CN114552584A - Low-voltage power grid distribution area topology identification system and identification method - Google Patents
Low-voltage power grid distribution area topology identification system and identification method 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
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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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- 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
A topology identification system and an identification method for a low-voltage power grid transformer area are disclosed, wherein the system comprises a concentrator arranged at a meter reading end and an electric meter arranged at a user end, a carrier communication module is arranged in the electric meter, and the concentrator is connected with the electric meter through a power line; the topology transmitting module is arranged in the ammeter and used for injecting current carrying a topology characteristic signal into a power line, the topology characteristic signal is a rectangular wave signal with the duty ratio not equal to 50%, and the topology characteristic signal comprises a meter address; the topology receiving module is arranged on each phase power line of the meter reading end and used for collecting magnetic field information generated by current carrying topology characteristic signals and converting and outputting the collected magnetic field information; and the topological data processing module is arranged at the meter reading end, one topological data processing module is correspondingly arranged on each three-phase power line, and the topological data processing module is used for receiving the information from the topological receiving module and carrying out analytic calculation to obtain a topological result and a station area family change relationship.
Description
Technical Field
The invention belongs to the technical field of distribution automation, and particularly relates to a low-voltage power grid distribution area topology identification system and an identification method.
Background
With the rise of intelligent power and smart grid technologies, grid system management gradually becomes intelligent and remote. The transformer area refers to the power supply line coverage area of one transformer. Taking a low-voltage three-phase power grid as an example, each phase of three-phase power of the transformer is provided with dozens 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 needs to be correctly obtained to realize the fine management of the power grid. The power distribution side can know which phase line each household electric meter is positioned under the transformer and the front and rear positions of the electric meter network through a topological technical means, when a power grid system breaks down, the power distribution side can determine a fault point in time, fixed-point power failure and fixed-point maintenance are realized by matching with a communication technology, the daily maintenance cost is reduced, the accident hazard is reduced, and the maintenance time is shortened.
In order to facilitate the identification of the topology of the distribution room, in the prior art, the topology identification is performed by injecting a characteristic current into a power supply branch, and for example, in the patent application of the invention in china with the publication number of CN111030303A, a functional topology is realized by injecting a rectangular wave signal with the frequency of 100kHz into a line. However, in the power grid environment, the switching frequency of the switching power supply used by a user is within 50 kHz-150 kHz, and a 100kHz rectangular wave signal is used for topology identification, so that the problem of noise interference is easily caused. The signal with the frequency lower than 1kHz is used for topology identification, and as can be seen from FIG. 1, the signal with the frequency lower than 1kHz can also have the problem of interference by power frequency harmonics of a 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 compete with noise, the safety risk is introduced while the signal current amount is increased, and the service life of a module is shortened.
Disclosure of Invention
The invention aims to provide a low-voltage power grid district topology identification system and an identification method which have strong anti-interference capability and can effectively realize district identification.
In order to achieve the purpose, the invention adopts the following technical solutions:
a topology identification system for a low-voltage power grid transformer area comprises a concentrator arranged at a meter reading end and an electric meter arranged at a user end, wherein a carrier communication module is arranged in the electric meter, and the concentrator is connected with the electric meter through a power line; further comprising: the topology transmitting module is arranged in the ammeter and used for injecting current carrying topology characteristic signals into a power line, the topology characteristic signals are rectangular wave signals with duty ratios not equal to 50%, and the topology characteristic signals comprise meter address information; the topology receiving module is arranged on each phase power line of the meter reading end and used for collecting magnetic field information generated by current carrying topology characteristic signals, converting the collected magnetic field information and outputting the converted magnetic field information; the topological data processing module is arranged at the meter reading end, one topological data processing module is correspondingly arranged on each three-phase power line, and the topological data processing module is used for receiving information from the topological receiving module, analyzing and calculating to obtain a topological result and a transformer area family 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 the interactive information between the carrier communication module and the ammeter, extracting the meter address information, converting the meter address information into the topological characteristic signal and sending the topological 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 and weak electric coupling cascade module; and 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 topological characteristic signal by adopting a PWM (pulse-width modulation) coding mode: the information receiving and processing control module splits the table address according to bytes, each bit of data in the bytes is processed based on physical layer logic, each PWM wave with fixed time length represents data 1, no PWM wave with fixed time length represents data 0, or two different-frequency PWM waves represent data 1 and 0 respectively.
Furthermore, 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.
