AC transmission line fault location method, device and medium without known parameters
By reconstructing the observation equation system and using the Newton-Raphson method, the pseudo-root and divergence problems caused by nonlinearity in AC transmission line fault ranging are solved, and fault ranging with high precision and strong parameter adaptability are achieved.
Patent Information
- Application Number
- CN202210765699.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-01
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2042-07-01
AI Technical Summary
In the prior art, due to the strong nonlinearity of the equation, iterative solution algorithms often have pseudo-root or divergence problems, making it difficult to achieve accurate fault ranging in actual engineering.
By constructing a new complex unknown quantity, reconstructing the system of observation equations to make it monotonic in the solution space, the solution is solved using the Newton-Raphson method to ensure convergence to the global optimal solution.
It realizes that any initial value in the solution space that is insensitive to the initial value can converge to the true solution, which improves the accuracy of fault ranging and parameter adaptability.
Smart Images
Figure CN115327291B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of transmission line fault distance measurement, and in particular to an alternating current transmission line fault distance measurement method, device and medium without requiring known parameters. Background Art
[0002] Considering that the transmission line parameters will be affected by factors such as ambient temperature, climate, and geology during actual operation and deviate from the standard parameters at the time of commissioning, and the use of inaccurate line parameters will bring large errors to the fault distance measurement results, therefore, fault distance measurement has high requirements for the adaptation of transmission line parameters. In the existing line parameter adaptation or line parameter identification methods, the method of using the transient recording data after the fault to construct the observation equation related to the fault distance and line parameters for solving the equation often has pseudo roots or divergence problems when using the iterative solution algorithm because the equation has strong nonlinearity. Because it is sensitive to the initial value, it is necessary to determine the reasonable range of the true solution in advance to ensure convergence to the global optimum, making the algorithm difficult to implement in actual engineering. Summary of the invention
[0003] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the present invention aims to provide a method, device and medium for fault location measurement of an AC transmission line without requiring known parameters.
[0004] The technical solution adopted by the present invention is:
[0005] A method for fault location of an AC transmission line without known parameters comprises the following steps:
[0006] Obtain the voltage and current recording data of each phase at both ends of the AC transmission line for a preset number of power frequency cycles after the fault;
[0007] According to the obtained waveform data of each phase voltage and current, the positive sequence voltage phasor and the positive sequence current phasor are obtained;
[0008] Take any 4 complex numbers whose real and imaginary parts are all positive as the initial values of variables A1, A2, A3 and A4. (0) ,A2 (0) ,A3 (0) and A4 (0) , according to the obtained positive sequence voltage phasor and positive sequence current phasor, obtain the initial value J of the Jacobian matrix J(A) (0) (A), and the initial value f of the function f(A) (0) (A);
[0009] Use the Newton-Raphson method to solve the equation system f(A) = 0, and after each iteration, the new iterative solution A (k+1) Substitute the Jacobian matrix J(A) and the function f(A) to update the Jacobian matrix J(k+1) (A) and the function value f (k+1) (A), until the iterative process reaches the convergence condition;
[0010] After iteration, the final solution A1 of variables A1, A2, A3 and A4 is obtained (n) ,A2 (n) ,A3 (n) and A4 (n) , according to the final solution A1 (n) ,A2 (n) ,A3 (n) and A4 (n) Calculate the fault distance result
[0011] Furthermore, the AC transmission line is a double-terminal power supply same-tower double-circuit transmission line, and the systems connected on both sides of the line are equivalent to the system equivalent impedance and constant voltage source connected in series; the busbars at both ends of the line are named M and N respectively, the total length of the line is l, and the equivalent positive sequence impedances of the systems on both sides are Z S.M With Z S.N , the line positive sequence wave impedance is Z c , the positive sequence propagation coefficient is γ.
