A new energy transmission line interphase fault location method and system

Abstract

The application discloses a new energy sending-out line phase-to-phase fault distance measurement method and system, after a fault occurs, a starting element acts, low-voltage ride-through control and complex frequency signal injection control are put into operation; fault phase selection is realized according to a voltage phase selection element, and fault phase voltage and current under two characteristic frequencies are extracted through filtering; if the fault is a two-phase short-circuit fault, the extraction is replaced by fault phase-to-phase voltage, and the transition resistance is replaced by R f / 2; if the fault is a three-phase short-circuit fault, the phase voltage and the current difference of any two phases are brought in; according to an equivalent circuit under the characteristic frequency, a frequency domain parameter equation about the fault distance is obtained; the real part and the imaginary part of the frequency domain parameter equation of the fault distance are respectively split to obtain a real coefficient equation group about the fault distance; when the non-power frequency electrical quantity is extracted, the real coefficient equation group is expanded to an over-determined equation with 4N equations, and a solution in the least square sense is solved; and the distance measurement result of the new energy sending-out line is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fault detection, and particularly relates to a new energy sending-out line phase-to-phase fault ranging method and system. BACKGROUND

[0002] Compared with the traditional power system dominated by synchronous machines, the new energy system represented by solar photovoltaic power generation and wind power generation operates through power electronic equipment, thereby causing a revolution in the protection and control technology of new power systems. A large number of power electronic equipment in the new power system, under the influence of its own vulnerability, causes weak fault characteristics and strong nonlinear fault evolution rules of the power grid, and the high controllability of the equipment itself also provides an opportunity for the accurate action of the traditional relay protection principle in the new power system or the construction of fault identification and fault location based on active signal injection.

[0003] Quick and accurate positioning of the fault point position is of great significance to the safe and reliable operation of the power grid. The single-ended fault ranging method based on power frequency quantity is simple, economical and easy to implement, but due to the limitations of fault information, it is difficult for the traditional single-ended fault ranging method to make breakthrough progress. With the high proportion of new energy access to the system, the regulation and control characteristics of power electronic equipment have destroyed the assumption of the traditional power frequency quantity single-ended ranging method based on the in-phase of the fault branch current and the current at the installation site, resulting in a decrease in the ranging accuracy of the traditional power frequency quantity method.

[0004] In summary, based on the control and protection cooperation idea, the high controllability of power electronic converter devices is fully utilized, an additional harmonic injection strategy is designed after the fault of the grid-connected line to realize active detection of the fault nature, and then the fault ranging of the line is realized, which has important value for improving the operation reliability of the new energy high proportion system. SUMMARY

[0005] The technical problem to be solved by the application is to provide a new energy sending-out line phase-to-phase fault ranging method and system to solve the technical problem of the decrease in the ranging accuracy of the traditional power frequency quantity method after the high proportion of new energy system access, by constructing a fault topology based on the injection of two non-power frequency signals by the inverter at the outlet, realizing the fault ranging after the phase-to-phase fault of the sending-out line.

[0006] The application adopts the following technical scheme:

[0007] A new energy sending-out line phase-to-phase fault ranging method, comprising the following steps:

[0008] S1, after the fault occurs, the starting element acts, and the low voltage ride through control and the complex frequency signal injection control are put into operation;

[0009] S2, the grid-connected inverter is in a dynamic regulation stage, low voltage ride through control and complex frequency signal injection control reach steady state in 20-40 ms;

[0010] S3, fault phase selection is realized according to the voltage phase selection element, and fault phase voltage and current under two characteristic frequencies are extracted through filtering and

[0011] S4, based on the obtained fault phase voltage and current and determine the circuit topology of the phase-to-phase fault under the characteristic frequency; if the fault is a two-phase short circuit fault, the fault phase-to-phase voltage is extracted and replaced, and the transition resistance is replaced by R f / 2; if the fault is a three-phase short circuit fault, the phase voltage and current difference of any two phases are brought in as phase quantities;

[0012] S5, according to the equivalent circuit under the characteristic frequency, network equations are written at the head of the line to be measured, and a frequency domain parameter equation about the fault distance is obtained;

[0013] S6, the real part and the imaginary part of the frequency domain parameter equation of the fault distance obtained in step S5 are separated respectively, and two equations are obtained; based on the complex frequency signal injected by the inverter containing two characteristic frequencies, a real coefficient equation group about the fault distance is obtained;

[0014] S7, when the non-power frequency electrical quantity is extracted in step S3, the phase quantities of the detection signal under the characteristic frequency are extracted N times in a data window through sliding window extraction, the real coefficient equation group is expanded to an over-determined equation with 4N equations, and the solution in the least square sense is solved; a solving expression of the fault distance is obtained, the result of the fault distance d is obtained, and the distance measurement result of the new energy transmission line is obtained.

