New energy transmission line inter-phase fault distance measurement method and system

Abstract

The invention discloses a new energy transmission line inter-phase fault distance measurement method and system, and the method comprises the steps: starting an element to act after a fault occurs, and inputting low-voltage ride-through control and complex-frequency signal injection control; fault phase selection is realized according to a voltage phase selection element, and fault phase voltages and currents under two characteristic frequencies are extracted through filtering; if the fault is a two-phase short-circuit fault, extracting and replacing the fault phase-to-phase voltage, and replacing the transition resistor with Rf / 2; if the fault is a three-phase short-circuit fault, the phasors of the phase voltage and current difference of any two phases are brought in; according to the equivalent circuit under the characteristic frequency, a frequency domain parameter equation about the fault distance is obtained; respectively splitting a real part and an imaginary part of the frequency domain parameter equation of the fault distance to obtain a real coefficient equation set about the fault distance; when the non-power-frequency electrical quantity is extracted, the real coefficient equation set is expanded into an overdetermined equation with the equation number of 4N, and the solution of the overdetermined equation in the least square meaning is solved; and obtaining a distance measurement result of the new energy transmission line.

Description

Background Art

[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 is connected to the grid through power electronic equipment, which has triggered a revolution in the protection and control technology of the new power system. The large number of power electronic equipment connected in the new power system, under the influence of their own fragility, causes the grid fault characteristics to be weak and the fault evolution law to be highly nonlinear. At the same time, the high controllability of the equipment itself also provides an opportunity to actively support the accurate operation of the traditional relay protection principle in the new power system, or to build fault identification and fault location based on active signal injection.

[0003] Rapidly and accurately locating the fault point is of great significance to the safe and reliable operation of the power grid. The single-ended fault distance measurement method based on power frequency is simple, economical and easy to implement, but due to the limitations of fault information, it is difficult for the traditional single-ended fault distance measurement method to make breakthrough progress. With the high proportion of new energy access systems, the regulation characteristics of power electronic equipment have destroyed the assumption of the traditional power frequency single-ended distance measurement method based on the same phase of the fault branch current and the current at the installation point of the distance measurement device, resulting in a decrease in the distance measurement accuracy of the traditional power frequency method.

[0004] In summary, based on the idea of ​​coordinated control and protection, the high controllability of power electronic commutation devices is fully utilized, and an additional harmonic injection strategy is designed after a grid-connected line fault to achieve active detection of the nature of the fault, and then to achieve line fault ranging, which is of great value for improving the operational reliability of systems with a high proportion of new energy. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for measuring phase-to-phase faults in a new energy transmission line in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the ranging accuracy of the traditional industrial frequency method decreases after a high proportion of new energy systems are connected. By constructing a fault topology based on two non-industrial frequency signals injected by the inverter at the outgoing line, the fault ranging after a phase-to-phase fault occurs in the transmission line can be achieved.

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

[0007] A method for measuring phase-to-phase fault distance of a new energy transmission line comprises the following steps:

[0008] S1. After a fault occurs, the starting element is activated, and low voltage ride-through control and complex frequency signal injection control are put into operation;

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

[0010] S3, realize fault phase selection based on voltage phase selection element, and extract fault phase voltage and current at two characteristic frequencies through filtering and

[0011] S4, based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference of any two phases;

[0012] S5. According to the equivalent circuit at the characteristic frequency, write the network equation at the head end of the line to be measured to obtain the frequency domain parameter equation about the fault distance;

[0013] S6, splitting the real part and the imaginary part of the frequency domain parameter equation of the fault distance obtained in step S5 respectively to obtain two equations; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, obtaining a real coefficient equation group about the fault distance;

[0014] S7. When extracting non-industrial frequency electrical quantities in step S3, extract the phasor of the detection signal at the Nth characteristic frequency through a sliding window within a data window, expand the real coefficient equation group into an overdetermined equation with the number of equations 4N, and solve its solution in the least squares sense; obtain the solution expression of the fault distance, measure the result of the fault distance d, and obtain the distance measurement result of the new energy transmission line.

