Flexible DC power transmission line fault location method and system, and storage medium

Abstract

The invention provides a flexible DC power transmission line fault distance measurement method and system and a storage medium, and the method comprises the steps: obtaining line voltage time sequence data, carrying out the decoupling based on the line voltage time sequence data, and obtaining an original line mode signal; based on the original line mode signal, performing disturbance processing under a random noise set to obtain a noise adding signal corresponding to each random noise in the random noise set; wherein the random noise set comprises a plurality of random noises with different intensities; based on the noise adding signal corresponding to each random noise, performing frequency measurement processing to obtain a spectrum peak frequency set; performing clustering processing based on the spectrum peak frequency set to obtain an inherent frequency set; and based on the inherent frequency set, obtaining a fault distance under a preset distance calculation strategy. According to the invention, disturbance processing is carried out on the original line mode signal under the random noise set containing a plurality of random noises with different intensities, and the feature distribution of the noises in the original line mode signal is influenced, so that the interference of false spectral peaks on the frequency measurement process is reduced, and the accuracy of a fault distance measurement result is improved.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection technology, and particularly relates to a method, system and storage medium for fault location of flexible DC transmission lines. Background Technology

[0002] Following a fault in a flexible DC transmission line, a fault location scheme capable of accurately and quickly determining the fault distance is needed to minimize the fault's impact area. Existing fault location methods utilize the MUSIC algorithm to perform frequency measurement processing on the original line-mode signal, obtaining a set of spectral peak frequencies. These peak frequencies are then aggregated to obtain the inherent frequencies, which are then used to confirm the fault location. However, the MUSIC algorithm requires a pre-set number of frequencies. If the set number of frequencies differs from the actual number, false peaks may appear in the captured frequency spectrum. These false peaks interfere with the frequency measurement process, leading to erroneous results and significantly reducing the accuracy of the fault location. Summary of the Invention

[0003] The present invention aims to provide a method, system and storage medium for fault location of flexible DC transmission lines, so as to solve the above-mentioned technical problems and improve the accuracy of fault location results.

[0004] To address the aforementioned technical problems, this invention provides a method for fault location in flexible DC transmission lines, comprising the following steps: The line voltage timing data is acquired, and decoupled based on the line voltage timing data to obtain the original line mode signal; Based on the original line-mode signal, perturbation processing is performed on a random noise set to obtain the noise-added signal corresponding to each noise in the random noise set; wherein, the random noise set contains multiple random noises of different intensities; Based on the noise-added signal corresponding to each random noise, frequency measurement processing is performed to obtain the set of peak frequencies of the spectrum; Based on the set of peak frequencies in the spectrum, clustering is performed to obtain the set of inherent frequencies; Based on the inherent frequency set, the fault distance is obtained under a preset distance calculation strategy.

[0005] The above-described scheme perturbs the original line-mode signal under a random noise set, affecting the characteristic distribution of noise in the original line-mode signal. This causes the frequencies corresponding to false spectral peaks to vary randomly, exhibiting a relatively dispersed characteristic. Meanwhile, the frequencies corresponding to the true signal spectral peaks in the original line-mode signal are unaffected by the noise perturbation, exhibiting a relatively stable characteristic. Therefore, this scheme can more accurately eliminate the frequencies corresponding to false spectral peaks during clustering, reducing the interference of false spectral peaks on the frequency measurement process, improving the accuracy of the obtained intrinsic frequency set, and thus improving the accuracy of fault location results.

[0006] Furthermore, before acquiring the line voltage timing data and decoupling based on the line voltage timing data to obtain the original line mode signal, the method further includes: acquiring the fault state; if the fault state is a permanent fault, generating a converter state transition signal; the converter state transition signal is used to control the converter of the flexible DC transmission line to enter the uncontrolled rectification state.

[0007] After determining that a permanent fault exists in the flexible DC transmission line, the above scheme controls the converter to enter an uncontrolled rectification state. In this state, there is no resonant frequency of inductance and capacitance in the bypass of the capacitor elements in the converter, so that the obtained line voltage timing data is not affected by the high-frequency switching process of the converter. Moreover, the original line mode signal obtained based on the line voltage timing data is used for frequency measurement. Compared with the existing technology that directly uses the signal in the early stage of the fault for frequency measurement, this significantly increases the inherent main frequency of the line voltage signal, improves the reliability of the inherent main frequency value extracted by the frequency measurement algorithm, and can provide a sufficiently long data window for fault location, thereby improving the accuracy of fault location results.

