A method for single-ended fault location of flexible HVDC transmission line based on frequency domain analysis

Abstract

The application provides a flexible direct current transmission line single-end fault distance measurement method based on frequency domain analysis, which comprises the following steps: collecting a reclosing end real-time voltage value and a reclosing end real-time current value, determining equivalent resistance values of each point along a line based on the reclosing end real-time voltage value and the reclosing end real-time current value; performing frequency spectrum analysis on the equivalent resistance values of each point along the line to generate frequency spectrums of each point along the line; respectively calculating a center of gravity frequency of each point along the line based on the frequency spectrums of each point along the line; and sorting the center of gravity frequencies of each point along the line, and determining a fault distance by selecting a line position corresponding to the smallest center of gravity frequency. The method realizes flexible direct current transmission line single-end fault distance measurement, and improves positioning accuracy and stability of flexible direct current transmission line single-end fault distance measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of relay protection control, in particular to a flexible DC transmission line single-end fault location method based on frequency domain analysis. BACKGROUND

[0002] Flexible DC transmission has the advantages of high commutation reliability, great control flexibility, and small operation loss, and is one of the important supporting technologies for China to realize energy structure transformation. With the continuous increase of voltage level and transmission distance, overhead lines with better economy are widely used in actual projects for power transmission, and the operation environment is relatively complex, and line faults are difficult to avoid. Rapid and accurate fault location can effectively shorten the fault clearing time, which is very important for ensuring system safety and stability.

[0003] At present, the methods for fault location of DC transmission lines can be mainly divided into traveling wave method, double-end fault analysis method and single-end fault analysis method according to their principles. The traveling wave method uses mathematical methods such as derivative method, wavelet transform method and Hilbert-Huang transform method to identify the traveling wave front, and realizes fault location through the time information of the traveling wave arrival; the double-end fault analysis method and the single-end fault analysis method are based on the voltage, current and system parameters measured by double-end or single-end, and realize fault location through analysis and calculation.

[0004] The accuracy of the traveling wave method depends on the traveling wave detection accuracy, and the wave front energy is easily affected by the fault resistance, and the stability is poor; the double-end fault analysis method needs relatively strict synchronous data communication, and the communication delay, interference and other problems in the long-distance scene will affect the location result; the single-end fault analysis method is easily affected by interference signals, and the location accuracy is unstable. SUMMARY

[0005] Therefore, the technical scheme of the present application mainly solves the defects of low accuracy and poor stability of the prior art for positioning the fault of the DC transmission line, thereby providing a flexible DC transmission line single-end fault location method based on frequency domain analysis.

[0006] In a first aspect, an embodiment of the present application provides a flexible DC transmission line single-end fault location method based on frequency domain analysis, comprising:

[0007] Collecting the reclosing end real-time voltage value and the reclosing end real-time current value, and determining the equivalent resistance value of each point along the line based on the reclosing end real-time voltage value and the reclosing end real-time current value;

[0008] Performing frequency spectrum analysis on the equivalent resistance value of each point along the line to generate the frequency spectrum of each point along the line.

[0009] calculating the center of gravity frequency of each point along the line based on the spectrum of each point along the line;

[0010] sorting the center of gravity frequency of each point along the line, and determining the fault distance by selecting the line position corresponding to the minimum center of gravity frequency.

[0011] The flexible DC transmission line single-end fault distance measurement method based on frequency domain analysis provided by the embodiment of the application realizes the flexible DC transmission line single-end fault distance measurement by performing spectrum analysis on the equivalent resistance values of each point along the line, and calculating the center of gravity frequency of each point along the line based on the spectrum of each point along the line, has strong anti-interference ability and anti-transition resistance ability, has good stability and robustness, and improves the positioning accuracy of the flexible DC transmission line single-end fault distance measurement.

[0012] In combination with the first aspect, in a possible implementation manner, the equivalent resistance value of each point along the line is determined based on the real-time voltage value and the real-time current value of the reclosing end, and the equivalent resistance value of each point along the line is determined based on the real-time voltage value and the real-time current value of the reclosing end.

