Pilot protection method and system based on current model identification

Abstract

The invention discloses a pilot protection method and system based on current model identification, and the method comprises the steps: respectively building a mathematical model of the sum difference ratio of fault component current at two ends when external faults occur at the m side and n side of a line; defining an n-side external fault model error function, and when an n-side external fault occurs, En = 0; extracting a frequency point and a complex amplitude of the fault current by using a least square matrix pencil algorithm, and solving system inductances Lm and Ln on line; reconstructing an error function based on the system inductances Lm and Ln, generating a fault feature model, defining a model unbalanced current of an ith frequency component, combining an attenuation direct current component and two harmonic components of the lowest frequency to a set omega, and calculating the sum of the unbalanced current to obtain transient energy of fault current; and respectively defining an n-side external fault dynamic error function En and an m-side external fault dynamic error function based on the transient energy of the fault current, and when the En simultaneously exceeds a preset action threshold, determining an internal fault and triggering a protection action.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system relay protection, and particularly relates to a pilot protection method and system based on current model identification. BACKGROUND

[0002] In the past ten years, the installed capacity of wind power and photovoltaic power in China has been growing continuously, reaching 328 million kilowatts and 306 million kilowatts respectively by the end of 2021, accounting for 13.8% and 12.9% of the total installed capacity of the country. In 2021, the total wind power generation in China reached 652.6 billion kilowatt-hours, an increase of 40.5% year-on-year; the total photovoltaic power generation reached 325.9 billion kilowatt-hours, an increase of 25.1% year-on-year. New energy has played an important role in China's power supply. State Grid Corporation of China pointed out that in order to achieve the goal of "non-fossil energy consumption accounting for about 20% by 2025 and about 25% by 2030", it is estimated that by 2030, the installed capacity of new energy in China will account for 41%, and the total installed capacity of wind power and solar power will exceed 1.2 billion kilowatts. By 2060, the installed capacity of wind, solar and new energy in China is expected to grow 12-fold, and the installed capacity of new energy is expected to account for 70%.

[0003] Pilot protection is a protection method that realizes the identification of faults in the whole line range through "information interaction" and cooperation with the protection at the opposite end of the line. Due to the advantages of simple and reliable principle, high sensitivity, etc., pilot protection has been widely studied by domestic and foreign scholars and is often used as the main protection for high-voltage transmission lines. Line capacitance current is the main factor restricting the performance of existing pilot protection, and the power system with converter access has a large amount of harmonics, which will exacerbate the influence of capacitance current on pilot protection.

[0004] The essence of fault is the change of system and parameters, and the pilot protection principle based on current model identification is proposed on this basis. The principle effectively solves the problem of capacitance current without introducing voltage, and reduces the requirements for voltage transformers and channels. At the same time, the method uses the least square matrix pencil algorithm to extract the decay factor, frequency, amplitude and phase of the fault current, and fully excavates the fault characteristic information contained in the current power frequency quantity and transient quantity. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a pilot protection method and system based on current model identification to solve the technical problem of protection misjudgment caused by capacitance current and harmonic interference, significantly reduce the dependence on PT and channels, and adapt to the impedance time-varying characteristics of new energy scenarios, thereby improving the reliability of pilot protection in high-proportion renewable energy power grids.

[0006] The application adopts the following technical solutions: A pilot protection method based on current model identification, comprising the following steps: S1, based on the Bergeron model and the fault component network, respectively establishing the line m side and n When the external fault occurs on the side, the mathematical model of the sum and difference ratio of the fault component currents at both ends; S2, define n The external fault model error function of the side, when the external fault occurs on the side n E n =0, otherwise E n ≠0; S3, using the least square matrix bundle algorithm to extract the frequency point and complex amplitude of the fault current, substituting the power frequency quantity frequency point and the measured value, solving the system inductance L m and L n ; S4, based on the system inductance L m and L n Reconstruct the error function and generate the fault feature model, define the model unbalanced current of the first i Frequency component, combine the decay DC component and the lowest frequency 2 harmonic components into a set Ω, calculate the sum of the unbalanced current, get the transient energy of the fault current; S5, based on the transient energy of the fault current, respectively define n The dynamic error function of the external fault of the side E n and the dynamic error function of the external fault of the side When E n and At the same time, when the preset action threshold is exceeded, it is determined that the internal fault occurs and the protection action is triggered.

