CN114520674B - Low-voltage line carrier communication signal input impedance characteristic test method - Google Patents
Low-voltage line carrier communication signal input impedance characteristic test method Download PDFInfo
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- CN114520674B CN114520674B CN202210412987.2A CN202210412987A CN114520674B CN 114520674 B CN114520674 B CN 114520674B CN 202210412987 A CN202210412987 A CN 202210412987A CN 114520674 B CN114520674 B CN 114520674B
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Abstract
The invention relates to the technical field of power line carrier communication, and discloses a method for testing input impedance characteristics of a carrier communication signal of a low-voltage line. Testing input impedance characteristics of a low-voltage power line, including separating test signal output from input; generating an input impedance test signal for a carrier communication frequency band section by section according to the subcarrier number; connecting a node to be tested of a low-voltage line with a standard 50 omega non-inductive resistor in series, outputting a test signal to two ends of the circuit after the connection in series, and simultaneously collecting signals received by two impedances; and carrying out synchronization, grouping, moving average, FFT (fast Fourier transform) and gain adjustment on the received test signals, and obtaining the amplitude and the phase of the input impedance of the node to be tested by using a voltammetry method. The method ensures the accuracy of the input impedance characteristic of the carrier communication signal of the low-voltage line; the complexity is low, and a large amount of power line input impedance characteristic data acquisition work is facilitated; the carrier communication equipment is facilitated to determine the optimal impedance matching scheme, and the communication success rate is improved.
Description
Technical Field
The invention relates to the technical field of power line carrier communication, in particular to a method for testing input impedance characteristics of a carrier communication signal of a low-voltage line.
Background
In order to build a solid communication network foundation, power grid companies lead a plurality of manufacturers to deeply research the power line carrier communication technology and establish interconnection and intercommunication technical specifications of low-voltage power line broadband carrier communication.
The main characteristics of the power line communication channel are channel impedance, noise, attenuation, etc., wherein the impedance characteristics of the low voltage power line serve as one of the main factors affecting the transmission of the carrier communication signal on the low voltage line. As the residential electric equipment is complex and various and can be accessed and switched out at any time and any place, the low-voltage power line network has the characteristics of large time variation, frequent load access and switching-out, various load types and the like, and a universal power impedance model is difficult to obtain.
The method is one of the mainstream research ideas of the impedance characteristics of the current power line channel, and is used for researching the impedance characteristics of the low-voltage power line channel from the actual input impedance value of the low-voltage power line in a specific environment. According to the idea, firstly, the input impedance of the power line in a specific environment needs to be measured, so that the input impedance testing method which is simple, effective and accurate and is suitable for the low-voltage power environment becomes one of the research directions in the field of low-voltage power line carrier communication at present.
Disclosure of Invention
The embodiment of the invention provides a method for testing the input impedance characteristic of a carrier communication signal of a low-voltage line, which mainly solves the problem that the input impedance of the carrier communication signal of the low-voltage line cannot be accurately measured in the prior art.
Therefore, the technical scheme provided by the embodiment of the invention is as follows:
a method for testing the input impedance characteristic of a carrier communication signal of a low-voltage line is characterized by comprising the following steps: and (3) by using a voltammetry principle, the output and the input of a test signal are separated, and the input impedance of a 0.7-12 MHz frequency band applied to power line carrier communication in a low-voltage power channel is measured.
A method for testing the input impedance characteristic of a carrier communication signal of a low-voltage line comprises the following steps:
step 1, carrying out frequency band segmentation on the frequency band of a low-voltage power line carrier communication signal according to the subcarrier number;
and 7, repeating the steps 3 to 6, splicing the test results of different frequency bands in a segmented manner, and obtaining the amplitude characteristic and the phase characteristic of the input impedance to be tested finally.