[0013] The real-time voltage value and the real-time current value of the reclosing end are subjected to phase-mode conversion to generate a reclosing end mode voltage and a reclosing end mode current;

[0014] The distribution of the mode voltage and the mode current along the line is calculated based on the reclosing end mode voltage and the reclosing end mode current;

[0015] The positive and negative voltage values and the positive and negative current values of each point along the line are generated by subjecting the distribution of the mode voltage and the mode current along the line to phase-mode inverse conversion;

[0016] The equivalent resistance value of each point along the line is determined based on the positive and negative voltage values and the positive and negative current values of each point along the line.

[0017] In combination with the first aspect, in another possible implementation manner, the equivalent resistance value of each point along the line is determined based on the positive and negative voltage values and the positive and negative current values of each point along the line, and the calculation formula of the equivalent resistance value is as follows:

[0018] R u (x,t)=(u p (x,t)-u n (x,t)) / (i p (x,t)+i n (x,t))

[0019] In the above formula, R u (x,t) represents the equivalent resistance value of the point x at the time t away from the reclosing end, up (x, t) represents the positive electrode voltage value at the distance x from the reclosing end at time t, u n (x, t) represents the negative electrode voltage value at the distance x from the reclosing end at time t, i p (x, t) represents the positive electrode current value at the distance x from the reclosing end at time t, i n (x, t) represents the negative electrode current value at the distance x from the reclosing end at time t.

[0020] In combination with the first aspect, in another possible implementation manner, the frequency spectrum of each point along the line is generated by performing spectrum analysis on the equivalent resistance values of each point along the line, including:

[0021] The equivalent resistance values of each point along the line are combined into a resistance sequence of each point along the line according to a time sequence respectively, and a Fourier transform is performed on the resistance sequence to generate the frequency spectrum of each point along the line.

[0022] In combination with the first aspect, in another possible implementation manner, the center frequency of each point along the line is calculated based on the frequency spectrum of each point along the line, including:

[0023] The frequency corresponding to each spectrum line and the amplitude corresponding to the frequency corresponding to each spectrum line are determined based on the frequency spectrum of each point along the line, and the center frequency of each point along the line is calculated based on the frequency corresponding to each spectrum line and the amplitude corresponding to the frequency corresponding to each spectrum line.

[0024] In combination with the first aspect, in another possible implementation manner, the center frequency of each point along the line is calculated based on the frequency corresponding to each spectrum line and the amplitude corresponding to the frequency corresponding to each spectrum line, and the calculation formula of the center frequency is as follows:

[0025]

[0026] In the above formula, FC represents the center frequency, n represents the serial number of the spectrum line, N represents the total number of the spectrum line, f n f(n) represents the frequency corresponding to the nth spectrum line, and A(n) represents the amplitude corresponding to the nth spectrum line.

[0027] In combination with the first aspect, in another possible implementation manner, before the real-time voltage value of the reclosing end and the real-time current value of the reclosing end are collected, and the equivalent resistance value of each point along the line is determined based on the real-time voltage value of the reclosing end and the real-time current value of the reclosing end, the method further includes:

[0028] When it is detected that the flexible DC transmission line has a fault, a cutting instruction is sent to the DC circuit breaker, and a control instruction is sent to the reclosing device after a preset time period, so as to collect the real-time voltage value of the reclosing end and the real-time current value of the reclosing end.

[0029] In a second aspect, the embodiments of the present application further provide a flexible DC transmission line single-end fault location device based on frequency domain analysis, comprising:

[0030] A determination module is configured to collect reclosing end real-time voltage values and reclosing end real-time current values, and determine equivalent resistance values of each point along the line based on the reclosing end real-time voltage values and the reclosing end real-time current values;

[0031] A spectrum analysis module is configured to perform spectrum analysis on the equivalent resistance values of each point along the line, and generate a spectrum of each point along the line;

[0032] A calculation module is configured to calculate a center of gravity frequency of each point along the line based on the spectrum of each point along the line, respectively;

[0033] A sorting module is configured to sort the center of gravity frequencies of each point along the line, and select a line position corresponding to a minimum center of gravity frequency to determine a fault distance.

[0034] In a third aspect, the embodiments of the present application further disclose an electronic device, comprising at least one processor, and a memory connected with the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the steps of the flexible DC transmission line single-end fault location method based on frequency domain analysis as described in the first aspect or any optional implementation manner of the first aspect.