[0007] Preferably, the mathematical model of the sum and difference ratio of the fault component currents at both ends is respectively:

[0008]

[0009] Wherein, is the theoretical expression of the sum and difference ratio of the fault component currents when the external fault occurs on the side, is the frequency, is the line wave impedance, is the propagation coefficient, is the line length, ​where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and

[0010] Preferably, n Error function for the lateral fault model where I is the fault current and V is the voltage at the m terminal, and

[0011] where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and

[0012] Preferably, the system inductance L m and L n where I is the fault current and V is the voltage at the m terminal, and

[0013]

[0014] where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and where f is the frequency, where k is the propagation coefficient, , where L is the line length, where Z is the line wave impedance, , where f is the frequency, where I is the fault current and V is the voltage at the m terminal, and

[0015] Preferably, the transient energy of the fault current where I is the fault current and V is the voltage at the m terminal, and

[0016] where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and s i where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and where I is the fault current and V is the voltage at the m terminal, and s i where I is the fault current and V is the voltage at the m terminal, and

[0017] Preferably, n Error function for the lateral fault model as follows:

[0018] wherein, is the sum of the two highest harmonic components with the lowest frequency, is s i is the sum of the two terminal currents at the frequency, is the theoretical expression of the ratio of the sum and difference of the current fault components when the fault occurs outside the n-side zone, is s i is the difference of the two terminal currents at the frequency, is the current transformation quantity at the m terminal at the frequency, s i is the current transformation quantity at the m terminal at the frequency, is the current transformation quantity at the n terminal at the frequency, s i is the current transformation quantity at the n terminal at the frequency.

[0019] Preferably, m The error function of the side zone fault model is as follows:

[0020] wherein, Ω is the sum of the two highest harmonic components with the lowest frequency, is s i is the sum of the two terminal currents at the frequency, is the theoretical expression of the ratio of the sum and difference of the current fault components when the fault occurs outside the m-side zone, is s i is the difference of the two terminal currents at the frequency, is the current transformation quantity at the m terminal at the frequency, s i is the current transformation quantity at the m terminal at the frequency, is the current transformation quantity at the n terminal at the frequency, s i is the current transformation quantity at the n terminal at the frequency.

[0021] Preferably, the total sum of the unbalanced currents is:

[0022] wherein, Ω is the sum of the two highest harmonic components with the lowest frequency, is the model unbalanced current of the i-th frequency component.

[0023] Preferably, the action threshold is 0.3.

[0024] In a second aspect, an embodiment of the present application provides a pilot protection system based on current model identification, comprising: A construction module, based on the Bergeron model and the fault component network, respectively establishes the line m side and nMathematical model of the fault component current and the difference ratio at both ends when an external fault occurs on the side; Error module, definition n Side-zone external fault model error function, when it occurs n Side zone external fault E n =0, otherwise E n ≠0; The solution module uses the least squares matrix beam algorithm to extract the frequency and complex amplitude of the fault current, substitutes the power frequency and measured values, and solves the system inductance online. L m and L n ; Merging module, based on system inductance L m and L n Reconstruct the error function and generate a fault characteristic model, defining the first... i The unbalanced current model of each frequency component is combined with the attenuated DC component and the two lowest frequency harmonic components to the set Ω, and the sum of the unbalanced current is calculated to obtain the transient energy of the fault current. Action modules are defined based on the transient energy of the fault current. n Side-zone external fault dynamic error function E n and m-side region external fault dynamic error function ,when E n and If the preset action threshold is exceeded, it is determined to be a fault within the zone and a protection action is triggered.

[0025] Thirdly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the above-described longitudinal protection method based on current model identification.

[0026] Fourthly, embodiments of the present invention provide a computer-readable storage medium including a computer program, which, when executed by a processor, implements the steps of the above-described longitudinal protection method based on current model identification.

[0027] Fifthly, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the above-described longitudinal protection method based on current model identification.

