CN114552584B - Topology identification system and identification method for low-voltage power grid area - Google Patents
Topology identification system and identification method for low-voltage power grid area Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00007—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using the power network as support for the transmission
- H02J13/00009—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using the power network as support for the transmission using pulsed signals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/126—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using wireless data transmission
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Abstract
The system comprises a concentrator arranged at a meter reading end and an ammeter arranged at a user end, wherein a carrier communication module is arranged in the ammeter, and the concentrator is connected with the ammeter through a power line; the topology transmission module is arranged in the ammeter and is used for injecting current carrying topology characteristic signals into the power line, wherein the topology characteristic signals are rectangular wave signals with duty ratios not equal to 50%, and the topology characteristic signals contain meter addresses; the topology receiving module is arranged on each phase of power line of the meter reading end and is used for collecting magnetic field information generated by current carrying topology characteristic signals and converting and outputting the collected magnetic field information; the topology data processing module is arranged at the meter reading end, each three-phase power line is correspondingly provided with one topology data processing module, and the topology data processing module is used for receiving information from the topology receiving module and analyzing and calculating to obtain a topology result and a substation area household change relation.
Description
Technical Field
The invention belongs to the technical field of power distribution automation, and particularly relates to a topology identification system and method for a low-voltage power network station.
Background
With the rise of intelligent power and intelligent power grid technology, power grid system management gradually goes to intellectualization and remodelling. The transformer area refers to the power supply line coverage area of a transformer. Taking a low-voltage three-phase power grid as an example, each phase of the three-phase power of the transformer has tens to hundreds of electric meters, the distribution of the electric meters in the whole area is complex, and the area membership of each intelligent electric meter must be correctly obtained in order to realize the fine management of the power grid. The power distribution party can know which phase line is located under the station and the front and back positions of the electric meter network through the topology technical means, when the power grid system fails, the power distribution party can timely determine the failure point, and the fixed-point power-off and fixed-point maintenance are realized by matching with the communication technology, so that the daily maintenance cost is reduced, the accident hazard is reduced, and the maintenance time is shortened.
In order to facilitate the topology identification of the transformer area, the prior art performs the topology identification by injecting the characteristic current into the power supply branch, for example, the Chinese patent application with publication number of CN111030303A, and realizes the functional topology by injecting a rectangular wave signal with frequency of 100kHz into the circuit. However, the switching frequency of a switching power supply used by a user in a power grid environment is kept within 50 kHz-150 kHz, and 100kHz rectangular wave signals are used for topology identification, so that the problem of noise interference is easy to occur. As can be seen from fig. 1, the signal with the frequency lower than 1kHz also has the problem of being interfered by the power frequency harmonic wave of the power grid. If the ultra-low frequency signal is used for topology identification, in order to reduce harmonic noise interference, the signal current value is increased to counter noise, the safety risk is introduced while the signal current amount is increased, and the service life of the module is reduced.
Disclosure of Invention
The invention aims to provide a system and a method for identifying the topology of a low-voltage network station area, which have strong anti-interference capability and can effectively realize station area identification.
In order to achieve the above object, the present invention adopts the following technical solutions:
The topology identification system of the low-voltage power network station comprises a concentrator arranged at a meter reading end and an ammeter arranged at a user end, wherein a carrier communication module is arranged in the ammeter, and the concentrator is connected with the ammeter through a power line; further comprises: the topology transmission module is arranged in the ammeter and is used for injecting current carrying topology characteristic signals into the power line, the topology characteristic signals are rectangular wave signals with duty ratios not equal to 50%, and the topology characteristic signals contain meter address information; the topology receiving module is arranged on each phase of power line of the meter reading end and is used for collecting magnetic field information generated by current carrying topology characteristic signals, converting the collected magnetic field information and outputting the magnetic field information; and each three-phase power line is correspondingly provided with a topology data processing module which is used for receiving information from the topology receiving module, analyzing and calculating the information to obtain a topology result and a substation area user change relation.
Further, the topology sending module comprises an information receiving and processing control module, a digital-to-analog conversion module, a strong and weak electric coupling cascade module and a first power supply module for supplying power to the modules; the information receiving and processing control module is connected with the carrier communication module and is used for monitoring interaction information of the carrier communication module and the ammeter, extracting table address information, converting the table address information into the topology characteristic signal and sending the topology characteristic signal to the digital-to-analog conversion module; the digital-to-analog conversion module is used for converting the topological characteristic signal into an analog signal and sending the analog signal to the strong-weak electric coupling cascade module; the strong and weak electric coupling cascade module is used for coupling and injecting the analog signals output by the digital-to-analog conversion module into a power line.
