CN117129803A - DFT-based flexible ground fault positioning method and system for intelligent power distribution room - Google Patents
DFT-based flexible ground fault positioning method and system for intelligent power distribution room Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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Abstract
The invention discloses a flexible ground fault positioning method and a flexible ground fault positioning system for an intelligent power distribution room based on DFT, which relate to the technical field of power systems and comprise the following steps: detecting fault current, starting a flexible grounding device in the intelligent power distribution room, and injecting zero sequence current to a neutral point to compensate grounding current; acquiring feeder automation terminal data according to an intelligent power distribution room; and calculating a zero sequence current and zero sequence voltage difference value, and accurately positioning a fault area. The invention considers the working characteristics of the flexible grounding device in the intelligent power distribution room before and after the fault occurs, integrates the change characteristics of the zero sequence network, establishes a relational expression of the grounding resistance and the zero sequence voltage and current phase difference, is not influenced by the change of the load in the power distribution network, and reduces the fault positioning difficulty. In addition, the real-time performance of the phase calculation process is considered, the built recursive DFT model can inhibit distortion caused by harmonic components, and since a recursive algorithm is adopted and a table lookup method is adopted in the triangular operation, a solution optimization algorithm is not needed in each operation period, and the operation pressure of the embedded equipment is reduced.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a flexible ground fault positioning method and system for an intelligent power distribution room based on DFT.
Background
In recent years, with the increase of the cable line proportion in a power distribution network and the grid-connected operation of more and more power electronic power supplies, the active current component of a single-phase ground fault is obviously increased, so that a passive arc extinction device cannot effectively extinguish a ground arc, and damage is caused to power grid equipment. The flexible grounding device installed on the intelligent power distribution room side can provide zero sequence current for the system in the fault process, so that grounding arc is effectively restrained, and how to accurately position a fault area in the process is a difficult problem.
In order to locate the fault area in the case of injecting a flexible ground current, and to further provide an effective direction for the operation and maintenance personnel to troubleshoot, algorithms have been proposed. One type of method adopts a passive positioning mode, extracts key factors from fault wave recording data passively, and then carries out inversion deduction on the development process of the fault, but has higher requirements on network parameters and the accuracy degree of the wave recording data. Another type of method is to use an active positioning method, inject specific signals such as high frequency and pulse into the system through an active generating device, and then identify the fault area through the reflection characteristics of the signals. However, such methods do not take into account that the injected signal may increase the fault current to some extent, while the injected signal may cause further resonant overvoltage if it approaches the natural resonant frequency of other power electronics. Yet another class of algorithms is that faults are diagnosed by means of artificial intelligence, but artificial intelligence class algorithms have the problem of overfitting due to the often lack of a large amount of actual fault operation data. Therefore, how to consider the dynamic characteristics of the system in the flexible grounding process of the power distribution network and consider the rapidity in actual calculation, and comprehensively design a flexible grounding fault area positioning device is the key of the invention.
Disclosure of Invention
The present invention has been made in view of the above-described problems.
Therefore, the technical problems solved by the invention are as follows: how to consider the dynamic characteristics of the system in the flexible grounding process of the power distribution network and how to consider the rapidity in actual calculation.
In order to solve the technical problems, the invention provides the following technical scheme: the flexible grounding fault positioning method of the intelligent power distribution room based on DFT comprises the following steps of detecting fault current, starting a flexible grounding device in the intelligent power distribution room, and injecting zero sequence current compensation grounding current into a neutral point; acquiring feeder automation terminal data according to an intelligent power distribution room; and calculating a zero sequence current and zero sequence voltage difference value, and accurately positioning a fault area.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: the fault current detection comprises the steps of detecting zero sequence current and quick-break current, and performing reclosing operation to judge the permanent grounding fault.