[0015] Preferably, the modulation wave output by the controller during the fault is:

[0016]

[0017] wherein U * 0 is the amplitude of the power frequency voltage modulation wave, ω0 is the power frequency angular frequency, ω k , are the angular frequency and initial phase of the injection signal of the characteristic frequencies f1 and f2 respectively, and t is the time of the harmonic signal injection.

[0018] Preferably, the criterion for the starting element to act is as follows:

[0019]

[0020] wherein I setAccording to the 2 times setting of the sum of the amplitudes under the characteristic frequencies f1 and f2 in the harmonics detected when the system is in normal operation, I1 and I2 are the amplitudes of the currents under the characteristic frequencies f1 and f2, respectively.

[0021] Preferably, the injected double-frequency signals are all positive sequence signals with a phase difference of 120°.

[0022] Preferably, the frequency domain parameter equation about the fault distance is as follows:

[0023]

[0024] wherein, is the voltage phasor of the characteristic frequency collected by the local measuring point, ω det is the characteristic frequency of the injected signal, R f is the transition resistance of the fault line, R n and L n is the combination of the line parameters and the parameters of the opposite side system after the fault point, l L is the inductance per unit length of the line, is the current phasor of the characteristic frequency collected by the local measuring point, r L is the resistance per unit length of the line.

[0025] Preferably, the real coefficient equation set is specifically as follows:

[0026]

[0027] wherein, ω1 and ω2 are the angular frequencies of the double-frequency characteristic signals, is the real part and the imaginary part of the current phasor of the double-frequency signal measured by the protection measuring point, is the real part and the imaginary part of the voltage phasor of the double-frequency signal measured by the protection measuring point, x1, x2, x3 and x4 are unknown quantity vectors.

[0028] Preferably, the unknown quantities x1, x2, x3 and x4 are as follows:

[0029]

[0030] wherein, R f is the transition resistance of the fault line, r L and l L are the resistance per unit length and the inductance per unit length of the line, R n and L n are the combination of the line parameters and the parameters of the opposite side system after the fault point.

[0031] Preferably, the solving expression of the fault distance is as follows:

[0032]

[0033] wherein A (4N×4) is the coefficient matrix obtained after the sliding window, b (4N×1) is a constant term vector, x is an unknown quantity vector, l L is the inductance per unit length of the line.

[0034] Preferably, N is 20, the length of the sampling data window is greater than or equal to 5 ms, and the sampling rate is greater than or equal to 4 kHz.

[0035] In a second aspect, an embodiment of the present application provides a new energy sending-out line inter-phase fault distance measurement system, comprising:

[0036] The injection module starts the element to act after the fault occurs, and injects low-voltage ride-through control and complex frequency signal injection control; the grid-connected inverter is in a dynamic adjustment stage, and the low-voltage ride-through control and the complex frequency signal injection control reach a steady state in 20-40 ms;

[0037] The extraction module realizes fault phase selection according to a voltage phase selection element, and extracts fault phase voltage and current under two characteristic frequencies through filtering and

[0038] The phasor module determines the circuit topology of the inter-phase fault under the characteristic frequencies based on the obtained fault phase voltage and current and If the fault is a two-phase short-circuit fault, the extraction is replaced by a fault inter-phase voltage, and the transition resistance is replaced by R f / 2; if the fault is a three-phase short-circuit fault, the phasor of the difference between the phase voltage and the current of any two phases is brought in;

[0039] The equation module writes network equations at the head of the line to be measured according to the equivalent circuit under the characteristic frequencies, and obtains a frequency domain parameter equation about the fault distance; the real part and the imaginary part of the frequency domain parameter equation of the fault distance are respectively split to obtain two equations; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, a real coefficient equation group about the fault distance is obtained;

[0040] The output module extracts the phasor of the detection signal under the N characteristic frequencies in a data window through sliding window extraction when extracting non-power frequency electrical quantities, expands the real coefficient equation group into an over-determined equation with an equation number of 4N, and solves the solution in the least square sense; obtains a solving expression of the fault distance, measures the result of the fault distance d, and obtains the distance measurement result of the new energy sending-out line.

