CN113589101A - Fault location method and system suitable for direct-current power transmission system - Google Patents
Fault location method and system suitable for direct-current power transmission system Download PDFInfo
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Abstract
The invention relates to a fault location method and a fault location system suitable for a direct current power transmission system. The method comprises extracting fault traveling waves of the electric signals; determining the abrupt change directions of current traveling waves at the rectifying side and the inverting side at the moment of the fault according to the electric signal fault traveling waves; judging whether the fault is an intra-area fault or an extra-area fault according to the mutation direction; when the fault is an intra-zone fault. Carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located; performing linear frequency modulation Z conversion on the frequency spectrum region where the inherent frequency principal component of the electric signal fault traveling wave is located to determine the inherent frequency principal component; establishing a corresponding relation between the fault distance of the direct current transmission system and the inherent frequency principal component; and determining the fault distance according to the corresponding relation and the natural frequency principal component. The invention can improve the fault location precision and speed of the direct current transmission system, avoid line outage caused by fault expansion and improve the power supply reliability.
Description
Technical Field
The invention relates to the field of fault location of high-voltage direct-current transmission lines, in particular to a fault location method and system suitable for a direct-current transmission system.
Background
The phenomenon of 'load source separation' exists in Chinese electric energy, eighty percent of energy is occupied by west and north parts, and seventy percent of electric load is occupied by middle and east China. The trans-regional trans-provincial power transmission capacity is expected to reach 3.6 hundred million kilowatts in 2025, and is expected to reach 6 hundred million kilowatts in 2035. The high-voltage direct-current transmission project plays an important role in cross-regional transmission projects in China, in 2018, the transmission capacity reaches 500 ten thousand kilowatts, an important channel for developing and delivering hydropower in the southwest is used for connecting a Yu Hubei back-to-back flexible direct-current networking project of a Chongqing power grid and a Chinese power grid, and the project is the first +/-420 kV flexible direct-current transmission voltage level project in the world. In 2019, the first offshore wind power in China is sent out through flexible direct current, namely the flexible direct current project of the offshore wind power in Jiangsu east-she Yang is started. In 2020, the first flexible direct-current power grid in the world, namely the north-expanding flexible direct-current power grid test demonstration project, completes the engineering construction, is erected in the whole line and is put into operation. The high-voltage direct-current transmission line passes through mountainous areas, rivers, Gobi and sea areas and is in severe climate environment, the direct-current transmission line is a component which is easy to break down in a direct-current system, and the fault types include a single-pole grounding fault and a double-pole grounding fault, wherein the single-pole fault is the highest frequency, so how to quickly measure and calculate the fault position at a far end, eliminate the fault and ensure the power supply reliability are particularly important.
In the prior art, a wave method mainly depends on a measuring point to capture the arrival time difference delta t of the fault traveling wave and combines the propagation velocity v to locate the fault distance, but the method is not easy to capture the traveling wave head and has large measurement error.
In summary, how to improve the accuracy and speed of fault location of the dc power transmission system is an urgent problem to be solved in the field.
Disclosure of Invention
The invention aims to provide a fault location method and a fault location system suitable for a direct current transmission system, which can improve the fault location precision and speed of the direct current transmission system, avoid line outage caused by fault expansion and improve power supply reliability.
In order to achieve the purpose, the invention provides the following scheme:
a fault location method suitable for a direct current transmission system comprises the following steps:
extracting fault traveling waves of the electric signals;
determining the abrupt change directions of current traveling waves at the rectifying side and the inverting side at the moment of the fault according to the electric signal fault traveling waves;
judging whether the fault is an intra-area fault or an extra-area fault according to the mutation direction; the fault in the area is a fault of a direct current line with a converter station as a boundary; the out-of-area fault is a fault of an alternating current line with a converter station as a boundary;
if the mutation directions are the same, the fault is an out-of-area fault;
if the mutation directions are different, the fault is an intra-area fault; performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
performing linear frequency modulation Z conversion on the frequency spectrum region where the inherent frequency principal component of the electric signal fault traveling wave is located to determine the inherent frequency principal component;
establishing a corresponding relation between the fault distance of the direct current transmission system and the inherent frequency principal component;
and determining the fault distance according to the corresponding relation and the natural frequency principal component.