[0008] Further, the step of performing frequency measurement processing on the noise-added signals corresponding to each random noise to obtain a set of peak frequencies includes: obtaining a MUSIC spectrum set based on the noise-added signals corresponding to each random noise using the MUSIC algorithm; and extracting frequencies based on the MUSIC spectrum set to obtain a set of peak frequencies.

[0009] Further, the step of performing clustering processing based on the set of peak frequencies to obtain an intrinsic frequency set includes: performing clustering processing based on the set of peak frequencies to obtain multiple frequency groups; and calculating the mean of the multiple frequency groups to obtain the intrinsic frequency set.

[0010] In the above scheme, the set of peak frequencies is obtained from the noisy signals corresponding to each random noise. Therefore, the frequencies corresponding to the false peaks will exhibit more dispersed and random characteristics, while the frequencies corresponding to the true signal peaks will exhibit more clustered and stable characteristics. This scheme performs clustering based on this set of peak frequencies, which can more accurately extract the frequencies corresponding to the relatively clustered true signal peaks, while the frequencies corresponding to the false peaks of the noise signals with greater randomness will be excluded. Therefore, this scheme can eliminate the interference of false peaks generated by frequency measurement when the number of frequencies is unknown, improve the accuracy of each inherent frequency in the inherent frequency set, and thus improve the accuracy of fault location results.

[0011] Further, obtaining the fault distance based on the inherent frequency set under a preset distance calculation strategy includes: obtaining an inherent primary frequency and a second inherent frequency based on the inherent frequency set under a preset frequency selection strategy; performing calculation processing based on the inherent primary frequency to obtain a first fault distance; performing calculation processing based on the second inherent frequency to obtain a second fault distance; and performing average calculation based on the first fault distance and the second fault distance to obtain the fault distance.

[0012] Furthermore, obtaining the intrinsic primary frequency and the second intrinsic frequency based on the intrinsic frequency set under a preset frequency selection strategy includes: taking the minimum value in the intrinsic frequency set as the intrinsic primary frequency; and taking the second minimum value in the intrinsic frequency set as the second intrinsic frequency.

[0013] Further, the calculation based on the inherent main frequency to obtain the first fault distance includes: obtaining the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity; and performing calculation based on the inherent main frequency, the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity to obtain the first fault distance.

[0014] Further, the calculation based on the second natural frequency to obtain the second fault distance includes: obtaining the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity; and performing calculation based on the second natural frequency, the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity to obtain the second fault distance.

[0015] In the above scheme, if the actual fault distance is far, its corresponding natural main frequency will also be relatively low. In this case, even a small frequency measurement error in the frequency measurement process can lead to a significant fault location error. Therefore, if only the natural main frequency is used for distance measurement, there may be a large distance measurement error. Thus, this scheme introduces a second natural frequency with a higher frequency for distance measurement based on the natural main frequency to reduce the impact of frequency measurement error on the fault distance. This results in a more accurate fault distance and improves the accuracy of the fault location results.

[0016] This invention also provides a flexible DC transmission line fault location system, comprising: a signal decoupling module for acquiring line voltage time-series data and decoupling it based on the line voltage time-series data to obtain an original line-mode signal; a multiple noise addition module for adding random noise of different intensities multiple times to the original line-mode signal obtained by the signal decoupling module to obtain a set of noise-added signals; wherein the set of random noise contains multiple random noises of different intensities; a frequency measurement module for performing frequency measurement processing on the set of noise-added signals corresponding to each random noise obtained by the multiple noise addition module to obtain a set of peak frequencies; a clustering module for performing clustering processing on the set of peak frequencies obtained by the frequency measurement module to obtain a set of inherent frequencies; and a fault distance calculation module for obtaining the fault distance based on the set of inherent frequencies obtained by the clustering module under a preset distance calculation strategy.