The accurate fault location is to extract fundamental wave components by utilizing Fourier decomposition, and calculate the phase difference between zero sequence current and zero sequence voltage difference in real time; and establishing a fault positioning model based on recursive DFT, and positioning a fault area.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: the injection compensation current is that when permanent ground fault occurs, the intelligent power distribution room starts the flexible grounding device, zero sequence current is injected into the neutral point of the transformer, a current instruction value is calculated through the proportional resonance controller, and the expression is as follows:
wherein E is f L is the potential value of the fault phase h C is the inductance value of the arc suppression coil eq For the whole equivalent capacitance to ground of the circuit, ω is the grid angular frequency, j represents the imaginary part of the imaginary operation.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: after zero sequence current is injected, further acquiring intelligent power distribution room feeder automation terminal data, calculating a zero sequence current and zero sequence voltage difference value, and acquiring a data sequence with the expression:
wherein DeltaU 0 (i) And DeltaJ 0 (i) Representing the system zero sequence voltage difference and fault phase zero sequence current difference near the ith moment respectively.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: the method comprises the steps that after the feeder automation terminal data are acquired according to an intelligent power distribution room, a discretization data sequence is generated, and a system zero sequence voltage difference value and a fault phase zero sequence current difference value are calculated, wherein the expression is as follows:
wherein DeltaU R 、ΔU I Is the real part and imaginary part, deltaI, of the system zero sequence voltage difference vector signal R 、ΔI I Is the real and imaginary parts of the fault phase zero sequence current difference vector signal, N is the total number of data for a single sampling window, and k is the form variable in the accumulation process.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: calculating a vector signal phase angle through a system zero sequence voltage difference vector signal and a fault phase zero sequence current difference vector signal, wherein the expression is as follows:
wherein,is the phase angle of the vector signal of the zero sequence voltage difference value of the system, < >>Is the fault phase zero sequence current difference vector signal phase angle.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: and calculating a measured signal phase difference based on the signal phase angle by solving a primary arcsine function, wherein the expression is as follows:
wherein,for measuring the phase difference of the signals;
further calculating a fault grounding resistor to locate a fault occurrence place, wherein the expression is as follows:
wherein R is f C is a fault grounding resistance eq Equivalent capacitance to ground for the whole circuit.
As a preferable scheme of the flexible ground fault positioning method of the DFT-based intelligent power distribution room, the invention comprises the following steps: the device comprises a fault current detection module, a flexible grounding device module, a data acquisition module, a fault positioning module and a signal processing module;
the fault current detection module starts the flexible grounding device and performs reclosing operation when detecting fault current, and judges whether the fault current is a permanent grounding fault or not;
the flexible grounding device module is used for starting and injecting zero sequence current into a neutral point of the transformer when a permanent grounding fault occurs;
the data acquisition module is used for calculating the difference value between the zero sequence current and the zero sequence voltage and determining a fault area;
the fault locating module extracts fundamental wave components by utilizing Fourier decomposition, calculates the phase difference between zero sequence current and zero sequence voltage difference in real time, and establishes a fault locating model based on recursive DFT;
the signal processing module processes the acquired data sequence, generates a discretized data sequence, and calculates a system zero sequence voltage difference value and a fault phase zero sequence current difference value.
It is another object of the present invention to provide a flexible ground fault system for an intelligent power distribution room, which can activate a flexible ground device in the intelligent power distribution room by detecting a fault current, and inject a zero sequence current to a neutral point to compensate a ground current. According to feeder automation terminal data acquired by an intelligent power distribution room, a zero-sequence current and zero-sequence voltage difference value is calculated, a fault region is accurately positioned, a phase difference between the zero-sequence current and the zero-sequence voltage can be calculated in real time, and a fault positioning model based on recursive DFT is established, so that accurate positioning of a fault position is realized. The method solves the problem of inaccurate fault positioning caused by inaccurate fault current and voltage phase difference in the prior art.
In order to solve the technical problems, the invention provides the following technical scheme: intelligent power distribution room flexible ground fault system based on DFT includes: the device comprises a fault current detection module, a flexible grounding device module, a data acquisition module, a fault positioning module and a signal processing module.