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

[0016]

[0017] Among them, 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 injected signal of characteristic frequencies f1 and f2 respectively, and t is the moment of harmonic signal injection.

[0018] Preferably, the criterion for the action of the starting element is as follows:

[0019]

[0020] Among them, I set It is set to twice the sum of the amplitudes of the harmonics detected during normal system operation at the characteristic frequencies f1 and f2. I1 and I2 are the current amplitudes at the characteristic frequencies f1 and f2 respectively.

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

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

[0023]

[0024] in, is the voltage phasor at 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 after the fault point and the opposite system parameters, l L is the inductance per unit length of the line, is the current phasor at 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 system is specifically:

[0026]

[0027] Among them, ω1 and ω2 are the angular frequencies of the dual-frequency characteristic signals, To protect the measuring point, the real and imaginary parts of the current phasor of the dual-frequency signal are measured. To protect the measuring point, the real and imaginary parts of the voltage phasor of the dual-frequency signal are measured, and x1, x2, x3, and x4 are unknown quantity vectors.

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

[0029]

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

[0031] Preferably, the solution expression of the fault distance is:

[0032]

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

[0034] Preferably, N is 20, the sampling data window length 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 invention provides a phase-to-phase fault distance measurement system for a new energy transmission line, comprising:

[0036] Injection module, after a fault occurs, the starting element is activated, and low voltage ride-through control and complex frequency signal injection control are put into operation; the grid-connected inverter is in the dynamic adjustment stage, and the low voltage ride-through control and complex frequency signal injection control reach a steady state in 20-40ms;

[0037] The extraction module realizes fault phase selection based on the voltage phase selection element, and extracts the fault phase voltage and current at two characteristic frequencies through filtering and

[0038] Phase module, based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference of any two phases;

[0039] The equation module writes the network equation at the head end of the line to be measured according to the equivalent circuit at the characteristic frequency to obtain the 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 split respectively to obtain two equations; 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;

[0040] The output module extracts non-industrial frequency electrical quantities. The phasor of the detection signal at the Nth characteristic frequency is extracted through a sliding window within a data window, and the real coefficient equation group is expanded into an overdetermined equation with the number of equations 4N, and its solution in the least squares sense is solved; the solution 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 transmission line is obtained.

[0041] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for measuring interphase fault distance of new energy transmission lines when executing the computer program.

[0042] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned new energy transmission line phase-to-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 above-mentioned method for measuring interphase faults of new energy transmission lines when executing the computer program.

[0044] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned new energy transmission line phase-to-phase fault distance measurement method.

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

[0046] A method for phase-to-phase fault distance measurement of a new energy transmission line is quickly started after a fault occurs, and reaches a stable state within 20 to 40 ms through low voltage ride-through control and complex frequency signal injection control, and can quickly perform fault distance measurement; the fault phase voltage and current at the characteristic frequency are used, combined with an equivalent circuit and a network equation, and an accurate solution expression for the fault distance is obtained by establishing and solving a group of real coefficient equations. This method effectively improves the accuracy of fault distance measurement; it is applicable to various types of phase-to-phase faults, including two-phase short circuit faults and three-phase short circuit faults. By processing different types of faults, the method of the present invention has good versatility and adaptability; by extracting the phasor of the detection signal at the characteristic frequency through a sliding window, the influence of noise and other interference factors on fault distance measurement can be effectively reduced, and the reliability of the distance measurement result can be improved.

[0047] Furthermore, the converter control strategy is used to superimpose orthogonal characteristic frequencies under the original fault strategy to ensure the injection of dual-frequency signals, thereby avoiding the impact on the original low voltage ride-through strategy under the power frequency.

[0048] Furthermore, the characteristic electrical quantity is used as the starting criterion, which ensures the injection of dual-frequency signals on the one hand, and avoids the weak feedback characteristics caused by the control characteristics of the converter when the power frequency quantity is used, thereby avoiding the lack of reliability.