[0017] Furthermore, before the signal decoupling module acquires line voltage timing data and decouples based on the line voltage timing data to obtain the original line-mode signal, it also includes a converter state transition module, which acquires the fault state. If the fault state is a permanent fault, a converter state transition signal is generated. The converter state transition signal is used to control the converter of the flexible DC transmission line to enter the uncontrolled rectification state.

[0018] The above-described scheme can more accurately eliminate frequencies corresponding to spurious spectral peaks during clustering, reducing the interference of spurious peaks on the frequency measurement process and improving the accuracy of the obtained intrinsic frequency set, thereby improving the accuracy of fault location results. Furthermore, after determining that a permanent fault exists in the flexible DC transmission line, the above scheme controls the converter to enter an uncontrolled rectification state, which increases the intrinsic main frequency of the line voltage signal, improves the reliability of the intrinsic main frequency value extracted by the frequency measurement algorithm, and provides a sufficiently long data window for fault location, thus improving the accuracy of the fault location results.

[0019] The present invention also provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform any of the flexible DC transmission line fault location methods described above. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the technical implementation of a fault location method for flexible DC transmission lines according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the fault location of a flexible DC transmission line with two ends provided in an embodiment of the present invention; Figure 3 This invention provides a frequency domain equivalent model of a fault loop when a fault occurs on line 1, according to an embodiment of the invention. Figure 4 The relationship between fault distance and main natural frequency in the initial stage of a fault is provided in an embodiment of the present invention. Figure 5 This is an implementation method for a full-bridge submodule to enter an uncontrolled rectification state, as provided in an embodiment of the present invention; Figure 6 This is another implementation method for the full-bridge submodule to enter the uncontrolled rectification state, as provided in one embodiment of the present invention; Figure 7 This invention provides a characteristic of the relationship between fault distance and main natural frequency in a flexible DC transmission line under uncontrolled rectifier conditions of the converter, according to an embodiment of the present invention. Figure 8 This is a schematic diagram of a flexible DC transmission line fault location system architecture provided in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 This embodiment provides a method for fault location in flexible DC transmission lines, including the following steps: Step S1: Obtain line voltage timing data and decouple based on the line voltage timing data to obtain the original line mode signal; Step S2: Based on the original line-mode signal, perturbation processing is performed on a random noise set to obtain the noise-added signal corresponding to each noise in the random noise set; wherein, the random noise set contains multiple random noises of different intensities; Step S3: Based on the noise-added signal corresponding to each random noise, perform frequency measurement processing to obtain the set of peak frequencies of the spectrum; Step S4: Based on the set of peak frequencies in the spectrum, perform clustering processing to obtain the set of inherent frequencies; Step S5: Based on the inherent frequency set, obtain the fault distance under the preset distance calculation strategy.

[0023] The above embodiments perturb the original line-mode signal under a random noise set, which can affect the characteristic distribution of noise in the original line-mode signal, causing the frequencies corresponding to false spectral peaks to change randomly and exhibit relatively dispersed characteristics; while the frequencies corresponding to the true signal spectral peaks in the original line-mode signal are not affected by the noise perturbation and exhibit relatively stable characteristics. Therefore, this embodiment can more accurately eliminate the frequencies corresponding to false spectral peaks when performing clustering processing, reduce the interference of false spectral peaks on the frequency measurement process, improve the accuracy of the obtained intrinsic frequency set, and thus improve the accuracy of fault location results.

[0024] It should be noted that due to inherent limitations in the frequency measurement of the MUSIC algorithm, false spectral peaks may appear within the inherent frequency clusters, affecting the accuracy of fault location results. Therefore, the above embodiments, by repeatedly adding random noise of varying intensities to the original linear mode signal, can influence the characteristic distribution of the original linear mode signal noise, causing the frequencies of false spectral peaks to change randomly and exhibit relatively dispersed characteristics. Conversely, the frequencies corresponding to the true signal are almost unaffected by noise, exhibiting relatively stable characteristics even after multiple additions of random noise of varying intensities. Therefore, in the above embodiments, clustering based on the set of spectral peak frequencies can extract the frequencies corresponding to the relatively clustered true signal spectral peaks, while the frequencies corresponding to the false spectral peaks of the more random noise signal are naturally excluded during the clustering process.