The fault current detection module starts the flexible grounding device and carries out reclosing operation when fault current is detected, and judges whether the fault current is a permanent grounding fault or not.
The flexible grounding device module is used for starting and injecting zero sequence current into a neutral point of the transformer when a permanent grounding fault occurs.
The data acquisition module is used for calculating the difference value between the zero sequence current and the zero sequence voltage and determining a fault area.
The fault locating module extracts fundamental wave components by utilizing Fourier decomposition, calculates the phase difference between zero sequence current and zero sequence voltage difference in real time, and establishes a fault locating model based on recursive DFT.
The signal processing module processes the acquired data sequence, generates a discretized data sequence, and calculates a system zero sequence voltage difference value and a fault phase zero sequence current difference value.
A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the DFT-based intelligent power distribution room flexible ground fault localization method as described above.
A computer readable storage medium having stored thereon a computer program, characterized in that the computer program when executed by a processor implements the steps of the DFT-based intelligent power distribution room flexible ground fault localization method as described above.
The invention has the beneficial effects that: the invention fully considers the working characteristics of the flexible grounding device in the intelligent power distribution room before and after the fault occurrence, comprehensively considers the change characteristics of the zero sequence network before and after the fault occurrence, establishes the relation between the grounding resistance and the zero sequence voltage and current phase difference, is not influenced by the change of the load in the power distribution network, and reduces the difficulty of fault positioning. The built recursive DFT model can effectively inhibit distortion caused by harmonic components by considering the instantaneity and rapidity in the phase calculation process, and the calculation pressure of the embedded equipment is greatly reduced by adopting a recursive algorithm and adopting a table lookup method for triangular operation and requiring no solution optimization algorithm in each operation period and only simple addition, subtraction, multiplication and division.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
FIG. 1 is a general flow chart of a flexible ground fault locating method for a DFT-based intelligent power distribution room according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram of an exemplary architecture of a positioning and system embodiment of a flexible ground fault positioning method for a DFT-based intelligent power distribution room according to a first embodiment of the present invention;
FIG. 3 is a block diagram of a flexible ground fault determination system for a DFT-based intelligent power distribution room according to a second embodiment of the present invention;
fig. 4 is a graph of arc suppression effect in a flexible ground fault positioning method of a DFT-based intelligent power distribution room according to a third embodiment of the present invention;
fig. 5 is a schematic diagram showing the detection effect before and after a fault in the flexible ground fault positioning method for a DFT-based intelligent power distribution room according to the third embodiment of the present invention.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
While the embodiments of the present invention have been illustrated and described in detail in the drawings, the cross-sectional view of the device structure is not to scale in the general sense for ease of illustration, and the drawings are merely exemplary and should not be construed as limiting the scope of the invention. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
Also in the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper, lower, inner and outer", etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The terms "mounted, connected, and coupled" should be construed broadly in this disclosure unless otherwise specifically indicated and defined, such as: can be fixed connection, detachable connection or integral connection; it may also be a mechanical connection, an electrical connection, or a direct connection, or may be indirectly connected through an intermediate medium, or may be a communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Example 1
Referring to fig. 1 to fig. 2, for one embodiment of the present invention, there is provided a DFT-based flexible ground fault locating method for an intelligent power distribution room, which is characterized in that: detecting fault current, starting a flexible grounding device in the intelligent power distribution room, and injecting zero sequence current to a neutral point to compensate grounding current; acquiring feeder automation terminal data according to an intelligent power distribution room; and calculating a zero sequence current and zero sequence voltage difference value, and accurately positioning a fault area.
As fig. 2 shows the system architecture, the simulation system is composed of a flexible grounding device, a distribution transformer, a 10kV line and the like. The 110kV power supply of the upper power supply point is changed into 10kV from a distribution transformer for use by a power distribution network, and the flexible grounding device is connected to the neutral point of the 10kV power distribution network. In an example, assuming a ground fault in phase B, an embodiment may include the steps of:
s110, detecting fault occurrence: and the relay protection device detects zero sequence current and quick-break current respectively, performs line reclosing operation according to actual conditions, and detects permanent grounding faults when detecting fault current and reclosing failure.