[0041] 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, and the processor implements the steps of the new energy sending-out line inter-phase fault distance measurement method when executing the computer program.

[0042] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium comprising a computer program which, when executed by a processor, implements the steps of the new energy transmission line inter-phase fault distance measurement method.

[0043] In a fifth aspect, a chip 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 new energy transmission line inter-phase fault distance measurement method when executing the computer program.

[0044] 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 new energy transmission line inter-phase fault distance measurement method.

[0045] Compared with the prior art, the present application has at least the following beneficial effects:

[0046] A new energy transmission line inter-phase fault distance measurement method, which is rapidly started after a fault occurs, reaches a stable state within 20-40 ms through low-voltage ride-through control and complex frequency signal injection control, and can quickly perform fault distance measurement; the accurate solution expression of the fault distance is obtained through the establishment and solution of a real coefficient equation set by using the fault phase voltage and current at the characteristic frequency and combining an equivalent circuit and a network equation. This method effectively improves the accuracy of fault distance measurement; it is suitable for various types of inter-phase faults, including two-phase short-circuit faults and three-phase short-circuit faults. Through the processing of different types of faults, the method has good universality and adaptability; the influence of noise and other interference factors on fault distance measurement is effectively reduced, and the reliability of the measurement result is improved by extracting the phasor of the detection signal at the characteristic frequency through a sliding window.

[0047] Further, the control strategy of the converter is used to superimpose the orthogonal characteristic frequency on the original fault strategy to ensure the injection of the double-frequency signal and avoid the influence on the original low-voltage ride-through strategy at the power frequency.

[0048] Further, the characteristic electrical quantity is used as a starting criterion, which on the one hand ensures the injection of the double-frequency signal and on the other hand avoids the weak feedback characteristic caused by the influence of the converter control characteristic when the power frequency quantity is used, thereby causing insufficient reliability.

[0049] Further, the double-frequency distance measurement can avoid the problem that the number of unknown quantities of the equation is too large and the number of distance measurement equations is not enough when single-frequency fault distance measurement is used; the injection of the positive sequence signal can reduce the asymmetry of the signal itself, reduce the damage to the power system, and avoid the suppression of the characteristic signal by the line element (such as a transformer).

[0050] Further, the sliding window sampling distance measurement can increase or decrease the stability of line distance measurement, and avoid distance measurement errors caused by electrical quantity fluctuations.

[0051] It can be understood that the beneficial effects of the above-mentioned second aspect to the sixth aspect can be referred to the related description in the above-mentioned first aspect, which will not be repeated here.

[0052] In summary, the application avoids the problem of the decline of the distance measurement accuracy of the traditional power frequency method caused by the high proportion of new energy access system, uses the converter regulation characteristics to inject a complex frequency signal, and further uses the injected characteristic signal as a basis to realize accurate distance measurement of the fault line, has the advantages of rapidity, accuracy, strong adaptability and strong anti-interference ability, and provides a strong guarantee for the safe and stable operation of the new energy power generation system.

[0053] The technical solutions of the application will be further described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0055] Figure 1 Equivalent circuit diagram for three-phase short circuit fault

[0056] Figure 2 Flow chart of the method of the present application

[0057] Figure 3 110kV centralized photovoltaic sending line model

[0058] Figure 4 Electrical quantity waveform diagram of three-phase short circuit fault at the first end 10km in the sending line area, wherein (a) is the voltage of the measuring point, (b) is the current of the measuring point, (c) is the voltage amplitude-frequency characteristic, and (d) is the current amplitude-frequency characteristic

[0059] Figure 5 Distance measurement result diagram of three-phase short circuit fault at the first end 10km of the sending line

[0060] Figure 6 Electrical quantity waveform diagram of two-phase short circuit fault at the first end 30km in the sending line area, wherein (a) is the voltage of the measuring point, (b) is the current of the measuring point, (c) is the voltage amplitude-frequency characteristic, and (d) is the current amplitude-frequency characteristic

[0061] Figure 7The sending-out line area is a first 30km two-phase short-circuit fault discrimination result graph;

[0062] Figure 8 A schematic diagram of a computer device provided by an embodiment of the present application is shown in FIG. 1.

[0063] Figure 9 A block diagram of an electronic device according to an embodiment of the present application is shown in FIG. 2. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0065] In the description of the present application, it should be understood that the terms "comprise" and "include" indicate the presence of described features, whole, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0066] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clear from the context, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0067] It should be further understood that the term "and / or" used in the present application specification and the appended claims 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 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.