[0025] Furthermore, before acquiring the line voltage timing data and decoupling based on the line voltage timing data to obtain the original line mode signal, the method further includes: acquiring the fault state; if the fault state is a permanent fault, generating a converter state transition signal; the converter state transition signal is used to control the converter of the flexible DC transmission line to enter the uncontrolled rectification state.

[0026] In the above embodiment, after determining that a permanent fault exists in the flexible DC transmission line, the converter is controlled to enter an uncontrolled rectification state. In this state, there is no resonant frequency of the inductor and capacitor in the bypass of the capacitor element in the converter, so that the obtained line voltage timing data is not affected by the high-frequency switching process of the converter. Moreover, the original line mode signal obtained based on the line voltage timing data is used for frequency measurement. Compared with the prior art, which directly uses the signal in the initial stage of the fault for frequency measurement, the inherent main frequency of the line voltage signal is significantly increased, the reliability of the inherent main frequency value extracted by the frequency measurement algorithm is improved, and a sufficiently long data window can be provided for fault location, thereby improving the accuracy of the fault location result.

[0027] In one embodiment, a schematic diagram of the fault location of the flexible DC transmission lines at both ends is shown below. Figure 2 As shown, the current-limiting reactor L FInstalled at the converter outlet. For line-end protection position P1, when a fault occurs on line 1, the DC transmission line can be equivalently represented as "input-state-output", and the frequency domain equivalent model of the fault loop when the fault occurs on line 1 is as follows: Figure 3 As shown. Among them, This is the voltage at the transmission line port of bus A. The voltage at the fault-side port. This is the equivalent voltage source for converter MMC1. The equivalent impedance on the S1 side of the converter (including the converter and the current-limiting reactor L) F ), Let the wave impedance of line 1 be... For the transition resistance at the fault point, and This is a controlled voltage source reflecting the propagation process of electromagnetic waves in a DC line, used to characterize the fault traveling wave. The voltage equation can be obtained from the superposition principle as follows: And the distance to the fault With traveling wave transient frequency The relationship is as follows: in, Let $\frac{ ... The reflection coefficient at converter S1 phase angle, The reflection coefficient at the fault point phase angle, The nth transient frequency of the converter-side line port voltage, also known as the natural frequency, is given by: ,and For the inherent main frequency, The second natural frequency, This is the third natural frequency, and so on. And... , It can be obtained from the following formula; It should be noted that flexible DC transmission systems generally utilize submodules with self-clearing fault capabilities to isolate faults. Taking a full bridge submodule (FBSM) as an example, when a DC fault occurs, the submodule capacitor voltage is reversed and applied to the fault current path by blocking the FBSM, thus blocking the fault current. Before the submodule is blocked, the converter MMC can be equivalently represented as a series RLC circuit consisting of a resistor, inductor, and capacitor, where the resistor is the submodule's on-resistance, the inductor is the bridge arm inductance, and the capacitor is the submodule's capacitance. Similarly, the converter MMC after the submodule is blocked is also equivalent to a series RLC circuit consisting of a resistor, inductor, and capacitor.

[0028] At this point, assume the number of submodules in the converter MMC is... The equivalent resistance of the bridge arm is The bridge arm inductance is The submodule capacitor is The parameters of the RLC circuit equivalent to the MMC converter are expressed as follows: And there exists a relation as follows , and The reflection coefficient at the line end protection position P1 is... As shown in the formula below: Select the relevant parameters of the MMC converter and the current-limiting reactor, based on the reflection coefficient in the above formula. The expression, combined with the fault distance With traveling wave transient frequency The relationship between the fault distance and the main natural frequency in the initial stage of a fault can be calculated using this formula. )like Figure 4 As shown. Taking a fault distance of 300km as an example, as... Figure 4 The dashed line corresponding to the fault distance of 300km intersects the characteristic curve at two points, with each intersection located on either side of the critical frequency. The component below the critical frequency is the principal component of the natural frequency. The natural frequency of the fault system is approximately 16.74Hz. This indicates that the natural frequency is low in the initial stage of the fault. Since the identification and isolation of DC faults in flexible HVDC grids are very rapid, typically within milliseconds, the available data window length in the initial stage is only a few milliseconds. Frequency measurement algorithms struggle to accurately measure frequencies of tens of hertz within a few milliseconds. Therefore, traditional natural frequency-based fault location methods based on extracting initial fault information are not applicable to flexible HVDC grids.