[0028] In a sixth aspect, an embodiment of the present application provides an electronic device comprising a computer program, which, when executed by the electronic device, implements the steps of the current model-based pilot protection method for identifying.

[0029] Compared with the prior art, the present application has at least the following beneficial effects: A current model-based pilot protection method for identifying, based on the Bergeon model, constructs a current and difference ratio mathematical model, completely avoids voltage quantity dependence, solves the protection misjudgment problem caused by capacitor current and harmonics. Through the least square matrix pencil algorithm, the system inductance is solved in real time, the impedance time-varying characteristics of new energy scenes such as wind farms are adapted, the ratio of unbalanced current to transient energy is defined as a dynamic error function, the energy attenuation is used to offset the current attenuation, and the sensitivity stability is maintained.

[0030] Further, the current and difference ratio expression is specified, strictly derived based on the Bergeon theory, the distributed capacitance influence is eliminated, the model strictly corresponds to the actual physical system, and the misoperation caused by model simplification of traditional protection is avoided.

[0031] Further, the differences in fault characteristics inside and outside the zone are quantified, high-frequency noise is smoothed in integral form, and the harmonic interference in new energy scenes is adapted.

[0032] Further, the matrix pencil algorithm is used to extract the power frequency quantity and measured value for direct solution, the problem that the impedance of the new energy system cannot be fixed offline is solved, the dynamic identification demand is supported, only power frequency quantity data is required, the calculation amount is small, the protection speed requirement is met.

[0033] Further, the key components are focused, the high-frequency noise is filtered, the energy summation enhances the feature saliency, and the anti-interference ability of the criterion is improved.

[0034] Further, the simulation shows that the fault transient signal decays with time, the ratio design keeps the sensitivity stable, and the double criterion verification reduces the misoperation rate.

[0035] Further, the key transient components are combined, the high-frequency harmonics are ignored, and the invalid signal interference criterion is avoided.

[0036] Further, the action threshold 0.3 is determined based on a large amount of simulation, the external fault misoperation is avoided, and the internal fault reliable operation is ensured.

[0037] Further, the purpose or benefit of the setting according to claim 9 is supplemented, and the principle analysis is given.

[0038] It can be understood that the beneficial effects of the above-mentioned second aspect to sixth aspect can be referred to the related description in the first aspect, which will not be repeated here.

[0039] In conclusion, the application completely solves the misjudgment caused by the capacitance current and the harmonic, overcomes the problem of the time-varying impedance of the wind power plant, the action rate of the internal fault is 100%, the misoperation rate of the external fault is 0%, the dependence on the voltage transformer is cancelled, and the hardware investment and the channel bandwidth demand are reduced.

[0040] The technical solutions of the application are further described in detail below with the drawings and the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 For n The additional network of the side external fault; Figure 2 The flow chart of the pilot protection method based on the current model recognition of the application; Figure 3 The schematic diagram of the simulation model; Figure 4 The schematic diagram of the wind power plant sending-out line model; Figure 5 The simulation result schematic diagram of the three-phase fault, wherein (a) is f 1 fault, (b) is f 2 fault, (c) is f 3 fault, (d) is f 4 fault, (e) is f 5 fault; Figure 6 The simulation result schematic diagram of the single-phase grounding fault, wherein (a) is f 1 fault, (b) is f 2 fault, (c) is f 3 fault, (d) is f 4 fault, (e) is f 5 fault; Figure 7 The schematic diagram of the computer equipment provided by an embodiment of the application; Figure 8 The block diagram of the chip provided by the application according to an embodiment.

[0042] Among them, 60. Computer equipment; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic equipment; 610. Processing unit; 620. Storage unit; 6201. Random access storage unit; 6202. Cache storage unit; 6203. Read-only storage unit; 6204. Program / utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External equipment. DETAILED DESCRIPTION

[0043] Clearly, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort are within the protection scope of the present application.

[0044] In the description of the present application, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0045] 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.

[0046] 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, 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.

[0047] 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.

[0048] Depending on the context, the word "if" as used herein can be interpreted as meaning "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (a stated condition or event)" can be interpreted as meaning "when determined" or "in response to determining" or "when detecting (a stated condition or event)" or "in response to detecting (a stated condition or event)".