Furthermore, the signal acquisition module also 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 induced magnetic field to the differential processing circuit in the form of differential voltage; the differential processing circuit amplifies the differential voltage output by the TMR chip, converts the amplified differential voltage into a voltage to ground and outputs the voltage to the filter circuit; the filtering circuit is used for filtering the voltage signal output by the differential processing circuit.
Furthermore, the signal processing module comprises a high-pass filter circuit, a band-pass filter circuit and an addition circuit which are connected in sequence.
The invention also provides a topology identification method for the low-voltage power grid transformer area, wherein a meter reading end of a power grid is provided with a concentrator, a user end is provided with an electric meter, a topology sending module is arranged at the electric meter end, a topology receiving module is arranged on each phase power line of the meter reading end, a 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, a carrier communication module is arranged in the electric meter, and the concentrator is connected with the electric meter through a power line;
the method for identifying the transformer area comprises the following steps:
the concentrator sends out a topology command, the ammeter topology is started, and the topology command is transmitted to the ammeter through a power line;
after receiving a topology command from the concentrator, the carrier communication module sends an instruction 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 comprises 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 a power line, and converts and outputs the collected magnetic field information to the topology signal processing module;
the topology signal processing module performs decompiling on the information received from the topology receiving module, analyzes the table address, calculates the topology result and determines the station area user-to-user relationship.
Further, the topological characteristic signal is a rectangular wave signal with the frequency of 46875Hz and the positive duty ratio equal to 75%.
According to the technical scheme, the rectangular wave signal with the duty ratio not equal to 50% is used as the topological characteristic signal, the special topological characteristic signal is used for injecting the topological characteristic signal into the power line, the topological characteristic signal carries even harmonic component, the method is equivalent to the method of adopting double-frequency communication, the rectangular wave fundamental frequency and the secondary frequency multiplication frequency are used as communication frequencies, the double frequency generated by the same rectangular wave has fixed phase difference, the double-frequency phase difference is fixed and is beneficial to processing signals by a receiving end, a large amount of same-frequency domain interference clutter can be filtered by determining the phase difference, 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 ultra-low frequency band power frequency harmonic wave, the interference of a switching power supply to the signals can be avoided, and the rectangular wave signal is different from other forms of signals, and effectively realizing the identification of the topology of the cell. In a preferred technical scheme, a rectangular wave signal with the frequency of 46875Hz and the positive duty ratio equal to 75% is used as a topological characteristic signal, the fundamental frequency of the signal is 46.875kHz at the power frequency of 940 subharmonic, the frequency multiplication of 93.750kHz at the power frequency of 1875 subharmonic, and the harmonic interference is small (the highest specified 25 subharmonic frequency in the list shown in FIG. 1 is 1.25 kHz).
Drawings
In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.
FIG. 1 is a table of allowable values of harmonic current in a power grid specified by the national standard;
fig. 2 is a block diagram of a platform area topology identification system according to an embodiment of the present invention;
FIG. 3 is a block diagram of a topology transmitting 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 on a grid line;
FIGS. 7a and 7b are a waveform diagram of a rectangular wave with a duty ratio of 50% and a signal diagram of a rectangular wave with a duty ratio of 50% after Fourier transform, respectively;
fig. 8a and 8b are a waveform diagram of a rectangular wave with a duty ratio not equal to 50% and a signal diagram of a rectangular wave with a duty ratio not equal to 50% after fourier transform, respectively.
Detailed Description
In order to make the aforementioned and other objects, features and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
When the duty ratio of the ac rectangular wave signal is 50%, after fourier transform, the rectangular wave signal is composed of a fundamental wave having the same frequency as the rectangular wave signal and odd harmonic components such as 3, 5, and 7 harmonics, and the positive and negative of the odd harmonic components are balanced out in one cycle, so that the calculation result is zero when the arithmetic average value of the rectangular wave signal is calculated. And when the duty ratio of the alternating-current rectangular wave signal is not 50%, after Fourier transformation, the rectangular wave signal not only comprises fundamental wave and odd harmonic component with the same frequency, but also comprises even harmonic component, and due to the existence of the even harmonic component, the arithmetic mean value of the rectangular wave signal is not equal to zero. Therefore, the rectangular wave signal with the duty ratio not equal to 50% is used as the topological characteristic signal and injected into the power supply line to identify the distribution area topology.