Further, the information receiving and processing control module generates the topology characteristic signal in a PWM coding mode: the information receiving and processing control module divides the table address according to bytes, each bit of data in the bytes is processed based on physical layer logic, PWM waves with fixed time length represent data 1, PWM waves without fixed time length represent data 0, or two different frequency PWM waves are used for representing the data 1 and 0 respectively.
Further, the topology receiving module comprises a signal acquisition module, a signal processing module and a second power supply module for supplying power to the signal acquisition module, and the signal acquisition module comprises a TMR chip for acquiring current signals on the power line.
Further, the signal acquisition module further comprises a differential signal processing circuit connected with the TMR chip and a filter circuit connected with the differential signal processing circuit; the TMR chip outputs the sensed magnetic field to the differential signal processing circuit in the form of differential voltage; the differential signal processing circuit amplifies the differential voltage output by the TMR chip, converts the differential voltage into a voltage to ground and outputs the voltage to the filter circuit; the filtering circuit filters the voltage signal output by the differential signal processing circuit.
Further, the signal processing module comprises a high-pass filter circuit, a band-pass filter circuit and an adder circuit which are connected in sequence.
The invention also provides a topology identification method of the power grid station, wherein a concentrator is arranged at a meter reading end of the power grid, an ammeter is arranged at a user end, a topology sending module is arranged at the ammeter end, a topology receiving module is arranged on each phase of power line at the meter reading end, a topology data processing module is arranged at the meter reading end, a topology data processing module is correspondingly arranged on each three-phase power line, a carrier communication module is arranged in the ammeter, and the concentrator is connected with the ammeter through the power line;
The method for identifying the topology of the station area comprises the following steps:
The concentrator sends out a topology command, starts the ammeter topology, and the topology command is transmitted to the ammeter through a power line;
After the carrier communication module receives a topology command from the concentrator, an instruction is sent to the topology sending module, the topology sending module compiles a topology characteristic signal, the topology characteristic signal is a rectangular wave signal with a duty ratio not equal to 50%, the topology characteristic signal contains table address information, and the topology sending module injects current carrying the topology characteristic signal into a power line;
the topology receiving module collects magnetic field signals generated by current carrying topology characteristic signals from the power line and converts and outputs the collected magnetic field information to the topology data processing module;
And the topology data processing module decompiles the information received from the topology receiving module, analyzes the table address, calculates the topology result and determines the user change relation of the station area.
Further, the topological characteristic signal adopts a rectangular wave signal with the frequency of 46875Hz and the positive duty ratio of 75 percent.
According to the technical scheme, the rectangular wave signal with the duty ratio not equal to 50% is adopted as the topological characteristic signal, the special topological characteristic signal is adopted, the topological characteristic signal is injected into the power line, the topological characteristic signal carries even harmonic components, the method is equivalent to adopting double-frequency communication, the rectangular wave fundamental frequency and the double-frequency are used as communication frequencies, the double frequencies generated by the same rectangular wave have fixed phase differences, the double-frequency phase differences are fixed to be beneficial to a receiving end to process signals, a large amount of interference clutter in the same frequency domain can be filtered by determining the phase differences, the anti-interference capability of the signals is improved, the rectangular wave signal with the specific duty ratio is adopted, the power load can be reduced, the frequency selection range can avoid the power frequency harmonic of the ultralow frequency band, the interference of a switching power supply on the signals can be avoided, the method is different from other forms of signals, and the topology identification of the station area is effectively realized. In the preferred technical scheme, a rectangular wave signal with the frequency of 46875Hz and the positive duty ratio of 75% is adopted as a topological characteristic signal, the fundamental frequency of the signal is 46.875kHz around the power frequency 940 harmonic, the frequency multiplication 93.750kHz around the power frequency 1875 harmonic, and the interference by the harmonic is small (the highest specified 25 harmonic frequency in the list shown in figure 1 is 1.25 kHz).
Drawings
In order to more clearly illustrate the embodiments of the present invention, the following description will briefly explain the embodiments or the drawings required for the description of the prior art, 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 to a person skilled in the art.