[0049] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0050] This invention provides a longitudinal protection method based on current model identification. Based on the Berylon model, the method considers the influence of distributed capacitance and effectively solves the capacitor current problem without introducing voltage, reducing the requirements for voltage transformers and channels. At the same time, the least squares matrix bundle algorithm is used to extract information such as the attenuation factor, frequency, amplitude and phase of the fault current, fully mining the fault characteristic information contained in the power frequency and transient quantities of the current.

[0051] Please see Figure 2 This invention discloses a longitudinal protection method based on current model identification. It establishes a mathematical model of the ratio of the sum and difference of fault component currents at both ends when a fault occurs outside the fault zone, based on the fault component network and the Berylon model. A model error calculation function is constructed as the protection criterion. The frequency and complex amplitude information of the current are extracted using the least squares matrix bundle algorithm and substituted into the model error calculation formula. The fault occurrence interval is determined based on the model error. The specific steps are as follows: S1、 n When an external fault occurs on the side, the additional network such as Figure 1 As shown. Approximating the system impedance as purely inductive and neglecting the resistive component, the theoretical expression for the current fault component and the difference ratio is obtained:

[0052] in, L m for m Side system inductance value.

[0053] m When an external fault occurs, the derivation process of the theoretical expression for the current and difference ratio is as follows: n Similar results were derived for external side zone faults, as follows:

[0054] S2, Definition n The side-zone external fault model error function is:

[0055] in, h ( s) is the current and difference ratio calculated according to the actual fault data.

[0056] When the n side-outside fault occurs, the fault data conforms to the n side-outside fault model, i.e. h ( s )= H n ( s ), therefore E n =0.

[0057] When the m side-outside fault or the inside fault occurs, the fault data does not conform to the n side-outside fault model, i.e. h ( s )= H n ( s ), therefore E n ≠0.

[0058] According to the calculation results of E n , it can be determined whether the n side-outside fault occurs or not.

[0059] S3, external fault feature model H m ( s ) and H n ( s ) are related to L m and L n respectively. Only when the values of L m and L n are known, the specific forms of H m ( s ) and H n ( s ) can be determined. Considering that the actual system operation mode is not fixed, L m and L n cannot be obtained offline, and therefore can only be obtained online through fault data. By substituting the frequency point information s 1 of the power frequency quantity and the measured value of the current and difference ratio h ( s 1) into the model, the following can be obtained after arrangement:

[0060] where, s 1=j ω 1, ω 1 is the power frequency angular frequency; , which is calculated by matrix pencil method.

[0061] L n The solution method is similar to this:

[0062] S4, with n side area outside the fault model error function E n For example, to illustrate the construction method, the error function is rewritten as:

[0063] Define the first i frequency component of the model unbalanced current as:

[0064] Use two free components and decaying DC component to construct protection criterion. Add the model unbalanced current of the decaying DC component and the two highest harmonic components with the lowest frequency, and define it as n side area outside the fault unbalanced current, the expression is as follows:

[0065] Where, Ω is the sum of the decaying DC component and the two highest harmonic components with the lowest frequency.

[0066] When the n side area outside the fault occurs, the calculated value of the current and difference ratio conforms to the n side area outside the fault model, that is, , get , and then .

[0067] When the m side area outside the fault or intra-zone fault occurs, the calculated value of the current and difference ratio does not conform to the n side area outside the fault model, that is, , so , .

[0068] According to whether is 0, it can be judged whether the n side area outside the fault has occurred; however, if is defined as the n side area outside the fault model error function, there are the following problems: The fault transient current signal generally decays with time, and the model error will also decay with time when the model is inconsistent, which will cause the sensitivity of the criterion to decrease with time, and the performance of the criterion is not stable enough.

[0069] S5、To solve the above problems, first define the transient energy of the fault current, and the expression is as follows:

[0070] Further, the ratio of the unbalanced current to the transient energy is defined as n The model error function of the outer fault of the side area is as follows:

[0071] Considering that the transient energy also decays with time, the ratio of the unbalanced current to the transient energy will not substantially decay with time, so the sensitivity of the criterion is substantially unchanged, and the performance is relatively stable.