[0049] Furthermore, the use of dual-frequency ranging can avoid the problem of too many unknowns in the equation and insufficient number of ranging equations when measuring faults at a single frequency; injecting positive-sequence signals can reduce the asymmetry of the signal itself, reduce damage to the power system, and avoid the suppression of characteristic signals by line elements (such as transformers).

[0050] Furthermore, 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. Increasing the sampling rate can shorten the time to collect data under a given sample size and speed up the distance measurement.

[0051] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0052] In summary, the present invention avoids the problem of decreased ranging accuracy of traditional power frequency measurement methods caused by a high proportion of new energy access systems, utilizes the converter control characteristics to inject complex frequency signals, and further utilizes the injected characteristic signals as a basis to achieve accurate ranging of fault lines. It 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 new energy power generation systems.

[0053] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0055] Figure 1 It is the equivalent circuit diagram of three-phase short circuit fault;

[0056] Figure 2 is a flow chart of the method of the present invention;

[0057] Figure 3 It is a 110kV centralized photovoltaic transmission line model;

[0058] Figure 4 The waveform diagram of the electrical quantity of the three-phase short-circuit fault at 10 km from the head end of the transmission line area, where (a) is the voltage at the measuring point, (b) is the current at the measuring point, (c) is the voltage amplitude-frequency characteristic, and (d) is the current amplitude-frequency characteristic;

[0059] Figure 5 This is the three-phase short-circuit fault distance measurement result diagram at 10km from the head end of the transmission line;

[0060] Figure 6 The waveform diagram of the electrical quantity of a two-phase short-circuit fault at 30 km from the head end of the transmission line area, where (a) is the voltage at the measuring point, (b) is the current at the measuring point, (c) is the voltage amplitude-frequency characteristic, and (d) is the current amplitude-frequency characteristic.

[0061] Figure 7 This is the result diagram of two-phase short-circuit fault identification at 30km from the head end of the transmission line area;

[0062] Figure 8 A schematic diagram of a computer device provided by an embodiment of the present invention;

[0063] Fig. 9 The present invention is a block diagram of an electronic device provided according to an embodiment. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

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

[0067] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0068] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0069] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0070] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0071] The present invention provides a method for phase-to-phase fault distance measurement of a new energy transmission line. The method only utilizes the control characteristics of an inverter to inject a complex frequency signal into the transmission line. After a phase-to-phase fault occurs, a fault circuit topology under non-power frequency characteristics is constructed. A single-ended distance measurement frequency domain equation and algorithm containing fault distance under non-power frequency electrical quantities are further provided to achieve fault distance measurement for centralized new energy transmission lines. The method has high accuracy for both three-phase short circuit and two-phase short circuit fault distance measurement, and has a certain ability to withstand transition resistance.

[0072] See also Figure 2 The present invention provides a method for measuring phase-to-phase fault distance of a new energy transmission line, comprising the following steps:

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

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

[0075]

[0076] Among them, 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 injected signal with characteristic frequencies f1 and f2 respectively.

[0077] The injected dual-frequency signals are both of "positive sequence" nature with a phase difference of 120°.

[0078] S2. At the initial stage of the fault, the grid-connected inverter is in the dynamic adjustment stage, and the low-throughput and injection strategies will reach a steady state within 20 to 40 ms;

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

[0080]

[0081] Among them, I setThe setting is made according to twice the sum of the amplitudes of the harmonics detected during normal system operation, corresponding to the characteristic frequencies f1 and f2.

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

[0083] S3, realize fault phase selection based on voltage phase selection element, and extract fault phase voltage and current at two characteristic frequencies 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 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, then the phase difference of the phase voltage and current of any two phases is brought in;

[0085] For the ranging algorithm, excluding the above factors, the circuit topology in the two cases remains the same. Taking the three-phase short circuit as an example, the frequency domain equivalent circuits under the power frequency and the characteristic frequency are obtained as follows Figure 1 shown.

[0086] S5. According to Figure 1 The equivalent circuit under the obtained characteristic frequency is used to write the network equation at the head end of the line to be measured;

[0087]

[0088] Among them, r L and l L is the line resistance and inductance per unit length, R n and L n It is the combination of the line parameters after the fault point and the opposite system parameters.