Optionally, if the abrupt change directions are different, the fault is an intra-area fault; and carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which the inherent frequency principal component of the electric signal fault traveling wave is located, wherein the method specifically comprises the following steps:
judging whether the direct current transmission system is a single-pole transmission line or a double-pole transmission line;
if the direct-current power transmission system is a single-pole power transmission line, performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
if the direct current transmission system is a bipolar transmission line, performing modulus decoupling on the electric signal fault traveling wave;
and carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave after the modulus decoupling, and determining a frequency spectrum interval where the inherent frequency principal component of the electric signal fault traveling wave is located.
Optionally, if the direct-current power transmission system is a bipolar power transmission line, performing modulus decoupling on the electric signal fault traveling wave, specifically including:
determining a Karenbauer modulus transformation matrix of the direct-current transmission system based on Karenbauer transformation;
solving the Karenbauer modulus transformation matrix;
and performing modulus decomposition on the electric signal fault traveling wave by using the solved Karenbauer modulus transformation matrix.
Optionally, the establishing a corresponding relationship between a fault distance of the direct current transmission system and a principal component of a natural frequency specifically includes:
using formulas
And
determining a fault distance from a rectifying side;
where w is 2 pi f, f is a main component of the natural frequency, and θ1For rectifying side fault travelling wave reflection angle, theta2A fault traveling wave reflection angle of a fault point, v a traveling wave speed at a corresponding frequency, Re an achievement part, d1To the fault distance from the rectifying side, S1Is the Laplace transform of the reflection coefficient at the rectification side; s2Is the laplace transform of the reflection coefficient at the fault point.
Optionally, the determining the fault distance according to the correspondence and the natural frequency principal component specifically includes:
using the formula d2＝D-d1Determining a fault distance from an inversion side; wherein d is2D is the distance between the rectification side and the inversion side;
judging the fault distance from the rectifying side and the fault distance from the inverting side;
if the fault distance from the rectification side is smaller than the fault distance from the inversion side, the fault distance from the rectification side is the fault distance;
and if the fault distance from the rectification side is greater than the fault distance from the inversion side, the fault distance from the inversion side is the fault distance.
A fault location system adapted for use in a dc power transmission system, comprising:
the electric signal fault traveling wave extraction module is used for extracting electric signal fault traveling waves;
the sudden change direction determining module is used for determining the sudden change directions of the current traveling waves at the rectifying side and the inverting side at the moment of the fault according to the electric signal fault traveling waves;
the first judgment module is used for judging whether the fault is an intra-area fault or an extra-area fault according to the mutation direction; the fault in the area is a fault of a direct current line with a converter station as a boundary; the out-of-area fault is a fault of an alternating current line with a converter station as a boundary;
the outside fault determining module is used for determining that the fault is an outside fault if the mutation directions are the same;
a spectrum interval determining module, configured to determine that the fault is an intra-area fault if the abrupt change directions are different; performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
the inherent frequency principal component determining module is used for carrying out linear frequency modulation Z conversion on the frequency spectrum region where the inherent frequency principal component of the electric signal fault traveling wave is located to determine the inherent frequency principal component;
the corresponding relation establishing module is used for establishing the corresponding relation between the fault distance of the direct current power transmission system and the inherent frequency principal component;
and the fault distance determining module is used for determining the fault distance according to the corresponding relation and the inherent frequency principal component.
Optionally, the spectrum interval determining module specifically includes:
the first judging unit is used for judging whether the direct-current power transmission system is a single-pole power transmission line or a double-pole power transmission line;
a frequency spectrum interval first determining unit, configured to perform fast fourier spectrum analysis on the electrical signal fault traveling wave if the direct-current power transmission system is a single-pole power transmission line, and determine a frequency spectrum interval in which a principal component of a natural frequency of the electrical signal fault traveling wave is located;
the modulus decoupling unit is used for performing modulus decoupling on the electric signal fault traveling wave if the direct current transmission system is a bipolar transmission line;
and the frequency spectrum interval second determining unit is used for carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave after modulus decoupling and determining the frequency spectrum interval where the inherent frequency principal component of the electric signal fault traveling wave is located.