[0012] Furthermore, the step of obtaining the positive-sequence voltage phasor and the positive-sequence current phasor according to the obtained waveform data of each phase voltage and current includes:
[0013] The DFT algorithm is used to process the voltage and current recording data of each phase to obtain the corresponding phase voltage and phase current phasors. in Corresponding to three phases;
[0014] The line voltage phasor is obtained by making a difference between the phases The phase current difference phasor,
[0015] Use symmetrical component transformation to convert to positive sequence voltage phasor and the positive sequence current phasor
[0016] Furthermore, the expression of the Jacobian matrix J(A) is:
[0017]
[0018] The expression of the function f(A) is:
[0019]
[0020] In the formula, is the positive sequence voltage phasor, is the positive sequence current phasor.
[0021] Furthermore, the Jacobian matrix J(A) is obtained by:
[0022] If a short circuit fault occurs on the I loop at a distance d from the M end on the AC transmission line; there is no fault on the II loop, which is a sound loop; according to the long-line transmission equation, the compensation voltage calculated from both ends of the line to the fault point is equal on the fault loop I:
[0023]
[0024] On the healthy loop II, any point satisfies the condition that the compensation voltage calculated from both ends of the line to the fault point is equal. To calculate the fault distance d, the observation point is taken at a distance d and (ld) from the M end of the line:
[0025]
[0026]
[0027] From equations (1) to (3), we can get the line parameters γ, Z c And the multidimensional nonlinear equations of fault distance d:
[0028]
[0029] In order to solve the problem of convergence to pseudo roots and non-convergence when solving the nonlinear equations of Eq. (4) using the Newton-Raphson algorithm, the equations and unknown quantities d, γ, Z in the equations are extracted. c , reconstructing the new complex variables:
[0030]
[0031] Since the equation group (5) has only three equations, and there are four unknown quantities A1, A2, A3 and A4, it is necessary to add another equation related to the unknown quantities A1, A2, A3 and A4. According to the mathematical relationship between the unknown quantities, we can get:
[0032]
[0033] On the sound loop II, with both ends of the line as observation points, the following relationship is satisfied:
[0034]
[0035] From formula (7), we can get:
[0036]
[0037] Therefore, the supplementary equation is:
[0038]
[0039] The Jacobian matrix is:
[0040]
[0041] Furthermore, the expression of the convergence condition is:
[0042]
[0043] in, represents the solution obtained at the kth iteration and The difference between , ε is a very small positive real number.
[0044] Further, according to the final solution A1 (n) ,A2 (n) ,A3 (n) and A4 (n) Calculate the fault distance result include:
[0045] The final solution A1 (n) ,A2 (n) ,A3 (n) and A4 (n) Substitute into the first formula and calculate the fault distance result The line parameter estimation results
[0046] The expression of the first formula is:
[0047]
[0048] Furthermore, the elements of the first three rows of the Jacobian matrix J(A) are the obtained positive-sequence voltage phasors and positive-sequence current phasors, which are constant quantities, and the elements of each column of the fourth row are the four newly constructed complex unknown quantities;
[0049] In the case of far more than the original unknown quantities d, γ, Z c In the solution space of the reasonable value range of , A1, A2, A3 and A4 all fall in the first quadrant of the complex plane, that is, the real and imaginary parts of the complex numbers are all positive; therefore, the solution space of A is taken in the first quadrant of the complex plane. At this time, J(A) still has sign invariance when the value of the unknown quantity changes, so the function f(A) is monotonic in the solution space, and solving the maximum value will definitely converge to the global optimum.
[0050] Another technical solution adopted by the present invention is:
[0051] A fault distance measuring device for an AC power transmission line without requiring known parameters, comprising:
[0052] at least one processor;
[0053] at least one memory for storing at least one program;
[0054] When the at least one program is executed by the at least one processor, the at least one processor implements the above method.
[0055] Another technical solution adopted by the present invention is:
[0056] A computer-readable storage medium stores a program executable by a processor, wherein the program executable by the processor is used to execute the method described above when executed by the processor.
[0057] The beneficial effects of the present invention are as follows: the present invention reconstructs the original observation equation group with strong nonlinearity into a nonlinear equation group by constructing new complex unknowns. The present invention is insensitive to initial values, and any initial value in the solution space can be guaranteed to converge to the true solution. The present invention has strong parameter adaptability and high fault distance measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS
[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.