[0089] By moving and simplifying equation (3), we can obtain the frequency domain parameter equation for the fault distance:

[0090]

[0091] S6. The equation (4) obtained in step S5 is a complex equation. The real part and the imaginary part of the equation are further split to obtain two equations. Furthermore, 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 equations are:

[0093]

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

[0095]

[0096] According to equations (5) and (6), the above parameter identification equation is about d, R f , R n and L n The nonlinear equation of (5) is its linear part and (6) is its nonlinear part. For fault distance measurement, only the fault distance d needs to be solved, without solving the other three unknowns. Therefore, the method of solving the linear equation system is first used to solve (5) to obtain the unknowns x1~x4. Then, the fault distance d is obtained by dividing x1 and x4 without solving (6). Formula (5) includes four unknowns, so theoretically two frequencies can be solved.

[0097] S7. In order to improve the stability of solving equation (5), when extracting non-industrial frequency electrical quantities in step S3, the phasor of the detection signal at the Nth characteristic frequency is extracted through a sliding window within a data window, so that equation (5) is expanded to an overdetermined equation with the number of equations 4N, and then its solution in the least squares sense is solved; the solution expression of the fault distance is obtained, and the result of the fault distance d is measured, so as to obtain the distance measurement result of the new energy transmission line.

[0098] The solution expression for the fault distance is:

[0099]

[0100] Among them, N is 20. Considering the frequency of the injected characteristic signal, the sampling data window length is at least 5ms, which requires the sampling rate of the measurement device to be at least 4kHz. (4N×4) is the coefficient matrix obtained after sliding window in formula (5), b (4N×1) is the constant term vector, and x is the unknown quantity vector.

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

[0102] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

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

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

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

[0106] Phase module, based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference of any two phases;

[0107] The equation module writes the network equation at the head end of the line to be measured according to the equivalent circuit at the characteristic frequency to obtain the 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 split respectively to obtain two equations; 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;

[0108] The output module extracts non-industrial frequency electrical quantities. The phasor of the detection signal at the Nth characteristic frequency is extracted through a sliding window within a data window, and the real coefficient equation group is expanded into an overdetermined equation with the number of equations 4N, and its solution in the least squares sense is solved; the solution 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 transmission line is obtained.

[0109] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, graphics processors (GPU), tensor processors (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding functions; the processor described in the embodiment of the present invention can be used for the operation of the phase-to-phase fault distance measurement method of the new energy transmission line, including:

[0110] After the fault occurs, the starting element is activated, and low voltage ride-through control and complex frequency signal injection control are put into operation; the grid-connected inverter is in the dynamic adjustment stage, and the low voltage ride-through control and complex frequency signal injection control reach a steady state in 20-40ms; the fault phase is selected based on the voltage phase selection element, and the fault phase voltage and current at two characteristic frequencies are extracted through filtering. and Based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference phasors of any two phases; according to the equivalent circuit at the characteristic frequency, write the network equation at the head end of the line to be measured to obtain the frequency domain parameter equation about the fault distance; split the real part and the imaginary part of the frequency domain parameter equation of the fault distance respectively to obtain two equations; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, obtain the real coefficient equation group about the fault distance; when extracting non-power frequency electrical quantities, extract the phasor of the detection signal at the characteristic frequency N times through the sliding window within a data window, expand the real coefficient equation group into an overdetermined equation with the number of equations 4N, and solve its solution in the least squares sense; obtain the solution expression of the fault distance, measure the result of the fault distance d, and obtain the distance measurement result of the new energy transmission line.

[0111] See also Figure 8 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the phase-to-phase fault distance measurement method of the new energy transmission line in the embodiment is realized. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the phase-to-phase fault distance measurement system of the new energy transmission line in the embodiment are realized. To avoid repetition, it is not described one by one here.

[0112] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 8 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0113] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0114] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0115] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0116] See also Fig. 9 The terminal device 600 is an electronic device, and the electronic device is in the form of a general computing device. The components of the electronic device may include but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0117] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 2 Follow the steps shown in .