FIG. 1 is a table of allowable values of harmonic currents in a power grid specified by national standards;
FIG. 2 is a block diagram of a system for identifying a topology of a cell in accordance with an embodiment of the present invention;
FIG. 3 is a block diagram of a topology sending module according to an embodiment of the present invention;
FIG. 4 is a block diagram of a topology receiving module according to an embodiment of the present invention;
FIG. 5 is a flow chart of the method of the present invention;
FIG. 6 is a graph of noise data over a certain power network line;
Fig. 7a and 7b are waveform diagrams of rectangular waves with 50% duty ratio and signal diagrams after fourier transform of rectangular waves with 50% duty ratio, respectively;
Fig. 8a and 8b are waveform diagrams of rectangular waves with a duty ratio of not equal to 50% and signal diagrams after fourier transform of rectangular waves with a duty ratio of not equal to 50%, respectively.
Detailed Description
To make the above and other objects, features and advantages of the present invention more apparent, the following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings.
When the duty ratio of the alternating current rectangular wave signal is 50%, after fourier transformation, the rectangular wave signal is composed of fundamental wave with the same frequency as the rectangular wave signal and odd harmonic components such as 3, 5, 7 times harmonic, etc., and in one period, the positive and negative of the odd harmonic components are balanced, so that the calculation result is zero when the arithmetic average value of the rectangular wave signal is calculated. When the duty ratio of the alternating current rectangular wave signal is not 50%, the rectangular wave signal comprises fundamental wave and odd harmonic components with the same frequency and even harmonic components after Fourier transformation, and the arithmetic average value of the rectangular wave signal is not equal to zero due to the existence of the even harmonic components. Therefore, the invention adopts rectangular wave signals with the duty ratio not equal to 50% as topology characteristic signals, and the topology characteristic signals are injected into a power supply line to perform the topology identification of the transformer area.
The characteristic information carried by the rectangular wave signal with the duty ratio not equal to 50% contains fundamental frequency signals and even harmonic components (frequency multiplication signals), the fundamental frequency signals and the even harmonic components are detected simultaneously in the topological process by distinguishing the even harmonic components from other signals, the reliability of the signal topology can be improved, the double-frequency phase difference is fixed, and the interference of bus noise with different phases in the same frequency on the topological information can be eliminated. And from the technical point of waveform superposition, compared with other waveforms, the rectangular wave has higher energy storage, can ensure that the fundamental frequency and the frequency doubling phase difference are fixed, and the amplitude of the double-frequency signal can be accurately sensed by TMR. In addition, compared with other types of waveforms, the rectangular wave is easier to generate, and can be realized by using an MCU or a crystal oscillator and an analog oscillating circuit, so that the cost is advantageous.
As shown in fig. 2, the topology identification system of the power grid area in this embodiment includes a concentrator 1, a topology data processing module 2, a topology receiving module 3, and an electric meter 4 disposed at a user end, in which a carrier communication module 5 and a topology sending module 6 are disposed in the electric meter 4, and communication connection is implemented between the concentrator 1 and the electric meter through a power line. The invention carries out topology identification by injecting micro current carrying a topology characteristic signal into a power supply line, wherein the topology characteristic signal is a rectangular wave signal with a duty ratio not equal to 50%.
In the district topology identification system, the concentrator 1 transmits a topology command to the ammeter 4 via the power line, and the ammeter 4 receives the topology command transmitted by the concentrator 1 through the carrier communication module 5 and controls the topology transmitting module 6 to transmit a specific topology code to the concentrator 1. As shown in fig. 3, the topology sending module 6 of the present embodiment includes an information receiving and processing control module 6-1, a digital-to-analog conversion module 6-2, a strong-weak electric coupling cascade module 6-3, and a first power supply module 6-4 for supplying power to the above modules and circuits. The first power supply module 6-4 of the present embodiment is powered by the carrier communication module 5, and can provide two voltages of 12V and 3.3V to implement the topology transmission function.