[0068] 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.

[0069] Depending on the context, the word "if" as used herein can be interpreted to mean "when" or "while" or "in response to determining" or "in response to detecting." Similarly, the phrase "if it is determined" or "if [a stated condition or event] is detected" can be interpreted to mean "when it is determined" or "in response to determining" or "when [the stated condition or event] is detected" or "in response to detecting [the stated condition or event]."

[0070] The various structural diagrams according to the disclosed embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity and others omitted. The shapes and relative sizes of the various regions, layers, and the relative positions of these regions / layers shown in the drawings are merely examples and may, in actuality, deviate from what is shown in the drawings due to manufacturing tolerances and technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed by those skilled in the art according to actual needs.

[0071] The present application provides a new energy sending-out line inter-phase fault location method, only using the regulation and control characteristics of the inverter to inject complex frequency signals to the sending-out line, constructing the fault circuit topology under non-power frequency characteristics after the inter-phase fault occurs, further giving the single-end location frequency domain equation and algorithm containing fault distance under non-power frequency electrical quantity, realizing the fault location of the centralized new energy sending-out line. The method has high precision for three-phase short-circuit and two-phase short-circuit fault location, and has certain transition resistance resistance.

[0072] Referring to Figure 2 The new energy sending-out line inter-phase fault location method of the present application comprises the following steps:

[0073] S1, after the fault occurs, the starting element acts, and the low voltage ride through (LVRT) control and the complex frequency signal injection control are put into operation;

[0074] The modulation wave output by the controller during the fault is:

[0075]

[0076] Wherein, U * 0 is the amplitude of the power frequency voltage modulation wave, ω0 is the power frequency angular frequency, ω k 、 The angular frequency and initial phase of the injection signal of the characteristic frequency f1 and f2 are respectively.

[0077] Wherein, the injected double-frequency signals are all "positive sequence" nature with a phase difference of 120°.

[0078] S2, the grid-connected inverter is in the dynamic adjustment stage at the initial stage of fault occurrence, and the low-pass and injection strategy will reach steady state within 20-40 ms;

[0079] The start criterion of the distance measuring device is shown in equation (2):

[0080]

[0081] where I set According to the 2 times of the sum of the amplitudes of the components corresponding to the characteristic frequencies f1 and f2 in the detected harmonics when the system is normally running.

[0082] The fault detection method of the distance measuring device is started according to the amplitude criterion of the injected probe signal current.

[0083] S3, the voltage phase selection element is used to realize fault phase selection, and the fault phase voltage and current at the two characteristic frequencies are extracted through filtering and

[0084] S4, after the fault phase voltage and current are collected, the circuit topology of the phase-to-phase fault at the characteristic frequency is obtained; if the fault is a two-phase short circuit fault, the fault phase-to-phase voltage is extracted and replaced, and the transition resistance is replaced by R f / 2; if the fault is a three-phase short circuit fault, the phase voltage and current difference of any two phases are brought in;

[0085] For the distance measurement algorithm, the above factors are excluded, and the circuit topologies in the two cases remain the same. Taking a three-phase short circuit as an example, the frequency domain equivalent circuit at power frequency and at the characteristic frequency is shown in Figure 1 .

[0086] S5, according to the equivalent circuit at the characteristic frequency obtained by Figure 1 , the network equation is written at the head of the line to be measured;

[0087]

[0088] where r L and l L are the unit length resistance and inductance of the line, R n and L n are the combination of the line parameters after the fault point and the parameters of the opposite side system.

[0089] The shift simplification of equation (3) is obtained, and the frequency domain parameter equation about the fault distance is obtained:

[0090]

[0091] S6, the equation of formula (4) obtained in step S5 is a complex equation, further, the real part and the imaginary part of the equation are separated respectively to obtain two equations; further, since the inverter injection is a complex frequency signal, that is, it contains two characteristic frequencies, four equations about the fault distance are obtained, and a real coefficient equation group is obtained;

[0092] The real coefficient equation group is specifically:

[0093]

[0094] In formula (5), x1-x4 are as follows respectively:

[0095]

[0096] According to formula (5) and formula (6), the above parameter identification equation is a nonlinear equation about d, R f , R n and L n , formula (5) is a linear part thereof, and formula (6) is a nonlinear part thereof. For fault distance measurement, only the fault distance d needs to be solved, and the remaining three unknowns do not need to be solved. Therefore, formula (5) is solved by using a method for solving a linear equation group, and unknowns x1-x4 are obtained. The fault distance d is solved by dividing x1 by x4, and formula (6) does not need to be solved. Formula (5) includes four unknowns, and thus two frequencies can be solved in theory.