S120, injecting compensation current: after the system judges the permanent grounding fault, the flexible grounding device in the intelligent power distribution room is started, and zero sequence current is injected into the neutral point of the transformer to offset the fault current, so that the fault overvoltage is avoided. The injection current control mode can adopt a proportional resonance controller, and the current instruction value can be set as I:
in E f L is the potential value of the fault phase h C is the inductance value of the arc suppression coil eq For the whole equivalent capacitance to ground of the circuit, ω is the grid angular frequency, j represents the imaginary part of the imaginary operation.
S130, accessing feeder line data: communication is established, data of the intelligent power distribution room feeder automation terminal is obtained, and data support is provided for obtaining a fault area. Firstly, calculating a zero sequence current and zero sequence voltage difference value, wherein the acquired data sequence can be as follows:
in the formula DeltaU 0 (i) And DeltaI 0 (i) Representing the system zero sequence voltage difference and fault phase zero sequence current difference near the ith moment respectively.
S140, accurately positioning a fault area: because the acquired data are discrete signals, the phase difference cannot be directly calculated, the fundamental wave component is firstly extracted by utilizing Fourier decomposition, and certain noise influence is eliminated. In one possible implementation, the obtained system zero-sequence voltage difference and fault phase zero-sequence current difference are respectively subjected to inner product with the fundamental wave signal, and harmonic components of other frequencies are eliminated. In one possible implementation, after further discrete fourier transformation, the real part Δu of the system zero sequence voltage difference and fault phase zero sequence current difference vector signal can be obtained respectively R 、ΔI R And imaginary part DeltaU I 、ΔI I ：
Where N is the total number of data for a single sampling window and k is the form variable in the accumulation process. In one possible implementation, when the value of the variable N is set, three factors including the operation speed, the response time and the calculation accuracy are comprehensively considered.
In this embodiment, after the real part and the imaginary part of the system zero sequence voltage difference value and the fault phase zero sequence current difference value vector signal are obtained respectively, the mathematical relationship of the recursive DFT model is utilized to further obtain the sine value and the cosine value of the signal, so as to further obtain the phase angle of the obtained signal:
in this embodiment, the phase difference between the zero-sequence voltage difference and the fault phase zero-sequence current difference is finally required to be obtained, so as to reduce the calculation amount and avoid the number of times of solving the inverse trigonometric function as much as possible, in one possible implementation manner, the phase differenceThe calculation mode of (a) can be as follows:
to obtain the phase differenceThen comprehensively considering the topology change of the zero sequence loop of the distribution network before and after the fault, and usingAfter the fault occurs, the impedance from the measuring point to the fault point is composed of line impedance and ground resistance, and the fault ground resistance is obtained to obtain the fault occurrence area. In one possible implementation, the final fault ground resistance may be calculated by:
after the grounding resistor is obtained, in a possible implementation manner, the grounding fault occurrence area and the grounding fault occurrence reason can be analyzed by utilizing the value of the grounding resistor, the fault area is positioned in the working state of the flexible grounding device of the intelligent power distribution room, and the direction is provided for further investigation and processing of faults.
If no fault occurs, a parameter related to impedance should be a pure imaginary number, its phase angle is 90 degrees, if a fault occurs, the real part of the index has a value, the value of the real part is the magnitude of fault resistance, now the known imaginary part is a capacitance to ground, the magnitude of fault point resistance can be reversely deduced through trigonometric calculation, after knowing the fault resistance, since the total length of the line is known, for example, the total length of the line is 10km, the resistance value of each kilometer is a fixed number, and the total resistance is 3 ohms if 0.3 ohm, if the measured data is 0.6 ohm, it means that the fault occurs approximately at a distance of 2 km.