Compared with the prior art, the invention has the advantages that:
1. according to the invention, an algorithm with lower complexity is used, so that the influence of power line pulse noise and instantaneous narrow-band noise on the input impedance result to be measured is reduced, and the reliability of the input impedance characteristic measurement result in the low-voltage line is improved; 2. the power line carrier communication signal is used as the test signal, the requirement of the low-voltage power line broadband carrier communication interconnection technical specification is met, and the test result has stronger pertinence corresponding to the frequency band used by the current actual power line carrier communication signal; 3. the method is realized on the basis of a resistance measuring principle of a classical voltammetry method, has high feasibility, is easy to realize, has strong practicability, and is suitable for measuring and collecting a large amount of input impedance characteristic data of carrier communication signals of the low-voltage line; 4. according to the input impedance characteristic result, the input impedance characteristic measured by the user node in the low-voltage line can be accurately reflected, so that the ideal impedance matching of the power line carrier communication equipment is favorably determined, and the communication success rate is improved.
Drawings
The drawings are examples of the invention for further understanding and explanation and therefore should not be considered as limiting the invention.
Fig. 1 is a processing flow chart of a method for testing the input impedance characteristic of a carrier communication signal of a low-voltage line according to the invention.
Fig. 2 is a schematic diagram of physical connection of the method for testing the input impedance characteristics of the carrier communication signal of the low-voltage line according to the invention.
Fig. 3 is an impedance amplitude comparison graph of the test result of the low-voltage line carrier communication signal input impedance characteristic test method and the measurement result of the network analysis instrument.
Fig. 4 is an impedance phase comparison diagram of the test result of the low-voltage line carrier communication signal input impedance characteristic test method and the measurement result of the network analysis instrument.
Fig. 5 is a graph of the percentage deviation between the test result of the low-voltage line carrier communication signal input impedance characteristic test method and the measurement result of the network analysis instrument.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.
In the method for testing the input impedance characteristic of the carrier communication signal of the low-voltage line, the parameters are set as shown in the following table.
As shown in fig. 1, the subcarrier signal-to-noise ratio estimation method of the present embodiment includes the following processing steps: firstly, segmenting a low-voltage power line carrier communication signal frequency band according to subcarrier numbers, generating carrier communication test signals corresponding to subcarriers of each segment, connecting impedance of a node to be tested and a 50 omega non-inductive resistor in series, outputting the test signals to two ends of a reactor after the connection in series, continuously outputting the test signals for 20ms, simultaneously respectively collecting signals received by two ends of the 50 omega resistor and input impedance of the node to be tested, calculating input impedance characteristics of the node to be tested in a low-voltage line by utilizing a volt-ampere method resistance measuring principle through synchronization, grouping, sliding average, FFT (fast Fourier transform) and gain adjustment of the test signals, and splicing results according to the frequency band.
As shown in fig. 1, a processing flow of the method for testing the input impedance characteristic of the low-voltage line carrier communication signal of the embodiment includes 7 steps:
step 1: carrying out frequency band segmentation on the frequency band of the low-voltage power line carrier communication signal according to the subcarrier number; in this step, in this example, an HPLC carrier communication signal that meets the low-voltage power line broadband carrier communication interconnection technical specification is selected as a test signal, which includes 512 subcarriers, in this example, subcarriers No. 29 to 491 are used, and each 33 subcarriers are divided into one group from low to high according to the subcarrier number, and are divided into 14 groups in total, that is, the test frequency band is correspondingly divided into 14 segments.
Step 2: respectively generating carrier communication test signals corresponding to each carrier communication signal frequency band segment; in this step, in this example, an HPLC carrier communication signal is selected as a test signal, corresponding to 33 subcarriers in each packet, an HPLC carrier communication signal preamble sequence is used to perform 1024-point IFFT to obtain an OFDM symbol, and after signal modulation, frequency shift is performed to 0-12 MHz, so as to obtain a final carrier communication test signal.
And step 3: the node to be tested of the low-voltage line is connected with a standard 50 omega non-inductive resistor in series, and the generated carrier communication test signal is output to two ends of the 50 omega and the resistor to be tested which are connected in series through an isolating device; the connection mode of the input impedance characteristic test of the node to be tested of the low-voltage line is shown in figure 2; after passing through the isolation capacitor, the 50 omega noninductive resistor is connected in series with the low-voltage node to be tested by using a clamp; the test signal transmitting apparatus outputs the generated carrier communication test signal to the differential transmission signal line. The test signal is sent for 20 ms.
