CN117991048B - Method and system for detecting short-circuit fault of power distribution network accessed by high-proportion distributed power supply - Google Patents
Method and system for detecting short-circuit fault of power distribution network accessed by high-proportion distributed power supply Download PDFInfo
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Abstract
The invention discloses a method and a system for detecting short-circuit faults of a power distribution network accessed by a high-proportion distributed power supply, wherein the method comprises the following steps: performing fast Fourier decomposition on access point voltage and output current of a distributed power supply respectively to obtain harmonic amplitude values of the access point voltage and the output current at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law; selecting harmonic frequencies with virtual impedance to obtain a harmonic frequency set; and screening out a target harmonic frequency corresponding to the maximum virtual impedance value in the harmonic frequency set, and identifying the short-circuit fault of the power distribution network by detecting the deviation of the target harmonic frequency in the harmonic frequency set range. The detection precision of the short-circuit fault of the power distribution network can be improved.
Description
Technical Field
The invention belongs to the technical field of safe operation of power systems, and particularly relates to a method and a system for detecting short-circuit faults of a power distribution network accessed by a high-proportion distributed power supply.
Background
With the access of a high-proportion distributed power system, the operation mode of the traditional power distribution network is changed, and the fault detection of the power distribution network is greatly affected. And the fault detection method for the traditional power distribution network is not applicable to the existing network. In the conventional fault detection, steady-state signals are often used as detection features, the electrical quantities such as voltage, current and the like are obviously changed before and after the fault, and the fault detection can be performed by identifying the steady-state abrupt quantities.
However, the electrical quantity of the high-resistance fault is weak, the traditional protection device is difficult to detect, is easy to miss judgment and misjudgment, and cannot guarantee reliability. It is highly desirable to fully discover fault features under a novel power distribution network, and particularly to extract and analyze features of high-resistance ground faults with weak fault signals and difficult detection.
Disclosure of Invention
The invention provides a method and a system for detecting a short-circuit fault of a power distribution network accessed by a high-proportion distributed power supply, which are used for solving the technical problem that feature extraction and analysis cannot be carried out in a high-resistance grounding fault with weak fault signals and difficult detection.
In a first aspect, the present invention provides a method for detecting a short-circuit fault of a power distribution network with a high-proportion distributed power access, including:
collecting access point voltage of distributed power supply And output current；
Respectively to the access point voltageAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude values at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law;
Selecting harmonic frequency with virtual impedance to obtain harmonic frequency set Wherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2);
screening out the maximum virtual impedance value in the harmonic frequency set Corresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time And if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
In a second aspect, the present invention provides a power distribution network short-circuit fault detection system for high-proportion distributed power access, including:
An acquisition module configured to acquire access point voltages of the distributed power supply And output current；
A calculation module configured to respectively calculate the access point voltagesAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude values at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law;
a selection module configured to select harmonic frequencies with virtual impedance to obtain a harmonic frequency set Wherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2);
an identification module configured to screen out a maximum virtual impedance value in the harmonic frequency set Corresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time And if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
In a third aspect, there is provided an electronic device, comprising: the system comprises at least one processor and a memory communicatively connected with the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the steps of the power distribution network short circuit fault detection method of the high-proportion distributed power access of any embodiment of the invention.
In a fourth aspect, the present invention also provides a computer readable storage medium, on which a computer program is stored, where the program instructions, when executed by a processor, cause the processor to execute the steps of the method for detecting a short-circuit fault in a power distribution network for high-proportion distributed power access according to any embodiment of the present invention.
According to the method and the system for detecting the short-circuit fault of the power distribution network, which are disclosed by the application, the access point voltage of the distributed power supply and the output current of the distributed power supply are collected, the fast Fourier decomposition is respectively carried out on the access point voltage and the output current of the distributed power supply, the information such as the amplitude value, the phase angle and the like of the voltage and the current at each harmonic frequency is obtained, and the virtual impedance value at each harmonic frequency is calculated through ohm law; selecting a harmonic frequency set, and recording the frequency of the maximum amplitude of the virtual impedance at each selected harmonic frequency; the short-circuit fault is effectively identified by detecting the deviation of the frequency of the maximum value of the virtual impedance in the selected harmonic frequency range, so that the detection precision of the short-circuit fault of the power distribution network can be improved, and a new idea can be provided for the fault protection of the distributed power supply circuit of the power distribution network.