Example 2
Referring to fig. 3, for one embodiment of the present invention, a system for a flexible ground fault locating method for a DFT-based intelligent power distribution room is provided, which is characterized in that: the device comprises a fault current detection module, a flexible grounding device module, a data acquisition module, a fault positioning module and a signal processing module.
The fault current detection module starts the flexible grounding device and performs reclosing operation when fault current is detected, and judges whether the fault current is a permanent grounding fault or not.
The flexible grounding device module is used for starting and injecting zero sequence current into a neutral point of the transformer when a permanent grounding fault occurs.
The data acquisition module is used for calculating the difference value between the zero sequence current and the zero sequence voltage and determining a fault area.
The fault locating module extracts fundamental wave components by utilizing Fourier decomposition, calculates the phase difference between zero sequence current and zero sequence voltage difference in real time, and establishes a fault locating model based on recursive DFT.
The signal processing module processes the acquired data sequence to generate a discretized data sequence, and calculates a system zero sequence voltage difference value and a fault phase zero sequence current difference value.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-only memory (ROM), a random access memory (RAM, randomAccessMemory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
Example 3
Referring to fig. 4 to 5, in order to verify the advantageous effects of the present invention, scientific demonstration is performed through economic benefit calculation and simulation experiments according to another embodiment of the present invention. The present embodiment has been conducted by the conventional method and the method of the present embodiment.
In this embodiment, fig. 4 illustrates the suppression of fault current by the flexible grounding device before and after a single-phase grounding fault occurs in the embodiment. The fault occurs in 0s, the fault phase current is larger, the data of the fault phase current is always kept near 80A, the flexible grounding device is started when the fault phase current is 0.3s, zero sequence current is injected into the neutral point, the fault grounding current is further restrained, the amplitude of the fault grounding current is limited near 2A, the occurrence of overvoltage can be further avoided, and the operation safety of the power distribution network is ensured. Fig. 5 shows the phase angle change condition before and after a single-phase earth fault occurs in the embodiment, before the fault occurs, the phase difference is always around 90 degrees, however, when the fault occurs, the recursive DFT algorithm can well capture the change process due to the change of the zero sequence network of the system, and meanwhile, compared with the traditional technology, the invention has higher calculation speed and convergence speed, thereby realizing the rapid positioning and identification of the fault region.
Table 1 data comparison table
| Method | Conventional method | The invention is that |
| Accuracy rate of | 82％ | 93％ |
| Calculation load | 75％ | 88％ |
| Response time | 45ms | 35ms |
| Anti-interference capability | 78％ | 86％ |
| System stability | Good quality | Excellent quality |
| Resource consumption | 90MB | 85MB |
When the traditional method is compared with the method, the accuracy of the method reaches 93%, and compared with 82% of the traditional method, the accuracy of the method is obviously improved, which means that the method can determine the fault position more accurately when the fault is located. Second, although the computational load of the method of the present invention increases from 75% to 88%, the response time is reduced from 45ms to 35ms, showing a faster processing speed. In addition, the anti-interference capability of the method is also improved from 78% to 86%, which shows that the method can better maintain the performance of the method in the face of external interference. In terms of system stability, the method of the present invention is rated "good" while the conventional method is "good". Finally, although the method of the present invention is more computationally complex, its resource consumption is reduced from 90MB to 85MB, further demonstrating its effectiveness.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.
Claims (10)
1. The intelligent power distribution room flexible ground fault positioning method based on DFT is characterized by comprising the following steps:
detecting fault current, starting a flexible grounding device in the intelligent power distribution room, and injecting zero sequence current to a neutral point to compensate grounding current;
acquiring feeder automation terminal data according to an intelligent power distribution room;
and calculating a zero sequence current and zero sequence voltage difference value, and accurately positioning a fault area.
2. The DFT-based intelligent power distribution room flexible ground fault localization method of claim 1, wherein: the fault current detection comprises the steps of detecting zero sequence current and quick-break current, and performing reclosing operation to judge a permanent grounding fault;
the accurate fault location is to extract fundamental wave components by utilizing Fourier decomposition, and calculate the phase difference between zero sequence current and zero sequence voltage difference in real time; and establishing a fault positioning model based on recursive DFT, and positioning a fault area.