[0035] In a fourth aspect, the embodiments of the present application further disclose a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the flexible DC transmission line single-end fault location method based on frequency domain analysis as described in the first aspect or any optional implementation manner of the first aspect. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0037] Figure 1 A flowchart of the flexible DC transmission line single-end fault location method based on frequency domain analysis provided by the embodiments of the present application;

[0038] Figure 2A topological structure diagram of a high-voltage large-capacity flexible DC power grid provided for an embodiment of the present application is shown in the figure.

[0039] Figure 3 A flowchart of S101 provided for an embodiment of the present application is shown in the figure.

[0040] Figure 4 A block diagram of a flexible DC transmission line single-end fault ranging device based on frequency domain analysis provided for an embodiment of the present application is shown in the figure.

[0041] Figure 5 A specific example diagram of an electronic device in an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be described clearly and completely in the following with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0043] In the description of the present application, it should be noted that the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, mechanical connection, or electrical connection; or it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements, which can be wireless connection or wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] The embodiment of the present application provides a flexible DC transmission line single-end fault ranging method based on frequency domain analysis, as shown in the figure, which comprises the following steps: Figure 1

[0045] S101, collecting reclosing end real-time voltage value and reclosing end real-time current value, and determining the equivalent resistance value of each point along the line based on the reclosing end real-time voltage value and the reclosing end real-time current value.

[0046] Specifically, when it is obtained that the flexible DC transmission line has a fault, a tripping instruction is sent to the DC circuit breaker, and a control instruction is sent to the recloser after a preset time period to collect the reclosing end real-time voltage value and the reclosing end real-time current value.

[0047] Further, as shown in the figure, Figure 2 ​As shown, high-voltage, high-capacity flexible DC grids often adopt the topology of "half-bridge submodule structure (MMC) + high-voltage DC circuit breaker" for overhead lines. After a fault occurs, the fault current is quickly cut off by the DC circuit breaker. Considering that the overhead lines of flexible DC grids operate in a complex environment and are prone to faults, which are mostly transient, a reclosing operation is performed after a period of fault deionization to ensure that the system can quickly restore power supply.

[0048] S102. Perform spectral analysis on the equivalent resistance values ​​at various points along the above-mentioned line to generate the spectrum of each point along the line.

[0049] Specifically, the equivalent resistance values ​​at each point along the line are combined according to the time series to form the resistance sequence at each point along the line, and the Fourier transform of the resistance sequence is performed to generate the spectrum at each point along the line.

[0050] Furthermore, based on the above-mentioned line, the equivalent resistance values ​​at different times are calculated for each point along the line, and the equivalent resistance value of the point at a distance of x1 is denoted as R. u (x1,t1),…,R u (x1,t n For sequence R u (x1,t1),…,R u (x1,t n Perform a Fourier transform to obtain the spectrum of the resistance at a point at a distance x1; denoted as R at a point at a distance x2. u (x2,t1),…,R u (x2,t n For sequence R u (x2,t1),…,R u (x2,t n Perform a Fourier transform to obtain the spectrum of the resistance at a point at a distance of x2, and so on.

[0051] S103. Calculate the centroid frequency of each point along the line based on the spectrum of each point along the line.

[0052] Specifically, based on the spectrum of each point along the aforementioned line, the frequency corresponding to each spectral line and the amplitude corresponding to each frequency are determined. Then, based on the frequency and amplitude corresponding to each spectral line, the centroid frequency of each point along the aforementioned line is calculated. The formula for calculating the centroid frequency is as follows:

[0053]

[0054] In the above formula, FC represents the centroid frequency, n represents the spectral line number, N represents the total number of spectral lines, and f nLet A(n) represent the frequency corresponding to the nth spectral line, and let A(n) represent the amplitude corresponding to the nth spectral line.

[0055] S104. Sort the centroid frequencies of all points along the above line, and select the line location corresponding to the smallest centroid frequency to determine the fault distance.