[0029] Therefore, this invention proposes frequency measurement when the converter enters the uncontrolled rectification state. This embodiment first defines a new operating state for a submodule. For the FBSM, its uncontrolled rectification state has two specific implementation methods, as follows: Figure 5 and Figure 6 As shown. Figure 5 As shown, IGBT T1 in the FBSM is turned on, and T2~T4 are kept in the latch-up state. At this time, current can only flow through the freewheeling diode D3 and IGBT T1. The physical characteristics are the same as those of a half-bridge module in the latch-up state, hence the name "half-bridge latch-up state". Similarly, as... Figure 5 As shown, IGBT T4 in the FBSM is turned on, while T1~T3 remain in a latched state. At this time, current can only flow through the freewheeling diode D2 and IGBT T4, and the physical characteristics are the same as those of a half-bridge module in the latched state. In this embodiment, operating all FBSMs in the bridge arm in a near-half-bridge latched state allows the converter to enter an uncontrolled rectification state.

[0030] After operating the converter in uncontrolled rectification mode, the reflection coefficient at the line-end protection position P1 The calculation formula is as follows: ; Select the relevant parameters of the MMC converter station and the current-limiting reactor, and based on the above formula, the reflection coefficient... The calculation formula, combined with the fault distance With traveling wave transient frequency The relationship can be used to calculate the fault distance during this stage when the converter is operating in uncontrolled rectification mode. With traveling wave transient frequency The relation (k=0) is as follows Figure 7 As shown. It can be seen that the relationship curve between fault distance and natural frequency has no abrupt change point at this time. Therefore, after the converter enters the uncontrolled rectification state, there is no resonant frequency of the inductor and capacitor in the bypass of the capacitor elements in the converter. This embodiment takes an actual fault distance of 300km as an example. Figure 7 The curve showing the relationship between fault distance and natural frequency corresponds to a main natural frequency of 313.45Hz. It can be seen that the main natural frequency is relatively large and the available data window is long enough to improve the accuracy of frequency measurement by the frequency measurement algorithm.

[0031] Further, the step of performing frequency measurement processing on the noise-added signals corresponding to each random noise to obtain a set of peak frequencies includes: obtaining a MUSIC spectrum set based on the noise-added signals corresponding to each random noise using the MUSIC algorithm; and extracting frequencies based on the MUSIC spectrum set to obtain a set of peak frequencies.

[0032] Further, the step of performing clustering processing based on the set of peak frequencies to obtain an intrinsic frequency set includes: performing clustering processing based on the set of peak frequencies to obtain multiple frequency groups; and calculating the mean of the multiple frequency groups to obtain the intrinsic frequency set.

[0033] In the above embodiments, the set of peak frequencies is obtained from the noise-added signals corresponding to each random noise. Therefore, the frequencies corresponding to the false peaks will exhibit more dispersed and random characteristics, while the frequencies corresponding to the true signal peaks will exhibit more clustered and stable characteristics. This embodiment performs clustering based on this set of peak frequencies, which can more accurately extract the frequencies corresponding to the relatively clustered true signal peaks, while the frequencies corresponding to the false peaks of the noise signals with greater randomness will be excluded. Therefore, this embodiment can eliminate the interference of false peaks generated by frequency measurement when the number of frequencies is unknown, improve the accuracy of each inherent frequency in the inherent frequency set, and thus improve the accuracy of fault location results.

[0034] The DBSCAN clustering algorithm is used as the preferred method for clustering.

[0035] Further, obtaining the fault distance based on the inherent frequency set under a preset distance calculation strategy includes: obtaining an inherent primary frequency and a second inherent frequency based on the inherent frequency set under a preset frequency selection strategy; performing calculation processing based on the inherent primary frequency to obtain a first fault distance; performing calculation processing based on the second inherent frequency to obtain a second fault distance; and performing average calculation based on the first fault distance and the second fault distance to obtain the fault distance.