And 4, step 4: respectively and simultaneously acquiring carrier communication test signals received by a node to be tested of a low-voltage line and a standard 50 omega non-inductive resistor end; in this step, as shown in fig. 2, while the carrier communication test signal is sent, the test signal receiving device acquires the two ends of the 50 Ω non-inductive resistor through differential receiving signal lines to obtain the received signal
Collecting the received signals from the two ends of the node to be tested of the low-voltage line
。
And 5: synchronizing, grouping, taking a moving average, FFT and gain adjustment are carried out on the test signals received by the two sides; the step of subjecting the product obtained in the step 4 to
And
performing signal synchronization processing, then grouping data according to the length of 1024 × OFDM symbols, performing moving average processing on the data of each group, and performing 1024-point FFT on the data subjected to moving average; because the carrier communication test signal is output to the two ends of the node impedance to be tested and the 50 omega noninductive resistor through the clamp, and the signals obtained after respective acquisition have certain attenuation, the signal gain adjustment is needed to be carried out on the obtained FFT result to compensate the attenuation.
Step 6: calculating an impedance value and a phase value of each frequency point corresponding to the input impedance of the node to be tested of the low-voltage line by using a voltammetry principle; a step of performing the treatment of step 5
And
the principle of measuring resistance by voltammetry is utilized, and the formula is adopted
And 7, repeating the steps 3-6, and splicing the segmented results of different frequency bands to obtain the amplitude characteristic and the phase characteristic of the input impedance to be detected finally. And 3-6, performing the same treatment on 14 sections of frequency bands, increasing the impedance value and the phase value of the input impedance of the node to be tested from point to high according to the subcarrier number sequence, and splicing the results to obtain the input impedance characteristic result of the input impedance of the low-voltage node to be tested within the frequency band range of 0.7-12 MHz.
In order to verify the performance of the input impedance characterization method of the present embodiment, a network analyzer is used to measure the input impedance of a known node to be measured (in the present embodiment, the reactance combination of 10 Ω +15nF is taken as an example), and the impedance is measured in the frequency band range of 0.7 to 12MHz, and the result is used as a reference value to compare and analyze the measurement result obtained by the method of the present invention. As shown in fig. 3, the abscissa axis represents different frequency points, the ordinate axis represents the amplitude of the input impedance, and for the input impedance of the known node to be tested, in the frequency band range of 0.7 to 12MHz, the input impedance amplitude obtained by using the method for testing the input impedance characteristic of the carrier communication signal of the low-voltage line of the invention is compared with the impedance amplitude obtained by measuring through a network analyzer, and the impedance amplitude result lines have the same trend; as shown in fig. 4, the axis of abscissa represents different frequency points, the axis of ordinate represents the phase value of the input impedance, the phase value of the input impedance obtained by the testing method of the present invention is compared with the phase value of the impedance obtained by the measurement of the network analyzer, and the line trend of the impedance phase result is consistent; as shown in fig. 5, the abscissa axis represents different frequency points, and the ordinate axis represents the percentage of deviation from the net minute measurement result, and compared with the impedance characteristic measured by the network analyzer, the input impedance characteristic obtained by using the test method of the present invention has an amplitude deviation of less than 2% and a phase deviation of less than 13%. The input impedance characteristic tested by the invention is ideal, and the method for testing the input impedance characteristic of the low-voltage line carrier communication signal is simple and reliable. Therefore, the present embodiment is an excellent input impedance characteristic testing method, and is suitable for complex power line environments.
The above-mentioned embodiments are illustrative of the specific embodiments of the present invention, and not restrictive, and it should be understood that various changes and modifications may be made without departing from the spirit and scope of the invention by those skilled in the art that all equivalent embodiments are intended to be included within the scope of the invention.