[0056] Specifically, for permanent faults, when the circuit breaker trips, its transition resistance is generally a stable resistance close to the actual value, and the fault point can be considered as a purely resistive stable resistance. Therefore, the centroid frequency FC of the spectrum at each point along the line is calculated. The resistance value at the position with the minimum centroid frequency is the most stable, which is the fault point, thereby realizing single-end fault location of flexible DC transmission lines.

[0057] This embodiment proposes a single-end fault location method for flexible DC transmission lines based on frequency domain analysis. By performing spectral analysis on the equivalent resistance values ​​at various points along the line and calculating the centroid frequency at each point based on the spectrum, the method utilizes the characteristic that the centroid frequency of the fault point is the smallest to achieve single-end fault location for flexible DC transmission lines. It has strong anti-interference and anti-transition resistance capabilities, good stability and robustness, and improves the positioning accuracy of single-end fault location for flexible DC transmission lines.

[0058] As an optional embodiment of the present invention, such as Figure 3 As shown, S101 above, namely, determining the equivalent resistance value at each point along the line based on the real-time voltage value and the real-time current value at the reclosing terminal, includes:

[0059] S1011. Perform phase-mode conversion on the above-mentioned real-time voltage value and real-time current value of the reclosing terminal to generate the reclosing terminal mode voltage and reclosing terminal mode current.

[0060] Specifically, the reclosing terminal is designated as terminal A. The real-time voltage and current measured at terminal A are used to calculate the modal voltage and current at terminal A through phase-mode transformation. The calculation formula is as follows:

[0061]

[0062] In the above formula, u p (t) and u n (t) represents the positive and negative DC voltages at terminal A at time t, i p (t) and i n (t) represents the positive and negative DC currents at terminal A at time t, u m0 (t) and u m1 (t) represents the 0-mode voltage and 1-mode voltage at terminal A at time t, i m0 (t) and i m1 (t) represents the 0-mode current and 1-mode current at terminal A at time t.

[0063] S1012. Based on the above-mentioned reclosing terminal mode voltage and reclosing terminal mode current, calculate the mode voltage and mode current distributed along the line.

[0064] Specifically, this is achieved by calculating the modal voltage and modal current distributed along the line:

[0065]

[0066]

[0067] In the above formula, k is the modulus, which can be 1 or 0, and u mk and i mk Let u be the k-mode voltage and k-mode current at terminal A. k (x,t) and i k (x,t) represents the k-mode voltage and k-mode current at a distance x from terminal A at time t, r k Z is the resistance in k-mode. ck The wave impedance in k-mode is v. k Let be the wave velocity in mode k.

[0068] S1013. Perform phase-to-mode inverse transformation on the modal voltage and modal current distributed along the line to generate positive and negative voltage values ​​and positive and negative current values ​​at each point along the line.

[0069] Specifically, the positive and negative voltages and currents at each point on the line are obtained through phase-mode inverse transformation.

[0070]

[0071] In the above formula, u p (x,t) and u n (x,t) represents the DC voltage at time t at a distance x from terminal A, where i is the positive and negative terminals. p (x,t) and i n (x,t) represents the DC current at a distance x from terminal A at time t, u0(x,t) and u1(x,t) represent the 0-mode voltage and 1-mode voltage at a distance x from terminal A at time t, and i0(x,t) and i1(x,t) represent the 0-mode current and 1-mode current at a distance x from terminal A at time t.

[0072] S1014. Determine the equivalent resistance value of each point along the line based on the positive and negative voltage values ​​and positive and negative current values ​​of each point along the line.

[0073] Specifically, if a permanent unipolar ground fault occurs in a flexible DC transmission system, the resistance R at the point of the permanent unipolar ground fault is determined based on the DC voltage and current of the positive and negative poles. S The calculation formula is:

[0074] Rs =u / i (6)

[0075] In the above formula, u is the voltage at the fault point, and i is the current at the fault point.

[0076] Furthermore, if a permanent bipolar short-circuit fault occurs in the flexible DC transmission system, the resistance R at the point of the permanent bipolar short-circuit fault will be determined based on the DC voltage and current at the positive and negative poles. d The calculation formula is:

[0077] R d =u p -u n / i (7)

[0078] In the above formula, u p and u n denoted as the positive and negative voltages at the fault point, and i represents the current at the fault point.