[0059] Figure 1 It is a flowchart of the steps of a method for fault location of an AC power transmission line without requiring known parameters in an embodiment of the present invention;
[0060] Figure 2 It is a schematic diagram of a double-circuit transmission line with double-terminal power supplies on the same tower according to an embodiment of the present invention. DETAILED DESCRIPTION
[0061] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.
[0062] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.
[0063] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.
[0064] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0065] like Figure 1 As shown, this embodiment provides an AC transmission line fault location method without known parameters, comprising the following steps:
[0066] S1. Obtain the voltage and current waveform data of each phase at both ends of the AC transmission line for a preset number of power frequency cycles after the fault.
[0067] See also Figure 2 , attached Figure 2 The figure is a schematic diagram of a double-circuit transmission line with a double-end power supply on the same tower. The three-phase parameters of the system under analysis are symmetrical. The systems connected on both sides of the line are equivalent to the system equivalent impedance and constant voltage source in series. The frequency of the AC system is 50Hz. After the loops are transposed, there is only zero-sequence mutual inductance between the loops, and the positive and negative sequence mutual inductances can be ignored. The busbars at both ends of the line are named M and N respectively. The total length of the line is l. The equivalent positive sequence impedances of the systems on both sides are Z S.M With Z S.N , the line positive sequence wave impedance is Z c , the positive sequence propagation coefficient is γ.
[0068] In this embodiment, the voltage and current recording data of each phase at both ends within 1.5 power frequency cycles after the fault is obtained.
[0069] S2. Obtain the positive-sequence voltage phasor and the positive-sequence current phasor according to the obtained waveform data of each phase voltage and current.
[0070] The corresponding phase voltage and phase current phasors are obtained using the DFT (discrete Fourier transform) algorithm. The line voltage phasor is obtained by making a difference between the phases The phase current difference phasor, And use symmetrical component transformation to convert into positive sequence voltage and current phasors
[0071] S3, select any 4 complex numbers whose real and imaginary parts are all positive as the initial values of variables A1, A2, A3 and A4 (0) , A2 (0) , A3 (0) and A4 (0) , according to the obtained positive sequence voltage phasor and positive sequence current phasor, obtain the initial value J of the Jacobian matrix J(A) (0) (A), and the initial value f of the function f(A) (0) (A).
[0072] Take any 4 complex numbers whose real and imaginary parts are all positive as the initial values of variables A1, A2, A3 and A4. (0) , A2 (0) , A3 (0) and A4 (0) , obtained from step S2 The initial value J of the Jacobian matrix J(A) calculated according to formula (1) (0) (A), and calculate the initial value f of the function f(A) on the left side of the equation f(A)=0 according to equation (2). (0) (A).
[0073]
[0074]
[0075] As an optional implementation, the Jacobian matrix J(A) is obtained by:
[0076] If a short circuit fault occurs on the I loop at a position d (0≤d≤l) away from the M end; there is no fault in the II loop and it is a sound loop.
[0077] According to the long-line transmission equation, the compensation voltage calculated from both ends of the line to the fault point is equal on the fault loop I:
[0078]
[0079] On the healthy loop II, any point satisfies the condition that the compensation voltage calculated from both ends of the line to the fault point is equal. To calculate the fault distance d, the observation point is taken at a distance d and (ld) from the M end of the line:
[0080]
[0081]
[0082] From equations (4) to (6), we can get the line parameters γ, Z c And the multidimensional nonlinear equations of fault distance d:
[0083]
[0084] In order to solve the problem of convergence to pseudo roots and non-convergence when solving nonlinear equations (7) using iterative search algorithms such as Newton-Raphson, the equations and unknown quantities d, γ, Z in the equations are extracted. c , reconstructing the new complex variables:
[0085]
[0086] Substituting equation (8) into equation (7), the system of equations with strong nonlinearity is transformed into a system of linear equations:
[0087]
[0088] Since the equation group (9) has only three equations, and there are four unknown quantities A1, A2, A3 and A4, it is necessary to add another equation related to the unknown quantities A1, A2, A3 and A4. According to the mathematical relationship between the unknown quantities, we can get:
[0089]
[0090] On the sound loop II, with both ends of the line as observation points, the following relationship is satisfied:
[0091]
[0092] From formula (11), we can get:
[0093]
[0094] Therefore, the supplementary equation is:
[0095]
[0096] The Jacobian matrix is:
[0097]
[0098] S4. Use the Newton-Raphson method to solve the equation system f(A) = 0. After each iteration, the new iterative solution A (k+1) Substitute the Jacobian matrix J(A) and the function f(A) to update the Jacobian matrix J (k+1) (A) and the function value f (k+1)(A) until the iterative process reaches the convergence condition.