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, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a method for detecting a short-circuit fault of a power distribution network with high-proportion distributed power access according to an embodiment of the present invention;
FIG. 2 is a topology diagram of a first harmonic domain topology model in a normal operating state according to an embodiment of the present invention;
FIG. 3 is a topology diagram of a second harmonic domain topology model when a short circuit fault occurs on a line from a distributed power source to a main network according to an embodiment of the present invention;
Fig. 4 is a block diagram of a power distribution network short-circuit fault detection system with high-proportion distributed power access according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a flowchart of a method for detecting a short-circuit fault of a power distribution network with high-ratio distributed power access according to the present application is shown.
As shown in fig. 1, the method for detecting the short-circuit fault of the power distribution network with high-proportion distributed power access specifically comprises the following steps:
step S101, collecting access point voltage of distributed power supply And output current。
Step S102, for the access point voltages respectivelyAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentThe magnitude of the harmonic at each harmonic frequency and the virtual impedance value at each harmonic frequency is calculated by ohm's law.
In the step, a first harmonic domain topology model under the normal running state is constructed, wherein the first harmonic domain topology model uses a harmonic current sourceInstead of network side current harmonics, current sources are usedInstead of harmonic waves in output current of distributed power supply, the internal resistance of the power grid isThe parallel output impedance when the distributed power source is equivalent to a current source isThe local load isThe line impedance from the network side to the distributed power supply isThe impedance of the distributed power supply to the load isAs shown in fig. 2.
Calculating the access point voltage of the distributed power supply before the short circuit fault occurs and the output current of the distributed power supply, wherein the expression for calculating the access point voltage of the distributed power supply before the short circuit fault occurs is as follows:
，
In the method, in the process of the invention, The voltage of the access point of the distributed power supply before the occurrence of the short circuit fault;
the expression for calculating the output current of the distributed power supply before the occurrence of the short-circuit fault is as follows:
，
In the method, in the process of the invention, The output current of the distributed power supply before the occurrence of the short circuit fault;
Performing fast Fourier decomposition on the access point voltage of the distributed power supply before the short circuit fault and the output current of the distributed power supply before the short circuit fault to obtain harmonic amplitudes of the access point voltage of the distributed power supply before the short circuit fault and the output current of the distributed power supply before the short circuit fault at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency before the short circuit fault through ohm's law, wherein the expression for calculating the virtual impedance values at each harmonic frequency before the short circuit fault is:
，
In the method, in the process of the invention, Is the virtual impedance value at any one of the harmonic frequencies before the occurrence of the short-circuit fault.
Constructing a second harmonic domain topology model when a short circuit fault occurs on a line from a distributed power supply to a main network, wherein the second harmonic domain topology model uses a harmonic current sourceInstead of network side current harmonics, current sources are usedInstead of harmonic waves in output current of distributed power supply, the internal resistance of the power grid isThe parallel output impedance when the distributed power source is equivalent to a current source isThe local load isThe line impedance from the network side to the distributed power supply isThe impedance of the distributed power supply to the load isAs shown in fig. 3.
Calculating the access point voltage of the distributed power supply and the output current of the distributed power supply after the occurrence of the short circuit fault, wherein the expression for calculating the access point voltage of the distributed power supply after the occurrence of the short circuit fault is as follows:
，
In the method, in the process of the invention, For the access point voltage of the distributed power supply after a short circuit fault occurs,The value range is the proportionality coefficient of [0,1] and is used for representing the distance between the access points of the fault points;
the expression for calculating the output current of the distributed power supply after the occurrence of the short-circuit fault is as follows:
，
In the method, in the process of the invention, The output current of the distributed power supply after the occurrence of the short circuit fault;
Performing fast Fourier decomposition on the access point voltage of the distributed power supply after the short circuit fault and the output current of the distributed power supply after the short circuit fault to obtain harmonic amplitudes of the access point voltage of the distributed power supply after the short circuit fault and the output current of the distributed power supply after the short circuit fault at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency after the short circuit fault through ohm law, wherein the expression for calculating the virtual impedance values at each harmonic frequency after the short circuit fault is as follows:
，
In the method, in the process of the invention, To calculate the virtual impedance value at any one of the harmonic frequencies after the occurrence of the short-circuit fault.
Step S103, selecting harmonic frequencies with virtual impedance to obtain a harmonic frequency setWherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the number of (c).
Step S104, screening out the maximum virtual impedance value in the harmonic frequency setCorresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsAnd detecting the deviation of the range to identify the short-circuit fault of the power distribution network.