[0079] Furthermore, to facilitate a unified analysis of permanent unipolar ground faults and permanent bipolar short-circuit faults, the formula for calculating the equivalent resistance value is as follows:

[0080] R u (x,t)=(u p (x,t)-u n (x,t)) / (i p (x,t)+i n (x,t)) (8)

[0081] In the above formula, R u (x,t) represents the equivalent resistance value at time t at a distance x from the reclosing terminal, u p (x,t) represents the positive voltage value at time t at a distance x from the reclosing terminal, u n (x,t) represents the negative electrode voltage at time t, which is x distance from the reclosing terminal. p (x,t) represents the positive current value at time t at a distance x from the reclosing terminal, i n (x,t) represents the negative current value at time t at a distance x from the reclosing terminal.

[0082] Furthermore, when calculating the equivalent resistance value using the above formula (6), when a permanent unipolar ground fault occurs in the flexible DC transmission system, R u Compared to R s The voltage of the pole without grounding faults is added to the numerator, approaching a constant term; the current of the pole without grounding faults is added to the denominator, approaching zero, and does not affect the frequency domain analysis; when a permanent single-pole grounding fault occurs in the flexible DC transmission system, R u Compared to R d Doubling the current in the denominator does not affect the frequency domain analysis.

[0083] This invention also discloses a single-end fault location device for flexible DC transmission lines based on frequency domain analysis, such as... Figure 4 As shown, it includes:

[0084] The determination module 41 is used to collect the real-time voltage value and the real-time current value of the reclosing terminal, and determine the equivalent resistance value of each point along the line based on the real-time voltage value and the real-time current value of the reclosing terminal.

[0085] Specifically, when a fault is detected in the flexible DC transmission line, a disconnection command is sent to the DC circuit breaker, and a control command is sent to the reclosing device after a preset time period, so as to collect the real-time voltage value and the real-time current value of the reclosing device.

[0086] Furthermore, high-voltage, high-capacity flexible DC grids often adopt the topology of "half-bridge submodule structure (MMC) + high-voltage DC circuit breaker" for overhead lines. After a fault occurs, the fault current is quickly cut off by the DC circuit breaker. Considering that the overhead lines of flexible DC grids operate in a complex environment and are prone to faults, which are mostly transient, a reclosing operation is performed after a period of fault deionization to ensure that the system can quickly restore power supply.

[0087] The spectrum analysis module 42 is used to perform spectrum analysis on the equivalent resistance values ​​at various points along the line and generate the spectrum of each point along the line.

[0088] Specifically, the equivalent resistance values ​​at each point along the line are combined according to the time series to form the resistance sequence at each point along the line, and the Fourier transform of the resistance sequence is performed to generate the spectrum at each point along the line.

[0089] Furthermore, based on the above-mentioned line, the equivalent resistance values ​​at different times are calculated for each point along the line, and the equivalent resistance value of the point at a distance of x1 is denoted as R. u (x1,t1),…,R u (x1,t n For sequence R u (x1,t1),…,R u (x1,t n Perform a Fourier transform to obtain the spectrum of the resistance at a point at a distance x1; denoted as R at a point at a distance x2. u (x2,t1),…,R u (x2,t n For sequence R u (x2,t1),…,R u (x2,t n Perform a Fourier transform to obtain the spectrum of the resistance at a point at a distance of x2, and so on.

[0090] The calculation module 43 is used to calculate the centroid frequency of each point along the line based on the spectrum of each point along the line.

[0091] Specifically, based on the spectrum of each point along the aforementioned line, the frequency corresponding to each spectral line and the amplitude corresponding to each frequency are determined. Then, based on the frequency and amplitude corresponding to each spectral line, the centroid frequency of each point along the aforementioned line is calculated. The formula for calculating the centroid frequency is as follows:

[0092]

[0093] In the above formula, FC represents the centroid frequency, n represents the spectral line number, N represents the total number of spectral lines, and f n Let A(n) represent the frequency corresponding to the nth spectral line, and let A(n) represent the amplitude corresponding to the nth spectral line.

[0094] The sorting module 44 is used to sort the centroid frequencies of each point along the line and select the line location corresponding to the smallest centroid frequency to determine the fault distance.