The characteristic information carried by the rectangular wave signal with the duty ratio not equal to 50% comprises a fundamental frequency signal and an even harmonic component (frequency multiplication signal), the even harmonic component is different from other signals, the fundamental frequency signal and the even harmonic component are detected simultaneously in the topological process, the reliability of signal topology can be increased, the dual-frequency phase difference is fixed, and the interference of bus noise with the same frequency and different phases on topological information can be eliminated. And from the technical perspective of waveform superposition, the rectangular wave is higher than other waveforms in stored energy, the fundamental frequency and the frequency doubling phase difference can be ensured to be fixed, and the amplitude of the double-frequency signal can be accurately sensed by TMR. In addition, the rectangular wave is easier to generate compared with other types of waveforms, can be realized by using an MCU (microprogrammed control Unit), a crystal oscillator and an analog oscillation circuit, and has the advantage of cost.
As shown in fig. 2, the low-voltage power grid region topology identification system of this embodiment includes a concentrator 1 disposed at a meter reading end, a topology data processing module 2, a topology receiving module 3, and an electric meter 4 disposed at a user end, where a carrier communication module 5 and a topology transmitting module 6 are disposed in the electric meter 4, and the concentrator 1 and the electric meter are in communication connection through a power line. The method carries out topology identification by injecting tiny current carrying topology characteristic signals into the power supply line, wherein the topology characteristic signals are rectangular wave signals with the duty ratio not equal to 50%.
In the district topology identification system, the concentrator 1 sends a topology command to the electric meter 4 through the power line, and the electric meter 4 receives the topology command sent by the concentrator 1 through the carrier communication module 5, and controls the topology sending module 6 to carry out specific topology coding and send the topology coding 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 and weak current 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 embodiment is powered by the carrier communication module 5, and can provide two voltages of 12V and 3.3V to realize the topology transmission function.
The information receiving and processing control module 6-1 comprises an MCU and peripheral circuits thereof, the information receiving and processing control module 6-1 is connected with the carrier communication module 5 and is used for monitoring the interactive information between the carrier communication module 5 and the ammeter 4 and extracting table address information from the interactive information, 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 the duty ratio not equal to 50 and sends the specific topology characteristic signal. The topological characteristic signal can be realized by PWM coding, and can be coded by 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 encoding method adopted in this 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 the physical layer logic (0, 1), so that the frame of data is completely transmitted. The physical layer based logic processing means: the PWM wave per fixed time length represents data 1, no PWM wave per fixed time length, i.e., high 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 power consumption noise have great interference on a topology process, a topology sending end needs to improve the frequency 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 the generation of a topology characteristic signal, for example, a rectangular wave signal of 46875Hz can be obtained through the frequency division of a 12MHz crystal oscillator 8.
The digital-to-analog conversion module 6-2 is used for converting the digital signal received from the information receiving and processing control module 6-1 into an analog signal so as to be different from the voltage form of the traditional carrier signal, thereby avoiding the defect of the transmission of the carrier signal across a transformer on site.
The strong and weak current coupling cascade module 6-3 is used for coupling and injecting the analog signals output by the digital-to-analog conversion module into a 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 the power line after passing through the strong and weak current coupling cascade module 6-3. The strong current and weak current coupling cascade module 6-3 of the embodiment includes a transformer and an LC wave trap, the transformer can be a transformer with a turn ratio of 1:1, the wave trap is connected with a secondary end of the transformer, and a current signal is injected from a primary side by using a coupling coil of the transformer, and then fed into a power grid through the wave trap connected with a secondary side. The wave trap is used for limiting power frequency and harmonic power consumption. Center frequency of wave trap
In the formula f1At PWM fundamental frequency, f2Is the PWM even geminal wave frequency.
Namely, the work flow of the topology sending module 6 is as follows: the information receiving and processing control module 6-1 is used for monitoring a meter address, converting the meter address into a topological characteristic signal (a rectangular wave signal carrying even harmonic components) after receiving a topological command, outputting the topological characteristic signal, converting the topological characteristic signal into a current signal through digital-analog conversion, injecting the current signal from a primary side by using a coupling coil, and feeding the current signal into a power grid for coupling and injecting the current signal into a 220V power system after a secondary measurement and trap.