In this step, the target harmonic frequencyAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference value is not greater than a preset threshold value, short-circuit fault protection is not triggered; if the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time If the second difference value between the detection value of (a) and the detection value of (a) is larger than a preset threshold value, identifying a short circuit fault, and controlling a relay switch to cut off the distributed power supply from the power distribution network; if the target harmonic frequency in the monitoring period is continuously preset after the initial offset timeIf the second difference value between the detection value of (a) and a is not larger than the preset threshold value, short-circuit fault protection is not triggered. The preset threshold is a set value combined with a system parameter.
In this embodiment, a simulation model is built using RT-LAB to study real-time simulation results. The semi-physical simulation platform comprises an RT-LAB upper computer, simulation equipment and the like; the upper computer is a computer and is used for building and operating the model; the lower computer is a real-time simulator and is used for running and calculating the model; the controller is a measured controller. The upper computer is connected with the lower computer through a network cable and is used for downloading the model and transmitting data. And building a power distribution network model containing a distributed power supply in a Simulink simulation tool of the RT-LAB upper computer, and downloading a main loop model into simulation equipment for real-time simulation to obtain an RT-LAB semi-physical simulation model, wherein the main loop model comprises the distributed power supply model, line impedance and the like.
In summary, the method of the application collects the access point voltage of the distributed power supply and the output current of the distributed power supply, respectively carries out fast Fourier decomposition on the access point voltage and the output current of the distributed power supply to obtain the amplitude, phase angle and other information of the voltage and the current at each harmonic frequency, and calculates the virtual impedance value at each harmonic frequency through ohm law; selecting a harmonic frequency set, and recording the frequency of the maximum amplitude of the virtual impedance at each selected harmonic frequency; the short-circuit fault is effectively identified by detecting the deviation of the frequency of the maximum value of the virtual impedance in the selected harmonic frequency range, so that the detection precision of the short-circuit fault of the power distribution network can be improved.
Referring to fig. 4, a block diagram of a power distribution network short-circuit fault detection system with high-ratio distributed power access according to the present application is shown.
As shown in fig. 4, the power distribution network short-circuit fault detection system 200 includes an acquisition module 210, a calculation module 220, a selection module 230, and an identification module 240.
Wherein the acquisition module 210 is configured to acquire access point voltages of the distributed power sourcesAnd output current; A calculation module 220 configured to respectively calculate the access point voltagesAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude values at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law; a selection module 230 configured to select harmonic frequencies at which virtual impedances exist, resulting in a set of harmonic frequenciesWherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2); an identification module 240 configured to screen out a maximum virtual impedance value in the harmonic frequency setCorresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes: respectively obtaining the target harmonic frequenciesFirst detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period; judging whether the first difference value is larger than a preset threshold value or not; if the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset timeThe detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold; if the target harmonic frequency in the monitoring period is continuously preset after the initial offset timeAnd if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
It should be understood that the modules depicted in fig. 4 correspond to the various steps in the method described with reference to fig. 1. Thus, the operations and features described above for the method and the corresponding technical effects are equally applicable to the modules in fig. 4, and are not described here again.
In other embodiments, the present invention further provides a computer readable storage medium, on which a computer program is stored, where the program instructions, when executed by a processor, cause the processor to perform the method for detecting a short-circuit fault of a power distribution network with high-proportion distributed power access in any of the method embodiments described above;
as one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions configured to:
collecting access point voltage of distributed power supply And output current；
Respectively to the access point voltageAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude values at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law;
Selecting harmonic frequency with virtual impedance to obtain harmonic frequency set Wherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2);
screening out the maximum virtual impedance value in the harmonic frequency set Corresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time And if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
The computer readable storage medium may include a storage program area and a storage data area, wherein the storage program area may store an operating system, at least one application program required for a function; the storage data area may store data created from the use of a power distribution network short-circuit fault detection system accessed by a high proportion of distributed power sources, and the like. In addition, the computer-readable storage medium may include high-speed random access memory, and may also include memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, the computer readable storage medium optionally includes memory remotely located with respect to the processor, which may be connected to the high-proportion distributed power-accessed distribution network short-circuit fault detection system via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Fig. 5 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, as shown in fig. 5, where the device includes: a processor 310 and a memory 320. The electronic device may further include: an input device 330 and an output device 340. The processor 310, memory 320, input device 330, and output device 340 may be connected by a bus or other means, for example in fig. 5. Memory 320 is the computer-readable storage medium described above. The processor 310 executes various functional applications and data processing of the server by running nonvolatile software programs, instructions and modules stored in the memory 320, that is, the method for detecting short-circuit faults of the power distribution network for implementing the high-proportion distributed power access in the method embodiment described above. The input device 330 may receive input numeric or character information and generate key signal inputs related to user settings and function control of the power distribution network short-circuit fault detection system for high-proportion distributed power access. The output device 340 may include a display device such as a display screen.
