in that: Quantitative index of the difference between the corrected 1-mode voltage reverse wave and the original waveform for: in, is the number of sampling points contained in the data window, is the first phase of the corrected 1-mode voltage reverse wave m sampling points, is the first reverse wave of the 1st mode voltage m sampling points.

8. A boundary protection system based on waveform difference quantization, characterized in that: include: A calculation module calculates the reverse traveling wave of the 1-mode fault voltage; A transformation module calculates the frequency domain component of the reverse traveling wave of the 1-mode fault voltage by using numerical Laplace transformation; A correction module is used to correct the frequency domain component of the reverse traveling wave of the 1-mode fault voltage; The time domain module calculates the time domain waveform of the corrected 1-mode fault voltage reverse wave; The protection module calculates the waveform difference quantification index based on the time domain wave of the modified 1-mode fault voltage reverse wave. When the waveform difference quantification index is greater than the setting value for distinguishing between internal and external faults, it is judged as an internal fault; when the waveform difference quantification index is less than or equal to the setting value for distinguishing between internal and external faults, it is judged as an external fault.

9. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions, which, when executed by a computing device, cause the computing device to perform the method of any one of claims 1 to 8.

10. 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 8.

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