Optionally, the modulus decoupling unit specifically includes:
the Karenbauer modulus transformation matrix determining subunit is used for determining a Karenbauer modulus transformation matrix of the direct-current transmission system based on Karenbauer transformation;
the modulus transformation matrix solving subunit is used for solving the Karenbauer modulus transformation matrix;
and the modulus decomposition subunit is used for performing modulus decomposition on the electric signal fault travelling wave by using the solved Karenbauer modulus transformation matrix.
Optionally, the correspondence relationship establishing module specifically includes:
a fault distance determination module from rectifying side for using formula
And
determining a fault distance from a rectifying side;
where w is 2 pi f, f is a main component of the natural frequency, and θ1For rectifying side fault travelling wave reflection angle, theta2A fault traveling wave reflection angle of a fault point, v a traveling wave speed at a corresponding frequency, Re an achievement part, d1To the fault distance from the rectifying side, S1Is the Laplace transform of the reflection coefficient at the rectification side; s2Is the laplace transform of the reflection coefficient at the fault point.
Optionally, the fault distance determining module specifically includes:
a fault distance determination unit from the inversion side for using the formula d2＝D-d1Determining a fault distance from an inversion side; wherein d is2D is the distance between the rectification side and the inversion side;
the second judgment unit is used for judging the fault distance from the rectifying side and the fault distance from the inverting side;
the first fault distance determining unit is used for determining the fault distance from the rectifying side to be the fault distance if the fault distance from the rectifying side is smaller than the fault distance from the inverting side;
and the fault distance second determining unit is used for determining the fault distance from the inverter side as the fault distance if the fault distance from the rectifier side is greater than the fault distance from the inverter side.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the fault location method and the fault location system suitable for the direct current transmission system provided by the invention have the advantages that the fault traveling wave natural frequency principal component frequency spectrum interval is located based on fast Fourier spectrum analysis, the interval frequency spectrum is subjected to spiral line sampling through linear frequency modulation Z conversion to obtain high-resolution and refined frequency spectrum information, further the natural frequency principal component is accurately extracted, and the traveling wave natural frequency direct current transmission single-end fault location method based on fast Fourier and linear frequency modulation Z conversion is established by utilizing the corresponding relation between the fault distance and the natural frequency principal component. Compared with the traditional fault traveling wave natural frequency ranging method, the method avoids the defects of large calculation amount, high requirement on hardware equipment, inconvenience for field engineering application and the like caused by complex algorithm. The method applies fast Fourier spectrum analysis and linear frequency modulation Z transformation to fault location of the direct current power transmission system, and has the advantages of simple procedure, small calculated amount, high calculation speed, high precision, higher sensitivity to transient resistance grounding faults and the like. The method can improve the fault location precision and speed of the direct-current power transmission system, avoid line outage caused by fault enlargement, and improve the power supply reliability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a schematic flow chart of a fault location method for a dc power transmission system according to the present invention;
fig. 2 is a schematic overall flow chart of a fault location method for a dc power transmission system according to the present invention;
FIG. 3 is a schematic diagram of a fault voltage traveling wave;
FIG. 4 is a diagram of a spectral analysis of a fast Fourier transform algorithm;
FIG. 5 is a graph of a spectral analysis of a chirp Z transform;
fig. 6 is a schematic structural diagram of a fault location system suitable for a dc power transmission system according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a fault location method and a fault location system suitable for a direct current transmission system, which can improve the fault location precision and speed of the direct current transmission system, avoid line outage caused by fault expansion and improve power supply reliability.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic flow chart of a fault location method applicable to a dc power transmission system according to the present invention, fig. 2 is a schematic flow chart of an entire fault location method applicable to a dc power transmission system according to the present invention, and as shown in fig. 1 and fig. 2, a fault location method applicable to a dc power transmission system according to the present invention includes:
s101, extracting electric signal fault traveling waves;
secondary relay protection device can be installed with the contravariant station at the construction process in current conversion station, draws the signal of telecommunication trouble travelling wave after the trouble takes place through detecting element such as mutual-inductor in the secondary relay protection device, and signal of telecommunication trouble travelling wave includes: fault voltage traveling waves or fault current traveling waves; fig. 3 shows a fault voltage traveling wave.