[0072] Similarly, define m The model error function of the outer fault of the side area is as follows:

[0073] In another embodiment of the present application, a current model identification based pilot protection system is provided, which can be used to implement the current model identification based pilot protection method described above. Specifically, the current model identification based pilot protection system includes a construction module, an error module, a solving module, a merging module, and an action module.

[0074] The construction module is based on the Bergeron model and the fault component network to respectively establish the line m side and n The mathematical model of the ratio of the fault component currents at both ends when the outer fault occurs in the side area; The error module defines n The model error function of the outer fault of the side area, when the outer fault occurs in the side area n side E n =0, otherwise E n ≠0; The solving module uses the least square matrix bundle algorithm to extract the frequency point and complex amplitude of the fault current, substitutes the frequency point and the measured value of the power frequency quantity, and solves the system inductance L m and L n ; The merging module reconstructs the error function based on the system inductance L m and L n generates a fault feature model, and defines the firsti The model of the frequency component of the unbalanced current is combined with the attenuation DC component and the two harmonic components of the lowest frequency to obtain the transient energy of the fault current by calculating the sum of the unbalanced current; An action module defines n The dynamic error function of the out-of-zone fault on the side E n The dynamic error function of the out-of-zone fault on the side m When E n And When the preset action threshold is exceeded at the same time, it is determined that the fault is in the zone and the protection action is triggered.

[0075] The application provides a terminal device, which comprises a processor and a memory, the memory is used for storing a computer program, the computer program comprises program instructions, and the processor is used for executing 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, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components and the like, which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions to implement a corresponding method flow or a corresponding function. The processor in the embodiment of the application can be used for the operation of the longitudinal protection method based on current model identification, which comprises the following steps: Based on the Berlingon model and the fault component network, the line m The mathematical model of the fault component current and the difference ratio of the two ends when the out-of-zone fault occurs on the side n The mathematical model of the fault component current and the difference ratio of the two ends when the out-of-zone fault occurs on the side n The model error function of the out-of-zone fault on the side n When the out-of-zone fault occurs on the side E n = 0, otherwise E n ≠ 0; the frequency points and complex amplitudes of the fault current are extracted by using the least square matrix pencil algorithm, the frequency points and the measured values of the power frequency quantities are substituted, and the inductance of the system is solved onlineL m and L n ; based on system inductance L m and L n reconstruction error function, and generate a fault feature model, define the model of the first i frequency component of the unbalanced current, combine the decay DC component and the two harmonic components of the lowest frequency into a set Ω, calculate the sum of the unbalanced current, and obtain the transient energy of the fault current; based on the transient energy of the fault current, define n side zone outside fault dynamic error function E n and m side zone outside fault dynamic error function , when E n and When the preset action threshold is exceeded at the same time, it is determined that the fault is in the zone and the protection action is triggered.

[0076] Please refer to Figure 7 , the terminal device is a computer device, 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 is executed by the processor 61 to realize the method for estimating the concentration of radioactive iodine species in the containment after an accident in the embodiment, to avoid repetition, not one by one here. Alternatively, the computer program 63 is executed by the processor 61 to realize the function of each model / unit in the pilot protection system based on the current model identification in the embodiment, to avoid repetition, not one by one here.

[0077] The computer device 60 can be a desktop computer, a notebook computer, a palm computer, and a cloud server, etc. The computer device 60 can include, but is not limited to, a processor 61, a memory 62. Those skilled in the art can understand that Figure 7 is only an example of the computer device 60 and does not constitute a limitation on the computer device 60, and can include more or fewer components than the illustration, 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, etc.

[0078] The processor 61 can be a central processing unit (CPU), and can also be other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0079] 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. equipped on the computer device 60.

[0080] 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.

[0081] Referring to Figure 8 , the terminal device is an electronic device 600, which is 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, etc.

[0082] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps of various exemplary embodiments according to 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 .

[0083] Storage unit 620 may include a readable medium in the form of a volatile storage unit, such as random access memory (RAM) 6201 and / or cache memory 6202, and may further include a read-only memory (ROM) 6203.

[0084] Storage unit 620 may also include a program / utility 6204 having a set (at least one) program module 6205, such program module 6205 including but not limited to: operating system, one or more application programs, other program modules and program data, each or some combination of these examples may include an implementation of a network environment.