[0036] Furthermore, obtaining the intrinsic primary frequency and the second intrinsic frequency based on the intrinsic frequency set under a preset frequency selection strategy includes: taking the minimum value in the intrinsic frequency set as the intrinsic primary frequency; and taking the second minimum value in the intrinsic frequency set as the second intrinsic frequency.

[0037] Further, the calculation based on the inherent main frequency to obtain the first fault distance includes: obtaining the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity; and performing calculation based on the inherent main frequency, the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity to obtain the first fault distance.

[0038] It should be noted that the specific formula for calculating the first fault distance is as follows: ; in, For the inherent main frequency, The first fault distance, The phase angle is the converter reflection coefficient. The phase angle is the reflection coefficient at the fault point. This represents the propagation speed of the traveling wave.

[0039] Further, the calculation based on the second natural frequency to obtain the second fault distance includes: obtaining the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity; and performing calculation based on the second natural frequency, the phase angle of the converter reflection coefficient, the phase angle of the fault point reflection coefficient, and the traveling wave propagation velocity to obtain the second fault distance.

[0040] It should be noted that the specific formula for calculating the second fault distance is as follows: ; in, The second natural frequency, This is the second fault distance.

[0041] In the above embodiments, if the actual fault distance is far, its corresponding natural main frequency will also be relatively low. In this case, even a small frequency measurement error in the frequency measurement process can lead to a significant fault location error. Therefore, if only the natural main frequency is used for distance measurement, there may be a large distance measurement error. Thus, this embodiment introduces a second natural frequency with a higher frequency for distance measurement based on the natural main frequency to reduce the impact of frequency measurement error on the fault distance. This results in a more accurate fault distance and improves the accuracy of the fault location results.

[0042] Please see Figure 8 This embodiment also provides a flexible DC transmission line fault location system, comprising: a signal decoupling module for acquiring line voltage time-series data and decoupling it based on the line voltage time-series data to obtain an original line-mode signal; a multiple noise addition module for adding random noise of different intensities multiple times to the original line-mode signal obtained by the signal decoupling module to obtain a set of noise-added signals; wherein the set of random noise contains multiple random noises of different intensities; a frequency measurement module for performing frequency measurement processing on the set of noise-added signals corresponding to each random noise obtained by the multiple noise addition module to obtain a set of peak frequencies; a clustering module for performing clustering processing on the set of peak frequencies obtained by the frequency measurement module to obtain a set of inherent frequencies; and a fault distance calculation module for obtaining the fault distance based on the set of inherent frequencies obtained by the clustering module under a preset distance calculation strategy.

[0043] Furthermore, before the signal decoupling module acquires line voltage timing data and decouples based on the line voltage timing data to obtain the original line-mode signal, it also includes a converter state transition module, which acquires the fault state. If the fault state is a permanent fault, a converter state transition signal is generated. The converter state transition signal is used to control the converter of the flexible DC transmission line to enter the uncontrolled rectification state.

[0044] The above embodiments can more accurately eliminate frequencies corresponding to false spectral peaks during clustering, reducing the interference of false spectral peaks on the frequency measurement process, improving the accuracy of the obtained intrinsic frequency set, and thus improving the accuracy of fault location results. Furthermore, after determining that a permanent fault exists in the flexible DC transmission line, the above embodiments control the converter to enter an uncontrolled rectification state, which can increase the intrinsic main frequency of the line voltage signal, improve the reliability of the intrinsic main frequency value extracted by the frequency measurement algorithm, and provide a sufficiently long data window for fault location, thereby improving the accuracy of fault location results.

[0045] This embodiment also provides a computer-readable storage medium, which includes a stored computer program, wherein the computer program, when running, controls the device where the computer-readable storage medium is located to perform the flexible DC transmission line fault location method as described above.

[0046] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method of fault location for a flexible DC power transmission line, characterized in that, The method comprises the following steps: obtaining line voltage time series data and decoupling based on the line voltage time series data to obtain an original line mode signal; based on the original line mode signal, performing perturbation processing under a random noise set to obtain a noise-added signal corresponding to each random noise in the random noise set; wherein the random noise set contains random noises of different intensities; based on the noise-added signal corresponding to each random noise, performing frequency measurement processing to obtain a frequency spectrum peak frequency set; based on the frequency spectrum peak frequency set, performing clustering processing to obtain an inherent frequency set; based on the inherent frequency set, obtaining a fault distance under a preset distance calculation strategy.