S102, determining the abrupt change directions of current traveling waves at the rectifying side and the inverting side at the moment of the fault according to the electric signal fault traveling waves;
s103, judging whether the fault is an intra-area fault or an extra-area fault according to the mutation direction; the fault in the area is a fault of a direct current line with a converter station as a boundary; the out-of-area fault is a fault of an alternating current line with a converter station as a boundary;
s104, if the mutation directions are the same, the fault is an out-of-area fault;
s105, if the mutation directions are different, the fault is an intra-area fault; performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
the Fast Fourier Transform (FFT) algorithm is the simplest algorithm for converting a time domain featureless signal into a frequency domain characteristic signal;
analyzing the obtained continuous spectrum, taking the corresponding frequency of the harmonic with low frequency and maximum amplitude as the natural frequency, and obtaining the main component interval (f) of the natural frequency according to the requirement1，f2) And as shown in fig. 4.
S105 specifically comprises the following steps:
judging whether the direct current transmission system is a single-pole transmission line or a double-pole transmission line; namely, one transmission line is a monopole, and two transmission lines are dipoles.
If the direct-current power transmission system is a single-pole power transmission line, performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
if the direct current transmission system is a bipolar transmission line, performing modulus decoupling on the electric signal fault traveling wave;
and carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave after the modulus decoupling, and determining a frequency spectrum interval where the inherent frequency principal component of the electric signal fault traveling wave is located.
If the direct-current power transmission system is a bipolar power transmission line, performing modulus decoupling on the electric signal fault traveling wave, specifically comprising:
determining a Karenbauer modulus transformation matrix of the direct-current transmission system based on Karenbauer transformation;
the direct-current transmission cable is equivalent to a uniform power line, a parameter matrix of the uniform power line is a balance matrix, a bipolar electric signal is based on a second-order parameter matrix, and a Karenbauer modulus transformation matrix is as follows:
wherein p issIs a self-inductance coefficient matrix; p is a radical ofmIs a mutual inductance coefficient matrix;
solving the Karenbauer modulus transformation matrix;
solving the eigenvalues λ of the matrix p1、λ2：
Correspondence solving eigenvectors x1、x2：
Solving to obtain:
x1＝-x2；
order to
Solving to obtain a modulus transformation matrix S;
and performing modulus decomposition on the electric signal fault traveling wave by using the solved Karenbauer modulus transformation matrix.
As shown in fig. 3, the voltage transient signal is taken as the simulation signal, i.e. the modulus decomposition formula is as follows:
wherein the content of the first and second substances,
a voltage fault recording matrix; kmIs a decoupled voltage matrix.
Wherein, KmFor the decoupled voltage matrix to
U+And time t form a continuous time domain decoupling signal x (t).
S106, performing linear frequency modulation Z conversion on the frequency spectrum region where the natural frequency principal component of the electric signal fault traveling wave is located to determine the natural frequency principal component;
as shown in fig. 5, the FFT is used to obtain the spectrum diagram of the whole transient electrical signal, and the band interval of the principal component of the natural frequency is initially located, and since only the band where the principal component of the natural frequency is located needs to be analyzed, the samples of the spectrum are expected to be concentrated in this band, so as to obtain a higher resolution. The Chirp-Z transformation is a frequency spectrum refining method which utilizes spiral line sampling and fast FFT calculation, and the principal component of the natural frequency of the fault traveling wave is accurately positioned after the Z transformation. The CZT conversion process is as follows:
natural frequency principal component region (f)1，f2) And performing Z transformation on the acquired time sequence x (n), and after the Z transformation is completed, analyzing a transformation result to acquire the abscissa of the maximum value so as to acquire the natural frequency f.
x(n)＝xa(nT)；
Wherein n is the number of sampling points, and T is the length of a time domain truncation window;
the value of Z adopts a formula:
wherein M is the number of points of the complex frequency spectrum; a and W are arbitrary complex numbers, and the positions of the starting points and the spiral trend are respectively related.
S107, establishing a corresponding relation between the fault distance of the direct current transmission system and the inherent frequency principal component;
s107 specifically comprises the following steps:
using formulas
And
determining a fault distance from a rectifying side;
where w is 2 pi f, f is a main component of the natural frequency, and θ1For rectifying side fault travelling wave reflection angle, theta2A fault traveling wave reflection angle of a fault point, v a traveling wave speed at a corresponding frequency, Re an achievement part, d1To the fault distance from the rectifying side, S1Is the Laplace transform of the reflection coefficient at the rectification side; s2Is the laplace transform of the reflection coefficient at the fault point.