[0097] S7, in order to improve the stability of solving formula (5), when the non-power frequency electrical quantity is extracted in step S3, the phasor of the detection signal at the N characteristic frequencies is extracted in a data window by a sliding window, so that formula (5) is expanded to an over-determined equation with 4N equations, and then the solution in the least square sense is solved. A solving expression of the fault distance is obtained, the result of the fault distance d is measured, and thus the distance measurement result of the new energy sending-out line is obtained.

[0098] The solving expression of the fault distance is:

[0099]

[0100] Wherein, N is 20, considering the frequency size of the injected characteristic signal, the length of the sampling data window is at least 5ms, that is, the sampling rate of the measuring device is required to be at least 4kHz, A (4N×4) is a coefficient matrix obtained by sliding window of formula (5), b (4N×1) is a constant term vector thereof, and x is an unknown quantity vector.

[0101] According to formula (7), the result of the fault distance d is measured, and thus the distance measurement result of the new energy sending-out line is obtained.

[0102] Those skilled in the art can understand that the various aspects of the application can be implemented as a system, a method or a program product. Therefore, various aspects of the application can be embodied as a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or an implementation combined with hardware and software aspects, which can be collectively referred to as "circuitry", "module" or "platform" here.

[0103] In another embodiment of the present application, a new energy transmission line interphase fault location system is provided, which can be used to implement the above-mentioned new energy transmission line interphase fault location method. Specifically, the new energy transmission line interphase fault location system comprises an injection module, an extraction module, a phasor module, an equation module and an output module.

[0104] The injection module starts the element action after the fault occurs, and the low voltage ride through control and the complex frequency signal injection control are put into operation. The grid-connected inverter is in a dynamic adjustment stage, and the low voltage ride through control and the complex frequency signal injection control reach a steady state in 20-40 ms.

[0105] The extraction module realizes fault phase selection by a voltage phase selection element, and extracts fault phase voltage and current at two characteristic frequencies through filtering and

[0106] The phasor module determines the circuit topology of the interphase fault at the characteristic frequency based on the obtained fault phase voltage and current and If the fault is a two-phase short circuit fault, the fault interphase voltage is extracted and the transition resistance is replaced by R f / 2; if the fault is a three-phase short circuit fault, the phase voltage and the current difference of any two phases are brought in.

[0107] The equation module writes network equations at the head of the to-be-measured line according to the equivalent circuit at the characteristic frequency, and obtains a frequency domain parameter equation about the fault distance. The real part and the imaginary part of the frequency domain parameter equation of the fault distance are separated respectively, and two equations are obtained. Based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, a real coefficient equation group about the fault distance is obtained.

[0108] The output module extracts the phasor of the detection signal at the characteristic frequency N times in a data window by sliding window extraction when extracting the non-power frequency electrical quantity, expands the real coefficient equation group to an over-determined equation with 4N equations, and solves the solution in the least square sense. The solving expression of the fault distance is obtained, the result of the fault distance d is measured, and the fault location result of the new energy transmission line is obtained.

[0109] In still another embodiment of the present application, a terminal device is provided, which comprises a processor and a memory, the memory being configured to store a computer program, the computer program comprising program instructions, and the processor being configured to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, 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., 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 embodiments of the present application can be used for the operation of the new energy sending-out line inter-phase fault location method, including:

[0110] After the fault occurs, the starting element acts, and the low-voltage ride-through control and the complex frequency signal injection control are put into operation; the grid-connected inverter is in a dynamic adjustment stage, and the low-voltage ride-through control and the complex frequency signal injection control reach a steady state in 20-40 ms; the voltage phase selection element is used to realize fault phase selection, and the fault phase voltage and current under two characteristic frequencies are extracted through filtering and Based on the obtained fault phase voltage and current and The circuit topology of the inter-phase fault under the characteristic frequency is determined; if the fault is a two-phase short-circuit fault, the fault phase voltage is extracted and replaced, and the transition resistance is replaced by R fif the fault is a three-phase short-circuit fault, the phase voltage and the phase current difference of any two phases are brought in; according to the equivalent circuit under the characteristic frequency, the network equation is written at the head of the line to be measured, and a frequency-domain parameter equation about the fault distance is obtained; the real part and the imaginary part of the frequency-domain parameter equation of the fault distance are respectively split to obtain two equations; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, a real coefficient equation group about the fault distance is obtained; when the non-power frequency electrical quantity is extracted, the phasor of the detection signal under the N characteristic frequencies is extracted in a data window through sliding window extraction, the real coefficient equation group is expanded to an over-determined equation with 4N equations, and the solution in the least square sense is solved; a solving expression of the fault distance is obtained, the result of the fault distance d is obtained, and the distance measurement result of the new energy sending-out line is obtained.