[0095] Specifically, for permanent faults, when the circuit breaker trips, its transition resistance is generally a stable resistance close to the actual value, and the fault point can be considered as a purely resistive stable resistance. Therefore, the centroid frequency FC of the spectrum at each point along the line is calculated. The resistance value at the position with the minimum centroid frequency is the most stable, which is the fault point, thereby realizing single-end fault location of flexible DC transmission lines.

[0096] This invention provides a single-end fault location device for flexible DC transmission lines based on frequency domain analysis. By performing spectral analysis on the equivalent resistance values ​​at various points along the line and calculating the centroid frequency at each point based on the spectrum of the fault point, the device achieves single-end fault location for flexible DC transmission lines by utilizing the characteristic that the centroid frequency of the fault point is the smallest. It has strong anti-interference ability and anti-transition resistance ability, good stability and robustness, and improves the positioning accuracy of single-end fault location for flexible DC transmission lines.

[0097] As an optional embodiment of the present invention, the determining module 41 includes:

[0098] The conversion unit is used to perform phase-mode conversion on the real-time voltage value and the real-time current value of the reclosing terminal to generate the reclosing terminal mode voltage and the reclosing terminal mode current.

[0099] Specifically, the reclosing terminal is designated as terminal A. The real-time voltage and current measured at terminal A are used to calculate the modal voltage and current at terminal A through phase-mode transformation. The calculation formula is as follows:

[0100]

[0101] In the above formula, u p (t) and u n (t) represents the positive and negative DC voltages at terminal A at time t, i p (t) and i n (t) represents the positive and negative DC currents at terminal A at time t, u m0 (t) and u m1 (t) represents the 0-mode voltage and 1-mode voltage at terminal A at time t, i m0 (t) and i m1 (t) represents the 0-mode current and 1-mode current at terminal A at time t.

[0102] The calculation unit is used to calculate the mode voltage and mode current distributed along the line based on the above-mentioned reclosing terminal mode voltage and reclosing terminal mode current.

[0103] Specifically, this is achieved by calculating the modal voltage and modal current distributed along the line:

[0104]

[0105]

[0106] In the above formula, k is the modulus, which can be 1 or 0, and u mk and i mk Let u be the k-mode voltage and k-mode current at terminal A. k (x,t) and i k (x,t) represents the k-mode voltage and k-mode current at a distance x from terminal A at time t, r k Z is the resistance in k-mode. ck The wave impedance in k-mode is v. k Let be the wave velocity in mode k.

[0107] The generation unit is used to perform phase-mode inverse transformation on the modal voltage and modal current distributed along the line to generate positive and negative voltage values ​​and positive and negative current values ​​at each point along the line.

[0108] Specifically, the positive and negative voltages and currents at each point on the line are obtained through phase-mode inverse transformation.

[0109]

[0110] In the above formula, u p (x,t) and u n (x,t) represents the DC voltage at time t at a distance x from terminal A, where i is the positive and negative terminals. p (x,t) and i n(x,t) represents the DC current at a distance x from terminal A at time t, u0(x,t) and u1(x,t) represent the 0-mode voltage and 1-mode voltage at a distance x from terminal A at time t, and i0(x,t) and i1(x,t) represent the 0-mode current and 1-mode current at a distance x from terminal A at time t.

[0111] The determining unit is used to determine the equivalent resistance value of each point along the line based on the positive and negative voltage values ​​and positive and negative current values ​​at each point along the line.

[0112] Specifically, if a permanent unipolar ground fault occurs in a flexible DC transmission system, the resistance R at the point of the permanent unipolar ground fault is determined based on the DC voltage and current of the positive and negative poles. S The calculation formula is:

[0113] R s =u / i (6)

[0114] In the above formula, u is the voltage at the fault point, and i is the current at the fault point.

[0115] Furthermore, if a permanent bipolar short-circuit fault occurs in the flexible DC transmission system, the resistance R at the point of the permanent bipolar short-circuit fault will be determined based on the DC voltage and current at the positive and negative poles. d The calculation formula is:

[0116] R d =u p -u n / i (7)

[0117] In the above formula, u p and u n denoted as the positive and negative voltages at the fault point, and i represents the current at the fault point.