[0099] The expression of the convergence condition is as follows:
[0100]
[0101] Among them, i=1,2,3,4; ε is a very small positive real number.
[0102] As an optional implementation, for the Jacobian matrix J(A) of formula (1), the elements of the first three rows are the positive sequence phasors of the voltage and current at both ends obtained in step S2, which are constant quantities, and the elements of each column of the fourth row are the four newly constructed complex unknown quantities. c In the solution space of the reasonable value range, for example, d∈[0,1500km],Re(γ)∈[0.0001,0.01],Im(γ)∈[0.0001,0.005],Re(Z c )∈[0,600],Im(Z c )∈[-300,0], A1, A2, A3 and A4 all fall in the first quadrant of the complex plane, that is, the real and imaginary parts of the complex numbers are all positive. Therefore, the solution space of A can be taken in the first quadrant of the complex plane. At this time, J(A) still has the sign invariance when the unknown value changes, so the function f(A) is monotonic in the solution space, and the solution of the maximum value can definitely converge to the global optimum, that is, the solution using the Newton-Raphson method in step S4 is not sensitive to the initial value of the iteration. Taking any point in the solution space as the initial value, the solution can definitely converge and converge to the true solution.
[0103] S5. After iteration, the final solution A1 of variables A1, A2, A3 and A4 is obtained (n) , A2 (n) , A3 (n) and A4 (n) , according to the final solution A1 (n) , A2 (n) , A3 (n) and A4 (n) Calculate the fault distance result
[0104] The final solution A1 of variables A1, A2, A3 and A4 is obtained by step S4. (n) , A2 (n) , A3 (n) and A4 (n) (n represents the number of iterations when step S4 terminates the iteration), and substitute into formula (15) to obtain the fault location results respectively: The line parameter estimation results
[0105]
[0106] The above method is similarly explained below in conjunction with specific embodiments.
[0107] In the attached Figure 2 In the system shown, it is assumed that the position of the single-phase grounding metallic fault on the I loop is d = 50 km. The system and line parameters shown in Table 1, as well as the waveform data of the voltage and current at both ends of the line after the fault, are known.
[0108] Table 1 System parameters of transmission lines
[0109] parameter Value System voltage 525kV System frequency 50Hz Transmission circuit length 300km The unit positive sequence wave impedance of the line is 206.40∠-4.67°Ω / km The line unit positive sequence propagation coefficient is γ=0.0001+j0.0011 / km
[0110] Step 1: Based on the voltage and current recording data of each phase at both ends of 1.5 power frequency cycles after the fault, use the DFT algorithm to obtain The line voltage phasor is obtained by making a difference between the phases Phase current difference phasor, And use symmetrical component transformation to convert into positive sequence voltage and current phasors
[0111] Step 2: Take the initial value of variables A1, A2, A3 and A4 as A1 (0) =1000+j1000,A2 (0) =1000+j1000,A3 (0) =1000+j1000 and A4 (0) =1000+j1000, then the initial Jacobian matrix is:
[0112]
[0113] The initial function value is:
[0114]
[0115] Step 3: Use the Newton-Raphson method to solve the equation system f(A)=0,
[0116]
[0117]
[0118] By A (1) Substituting into equation (1) and equation (2), we can get J (1) (A) and f (1)(A), and so on, the iteration is repeated, and the iteration convergence condition is reached at the 10th iteration. (i=1,2,3,4; ε is taken as 0.001). So the final solution is
[0119]
[0120] Step 4: The final solution A (10) Substituting into formula (15), we get
[0121]
[0122] Therefore, the required fault distance is 49.96 km. The adaptive positive sequence propagation coefficient is 0.0001+j0.0011 / km, and the positive sequence wave impedance is 206.29-j16.69Ω / km.