[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 unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0121] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output (I / O) interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms, etc.

[0122] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs. It should be noted that the computer-readable storage medium here can be a high-speed RAM memory, or a non-volatile memory (Non-VolatileMemory), such as at least one disk memory.

[0123] One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the method for phase-to-phase fault location measurement of a new energy transmission line in the above embodiment; one or more instructions in the computer-readable storage medium are loaded and executed by a processor as follows:

[0124] After the fault occurs, the starting element is activated, and low voltage ride-through control and complex frequency signal injection control are put into operation; the grid-connected inverter is in the dynamic adjustment stage, and the low voltage ride-through control and complex frequency signal injection control reach a steady state in 20-40ms; the fault phase is selected based on the voltage phase selection element, and the fault phase voltage and current at two characteristic frequencies are extracted through filtering. and Based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference phasors of any two phases; according to the equivalent circuit at the characteristic frequency, write the network equation at the head end of the line to be measured to obtain the frequency domain parameter equation about the fault distance; split the real part and the imaginary part of the frequency domain parameter equation of the fault distance respectively to obtain two equations; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, obtain the real coefficient equation group about the fault distance; when extracting non-power frequency electrical quantities, extract the phasor of the detection signal at the characteristic frequency N times through the sliding window within a data window, expand the real coefficient equation group into an overdetermined equation with the number of equations 4N, and solve its solution in the least squares sense; obtain the solution expression of the fault distance, measure the result of the fault distance d, and obtain the distance measurement result of the new energy transmission line.

[0125] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0126] Simulation Verification

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

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

[0129]

[0130]

[0131] Among them, section L1 is the transmission line for fault distance measurement, and single-end electrical quantities are collected through the local end measurement point. The length of section L1 is divided into: L1 = 60km.

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

[0133] for Figure 3 In the transmission line model shown, faults of different fault types and transition resistances are set in the middle section of section 11 to verify the accuracy of the phase-to-phase fault distance measurement method for the new energy transmission line.

[0134] Suppose a three-phase short circuit occurs in the transmission line area, the fault is 10km away from the head end, and the electrical quantity waveform of the protection measuring point is as follows Figure 4 The fault location results are shown in Figure 5 shown.

[0135] See also Figure 4 ,After the fault occurs, the inverter starts the additional ,control strategy and injects the positive sequence dual-frequency detection ,signals with frequencies of 200Hz and 300Hz into the faulty line.

[0136] See also Figure 5The fault distance solving method based on the dual-frequency signal of the present invention is not affected by the low-throw characteristics of the converter and can accurately and stably solve the fault distance.

[0137] Suppose a two-phase AB short circuit fault occurs in the transmission line area, the fault is 30km away from the head end, and the electrical quantity waveform of the protection measuring point is as follows Figure 6 The fault location results are shown in Figure 7 shown.

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

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

[0140]

[0141]

[0142] According to the simulation verification results, the present invention can achieve accurate distance measurement after a phase-to-phase fault occurs in the new energy transmission line, and the distance measurement error is within an acceptable range.

[0143] In summary, the present invention provides a method and system for measuring phase-to-phase faults in a new energy transmission line. After a phase-to-phase fault occurs in a new energy transmission line, a positive-sequence harmonic signal with a characteristic frequency is injected. The harmonic signal can help enhance the fault characteristics, increase fault information, and achieve accurate measurement of the fault line.

[0144] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0145] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0146] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0147] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0148] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0149] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0150] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0151] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0152] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0153] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0154] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for measuring phase-to-phase fault distance of a renewable energy transmission line, characterized in that: The following steps are involved: S1. After a fault occurs, the starting element is activated, and low voltage ride-through control and complex frequency signal injection control are put into operation; S2, the grid-connected inverter is in the dynamic adjustment stage, and the low voltage ride-through control and complex frequency signal injection control reach a steady state within 20-40ms; S3, realize fault phase selection based on voltage phase selection element, and extract fault phase voltage and current at two characteristic frequencies through filtering and S4, based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference of any two phases; S5. According to the equivalent circuit at the characteristic frequency, write the network equation at the head end of the line to be measured to obtain the frequency domain parameter equation about the fault distance; S6, splitting the real part and the imaginary part of the frequency domain parameter equation of the fault distance obtained in step S5 respectively to obtain two equations; based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, obtaining a real coefficient equation group about the fault distance; S7, when extracting non-power frequency electrical quantities in step S3, extract the phasor of the detection signal at the Nth characteristic frequency through the sliding window within a data window, expand the real coefficient equation group into an overdetermined equation with the number of equations 4N, and solve its solution in the sense of least squares; The solution 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 transmission line is obtained.

2. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 1 is characterized in that: The modulation wave output by the controller during the fault period is: Among them, 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 injected signal of characteristic frequencies f1 and f2 respectively, and t is the moment of harmonic signal injection.

3. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 1 is characterized in that: The criteria for the action of the starting element are as follows: Among them, I set It is set to twice the sum of the amplitudes of the harmonics detected during normal system operation at the characteristic frequencies f1 and f2. I1 and I2 are the current amplitudes at the characteristic frequencies f1 and f2 respectively.

4. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 1 is characterized in that: The injected dual-frequency signals are both positive sequence signals with a phase difference of 120°.

5. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 1 is characterized in that: The frequency domain parameter equation for fault distance is as follows: in, is the voltage phasor at 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 after the fault point and the opposite system parameters, l L is the inductance per unit length of the line, is the current phasor at the characteristic frequency collected by the local measuring point, r L is the resistance per unit length of the line.

6. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 5 is characterized in that: The real coefficient equations are: Among them, ω1 and ω2 are the angular frequencies of the dual-frequency characteristic signals, To protect the measuring point, the real and imaginary parts of the current phasor of the dual-frequency signal are measured. To protect the measuring point, the real and imaginary parts of the voltage phasor of the dual-frequency signal are measured, and x1, x2, x3, and x4 are unknown quantity vectors.

7. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 6 is characterized in that: The unknown quantities x1, x2, x3, x4 are: Among them, R f is the transition resistance of the fault line, r L and l L is the line resistance and inductance per unit length, R n and L n It is the combination of the line parameters after the fault point and the opposite system parameters.

8. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 1 is characterized in that: The solution expression for the fault distance is: Among them, A (4N×4) is the coefficient matrix obtained after sliding window, b (4N×1) is a constant term vector, x is an unknown quantity vector, l L is the line inductance per unit length.

9. The phase-to-phase fault distance measurement method for a new energy transmission line according to claim 8 is characterized in that: N is 20, the sampling data window length is greater than or equal to 5ms, and the sampling rate is greater than or equal to 4kHz.

10. A phase-to-phase fault distance measurement system for a new energy transmission line, characterized in that: include: Injection module, after a fault occurs, the starting element is activated to implement low voltage ride-through control and complex frequency signal injection control; The grid-connected inverter is in the dynamic adjustment stage, and the low voltage ride-through control and complex frequency signal injection control reach a steady state within 20-40ms; The extraction module realizes fault phase selection based on the voltage phase selection element, and extracts the fault phase voltage and current at two characteristic frequencies through filtering and Phase module, based on the fault phase voltage and current and Determine the circuit topology of the phase-to-phase fault at the characteristic frequency; if the fault is a two-phase short circuit fault, extract and replace it with the fault phase-to-phase voltage, and replace the transition resistance with R f / 2; if the fault is a three-phase short circuit fault, bring in the phase voltage and current difference of any two phases; The equation module writes the network equation at the head end of the line to be measured according to the equivalent circuit at the characteristic frequency to obtain the 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 split respectively to obtain two equations; Based on the fact that the complex frequency signal injected by the inverter contains two characteristic frequencies, a set of real coefficient equations about the fault distance is obtained; The output module, when extracting non-power frequency electrical quantities, extracts the phasor of the detection signal at the Nth characteristic frequency through a sliding window within a data window, expands the real coefficient equation group into an overdetermined equation with the number of equations 4N, and solves its solution in the sense of least squares; The solution 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 transmission line is obtained.

Images