[0118] Furthermore, to facilitate a unified analysis of permanent unipolar ground faults and permanent bipolar short-circuit faults, the formula for calculating the equivalent resistance value is as follows:

[0119] R u (x,t)=(u p (x,t)-u n (x,t)) / (i p (x,t)+i n (x,t)) (8)

[0120] In the above formula, R u (x,t) represents the equivalent resistance value at time t at a distance x from the reclosing terminal, u p (x,t) represents the positive voltage value at time t at a distance x from the reclosing terminal, u n (x,t) represents the negative electrode voltage at time t, which is x distance from the reclosing terminal.p (x,t) represents the positive current value at time t at a distance x from the reclosing terminal, i n (x,t) represents the negative current value at time t at a distance x from the reclosing terminal.

[0121] Furthermore, when calculating the equivalent resistance value using the above formula (6), when a permanent unipolar ground fault occurs in the flexible DC transmission system, R u Compared to R s The voltage of the pole without grounding faults is added to the numerator, approaching a constant term; the current of the pole without grounding faults is added to the denominator, approaching zero, and does not affect the frequency domain analysis; when a permanent single-pole grounding fault occurs in the flexible DC transmission system, R u Compared to R d Doubling the current in the denominator does not affect the frequency domain analysis.

[0122] In addition, embodiments of the present invention also provide an electronic device, such as... Figure 5 As shown, the electronic device may include a processor 110 and a memory 120, wherein the processor 110 and the memory 120 may be connected via a bus or other means. Figure 5 For example, the connection is via a bus. Furthermore, the electronic device also includes at least one interface 130, which can be a communication interface or other interface; this embodiment does not impose any limitations on this.

[0123] The processor 110 can be a central processing unit (CPU). The processor 110 can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations of the above types of chips.

[0124] The memory 120, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the video synthesis method in this embodiment of the invention. The processor 110 executes various processor functions and data processing by running the non-transitory software programs, instructions, and modules stored in the memory 120, thereby implementing a frequency domain analysis-based single-end fault location method for flexible DC transmission lines in the above method embodiment.

[0125] The memory 120 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created by the processor 110, etc. Furthermore, the memory 120 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 120 may optionally include memory remotely located relative to the processor 110, and these remote memories may be connected to the processor 110 via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0126] In addition, at least one interface 130 is used for communication between the electronic device and external devices, such as communication with a server. Optionally, at least one interface 130 can also be used to connect peripheral input / output devices, such as a keyboard or display screen.

[0127] The one or more modules are stored in the memory 120, and when executed by the processor 110, they perform actions such as... Figure 1 The embodiment shown illustrates a method for single-end fault location in flexible DC transmission lines based on frequency domain analysis.

[0128] For specific details regarding the aforementioned electronic devices, please refer to the relevant documentation. Figure 1 The relevant descriptions and effects in the illustrated embodiments are for understanding purposes only and will not be repeated here.

[0129] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium can also include combinations of the above types of memory.

[0130] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for single-end fault location in flexible DC transmission lines based on frequency domain analysis, characterized in that, include: Collect the real-time voltage and current values ​​at the reclosing terminal, and determine the equivalent resistance values ​​at each point along the line based on the real-time voltage and current values ​​at the reclosing terminal. Spectral analysis is performed on the equivalent resistance values ​​at various points along the line to generate the spectrum of each point along the line. The centroid frequency of each point along the line is calculated based on the spectrum of each point along the line. The centroid frequencies of each point along the line are sorted, and the line position corresponding to the smallest centroid frequency is selected to determine the fault distance. The determination of the equivalent resistance value at each point along the line based on the real-time voltage value and the real-time current value at the reclosing terminal includes: The real-time voltage value and the real-time current value of the reclosing terminal are converted into phase mode to generate the reclosing terminal mode voltage and the reclosing terminal mode current. The mode voltage and mode current distributed along the line are calculated based on the reclosing terminal mode voltage and reclosing terminal mode current. The mode voltage and mode current distributed along the line are subjected to phase-mode inverse transformation to generate positive and negative voltage values ​​and positive and negative current values ​​at each point along the line. The equivalent resistance value at each point along the line is determined based on the positive and negative voltage and current values ​​at each point along the line; the formula for calculating the equivalent resistance value is as follows: In the above formula, express Distance from reclosing terminal The equivalent resistance value at that point, express Distance from reclosing terminal The positive voltage value at that point. express Distance from reclosing terminal The negative voltage value at that point, express Distance from reclosing terminal The positive current value at the location, express Distance from reclosing terminal The negative current value at that point.