Claims (4)
1. A method for testing the input impedance characteristic of a carrier communication signal of a low-voltage line is characterized by comprising the following steps:
step 1, carrying out frequency band segmentation on the frequency band of a low-voltage power line carrier communication signal according to the subcarrier number;
step 2, respectively generating carrier communication test signals corresponding to each carrier communication frequency band segment;
step 3, connecting the node to be tested of the low-voltage line with a standard 50 omega non-inductive resistor in series, and outputting the generated carrier communication test signal to two ends of the 50 omega non-inductive resistor and the node to be tested which are connected in series through an isolating device;
step 4, respectively and simultaneously acquiring carrier communication test signals received by a node to be tested of the low-voltage line and a standard 50 omega non-inductive resistor end;
step 5, synchronizing, grouping, taking a moving average, FFT and gain adjustment are carried out on the test signals received by the two sides;
step 6, calculating an impedance value and a phase value of each frequency point corresponding to the input impedance of the node to be tested of the low-voltage line by using a voltammetry principle;
and 7, repeating the steps 3 to 6, splicing the test results of different frequency bands in a segmented manner, and obtaining the amplitude characteristic and the phase characteristic of the input impedance to be tested finally.
2. The method for testing the input impedance characteristic of the carrier communication signal of the low-voltage line as claimed in claim 1, wherein: in the step 2, a test signal for inputting an impedance characteristic test is generated by using a preamble sequence of a high-speed power line carrier HPLC signal, the HPLC signal conforms to a low-voltage power line broadband carrier communication interconnection technical specification set by a power grid company, the test signal includes 512 subcarriers, the frequency band corresponds to 24KHz to 12MHz, subcarriers 29 to 491 are selected according to the sequence of subcarrier numbers from low to high, each 33 subcarriers are used as a group to segment a carrier communication frequency band, each frequency band is segmented, and a carrier communication test signal for inputting the impedance characteristic test is generated by using the HPLC preamble sequence.
3. The method for testing the input impedance characteristic of the carrier communication signal of the low-voltage line as claimed in claim 1, wherein: in the step 3 and the step 4, the test signal sending device outputs the test signal to two sides of the 50 omega noninductive resistor and the input impedance of the node to be tested through the sending signal line; meanwhile, the test signal receiving device respectively receives test signals received by the 50 omega non-inductive resistor and the input impedance of the node to be tested through a receiving signal line; the sending channel and the receiving channel of the test signal are independent from each other, the sending signal line and the receiving signal line are independent from each other, and the sending signal line and the receiving signal line are differential two signal lines, so when physical connection is carried out, a clamp is needed to be used for connecting 4 signal lines to two ends of the input impedance of the node to be tested.
4. The method for testing the input impedance characteristic of the carrier communication signal of the low-voltage line as claimed in claim 1, wherein: in the step 5, the 50 Ω non-inductive resistor and the node to be tested are input to two sides of the impedance, after the received test signals are synchronized, the data are grouped according to the length of 1024 × OFDM symbols, and the grouped data are subjected to the sliding average operation, so that the instantaneous noise influence of the low-voltage power line is eliminated.
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| US7239155B2 (en) * | 2003-11-14 | 2007-07-03 | Impact Technologies Llc | Electrochemical impedance measurement system and method for use thereof |
| CN203054091U (en) * | 2012-11-29 | 2013-07-10 | 中国电力科学研究院 | Narrow-band carrier access impedance testing device for low-voltage power lines |
| CN104184494B (en) * | 2014-08-29 | 2016-09-21 | 国家电网公司 | A kind of test system and method for broadband power line carrier channel access impedance |
| CN106645965A (en) * | 2017-01-04 | 2017-05-10 | 西南科技大学 | Method for measuring RLC (Radio Link Control) parameters |
| CN209102805U (en) * | 2018-06-06 | 2019-07-12 | 青岛鼎信通讯股份有限公司 | A kind of midium voltage cable shielded layer narrowband carrier access impedance test system |
| CN114047384B (en) * | 2021-11-04 | 2024-05-07 | 展讯通信（上海）有限公司 | Low-impedance device testing module, system and method based on crosstalk principle |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2096778C1 (en) * | 1996-07-01 | 1997-11-20 | Евгений Михайлович Кулагин | Voltammetry method |
| CN103063926A (en) * | 2012-12-19 | 2013-04-24 | 中国电力科学研究院 | Test method and test device for low-voltage power line narrowband carrier access impedance |
| CN106209166A (en) * | 2016-08-30 | 2016-12-07 | 国家电网公司 | Power information acquisition system failure detector |
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