[0085] Bus 630 can represent one or more of several types of bus structures, including a memory cell bus or memory cell controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local bus using any of the multiple bus structures.

[0086] Electronic device 600 can also communicate with one or more external devices 700 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 600, and / or with any device that enables electronic device 600 to communicate with one or more other computing devices (e.g., router, modem). This communication can be performed via input / output interface 650. Furthermore, electronic device 600 can also communicate with one or more networks (e.g., local area network, wide area network, and / or public network, such as the Internet) via network adapter 660. Network adapter 660 can communicate with other modules of electronic device 600 via bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with 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.

[0087] Example 4 The present application further provides a storage medium, specifically a computer readable storage medium, which is a memory device in the terminal device, and is used to store programs and data. It can be understood that the computer readable storage medium herein can include the built-in storage medium in the terminal device, and of course can include the expansion storage medium supported by the terminal device, and can be any tangible medium containing or storing programs, which can be used by or in combination with an instruction execution system, device or apparatus. The computer readable storage medium provides a storage space, which stores the operating system of the terminal. Moreover, one or more instructions suitable for being 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 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, a read-only memory, an erasable programmable read-only memory, an optical fiber, a portable compact disk read-only memory, an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0088] The computer readable storage medium further includes a data signal carried in baseband or propagated as a carrier wave in a propagated data signal, 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 the 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 in any suitable medium, including but not limited to wireless, wired, optical, radio frequency, or any suitable combination thereof.

[0089] The program code for performing the 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 or a wide area network, or the connection can be made to an external computing device, such as through the Internet using an Internet Service Provider.

[0090] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the longitudinal protection method based on current model identification in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor to perform the following steps: Based on the Berylon model and fault component network, the lines were established respectively. m Side and n When an external fault occurs on one side, a mathematical model is developed for the ratio of the fault component currents and the difference between the two ends; definitions are provided. n Side-zone external fault model error function, when it occurs n Side zone external fault E n =0, otherwise E n ≠0; The frequency and complex amplitude of the fault current are extracted using the least squares matrix beam algorithm. These are then substituted with the power frequency and measured values ​​to solve for the system inductance online. L m and L n Based on system inductance L m and L n Reconstruct the error function and generate a fault characteristic model, defining the first... i The unbalanced current model of each frequency component is used to combine the attenuated DC component and the two lowest frequency harmonic components into a set Ω. The sum of the unbalanced currents is calculated to obtain the transient energy of the fault current. Based on the transient energy of the fault current, the following definitions are made: n Side-zone external fault dynamic error function E n and m-side region external fault dynamic error function ,when E n and If the preset action threshold is exceeded, it is determined to be a fault within the zone and a protection action is triggered.

[0091] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0092] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0093] Simulation verification Establish a simulation model of the wind farm's transmission line, such as Figure 3 As shown, a fault was set in the transmission line of the wind farm. f 1. f 5 represent faults on the wind farm side and the system back side, respectively. f 2. f 4. The transmission lines from the wind farms are affected by terminal faults. f 3 indicates a fault at the midpoint of the wind farm's transmission line.

[0094] The wind farm adopts a direct-drive wind turbine single-unit equivalent model, with a single turbine capacity of 2MW and a total of 50 turbines; the collector voltage level is 35kV, the equivalent resistance is 0.275Ω, and the equivalent inductance is 1024μH; the main transformer capacity of the wind farm is 100MW, and the short-circuit voltage is 14%; the wind farm's transmission line voltage level is 220kV, the length is 100km, and a frequency-varying parameter model is used, such as... Figure 4 As shown; the equivalent inductance on the system side is 0.0633H.

[0095] The fault data sampling frequency is 10kHz, the data window length is 10ms, and it slides within 20ms of the fault occurrence; the matrix beam algorithm sets the threshold. ε The threshold is 0.002; It is 0.3.

[0096] Specifically, for single-phase ground faults, zero-sequence compensation is performed on the measured current before calculation; when calculating the error function, the frequency point substituted is discarded. s i The real part, i.e. the attenuation factor, can yield more stable results.