The information receiving and processing control module 6-1 comprises an MCU and a peripheral circuit thereof, the information receiving and processing control module 6-1 is connected with the carrier communication module 5 and is used for sensing interaction information of the carrier communication module 5 and the ammeter 4 and extracting table address information therefrom, and when a topology command is received, the information receiving and processing control module 6-1 converts the table address into a specific topology characteristic signal, namely a rectangular wave signal with a duty ratio not equal to 50 and sends the specific topology characteristic signal. The topology characteristic signal can be realized by PWM coding, and can be coded by adopting conventional methods such as non-return-to-zero coding, manchester coding and the like, and the coding method has no specific requirements. The non-return-to-zero coding method adopted in the embodiment is specifically as follows: after intercepting the table address, the information receiving and processing control module 6-1 splits a frame of data (table address) according to bytes, and each bit of data in the bytes is processed based on physical layer logic (0, 1), so that the frame of data is completely transmitted. Physical layer based logic processing refers to: the PWM wave per fixed time length represents data 1, no PWM wave per fixed time length, i.e. high level or low level represents data 0, or two different frequency PWM waves represent data 1 and 0, respectively. In a real power grid environment, 50Hz harmonic waves and electric noise have great interference to a topological process, a topological transmitting end needs to improve the frequency generation precision, when a specific waveform signal is generated through PWM coding, a high-precision crystal oscillator frequency division and MCU control mode can be adopted to realize topology characteristic signal generation, for example, a 12MHz crystal oscillator 8 frequency division can obtain a 46875Hz rectangular wave signal.
The digital-to-analog conversion module 6-2 is configured to convert the digital signal received from the information receiving and processing control module 6-1 into an analog signal, so as to be different from a voltage form of a conventional carrier signal, thereby avoiding the disadvantage of on-site transmission of the carrier signal across a transformer.
The strong and weak electric coupling cascade module 6-3 is used for coupling and injecting the analog signals output by the digital-to-analog conversion module into the power supply line. The analog current signal output by the digital-to-analog conversion module 6-2 is a weak current end signal, and the current signal is output to a power line after passing through the strong-weak electric coupling cascade module 6-3. The strong and weak electric coupling cascade module 6-3 of this embodiment includes mutual inductor and LC trapper, and the mutual inductor can adopt the mutual inductor that the turn ratio is 1:1, and the trapper links to each other with the secondary end of mutual inductor, and the coupling coil of current signal utilization mutual inductor is after the injection from the primary side, feeds into the electric wire netting behind the trapper of being connected with the secondary survey. The wave trap is used for limiting power frequency and harmonic power consumption. Center frequency of wave trapWherein f1 is the PWM fundamental frequency, and f2 is the PWM even harmonic frequency.
Namely, the workflow of the topology transmission module 6 is: the information receiving and processing control module 6-1 listens for the meter address, converts the meter address into a topological characteristic signal (a rectangular wave signal carrying even harmonic components) after receiving the topological command and outputs the topological characteristic signal, the topological characteristic signal is converted into a current signal through digital-to-analog conversion, the current signal is injected from a primary side by using a coupling coil, and the current signal is fed into a power grid to be coupled and injected into a 220V power utilization system after being connected with a trap through secondary measurement.
The topology receiving module 3 is arranged on a power line of the meter reading end power distribution cabinet, and one topology receiving module is respectively arranged on each phase of power line of the power line. As shown in fig. 4, the topology receiving module 3 of the present embodiment includes a signal acquisition module 3-1, a signal processing module 3-2, and a second power supply module 3-3 for supplying power to the foregoing modules. The signal acquisition module 3-1 of the present embodiment includes a TMR chip, a differential signal processing circuit, and a filter circuit connected in order. The TMR chip is used for sensing a magnetic field generated by a current carrying a topological characteristic signal, which is coupled to a power supply line by the topological transmitting module 6, and outputting the sensed magnetic field to the differential signal processing circuit in the form of differential voltage. The differential signal processing circuit amplifies the differential voltage output by the TMR chip, converts the differential voltage into a voltage to ground and outputs the voltage to the filter circuit. The filtering circuit filters the voltage signal output by the differential signal processing circuit to filter out the voltage generated by the power frequency and harmonic interference magnetic field.
The signal processing module 3-2 receives the acquisition signal from the signal acquisition module 3-1, when the acquisition signal contains the topology characteristic signal, the signal processing module 3-2 extracts fundamental wave and even harmonic components in the topology characteristic signal from the acquisition signal, processes the physical layer information data 1 and 0 and outputs the processed physical layer information data to the topology data processing module 2. The signal processing module 3-2 of the present embodiment includes a high-pass filter circuit, a band-pass filter circuit, and an adder circuit connected in sequence. The filtering circuit is mainly used for filtering noise, the high-pass filtering circuit is used for carrying out strong filtering on 50Hz and power frequency harmonic noise, the frequency point of the high-pass filter is most suitable near 40kHz, and the higher frequency point possibly affects the received and transmitted signal waveform. The band-pass filter circuit is used for reprocessing the waveform after strong filtering, namely amplifying and attenuating harmonic wave and high-frequency noise for 46875Hz signals. The adder circuit is used for analyzing the table number information and consists of a phase-locked loop PLL, a multiplier and an operational amplifier circuit. The above circuits can all adopt the existing conventional circuits capable of completing the corresponding functions, and the specific structure of the circuits is not the key point of the present invention and will not be described in detail.