The topology receiving module 3 is arranged on a power supply line of a meter reading end power distribution cabinet, and one topology receiving module is arranged on each phase power line of the power supply line. As shown in fig. 4, the topology receiving module 3 of this embodiment includes a signal collecting 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 this embodiment includes a TMR chip, a differential signal processing circuit, and a filter circuit, which are connected in sequence. The TMR chip is used for sensing a magnetic field generated by current which is coupled to a power supply line by the topology transmitting module 6 and carries the topology characteristic signal, and outputs the sensed magnetic field to the differential processing circuit in the form of differential voltage. The difference processing circuit amplifies the differential voltage output by the TMR chip, converts the amplified differential voltage into a ground voltage and outputs the ground voltage to the filter circuit. The filtering circuit filters the voltage signal output by the differential processing circuit and filters out the voltage generated by the power frequency and harmonic interference magnetic field.
The signal processing module 3-2 receives the acquired signal from the signal acquisition module 3-1, and when the acquired signal contains the topological characteristic signal, the signal processing module 3-2 extracts the fundamental wave and the even harmonic component in the topological characteristic signal from the acquired signal, processes the physical layer information data 1 and 0, and outputs the physical layer information data to the topological data processing module 2. The signal processing module 3-2 of this embodiment includes a high-pass filter circuit, a band-pass filter circuit, and an adder circuit, which are connected in sequence. The filter circuit is mainly used for filtering noise, the high-pass filter 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 influences the waveform of a received and transmitted signal. The band-pass filter circuit is used for reprocessing the waveform after strong filtering, namely amplifying the 46875Hz signal and attenuating harmonic waves and high-frequency noise. The adder circuit is used for analyzing the table number information and comprises a phase-locked loop PLL, a multiplier and an operational amplifier circuit. The circuits can adopt the conventional circuits which can complete the corresponding functions, and the specific structure of the circuit is not the key point of the invention and is not described in detail.
The topology receiving module 3 on each three-phase line is correspondingly provided with one topology data processing module 2, and when the topology receiving module 3 on any phase line of the three-phase lines 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 perform decompiling on received physical layer data output by the topology receiving module 3 on a certain phase line according to a sending coding mode, so as to obtain table number information, calculate amplitude and information of the received signal through signal strength to obtain a topology result, obtain a station area household variable relationship (relationship between a user electric meter and a transformer) by combining a phase and a transformer lower branch relationship, and output a topology relationship diagram of a whole transformer lower branch, a phase line and a user (electric meter) based on the obtained station area household variable relationship. After the physical layer data is obtained, how to perform decompilation, calculate the topology result according to the table address and determine the station area change relationship according to the topology result are conventional technologies in the field, and the existing method can be adopted, which is not an innovation of the present invention and is not described herein again.
Fig. 5 is a flowchart of the method of the present invention, and the following describes the method for identifying the topology of the distribution room of the present invention with reference to fig. 1 and 4, where the method for identifying the topology of the distribution room includes the following steps:
the concentrator 1 sends out a topology command, starts the topology of the electric meter, and the topology command is transmitted to the electric meter 4 through the power line in a power line carrier mode;
after receiving the topology command from the concentrator 1, a carrier communication module 5 of the electric meter 4 sends a command to a 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 a topology receiving module 3 along the power supply line;
the topology receiving module 3 collects signals from the power supply line, and when magnetic field changes caused by current carrying topology characteristic signals are collected, the topology receiving module 3 outputs the detected magnetic field changes to the topology signal processing module 2 in the form of voltage signals;
the topology signal processing module 2 performs decompiling on the received physical layer data, analyzes the table address, calculates a topology result, and determines the station area user-to-user relationship.
In a real power grid environment, 50Hz harmonic waves and power utilization noise have great interference on a topology process, and in order to reduce the influence of a power grid on the topology, preferably, a rectangular wave signal with the frequency of 46875Hz and the duty ratio of 75% is adopted as a topology characteristic signal. Fig. 6 is a graph of noise data on a power grid line, the test sites are garden B5, B7 and B10 before the south sand vancoco mansion in Guangzhou, the test time is 2020 and 11 months, the test data is obtained by using a multi-invasive technology TMR2102 type TMR linear sensor probe, and the test result is output voltage to ground in unit/mV. As can be seen from FIG. 6, in order to ensure the receiving accuracy, improve the anti-noise capability of the topology, and consider the factors such as the current signal transmission characteristic and the TMR sensitivity to the frequency signal receiving, signals in the 40-50 kHz and 90-100 kHz sections are most suitable to be selected.