[0123] In summary, the present invention proposes a fault location method for double-circuit AC transmission lines on the same tower that does not require known line parameters. By constructing new complex unknowns, the original observation equation group with strong nonlinearity is reconstructed into a quadratic nonlinear equation group including three linear equations and one quaternary quadratic equation. The reconstructed equation group is monotonic in the solution space and is insensitive to initial values. Any initial value in the solution space can be guaranteed to converge to the true solution. Therefore, the proposed method has strong parameter adaptability and high fault location accuracy.
[0124] This embodiment also provides an AC transmission line fault distance measuring device without requiring known parameters, comprising:
[0125] at least one processor;
[0126] at least one memory for storing at least one program;
[0127] When the at least one program is executed by the at least one processor, the at least one processor implements Figure 1 The method shown.
[0128] An AC transmission line fault distance measurement device that does not require known parameters in this embodiment can execute an AC transmission line fault distance measurement method that does not require known parameters provided by the method embodiment of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.
[0129] The present application also discloses a computer program product or a computer program, which includes a computer instruction stored in a computer-readable storage medium. A processor of a computer device can read the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes Figure 1 The method shown.
[0130] This embodiment also provides a storage medium, which stores instructions or programs that can execute an AC transmission line fault location method that does not require known parameters provided by an embodiment of the method of the present invention. When the instructions or program are run, any combination of implementation steps of the method embodiment can be executed, and the corresponding functions and beneficial effects of the method can be obtained.
[0131] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.
[0132] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise specified, one or more of the functions and / or features described may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in separate physical devices or software modules. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the present invention. More specifically, in view of the properties, functions, and internal relationships of the various functional modules in the device disclosed herein, the actual implementation of the module will be understood within the conventional skills of the engineer. Therefore, those skilled in the art can implement the present invention set forth in the claims without excessive experimentation using ordinary techniques. It is also understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.
[0133] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.
[0134] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.
[0135] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.
[0136] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.
[0137] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0138] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.
[0139] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.
Claims
1. A method for fault location of an AC transmission line without known parameters, characterized in that: The following steps are involved: Obtain the voltage and current recording data of each phase at both ends of the AC transmission line for a preset number of power frequency cycles after the fault; According to the obtained waveform data of each phase voltage and current, the positive sequence voltage phasor and the positive sequence current phasor are obtained; Take any 4 complex numbers whose real and imaginary parts are all positive as the initial values of variables A1, A2, A3 and A4. (0) ,A2 (0) ,A3 (0) and A4 (0) , according to the obtained positive sequence voltage phasor and positive sequence current phasor, obtain the initial value j of the Jacobian matrix j(A) (0) (A), and the initial value f of the function f(A) (0) (A); Use the Newton-Raphson method to solve the equation system f(A) = 0, and after each iteration, the new iterative solution A (k+1) Substitute the Jacobian matrix J(A) and the function f(A) to update the Jacobian matrix J (k+1) (A) and the function value f (k+1) (A), until the iterative process reaches the convergence condition; After iteration, the final solution A1 of variables A1, A2, A3 and A4 is obtained (n) ,A2 (n) ,A3 (n) and A4 (n) , according to the final solution A1 (n) ,A2 (n) ,A3 (n) and A4 (n) Calculate the fault distance result The expression of the convergence condition is: in, represents the solution obtained at the kth iteration and The difference between , ε is a very small positive real number; According to the final solution A1 (n) ,A2 (n) ,A3 (n) and A4 (n) Calculate the fault distance result include: The final solution A1 (n) ,A2 (n) ,A3 (n) and A4 (n) Substitute into the first formula and calculate the fault distance result The line parameter estimation results The expression of the first formula is:
2. The method for fault location of an AC power transmission line without known parameters according to claim 1, characterized in that: The AC transmission line is a double-terminal power supply same-tower double-circuit transmission line, and the systems connected on both sides of the line are equivalent to the system equivalent impedance and constant voltage source in series; the busbars at both ends of the line are named M and N respectively, the total length of the line is l, and the equivalent positive sequence impedances of the systems on both sides are Z S.M With Z S.N , the line positive sequence wave impedance is Z c , the positive sequence propagation coefficient is γ.