Wherein the content of the first and second substances,
Z1is the system equivalent impedance, Ω; z1Characteristic impedance, omega, of the direct current transmission line; r is grounding resistance and omega; u is a system equivalent power supply, MW; u shapefIs an equivalent fault voltage source, MW.
Wherein, mu0Is a vacuum magnetic conductivity; mu.srThe air medium is the relative magnetic conductivity of the cable line; epsilonoIs a vacuum dielectric constant; epsilonrIs the relative dielectric constant. v is the travelling wave velocity at the corresponding frequency.
And S108, determining the fault distance according to the corresponding relation and the natural frequency principal component.
S108, specifically comprising:
using the formula d2＝D-d1Determining a fault distance from an inversion side; wherein d is2D is the distance between the rectification side and the inversion side;
judging the fault distance from the rectifying side and the fault distance from the inverting side;
if the fault distance from the rectification side is smaller than the fault distance from the inversion side, the fault distance from the rectification side is the fault distance;
and if the fault distance from the rectification side is greater than the fault distance from the inversion side, the fault distance from the inversion side is the fault distance.
That is, d is min (d)1，d2) If d is1＝d2When d is equal to d1＝d2. When d is1＜d2D is output1The fault d is a distance rectification side; when d is1＞d2D is output2The fault d is the distance inversion side.
Fig. 6 is a schematic structural diagram of a fault location system suitable for a dc power transmission system, and as shown in fig. 6, the fault location system suitable for a dc power transmission system provided by the present invention includes:
an electrical signal fault traveling wave extraction module 601, configured to extract an electrical signal fault traveling wave;
a sudden change direction determining module 602, configured to determine, according to the electrical signal fault traveling wave, a sudden change direction of the current traveling wave on the rectifying side and the inverting side at the moment of the fault occurrence;
a first judging module 603, configured to judge, according to the abrupt change direction, whether the fault is an intra-area fault or an extra-area fault; the fault in the area is a fault of a direct current line with a converter station as a boundary; the out-of-area fault is a fault of an alternating current line with a converter station as a boundary;
an outside-area fault determining module 604, configured to determine that the fault is an outside-area fault if the abrupt change directions are the same;
a spectrum interval determining module 605, configured to determine that the fault is an intra-area fault if the abrupt change directions are different; performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
a natural frequency principal component determining module 606, configured to perform chirp Z transform on a spectrum region where a natural frequency principal component of the electrical signal fault traveling wave is located to determine a natural frequency principal component;
a correspondence establishing module 607 for establishing a correspondence between a fault distance of the dc power transmission system and a principal component of the natural frequency;
and a fault distance determining module 608, configured to determine a fault distance according to the correspondence and the natural frequency principal component.
The spectrum interval determining module 605 specifically includes:
the first judging unit is used for judging whether the direct-current power transmission system is a single-pole power transmission line or a double-pole power transmission line;
a frequency spectrum interval first determining unit, configured to perform fast fourier spectrum analysis on the electrical signal fault traveling wave if the direct-current power transmission system is a single-pole power transmission line, and determine a frequency spectrum interval in which a principal component of a natural frequency of the electrical signal fault traveling wave is located;
the modulus decoupling unit is used for performing modulus decoupling on the electric signal fault traveling wave if the direct current transmission system is a bipolar transmission line;
and the frequency spectrum interval second determining unit is used for carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave after modulus decoupling and determining the frequency spectrum interval where the inherent frequency principal component of the electric signal fault traveling wave is located.
The modulus decoupling unit specifically comprises:
the Karenbauer modulus transformation matrix determining subunit is used for determining a Karenbauer modulus transformation matrix of the direct-current transmission system based on Karenbauer transformation;
the modulus transformation matrix solving subunit is used for solving the Karenbauer modulus transformation matrix;
and the modulus decomposition subunit is used for performing modulus decomposition on the electric signal fault travelling wave by using the solved Karenbauer modulus transformation matrix.