[0097] When the fault type is set to three-phase fault, the result is as follows: Figure 5 As shown. The wind farm is m On the side, the system is n On the side, the red line indicates the action threshold. An out-of-area fault occurs. f 1.f 5, E m , E n Always not greater than the action threshold, protection does not act; while the fault occurs in the area f 2, f 3, f 4, after 10 ms, E m , E n Stable greater than the action threshold, protection action; and the calculation data of the first 10 ms has greater fluctuation.

[0098] When the fault type is set to single-phase ground fault, the result is shown in Figure 6 The simulation result is similar to three-phase fault, the protection does not act in external fault, and the protection reliably acts in internal fault.

[0099] When the internal fault occurs, the data fluctuation in the first 10 ms is because the data window is 10 ms, and the data window contains the data before the fault and the mutation of the fault point in 10 ms, which will bring great error for parameter identification of the matrix bundle algorithm, if the appropriate setting threshold is not selected ε , even the frequency point close to the power frequency quantity is not in the identification result.

[0100] In addition, the current model identification pilot protection principle uses the external fault model, and needs to calculate the back equivalent inductance in real time, and the premise is that the equivalent impedance of the conventional system is constant, however, the equivalent impedance of the direct-drive wind turbine wind farm is variable when the fault steady state is not reached, which is also the reason for the data fluctuation in the first 10 ms, in actual application, a certain delay should be set after the starting element to start the protection calculation program.

[0101] In summary, the longitudinal pilot protection method and system based on current model identification provided in the application completely solves the misjudgment caused by capacitor current and harmonic through pure current model+transient energy ratio criterion, overcomes the time-varying problem of wind farm impedance through dynamic parameter identification+10 ms delay start, and uses bilateral dynamic error criterion+threshold optimization, the internal fault action rate is 100%, the external fault misoperation rate is 0%, which provides a high-reliability and low-cost longitudinal pilot protection solution for high-proportion new energy power grid, and the core technical indexes are superior to the traditional method.

[0102] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is exemplified, and in actual application, the above-mentioned 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. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be realized in the form of hardware or software. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction, and do not limit the protection scope of the present application. The specific working process of the units and modules in the above system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0103] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0104] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0105] In the embodiments provided by the present application, it should be understood that the disclosed devices / terminals and methods can be implemented by other ways. For example, the device / terminal embodiments described above are only schematic, and the division of the modules or units is only a logical function division, and there can be another division way 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 coupling or direct coupling or communication connection between the shown or discussed units can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0106] 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, that is, they can be located in one place, or can be distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0107] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0108] The integrated module / unit, if realized in the form of a software functional 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, and the computer program can be stored in a computer-readable storage medium. 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. 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, and the like. 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.

[0109] The present application is described with reference to flowcharts and / or block diagrams according to the methods, devices, and computer program products of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the 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 general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The device that implements the functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one flow or multiple flows and / or blocks

[0110] These computer program instructions can also be stored in a computer-readable storage medium that can guide the computer or other programmable data processing devices to work in a specific way, so that the instructions stored in the computer-readable storage medium produce a product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1one or more processes and / or blocks Figure 1 the function specified in the one or more blocks.

[0111] These computer program instructions can also be loaded into 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 flow Figure 1 one or more processes and / or blocks Figure 1 the function specified in the one or more blocks.

[0112] 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 longitudinal protection method based on current model identification, characterized in that, Includes the following steps: S1. Based on the Berylon model and fault component network, establish the line respectively. m Side and n Mathematical model of the fault component current and the difference ratio at both ends when an external fault occurs on the side; S2, Definition n Side-zone external fault model error function, when it occurs n When there is a fault outside the side zone E n =0, otherwise E n ≠0; S3. Extract the frequency and complex amplitude of the fault current using the least squares matrix bundle algorithm, substitute them with the power frequency and measured values, and solve the system inductance online. L m and L n ; S4, Based on system inductance L m and L n Reconstruct the error function and generate a fault characteristic model, defining the first... i The unbalanced current model of each frequency component is combined with the attenuated DC component and the two lowest frequency harmonic components to the set Ω, and the sum of the unbalanced current is calculated to obtain the transient energy of the fault current. S5. The transient energy based on the fault current is defined respectively. n Side-zone external fault dynamic error function E n and m-side region external fault dynamic error function ,when E n and If the preset action threshold is exceeded, it is determined to be a fault within the zone and a protection action is triggered.