The topology receiving module 3 on each three-phase line is correspondingly provided with a topology data processing module 2, and when the topology receiving module 3 on any phase line of the three-phase line receives the topology signal sent by the topology sending module 6, the topology signal is processed and output to the topology data processing module 2. The topology data processing module 2 is configured to decompil the physical layer data output by the topology receiving module 3 on a certain phase line according to a transmission coding mode, so as to obtain table number information, calculate the received signal amplitude and information through signal strength to obtain a topology result, combine the phase and the transformer lower branch relationship to obtain a transformer area household transformation relationship (relationship between a user ammeter and a transformer), and output a topology relationship diagram of the whole transformer lower branch, the phase line and the user ammeter based on the obtained transformer area household transformation relationship. After the physical layer data is obtained, how to decompil, calculate the topology result according to the table address, and determine the change relation of the station area user according to the topology result are all conventional techniques in the art, and the existing method can be adopted, which is not an innovation of the present invention and will not be repeated here.
Fig. 5 is a flowchart of the method of the present invention, and in the following, with reference to fig. 1 and fig. 4, the method for identifying a topology of a cell of the present invention is described, where the method for identifying a topology of a cell includes the following steps:
The concentrator 1 sends out a topology command, starts the ammeter topology, and the topology command is transmitted to the ammeter 4 through a power line in a power line carrier mode;
After the carrier communication module 5 of the ammeter 4 receives the topology command from the concentrator 1, an instruction is sent to the topology sending module 6, the topology sending module 6 compiles a topology characteristic signal, the topology characteristic signal is injected into a power supply line in a current mode, and the current carrying the topology characteristic signal is transmitted to the topology receiving module 3 along a power supply line;
The topology receiving module 3 collects signals from the power supply line, and when the magnetic field change caused by the current carrying the topology characteristic signals is collected, the topology receiving module 3 outputs the detected magnetic field change to the topology data processing module 2 in the form of voltage signals;
The topology data processing module 2 decompiles the received physical layer data, analyzes the table address, calculates the topology result and determines the change relation of the station area.
In a real power grid environment, 50Hz harmonic waves and electric noise have great interference on a topological process, and in order to reduce the influence of a power grid on topology, preferably, a rectangular wave signal with the frequency of 46875Hz and the duty ratio of 75% is adopted as a topological characteristic signal. Fig. 6 is a graph of noise data on a power network line, where test sites are front gardens B5, B7, and B10 in the front of vanvac, southern sand, and test time is 11 months in 2020, and test data is obtained by testing using a multi-creation technology TMR2102 type TMR linear sensor probe, and a test result is output voltage to ground in units/mV. As can be seen from fig. 6, to ensure the receiving accuracy and improve the topology noise immunity, the current signal transmission characteristics, the sensitivity of TMR to frequency signal receiving and other factors are considered, and signals in the sections 40-50 kHz and 90-100 kHz are selected to be most suitable.