The correspondence establishing module 607 specifically includes:
a fault distance determination module from rectifying side for using formula
And
determining a fault distance from a rectifying side;
where w is 2 pi f, f is a main component of the natural frequency, and θ1For rectifying side fault travelling wave reflection angle, theta2A fault traveling wave reflection angle of a fault point, v a traveling wave speed at a corresponding frequency, Re an achievement part, d1To the fault distance from the rectifying side, S1Is the Laplace transform of the reflection coefficient at the rectification side; s2Is the laplace transform of the reflection coefficient at the fault point.
The fault distance determination module 608 specifically includes:
a fault distance determination unit from the inversion side for using the formula d2＝D-d1Determining a fault distance from an inversion side; wherein d is2D is the distance between the rectification side and the inversion side;
the second judgment unit is used for judging the fault distance from the rectifying side and the fault distance from the inverting side;
the first fault distance determining unit is used for determining the fault distance from the rectifying side to be the fault distance if the fault distance from the rectifying side is smaller than the fault distance from the inverting side;
and the fault distance second determining unit is used for determining the fault distance from the inverter side as the fault distance if the fault distance from the rectifier side is greater than the fault distance from the inverter side.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. A fault location method suitable for a direct current transmission system is characterized by comprising the following steps:
extracting fault traveling waves of the electric signals;
determining the abrupt change directions of current traveling waves at the rectifying side and the inverting side at the moment of the fault according to the electric signal fault traveling waves;
judging whether the fault is an intra-area fault or an extra-area fault according to the mutation direction; the fault in the area is a fault of a direct current line with a converter station as a boundary; the out-of-area fault is a fault of an alternating current line with a converter station as a boundary;
if the mutation directions are the same, the fault is an out-of-area fault;
if the mutation directions are different, the fault is an intra-area fault; performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
performing linear frequency modulation Z conversion on the frequency spectrum region where the inherent frequency principal component of the electric signal fault traveling wave is located to determine the inherent frequency principal component;
establishing a corresponding relation between the fault distance of the direct current transmission system and the inherent frequency principal component;
and determining the fault distance according to the corresponding relation and the natural frequency principal component.
2. The method according to claim 1, wherein if the abrupt change directions are different, the fault is an intra-area fault; and carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which the inherent frequency principal component of the electric signal fault traveling wave is located, wherein the method specifically comprises the following steps:
judging whether the direct current transmission system is a single-pole transmission line or a double-pole transmission line;
if the direct-current power transmission system is a single-pole power transmission line, performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
if the direct current transmission system is a bipolar transmission line, performing modulus decoupling on the electric signal fault traveling wave;
and carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave after the modulus decoupling, and determining a frequency spectrum interval where the inherent frequency principal component of the electric signal fault traveling wave is located.
3. The method according to claim 2, wherein if the dc power transmission system is a bipolar power transmission line, the performing the modulus decoupling on the electrical signal fault traveling wave specifically comprises:
determining a Karenbauer modulus transformation matrix of the direct-current transmission system based on Karenbauer transformation;
solving the Karenbauer modulus transformation matrix;
and performing modulus decomposition on the electric signal fault traveling wave by using the solved Karenbauer modulus transformation matrix.
4. The method according to claim 1, wherein the establishing of the correspondence between the fault distance of the dc power transmission system and the principal component of the natural frequency specifically comprises:
using formulas
And
determining a fault distance from a rectifying side;
where w is 2 pi f, f is a main component of the natural frequency, and θ1For rectifying side fault travelling wave reflection angle, theta2A fault traveling wave reflection angle of a fault point, v a traveling wave speed at a corresponding frequency, Re an achievement part, d1To the fault distance from the rectifying side, S1Is the Laplace transform of the reflection coefficient at the rectification side; s2Is the laplace transform of the reflection coefficient at the fault point.
5. The method according to claim 1, wherein the determining the fault distance according to the correspondence and the principal component of the natural frequency specifically comprises:
using the formula d2＝D-d1Determining the distance to fault on the inverter side(ii) a Wherein d is2D is the distance between the rectification side and the inversion side;
judging the fault distance from the rectifying side and the fault distance from the inverting side;
if the fault distance from the rectification side is smaller than the fault distance from the inversion side, the fault distance from the rectification side is the fault distance;
and if the fault distance from the rectification side is greater than the fault distance from the inversion side, the fault distance from the inversion side is the fault distance.