2. A method of fault location for a flexible DC power transmission line according to claim 1, characterized in that, Before the step of obtaining line voltage time series data and decoupling based on the line voltage time series data to obtain an original line mode signal, the method further comprises: obtaining a fault state, and if the fault state is a permanent fault, generating a converter state transition signal; the converter state transition signal is used to control the converter of the flexible DC transmission line to enter the uncontrolled rectification state.

3. A method of fault location for a flexible DC power transmission line according to claim 1, characterized in that, The step of based on the noise-added signal corresponding to each random noise, performing frequency measurement processing to obtain a frequency spectrum peak frequency set, comprises: based on the noise-added signal corresponding to each random noise, obtaining a MUSIC spectrum set under the MUSIC algorithm; based on the MUSIC spectrum set, performing frequency extraction to obtain a frequency spectrum peak frequency set.

4. The method of claim 1, wherein, The step of based on the frequency spectrum peak frequency set, performing clustering processing to obtain an inherent frequency set, comprises: based on the frequency spectrum peak frequency set, performing clustering processing to obtain multiple frequency groupings; based on the multiple frequency groupings, performing mean value calculation to obtain an inherent frequency set.

5. A method of fault location for a flexible DC power transmission line according to claim 1, characterized in that, The step of based on the inherent frequency set, obtaining a fault distance under a preset distance calculation strategy, comprises: based on the inherent frequency set, obtaining an inherent main frequency and a second inherent frequency under a preset frequency selection strategy; based on the inherent main frequency, performing calculation processing to obtain a first fault distance; based on the second inherent frequency, performing calculation processing to obtain a second fault distance; based on the first fault distance and the second fault distance, performing mean value calculation to obtain a fault distance.

6. A method of fault location for a flexible DC power transmission line according to claim 5, characterised in that, The step of based on the inherent frequency set, obtaining an inherent main frequency and a second inherent frequency under a preset frequency selection strategy, comprises: taking the minimum value in the inherent frequency set as the inherent main frequency; taking the second minimum value in the inherent frequency set as the second inherent frequency.

7. A method of fault location for a flexible DC power transmission line according to claim 5, characterised in that, The step of based on the inherent main frequency, performing calculation processing to obtain a first fault distance, comprises: obtaining a converter reflection coefficient phase angle, a fault point reflection coefficient phase angle, and a traveling wave propagation speed; based on the inherent main frequency, the converter reflection coefficient phase angle, the fault point reflection coefficient phase angle, and the traveling wave propagation speed, performing calculation processing to obtain a first fault distance.

8. A method of fault location for a flexible DC power transmission line according to claim 5, characterized in that, The step of based on the second inherent frequency, performing calculation processing to obtain a second fault distance, comprises: obtaining a converter reflection coefficient phase angle, a fault point reflection coefficient phase angle, and a traveling wave propagation speed; based on the second inherent frequency, the converter reflection coefficient phase angle, the fault point reflection coefficient phase angle, and the traveling wave propagation speed, performing calculation processing to obtain a second fault distance.

9. A flexible HVDC power line fault location system characterized by, A method for implementing a flexible DC transmission line fault location method according to any one of claims 1-8, comprising: a signal decoupling module for obtaining line voltage time series data and decoupling based on the line voltage time series data to obtain original line mode signals; a multiple noise adding module for adding random noise of different intensities multiple times based on the original line mode signals obtained by the signal decoupling module to obtain a set of noise-added signals; wherein the set of random noise contains random noise of multiple different intensities; a frequency measurement module for performing frequency measurement processing based on the set of noise-added signals corresponding to each random noise obtained by the multiple noise adding module to obtain a set of spectral peak frequencies; a clustering module for performing clustering processing based on the set of spectral peak frequencies obtained by the frequency measurement module to obtain a set of natural frequencies; a fault distance calculation module for obtaining a fault distance under a preset distance calculation strategy based on the set of natural frequencies obtained by the clustering module.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium comprises a stored computer program, wherein the computer readable storage medium controls the device where the computer readable storage medium is located to execute a flexible DC transmission line fault location method according to any one of claims 1-8 when the computer program runs.

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