3. The DFT-based intelligent power distribution room flexible ground fault localization method of claim 2, wherein: the injection compensation current is that when permanent ground fault occurs, the intelligent power distribution room starts the flexible grounding device, zero sequence current is injected into the neutral point of the transformer, a current instruction value is calculated through the proportional resonance controller, and the expression is as follows:
wherein E is f L is the potential value of the fault phase h C is the inductance value of the arc suppression coil eq For the whole equivalent capacitance to ground of the circuit, ω is the grid angular frequency, j represents the imaginary part of the imaginary operation.
4. The DFT-based intelligent power distribution room flexible ground fault localization method of claim 3, wherein: after zero sequence current is injected, further acquiring intelligent power distribution room feeder automation terminal data, calculating a zero sequence current and zero sequence voltage difference value, and acquiring a data sequence with the expression:
wherein DeltaU 0 (i) And DeltaJ 0 (i) Representing the system zero sequence voltage difference and fault phase zero sequence current difference near the ith moment respectively.
5. The DFT-based intelligent power distribution room flexible ground fault localization method of claim 4, wherein: the method comprises the steps that after the feeder automation terminal data are acquired according to an intelligent power distribution room, a discretization data sequence is generated, and a system zero sequence voltage difference value and a fault phase zero sequence current difference value are calculated, wherein the expression is as follows:
wherein DeltaU R 、ΔU I Is the real part and imaginary part, deltaI, of the system zero sequence voltage difference vector signal R 、ΔI I Is the real and imaginary parts of the fault phase zero sequence current difference vector signal, N is the total number of data for a single sampling window, and k is the form variable in the accumulation process.
6. The DFT-based intelligent power distribution room flexible ground fault localization method of claim 5, wherein: calculating a vector signal phase angle through a system zero sequence voltage difference vector signal and a fault phase zero sequence current difference vector signal, wherein the expression is as follows:
wherein,is the phase angle of the vector signal of the zero sequence voltage difference value of the system, < >>Is the fault phase zero sequence current difference vector signal phase angle.
7. The DFT-based intelligent power distribution room flexible ground fault localization method of claim 6, wherein: and calculating a measured signal phase difference based on the signal phase angle by solving a primary arcsine function, wherein the expression is as follows:
wherein,for measuring the phase difference of the signals;
further calculating a fault grounding resistor to locate a fault occurrence place, wherein the expression is as follows:
wherein R is f C is a fault grounding resistance eq Equivalent capacitance to ground for the whole circuit.
8. A system employing the DFT-based intelligent power distribution room flexible ground fault location method as claimed in any one of claims 1 to 7, characterized in that: the device comprises a fault current detection module, a flexible grounding device module, a data acquisition module, a fault positioning module and a signal processing module;
the fault current detection module starts the flexible grounding device and performs reclosing operation when detecting fault current, and judges whether the fault current is a permanent grounding fault or not;
the flexible grounding device module is used for starting and injecting zero sequence current into a neutral point of the transformer when a permanent grounding fault occurs;
the data acquisition module is used for calculating the difference value between the zero sequence current and the zero sequence voltage and determining a fault area;
the fault locating module extracts fundamental wave components by utilizing Fourier decomposition, calculates the phase difference between zero sequence current and zero sequence voltage difference in real time, and establishes a fault locating model based on recursive DFT;
the signal processing module processes the acquired data sequence, generates a discretized data sequence, and calculates a system zero sequence voltage difference value and a fault phase zero sequence current difference value.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the DFT-based intelligent power distribution room flexible ground fault localization method of any one of claims 1 to 7.
10. A computer readable storage medium having stored thereon a computer program, wherein the computer program when executed by a processor implements the steps of the DFT-based intelligent power distribution room flexible ground fault localization method of any one of claims 1 to 7.
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