3. The method for fault location of an AC power transmission line without known parameters according to claim 2, characterized in that: The method of obtaining the positive-sequence voltage phasor and the positive-sequence current phasor according to the obtained waveform data of each phase voltage and current includes: The DFT algorithm is used to process the voltage and current recording data of each phase to obtain the corresponding phase voltage and phase current phasors. in Corresponding to three phases; The line voltage phasor is obtained by making a difference between the phases The phase current difference phasor, Use symmetrical component transformation to convert to positive sequence voltage phasor and the positive sequence current phasor 4. The method for fault location of an AC power transmission line without known parameters according to claim 3, characterized in that: The expression of the Jacobian matrix J(A) is: The expression of the function f(A) is: In the formula, is the positive sequence voltage phasor, is the positive sequence current phasor.
5. The method for fault location of an AC power transmission line without known parameters according to claim 4, characterized in that: The Jacobian matrix J(A) is obtained in the following way: If a short circuit fault occurs on the I loop at a distance d from the M end on the AC transmission line; there is no fault on the II loop, which is a sound loop; according to the long-line transmission equation, the compensation voltage calculated from both ends of the line to the fault point is equal on the fault loop I: On the healthy loop II, any point satisfies the condition that the compensation voltage calculated from both ends of the line to the fault point is equal. To calculate the fault distance d, the observation point is taken at a distance d and (ld) from the M end of the line: From equations (1) to (3), we can get the line parameters γ, Z c And the multidimensional nonlinear equations of fault distance d: In order to solve the problem of convergence to pseudo roots and non-convergence when solving the nonlinear equations of Eq. (4) using the Newton-Raphson algorithm, the equations and unknown quantities d, γ, Z in the equations are extracted. c , reconstructing the new complex variables: Since the equation group (5) has only three equations, and there are four unknown quantities A1, A2, A3 and A4, it is necessary to add another equation related to the unknown quantities A1, A2, A3 and A4. According to the mathematical relationship between the unknown quantities, we can get: On the sound loop II, with both ends of the line as observation points, the following relationship is satisfied: From formula (7), we can get: Therefore, the supplementary equation is: The Jacobian matrix is:
6. The method for fault location of an AC power transmission line without known parameters according to claim 4, characterized in that: The elements of the first three rows of the Jacobian matrix J(A) are the obtained positive-sequence voltage phasors and positive-sequence current phasors, which are constant quantities, and the elements of each column of the fourth row are the four newly constructed complex unknown quantities; In the case of far more than the original unknown quantities d, γ, Z c In the solution space of the reasonable value range of , A1, A2, A3 and A4 all fall in the first quadrant of the complex plane, that is, the real and imaginary parts of the complex numbers are all positive; therefore, the solution space of A is taken in the first quadrant of the complex plane. At this time, J(A) still has sign invariance when the value of the unknown quantity changes, so the function f(A) is monotonic in the solution space, and solving the maximum value will definitely converge to the global optimum.
7. An AC power transmission line fault distance measuring device without known parameters, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method according to any one of claims 1 to 6.
8. A computer-readable storage medium storing a program executable by a processor, characterized in that: The processor-executable program is used to perform the method according to any one of claims 1 to 6 when executed by the processor.