6. A fault location system suitable for a direct current transmission system, comprising:
the electric signal fault traveling wave extraction module is used for extracting electric signal fault traveling waves;
the sudden change direction determining module is used for determining the sudden change directions of the current traveling waves at the rectifying side and the inverting side at the moment of the fault according to the electric signal fault traveling waves;
the first judgment module is used for judging whether the fault is an intra-area fault or an extra-area fault according to the mutation direction; the fault in the area is a fault of a direct current line with a converter station as a boundary; the out-of-area fault is a fault of an alternating current line with a converter station as a boundary;
the outside fault determining module is used for determining that the fault is an outside fault if the mutation directions are the same;
a spectrum interval determining module, configured to determine that the fault is an intra-area fault if the abrupt change directions are different; performing fast Fourier spectrum analysis on the electric signal fault traveling wave, and determining a frequency spectrum interval in which a main component of the natural frequency of the electric signal fault traveling wave is located;
the inherent frequency principal component determining module is used for carrying out linear frequency modulation Z conversion on the frequency spectrum region where the inherent frequency principal component of the electric signal fault traveling wave is located to determine the inherent frequency principal component;
the corresponding relation establishing module is used for establishing the corresponding relation between the fault distance of the direct current power transmission system and the inherent frequency principal component;
and the fault distance determining module is used for determining the fault distance according to the corresponding relation and the inherent frequency principal component.
7. The system for fault location of a dc power transmission system according to claim 6, wherein the spectrum interval determining module specifically comprises:
the first judging unit is used for judging whether the direct-current power transmission system is a single-pole power transmission line or a double-pole power transmission line;
a frequency spectrum interval first determining unit, configured to perform fast fourier spectrum analysis on the electrical signal fault traveling wave if the direct-current power transmission system is a single-pole power transmission line, and determine a frequency spectrum interval in which a principal component of a natural frequency of the electrical signal fault traveling wave is located;
the modulus decoupling unit is used for performing modulus decoupling on the electric signal fault traveling wave if the direct current transmission system is a bipolar transmission line;
and the frequency spectrum interval second determining unit is used for carrying out fast Fourier spectrum analysis on the electric signal fault traveling wave after modulus decoupling and determining the frequency spectrum interval where the inherent frequency principal component of the electric signal fault traveling wave is located.
8. The fault location system suitable for the dc power transmission system according to claim 7, wherein the modulus decoupling unit specifically includes:
the Karenbauer modulus transformation matrix determining subunit is used for determining a Karenbauer modulus transformation matrix of the direct-current transmission system based on Karenbauer transformation;
the modulus transformation matrix solving subunit is used for solving the Karenbauer modulus transformation matrix;
and the modulus decomposition subunit is used for performing modulus decomposition on the electric signal fault travelling wave by using the solved Karenbauer modulus transformation matrix.
9. The fault location system applicable to the dc power transmission system according to claim 6, wherein the correspondence relationship establishing module specifically includes:
determining the fault distance from the rectifying sideA fixed module for utilizing a formula
And
determining a fault distance from a rectifying side;
where w is 2 pi f, f is a main component of the natural frequency, and θ1For rectifying side fault travelling wave reflection angle, theta2A fault traveling wave reflection angle of a fault point, v a traveling wave speed at a corresponding frequency, Re an achievement part, d1To the fault distance from the rectifying side, S1Is the Laplace transform of the reflection coefficient at the rectification side; s2Is the laplace transform of the reflection coefficient at the fault point.
10. The system for fault location of a dc power transmission system according to claim 6, wherein the fault distance determining module specifically comprises:
a fault distance determination unit from the inversion side for using the formula d2＝D-d1Determining a fault distance from an inversion side; wherein d is2D is the distance between the rectification side and the inversion side;
the second judgment unit is used for judging the fault distance from the rectifying side and the fault distance from the inverting side;
the first fault distance determining unit is used for determining the fault distance from the rectifying side to be the fault distance if the fault distance from the rectifying side is smaller than the fault distance from the inverting side;
and the fault distance second determining unit is used for determining the fault distance from the inverter side as the fault distance if the fault distance from the rectifier side is greater than the fault distance from the inverter side.
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