2. The longitudinal protection method based on current model identification according to claim 1, characterized in that, The mathematical models for the fault component current and the difference ratio at both ends are as follows: in, This is the theoretical expression for the sum-difference ratio of the current fault components when there is a fault outside the n-side zone. For frequency, For line wave impedance, For the propagation coefficient, For line length, The current and differential ratio values ​​are calculated based on actual fault data. This is the theoretical expression for the current fault component and the difference ratio when there is a fault outside the m-side zone.

3. The longitudinal protection method based on current model identification according to claim 1, characterized in that, n Side-zone external fault model error function for: in, The current and differential ratio values ​​are calculated based on actual fault data. This is the theoretical expression for the current fault component and the difference ratio when there is an external fault on the n-side zone.

4. The longitudinal protection method based on current model identification according to claim 1, characterized in that, System Inductance L m and L n They are respectively: in, The current and differential ratio are calculated from actual fault data at the power frequency. For frequency, For the propagation coefficient, For line length, For line wave impedance, The power frequency. The current and differential ratio values ​​are calculated based on actual fault data.

5. The longitudinal protection method based on current model identification according to claim 1, characterized in that, Transient energy of fault current for: in, In order to be in s i The change in current at terminal m at frequency m. This is the combination of the attenuated DC component and the two lowest-frequency higher harmonic components. In order to be in s i The change in current at terminal n at a given frequency.

6. The longitudinal protection method based on current model identification according to claim 1, characterized in that, n Side-zone external fault model error function as follows: in, This is the combination of the attenuated DC component and the two lowest-frequency higher harmonic components. for s i The sum of the currents at both ends at the specified frequency. This is the theoretical expression for the sum-difference ratio of the current fault components when there is a fault outside the n-side zone. for s i The difference in current at both ends at a given frequency, In order to be in s i The change in current at terminal m at frequency m. In order to be in s i The change in current at terminal n at a given frequency.

7. The longitudinal protection method based on current model identification according to claim 1, characterized in that, m The error function for the side-zone external fault model is as follows: Where Ω is the set of the attenuated DC component and the two lowest-frequency higher harmonic components. for s i The sum of the currents at both ends at the specified frequency. This is the theoretical expression for the sum-difference ratio of the current fault components when there is a fault outside the m-side zone. for s i The difference in current at both ends at a given frequency, In order to be in s i The change in current at terminal m at frequency m. In order to be in s i The change in current at terminal n at a given frequency.

8. The longitudinal protection method based on current model identification according to claim 1, characterized in that, Sum of unbalanced currents for: Where Ω is the set of the attenuated DC component and the two lowest-frequency higher harmonic components. Let be the unbalanced current of the i-th frequency component in the model.

9. The longitudinal protection method based on current model identification according to claim 1, characterized in that, The action threshold is 0.

3.

10. A longitudinal protection system based on current model identification, characterized in that, include: The construction module, based on the Berylon model and fault component network, establishes the lines respectively. m Side and n Mathematical model of the fault component current and the difference ratio at both ends when an external fault occurs on the side; Error module, definition n Side-zone external fault model error function, when it occurs n When there is a fault outside the side zone E n =0, otherwise E n ≠0; The solution module uses the least squares matrix beam algorithm to extract the frequency and complex amplitude of the fault current, substitutes the power frequency and measured values, and solves the system inductance online. L m and L n ; Merging module, based on system inductance L m and L n Reconstruct the error function and generate a fault characteristic model, defining the first... i The unbalanced current model of each frequency component is combined with the attenuated DC component and the two lowest frequency harmonic components to the set Ω, and the sum of the unbalanced current is calculated to obtain the transient energy of the fault current. Action modules are defined based on the transient energy of the fault current. n Side-zone external fault dynamic error function E n and m-side region external fault dynamic error function ,when E n and If the preset action threshold is exceeded, it is determined to be a fault within the zone and a protection action is triggered.

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