In order to improve the anti-interference capability, the precondition of adopting a dual-frequency communication means is to ensure that the two signals have a fixed phase relationship, and the fundamental frequency and the frequency multiplication of rectangular waves with the same fixed duty ratio meet the condition. Fig. 7a is a waveform diagram of a rectangular wave with a duty ratio of 50%, and fig. 7b is a signal diagram of a rectangular wave with a duty ratio of 50% after fourier transform. As can be seen from fig. 7a and 7b, the rectangular wave having a duty ratio of 50% does not contain even harmonic components after fourier transform, and although there is a third harmonic, this waveform cannot be used due to the influence of the noise range. Fig. 8a is a waveform diagram of a rectangular wave having a duty ratio of not equal to 50%, and fig. 8b is a signal diagram of a rectangular wave having a duty ratio of not equal to 50% after fourier transform. As can be seen from fig. 8a and 8b, when the rectangular wave duty ratio is not equal to 50%, even harmonic components exist, and the double frequency value accords with the noise screening interval, and simulation and test results show that when the positive duty ratio is 75% (the result of the rectangular wave characteristic 25% accords with 75%, and 75% is taken as an example here), the frequency multiplication amplitude is the largest, and the communication signal energy utilization rate is the highest.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (6)
1. The topology identification system of the low-voltage power network station comprises a concentrator arranged at a meter reading end and an ammeter arranged at a user end, wherein a carrier communication module is arranged in the ammeter, and the concentrator is connected with the ammeter through a power line; characterized by further comprising:
The topology transmission module is arranged in the ammeter and is used for injecting current carrying topology characteristic signals into the power line, the topology characteristic signals adopt rectangular wave signals with the frequency of 46875Hz and the positive duty ratio of 75%, and the topology characteristic signals contain meter address information;
the topology receiving module is arranged on each phase of power line of the meter reading end and is used for collecting magnetic field information generated by current carrying the topology characteristic signals, converting the collected magnetic field information and outputting the magnetic field information;
The topology data processing module is arranged at the meter reading end, each three-phase power line is correspondingly provided with a topology data processing module, and the topology data processing module is used for receiving information from the topology receiving module, analyzing and calculating the information to obtain a topology result and a substation area household change relation;
The topology sending module comprises an information receiving and processing control module, a digital-to-analog conversion module, a strong-weak electric coupling cascade module and a first power supply module for supplying power to the information receiving and processing control module, the digital-to-analog conversion module and the strong-weak electric coupling cascade module;
The information receiving and processing control module is connected with the carrier communication module and is used for monitoring the interaction information of the carrier communication module and the ammeter, extracting the table address information from the interaction information, converting the table address into the topology characteristic signal by the information receiving and processing control module when a topology command is received, and sending the topology characteristic signal to the digital-analog conversion module; the topology characteristic signals are realized by PWM codes, specifically, after the information receiving and processing control module intercepts the table address, splitting the table address according to bytes, and each bit of data in the bytes is processed based on physical layer logic;
The digital-to-analog conversion module is used for converting the topological characteristic signal into an analog signal and sending the analog signal to the strong-weak electric coupling cascade module;
The strong and weak electric coupling cascade module is used for coupling and injecting the analog signals into the power line.
2. The power grid site topology identification system of claim 1, wherein: the logical processing based on the physical layer refers to: the PWM wave per fixed time length represents data 1, the PWM wave per fixed time length does not represent data 0, or two different frequency PWM waves are used to characterize data 1 and 0, respectively.
3. The power grid site topology identification system of claim 1, wherein: the topology receiving module comprises a signal acquisition module, a signal processing module and a second power supply module for supplying power to the signal acquisition module and the signal processing module, and the signal acquisition module comprises a TMR chip for acquiring current signals on the power line.
4. A power grid section topology identification system as recited in claim 3, wherein: the signal acquisition module further comprises a differential signal processing circuit connected with the TMR chip and a filter circuit connected with the differential signal processing circuit; the TMR chip outputs the sensed magnetic field to the differential signal processing circuit in the form of differential voltage; the differential signal processing circuit amplifies the differential voltage output by the TMR chip, converts the differential voltage into a voltage to ground and outputs the voltage to the filter circuit; the filtering circuit filters the voltage signal output by the differential signal processing circuit.
5. A power grid section topology identification system as recited in claim 3, wherein: the signal processing module comprises a high-pass filter circuit, a band-pass filter circuit and an addition circuit which are sequentially connected.
6. A topology identification method for a low-voltage power network station is characterized by comprising the following steps: the platform region topology identification method is realized based on the platform region topology identification system of the low-voltage power network according to any one of claims 1 to 5;
The method for identifying the topology of the station area comprises the following steps:
The concentrator sends out a topology command, starts the ammeter topology, and the topology command is transmitted to the ammeter through the power line;
After the carrier communication module receives a topology command from the concentrator, an instruction is sent to the topology sending module, the topology sending module compiles a topology characteristic signal, the topology characteristic signal adopts a rectangular wave signal with the frequency of 46875Hz and the positive duty ratio of 75%, the topology characteristic signal contains table address information, and the topology sending module injects current carrying the topology characteristic signal into the power line;
The topology receiving module collects magnetic field signals generated by current carrying the topology characteristic signals from the power line and converts the collected magnetic field information to output to the topology data processing module;
And the topology data processing module decompiles the information received from the topology receiving module, analyzes the table address, calculates the topology result and determines the user change relation of the station area.
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