In order to improve the anti-interference capability, a dual-frequency communication means is adopted on the premise that the fixed phase relation of two signals is ensured, and the fundamental frequency and the frequency multiplication generated by rectangular waves with the same fixed duty ratio meet the condition. Fig. 7a is a waveform diagram of a square wave with a duty ratio of 50%, and fig. 7b is a signal diagram of a square wave with a duty ratio of 50% after fourier transform. As can be seen from fig. 7a and 7b, the rectangular wave with a duty ratio of 50% does not contain even harmonic components after fourier transform, and although the third harmonic exists, this waveform cannot be used due to the influence of the noise range. Fig. 8a is a waveform diagram of a rectangular wave with a duty ratio not equal to 50%, and fig. 8b is a signal diagram of a rectangular wave with a duty ratio not equal to 50% after fourier transform. As can be seen from fig. 8a and 8b, when the square wave duty ratio is not equal to 50%, there is even harmonic component, and the dual-frequency value conforms to the noise screening interval, as shown by simulation and test results, when the positive duty ratio is 75% (the result of 25% of the square wave characteristic is consistent with 75%, here, the example is 75%), the frequency multiplication amplitude ratio is the largest, and the energy utilization rate of the communication signal 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 (8)
1. A topology identification system for a low-voltage power grid transformer area comprises a concentrator arranged at a meter reading end and an electric meter arranged at a user end, wherein a carrier communication module is arranged in the electric meter, and the concentrator is connected with the electric meter through a power line; it is characterized by also comprising:
the topology transmitting module is arranged in the ammeter and used for injecting current carrying topology characteristic signals into a power line, the topology characteristic signals are rectangular wave signals with duty ratios not equal to 50%, and the topology characteristic signals comprise meter address information;
the topology receiving module is arranged on each phase power line of the meter reading end and used for collecting magnetic field information generated by current carrying topology characteristic signals, converting the collected magnetic field information and outputting the converted magnetic field information;
the topological data processing module is arranged at the meter reading end, one topological data processing module is correspondingly arranged on each three-phase power line, and the topological data processing module is used for receiving information from the topological receiving module, analyzing and calculating to obtain a topological result and a transformer area family change relation.
2. The low voltage grid block topology identification system of claim 1, wherein: 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 the interactive information between the carrier communication module and the ammeter, extracting the meter address information, converting the meter address information into the topological characteristic signal and sending the topological 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 and weak electric coupling cascade module;
and the strong and weak electric coupling cascade module is used for coupling and injecting the analog signal output by the digital-to-analog conversion module into a power line.
3. The low voltage grid block topology identification system of claim 2, wherein: the information receiving and processing control module adopts a PWM coding mode to generate the topological characteristic signal: the information receiving and processing control module splits the table address according to bytes, each bit of data in the bytes is processed based on physical layer logic, each PWM wave with fixed time length represents data 1, no PWM wave with fixed time length represents data 0, or two different-frequency PWM waves represent data 1 and 0 respectively.
4. The low voltage grid block topology identification system of claim 1, wherein: topology receiving module includes signal acquisition module, signal processing module and for the second power module of aforementioned module power supply, signal acquisition module is including being used for gathering electric current signal's on the power line TMR chip.
5. The low voltage grid block topology identification system of claim 4, wherein: the signal acquisition module also 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 induced magnetic field to the differential processing circuit in the form of differential voltage; the differential processing circuit amplifies the differential voltage output by the TMR chip, converts the amplified differential voltage into the voltage to ground and outputs the voltage to the filter circuit; the filtering circuit is used for filtering the voltage signal output by the differential processing circuit.
6. The low voltage grid block topology identification system of claim 4, wherein: the signal processing module comprises a high-pass filter circuit, a band-pass filter circuit and an addition circuit which are connected in sequence.
7. A low-voltage power grid region topology identification method is characterized by comprising the following steps: the method comprises the following steps that a concentrator is arranged at a meter reading end of a 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 power line of the meter reading end, a topology data processing module is arranged at the meter reading end, one 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 a power line;
the method for identifying the transformer area comprises the following steps:
the concentrator sends out a topology command, the ammeter topology is started, and the topology command is transmitted to the ammeter through a power line;
after receiving a topology command from the concentrator, the carrier communication module sends an instruction 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 comprises 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 a power line, and converts and outputs the collected magnetic field information to the topology signal processing module;
the topology signal processing module decompiles the information received from the topology receiving module, analyzes the table address, calculates the topology result and determines the station area user-to-user relationship.
8. The station area identifying method of claim 7, wherein: the topological characteristic signal is a rectangular wave signal with the frequency of 46875Hz and the positive duty ratio equal to 75%.
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