The electronic equipment can execute the method provided by the embodiment of the invention, and has the corresponding functional modules and beneficial effects of the execution method. Technical details not described in detail in this embodiment may be found in the methods provided in the embodiments of the present invention.
As an implementation manner, the electronic device is applied to a power distribution network short-circuit fault detection system accessed by a high-proportion distributed power supply, and is used for a client, and the electronic device comprises: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executable by the at least one processor to enable the at least one processor to:
collecting access point voltage of distributed power supply And output current；
Respectively to the access point voltageAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude values at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law;
Selecting harmonic frequency with virtual impedance to obtain harmonic frequency set Wherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2);
screening out the maximum virtual impedance value in the harmonic frequency set Corresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time And if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on such understanding, the foregoing technical solutions may be embodied essentially or in part in the form of a software product, which may be stored in a computer-readable storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform the various embodiments or methods of some parts of the embodiments.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. A power distribution network short-circuit fault detection method for high-proportion distributed power access is characterized by comprising the following steps:
collecting access point voltage of distributed power supply And output current；
Respectively to the access point voltageAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude at each harmonic frequency and calculating virtual impedance values at each harmonic frequency by ohm's law, wherein the voltage is applied to the access pointAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentThe harmonic magnitudes at each harmonic frequency and calculating virtual impedance values at each harmonic frequency by ohm's law includes:
Constructing a first harmonic domain topology model under a normal operation state, wherein the first harmonic domain topology model uses a harmonic current source Instead of network side current harmonics, current sources are usedInstead of harmonic waves in output current of distributed power supply, the internal resistance of the power grid isThe parallel output impedance when the distributed power source is equivalent to a current source isThe local load isThe line impedance from the network side to the distributed power supply isThe impedance of the distributed power supply to the load is；
Calculating the access point voltage of the distributed power supply before the short circuit fault occurs and the output current of the distributed power supply, wherein the expression for calculating the access point voltage of the distributed power supply before the short circuit fault occurs is as follows:
，
In the method, in the process of the invention, The voltage of the access point of the distributed power supply before the occurrence of the short circuit fault;
the expression for calculating the output current of the distributed power supply before the occurrence of the short-circuit fault is as follows:
，
In the method, in the process of the invention, The output current of the distributed power supply before the occurrence of the short circuit fault;
Performing fast Fourier decomposition on the access point voltage of the distributed power supply before the short circuit fault and the output current of the distributed power supply before the short circuit fault to obtain harmonic amplitudes of the access point voltage of the distributed power supply before the short circuit fault and the output current of the distributed power supply before the short circuit fault at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency before the short circuit fault through ohm's law, wherein the expression for calculating the virtual impedance values at each harmonic frequency before the short circuit fault is:
，
In the method, in the process of the invention, A virtual impedance value at any one of the harmonic frequencies before occurrence of the short-circuit fault;
the voltage of the access point is respectively equal to that of the access point And the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentThe harmonic amplitude at each harmonic frequency and calculating the virtual impedance value at each harmonic frequency by ohm's law further comprises:
constructing a second harmonic domain topology model when a short circuit fault occurs on a line from a distributed power supply to a main network, wherein the second harmonic domain topology model uses a harmonic current source Instead of network side current harmonics, current sources are usedInstead of harmonic waves in output current of distributed power supply, the internal resistance of the power grid isThe parallel output impedance when the distributed power source is equivalent to a current source isThe local load isThe line impedance from the network side to the distributed power supply isThe impedance of the distributed power supply to the load is；
Calculating the access point voltage of the distributed power supply and the output current of the distributed power supply after the occurrence of the short circuit fault, wherein the expression for calculating the access point voltage of the distributed power supply after the occurrence of the short circuit fault is as follows:
，
In the method, in the process of the invention, For the access point voltage of the distributed power supply after a short circuit fault occurs,The value range is the proportionality coefficient of [0,1] and is used for representing the distance between the access points of the fault points;
the expression for calculating the output current of the distributed power supply after the occurrence of the short-circuit fault is as follows:
，
In the method, in the process of the invention, The output current of the distributed power supply after the occurrence of the short circuit fault;
Performing fast Fourier decomposition on the access point voltage of the distributed power supply after the short circuit fault and the output current of the distributed power supply after the short circuit fault to obtain harmonic amplitudes of the access point voltage of the distributed power supply after the short circuit fault and the output current of the distributed power supply after the short circuit fault at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency after the short circuit fault through ohm law, wherein the expression for calculating the virtual impedance values at each harmonic frequency after the short circuit fault is as follows:
，
In the method, in the process of the invention, Calculating a virtual impedance value at any harmonic frequency after the occurrence of the short-circuit fault;
Selecting harmonic frequency with virtual impedance to obtain harmonic frequency set Wherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2);
screening out the maximum virtual impedance value in the harmonic frequency set Corresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time And if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
2. The method for detecting a short-circuit fault in a power distribution network for high-proportion distributed power access according to claim 1, wherein after determining whether the first difference is greater than a preset threshold, the method further comprises:
and if the first difference value is not greater than a preset threshold value, not triggering short-circuit fault protection.