[0111] Please refer to Figure 8 The terminal device is a computer device, and the computer device 60 of the embodiment includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. The computer program 63 realizes the new energy sending-out line phase-to-phase fault distance measurement method in the embodiment when executed by the processor 61. To avoid repetition, details are not described here. Alternatively, the computer program 63 realizes the functions of each model / unit in the new energy sending-out line phase-to-phase fault distance measurement system of the embodiment when executed by the processor 61. To avoid repetition, details are not described here.

[0112] 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 and a memory 62. Those skilled in the art can understand that Figure 8 The computer device 60 is only an example and does not constitute a limitation on the computer device 60, and can include more or fewer components than shown, or combine certain components, or different components, for example, the computer device can also include an input / output device, a network access device, a bus, etc.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] Please refer to Figure 9 , the terminal device 600 is an electronic device, 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.

[0117] Among them, the storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 executes the steps of various exemplary embodiments according to the present application described in the method part of the specification. For example, the processing unit 610 can execute the steps as shown in Figure 2 .

[0118] 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 .

[0119] 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.

[0120] Bus 630 may represent one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0121] The electronic device 600 can also communicate with one or more external devices 700 (e.g., a keyboard, a pointing device, a Bluetooth device, etc.), one or more devices that enable a user to interact with the electronic device 600, and / or any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., a router, a modem, etc.). Such communication can occur via an input / output (I / O) interface 650. Furthermore, the electronic device 600 can 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 can communicate with other modules of the electronic device 600 via the 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 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.

[0122] In still another embodiment of the present application, the present application also provides a storage medium, specifically a computer readable storage medium, which is a memory device in the terminal device, for storing 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 also include the extended storage medium supported by the terminal device. The computer readable storage medium provides a storage space, which stores the operating system of the terminal. 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. It should be noted that the computer readable storage medium herein can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory.

[0123] The one or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to realize the corresponding steps of the new energy sending line inter-phase fault distance measurement method in the above embodiments; the one or more instructions in the computer readable storage medium are loaded and executed by the processor to realize the following steps:

[0124] After the fault occurs, the starting element acts, and the low-voltage ride-through control and the complex frequency signal injection control are put into operation; the grid-connected inverter is in a dynamic adjustment stage, and the low-voltage ride-through control and the complex frequency signal injection control reach a steady state in 20-40 ms; the voltage phase selection element realizes fault phase selection, and the fault phase voltage and current under the two characteristic frequencies are extracted through filtering And Based on the obtained fault phase voltage and current And The circuit topology under the characteristic frequency of the inter-phase fault is determined; if the fault is a two-phase short-circuit fault, the fault phase voltage is extracted and replaced, and the transition resistance is replaced by R f / 2; if the fault is a three-phase short-circuit fault, the phase voltage and the current difference of any two phases are brought in; according to the equivalent circuit under the characteristic frequency, the network equation is written at the head of the to-be-measured line, and the frequency domain parameter equation about the fault distance is obtained; the real part and the imaginary part of the frequency domain parameter equation of the fault distance are respectively split, and two equations are obtained; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, the real coefficient equation group about the fault distance is obtained; when the non-power frequency electrical quantity is extracted, the phase quantity of the detection signal under the characteristic frequency is extracted N times in a sliding window in a data window, the real coefficient equation group is expanded to an over-determined equation with 4N equations, and the solution in the least square sense is solved; the solving expression of the fault distance is obtained, the result of the fault distance d is measured, and the distance measurement result of the new energy sending line is obtained.

[0125] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings of the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0126] Simulation verification

[0127] In order to verify the correctness of the proposed fault location method, taking a 110 kV transmission line as an example, a simulation model as shown in Figure 3 is established based on the Bergeron model of the electromagnetic transient simulation software PSCAD. The main parameters of the system are shown in Table 1:

[0128] Table 1 Main parameters of the photovoltaic grid-connected system model

[0129]

[0130]

[0131] Among them, the section L1 is the transmission line for fault location, and the single-end electrical quantity is collected through the measurement point at the end. The length of section L1 is divided as: L1 = 60 km.