2. The method for single-end fault location of flexible DC transmission lines based on frequency domain analysis according to claim 1, characterized in that, The step of performing spectral analysis on the equivalent resistance values ​​at various points along the line to generate the spectrum of each point along the line includes: The equivalent resistance values ​​at each point along the line are combined according to the time series to form a resistance sequence at each point along the line, and the Fourier transform is performed on the resistance sequence to generate the spectrum at each point along the line.

3. The method for single-end fault location of flexible DC transmission lines based on frequency domain analysis according to claim 1, characterized in that, The calculation of the centroid frequency at each point along the line based on the spectrum of each point along the line includes: Based on the spectrum of each point along the line, determine the frequency corresponding to each spectral line and the amplitude corresponding to each frequency of each spectral line, and calculate the centroid frequency of each point along the line based on the frequency corresponding to each spectral line and the amplitude corresponding to each frequency of each spectral line.

4. The method for single-end fault location of flexible DC transmission lines based on frequency domain analysis according to claim 3, characterized in that, The centroid frequency at each point along the line is calculated based on the frequency corresponding to each spectral line and the amplitude corresponding to that frequency. The formula for calculating the centroid frequency is as follows: In the above formula, Indicates the centroid frequency. Indicates the sequence number of the spectral line. This indicates the total number of spectral lines. Indicates the first The frequencies corresponding to the spectral lines, For the first The amplitude corresponding to each spectral line.

5. The method for single-end fault location of flexible DC transmission lines based on frequency domain analysis according to claim 1, characterized in that, Before acquiring the real-time voltage and current values ​​at the reclosing terminal, and determining the equivalent resistance values ​​at various points along the line based on the real-time voltage and current values ​​at the reclosing terminal, the method further includes: When a fault is detected in the flexible DC transmission line, a disconnection command is sent to the DC circuit breaker, and a control command is sent to the reclosing terminal after a preset time period to collect the real-time voltage value and the real-time current value of the reclosing terminal.

6. A single-end fault location device for flexible DC transmission lines based on frequency domain analysis, characterized in that, include: The determination module is used to collect the real-time voltage value and the real-time current value of the reclosing terminal, and determine the equivalent resistance value of each point along the line based on the real-time voltage value and the real-time current value of the reclosing terminal. The spectrum analysis module is used to perform spectrum analysis on the equivalent resistance values ​​at various points along the line and generate the spectrum at various points along the line. The calculation module is used to calculate the centroid frequency of each point along the line based on the spectrum of each point along the line. The sorting module is used to sort the centroid frequencies of each point along the line and select the line position corresponding to the smallest centroid frequency to determine the fault distance. The module to be determined includes: The conversion unit is used to perform phase-mode conversion on the real-time voltage value and the real-time current value of the reclosing terminal to generate the reclosing terminal mode voltage and the reclosing terminal mode current. The calculation unit is used to calculate the mode voltage and mode current distributed along the line based on the reclosing terminal mode voltage and reclosing terminal mode current; The generation unit is used to perform phase-mode inverse transformation on the modal voltage and modal current distributed along the line to generate positive and negative voltage values ​​and positive and negative current values ​​at each point along the line. The determining unit is used to determine the equivalent resistance value at each point along the line based on the positive and negative voltage values ​​and positive and negative current values ​​at each point along the line; wherein, the formula for calculating the equivalent resistance value is as follows: In the above formula, express Distance from reclosing terminal The equivalent resistance value at that point, express Distance from reclosing terminal The positive voltage value at that point. express Distance from reclosing terminal The negative voltage value at that point, express Distance from reclosing terminal The positive current value at the location, express Distance from reclosing terminal The negative current value at that point.

7. An electronic device, characterized in that, It includes a processor and a memory, wherein the memory is coupled to the processor; The memory stores computer-readable program instructions that, when executed by the processor, implement the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 5.

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