3. The method for detecting short-circuit faults in a power distribution network by high-proportion distributed power access as claimed in claim 1, wherein the target harmonic frequency in a continuous preset monitoring period after the initial offset time is judgedAfter whether the second difference between the detected value of a and a is greater than a preset threshold, the method further comprises:
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time If the second difference value between the detection value of (a) and a is not larger than the preset threshold value, short-circuit fault protection is not triggered.
4. A power distribution network short-circuit fault detection system with high-proportion distributed power access, for the method of any one of claims 1-3, comprising:
An acquisition module configured to acquire access point voltages of the distributed power supply And output current；
A calculation module configured to respectively calculate the access point voltagesAnd the output currentPerforming fast Fourier decomposition to obtain the access point voltageAnd the output currentHarmonic amplitude values at each harmonic frequency, and calculating virtual impedance values at each harmonic frequency through ohm's law;
a selection module configured to select harmonic frequencies with virtual impedance to obtain a harmonic frequency set Wherein the set of harmonic frequencies required by each harmonic frequency in the harmonic frequency set is，To the point ofSequentially increasing the values of (2);
an identification module configured to screen out a maximum virtual impedance value in the harmonic frequency set Corresponding target harmonic frequencyBy means of the frequency of the target harmonicAt harmonic frequency setsDetecting range-finding offset to identify power distribution network short-circuit faults, wherein the target harmonic frequency is calculatedAt harmonic frequency setsDetecting the range-occurring offset to identify a power distribution network short-circuit fault includes:
Respectively obtaining the target harmonic frequencies First detection value in front and back two periodsAnd a second detection valueAnd calculate the first detection valueAnd the second detection valueFirst difference betweenWherein, the method comprises the steps of, wherein,For a second detection value in the current signal monitoring period,A first detection value in a previous signal monitoring period;
Judging whether the first difference value is larger than a preset threshold value or not;
If the first difference is greater than the preset threshold, recording the target harmonic frequency of the previous monitoring period before the initial offset time The detection value of (a) is a, and the target harmonic frequency in the continuous preset monitoring period after the initial offset moment is judgedWhether the second difference between the detected value of (a) and a is greater than a preset threshold;
If the target harmonic frequency in the monitoring period is continuously preset after the initial offset time And if the second difference value between the detection value of the (a) and the detection value of the (a) is larger than a preset threshold value, identifying a short circuit fault and controlling the relay switch to cut off the distributed power supply from the power distribution network.
5. An electronic device, comprising: at least one processor, and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1 to 3.
6. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the method of any one of claims 1 to 3.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6144721A (en) * | 1996-01-05 | 2000-11-07 | Communications Technology Corporation | Apparatus and method for line pair testing and fault diagnostics |
| WO2023152424A1 (en) * | 2022-02-11 | 2023-08-17 | Safegrid Oy | Method and apparatus for fault detection in distribution grid |
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6144721A (en) * | 1996-01-05 | 2000-11-07 | Communications Technology Corporation | Apparatus and method for line pair testing and fault diagnostics |
| WO2023152424A1 (en) * | 2022-02-11 | 2023-08-17 | Safegrid Oy | Method and apparatus for fault detection in distribution grid |
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