[0132] Different fault types and transition resistances are set in the middle section of L1 to verify the accuracy of the single-end fault location algorithm using complex frequency signal injection.

[0133] For the transmission line model as shown in Figure 3 , different fault types and transition resistances are set in the middle section of L1 to verify the accuracy of the new energy transmission line interphase fault location method.

[0134] A three-phase short-circuit fault is set in the transmission line section, and the fault distance is 10 km from the head. The electrical quantity waveform diagram of the protection measurement point is as shown in Figure 4 , and the fault location result is as shown in Figure 5 .

[0135] Please refer to Figure 4 , after the fault occurs, the inverter starts the additional control strategy to inject positive sequence double-frequency detection signals with frequencies of 200 Hz and 300 Hz to the fault line.

[0136] Please refer to Figure 5The fault distance solving method based on the double-frequency signal is not affected by the low-pass characteristics of the converter, and can accurately and stably solve the fault distance.

[0137] AB two-phase short-circuit faults are set in the outgoing line area, the fault is 30km away from the first end, the protection measurement point electrical quantity waveform diagram is as shown in Figure 6 The fault distance solving method based on the double-frequency signal is not affected by the low-pass characteristics of the converter, and can accurately and stably solve the fault distance. Figure 7

[0138] The simulation results of different fault positions and different fault types are shown in Table 2:

[0139] Table 2 Simulation results of different fault positions and fault types

[0140]

[0141]

[0142] According to the simulation verification result, it is shown that the new energy outgoing line phase-to-phase fault distance measuring method and system can realize accurate distance measurement after the phase-to-phase fault of the new energy outgoing line, and the distance measurement error is within the acceptable range.

[0143] In summary, the new energy outgoing line phase-to-phase fault distance measuring method and system injects a positive sequence harmonic signal with a characteristic frequency after the phase-to-phase fault of the new energy outgoing line, the harmonic signal can help to strengthen the fault characteristics and increase the fault information, and accurate distance measurement of the fault line is realized.

[0144] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of software functional unit. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0145] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0146] ​Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized in electronic hardware or in combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0147] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / terminal and method can be implemented in other ways. For example, the apparatus / terminal embodiments described above are merely schematic. The division of the modules or units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between the units can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or in other forms.

[0148] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. they can be located in one place, or distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0149] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0150] The integrated module / unit, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer-readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the computer-readable medium can include or exclude contents according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0151] The present application is described with reference to flowcharts and / or block diagrams of methods, devices, and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The functions specified in one or more flows and / or blocks

[0152] These computer program instructions can also be stored in a computer-readable memory that can guide the computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The functions specified in one or more flows and / or blocks

[0153] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable data processing devices to generate a computer implemented process, so that the instructions executed on the computer or other programmable data processing devices provide a process for implementing the flowchart Figure 1 one flow or a plurality of flows and / or the functions specified in the block Figure 1 one block or a plurality of blocks.

[0154] 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 new energy sending-out line phase-to-phase fault location method, characterized in that, The method comprises the following steps: S1, after the fault occurs, the starting element acts, and low-voltage ride-through control and complex frequency signal injection control are put into operation; S2, the grid-connected inverter is in a dynamic adjustment stage, and the low-voltage ride-through control and the complex frequency signal injection control reach a steady state in 20-40 ms; S3, the voltage phase selection element realizes fault phase selection, and extracts the phase voltage and current of the phase-to-phase fault at two characteristic frequencies through filtering 、 and 、 ; S4, determining the circuit topology of the phase-to-phase fault at the characteristic frequency based on the obtained fault phase voltage and current 、 and 、 , if the fault is a two-phase short circuit fault, extracting the phase-to-phase voltage of the two-phase short circuit fault phase, and simultaneously replacing the transition resistance with R f / 2, R f being the transition resistance of the fault line; if the fault is a three-phase short circuit fault, extracting the phase voltage and the phase difference of the current of any two phases of the three-phase voltage and current. S5, according to an equivalent circuit under a characteristic frequency, network equations are written at a first end of a line to be measured, and a frequency domain parameter equation about the fault distance is obtained; S6, a real part and an imaginary part of the frequency domain parameter equation about the fault distance obtained in step S5 are respectively split, two equations are obtained, based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, real coefficient equation groups about the fault distance are obtained; S7, when extracting non-power frequency electrical quantities in step S3, extract the data by sliding window within a data window. N The phasor of the detection signal at the sub-characteristic frequency is expanded to the equation number 4 by the real coefficient equation group. N Overdetermined equation, solve its solution in the sense of least squares; a solving expression of the fault distance is obtained, a result of the fault distance d is measured, and a distance measurement result of the new energy sending line is obtained.

2. The method of claim 1, wherein, The controller outputs a modulated wave during the fault period: wherein, U * 0 is the amplitude of the power frequency voltage modulation, ω 0 is the angular frequency of the power frequency, ω k , φ k are the angular frequency and initial phase of the injection signal of characteristic frequency f 1 and f 2 respectively, is the time of the harmonic signal injection, , , are the modulation wave signals output by the controller.

3. The method of claim 1, wherein, The criterion for the starting element to act is as follows: wherein, I set The 2 times of the sum of the amplitudes of the 1 and 2 components is set according to the characteristic frequency f 1 and f 2 in the harmonics detected when the system is running normally, , The 2 times of the sum of the amplitudes of the 1 and 2 components is set according to the characteristic frequency f 1、 f The current amplitude at the 2 characteristic frequencies, The duration after the fault.

4. The method of claim 1, wherein, The injected complex frequency signals are all positive sequence signals with a phase difference of 120°.

5. The method of claim 1, wherein, The frequency domain parameter equation about the fault distance is as follows: wherein, is the voltage phasor at the characteristic frequency collected by the local measurement point, is the characteristic frequency of the injected signal, is the transition resistance of the fault line, R n and L n is the equivalent parameter of the line and the opposite system after the fault point, is the inductance per unit length of the line, is the current phasor at the characteristic frequency collected by the local measurement point, is the resistance per unit length of the line.

6. The method of claim 5, wherein, The real coefficient equation groups are specifically as follows: wherein , is the angular frequency of the complex frequency signal, , , , is the real part and the imaginary part of the current phasor of the complex frequency signal measured at the protection measuring point, , , , is the real part and the imaginary part of the voltage phasor of the complex frequency signal measured at the protection measuring point, is the unknown quantity vector.

7. The method of claim 6, wherein, unknown quantity is: wherein, Rtis the transition resistance of the faulted line, r L and l L R and L are the line resistance and inductance per unit length.

8. The method of claim 7, wherein, The solving expression of the fault distance is as follows: wherein, A (4N×4) is a coefficient matrix obtained after the sliding window, b (4N×1) is a constant term vector, x is an unknown quantity vector, l L is the line unit length inductance.

9. The method of claim 8, wherein, N For 20, the length of the sampling data window is greater than or equal to 5 ms, and the sampling rate is greater than or equal to 4 kHz.

10. A new energy transmission line interphase fault location system, characterized in that, The method comprises the following steps: an injection module, after the fault occurs, the starting element acts, and low-voltage ride-through control and complex frequency signal injection control are put into operation; the grid-connected inverter is in a dynamic adjustment stage, and the low-voltage ride-through control and the complex frequency signal injection control reach a steady state in 20-40 ms; The extraction module realizes fault phase selection according to the voltage phase selection element, and extracts the phase voltage and current of the phase-to-phase fault at two characteristic frequencies through filtering , and , ; a phasor module to determine the circuit topology at the characteristic frequency based on the obtained fault phase voltage and current 、 and 、 if the fault is a two-phase short circuit fault, extract the inter-phase voltage of the two-phase short circuit fault phase, while the transition resistance is replaced by R f / 2, R f the transition resistance of the fault line; if the fault is a three-phase short-circuit fault, a phase voltage and a current difference of a phase voltage and a current of any two phases of three-phase voltage and current are extracted; an equation module, according to an equivalent circuit under a characteristic frequency, network equations are written at a first end of a line to be measured, and a frequency domain parameter equation about the fault distance is obtained; a real part and an imaginary part of the frequency domain parameter equation about the fault distance are respectively split, two equations are obtained; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, real coefficient equation groups about the fault distance are obtained; The output module extracts the non-power frequency electrical quantity in a data window through sliding window extraction N The phasor of the detection signal at the secondary characteristic frequency is detected, and the real coefficient equation set is expanded to an overdetermined equation with 4 equations N The least square solution of the overdetermined equation is solved. a solving expression of the fault distance is obtained, a result of the fault distance d is measured, and a distance measurement result of the new energy sending line is obtained.

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