A low voltage line distance measurement method based on m-sequence

Abstract

The invention discloses a carrier communication line distance measurement method based on sequence correlation, and the technical scheme comprises the following steps: step 1: sending an m sequence to a low-voltage power line channel through a test host; step 2: through timing synchronization, a measurement device slave performs correlation operation on the collected sequence to obtain a correlation sequence; step 3: performing peak value judgment and peak-to-average ratio judgment on the correlation sequence to determine the synchronization moment of the first correlation peak; step 4: taking the synchronization moment of the first correlation peak as the standard, the test device slave adds a fixed delay time on the basis of the synchronization moment, and sends the same spread spectrum sequence to the low-voltage power line, and the test device host obtains the synchronization moment in the same manner as step 2 and step 3; step 5: calculating a single line transmission delay, and calculating the distance between the two ends of the test point according to the signal transmission rate in the power line.

Description

Technical Field

[0001] The invention relates to the technical field of distribution network automation, and in particular to a low-voltage line distance measurement method based on m-sequence. Background Art

[0002] At present, low-voltage power grid is an important part of smart grid, which generally refers to the power distribution network with voltage level of AC380V / AV220V. A typical low-voltage power grid consists of transformers, transmission lines, line branches, and user meters, and is often a T-shaped branch structure.

[0003] Low-voltage power grid meter reading has fully covered the power line carrier communication method, most of which use broadband power line carrier communication. In addition to using power lines as carrier communication lines to transmit data, carrier communication lines can also carry out some other additional functions. Carrier communication line ranging can be used as a supplement to the substation topology structure, which is convenient for power personnel to quickly locate and solve problems.

[0004] The structure of the power line channel is complex and the environment is harsh. There is currently no mature method to accurately measure the transmission distance between the two ends of the carrier communication line, thereby effectively supplementing the substation topology. Summary of the invention

[0005] The problem to be solved by the present invention is to solve the deficiencies and defects of the prior art and to accurately measure the transmission distance at both ends of a carrier communication line.

[0006] In view of the defects and shortcomings of the prior art, a low-voltage line distance measurement method based on m-sequence is proposed. The method generates an m-sequence to counter the power line noise, searches for the correlation peak by combining threshold judgment and peak-to-average ratio judgment for the correlation sequence processed by the slave, and performs two correlation peak searches to determine the first correlation peak. By using a complete interaction of the transceiver device, the time difference between the host sending time and the receiving time is calculated to calculate the carrier communication line distance, which specifically includes the following steps:

[0007] Step 1: Send the m sequence to the low-voltage power line channel through the test equipment host at one end of the line to be tested, and record the time T0 when the last data is sent.

[0008] Step 2: Through timing synchronization, the other end of the line to be tested turns on the test equipment slave in advance and starts receiving the power line signal.

[0009] Step 3: Perform a correlation operation on the collected sequence and the symbol sequence corresponding to the m-sequence stored locally in the test equipment slave to obtain a correlation sequence.

[0010] Step 4: Perform peak value judgment and peak-to-average ratio judgment on the correlation sequence. First, search for the maximum correlation peak time. After determining the maximum correlation peak time, perform a second search a period of time in the past to find the first correlation peak time.

[0011] Step 5: After the second search, determine the synchronization time of the first correlation peak.

[0012] Step 6: Based on the synchronization time of the first correlation peak, the test device slave adds a fixed delay time T on the basis of the synchronization time. delay After that, the same m sequence is sent to the low-voltage power line, and the host of the test equipment obtains the synchronization time T1 in the same manner as steps 3, 4, and 5.

[0013] Step 7: Calculate the single line transmission delay T tran , and calculate the distance L between the two ends of the test point based on the signal transmission rate in the power line.

[0014] Furthermore, the synchronization position determination method in step 4 determines whether the value in the correlation sequence satisfies: y(n-n0)<y(n)>y(n+n0), and y(n)>R, where y(n) is a value at a certain moment in the correlation sequence; n0 is the peak interval width; R is a preset peak-to-average ratio determination threshold value. Where N is the length of calculation points, and A is the threshold coefficient.

[0015] Furthermore, the method for determining the synchronization time of the first correlation peak in step 5 is to multiply the maximum peak result by the threshold coefficient G, and use the result as the threshold condition for whether there is a first correlation peak before the maximum correlation peak, and mark the position of the correlation peak greater than the threshold. If there are one or more correlation peaks, the first correlation peak moment is used as the synchronization moment, and if there is no correlation peak, the maximum correlation peak is used as the synchronization moment.

[0016] Furthermore, the specific formula for calculating the carrier communication line distance result L in step 7 is:

[0017]

[0018] L=T tran *V p

[0019] Among them, T a is the fixed transmission delay of the transceiver system, which is determined by the digital and analog components of the transceiver. p It is the speed at which signals travel in power lines.

[0020] The beneficial technical effect of the present invention is as follows: a low-voltage line distance measurement method based on an m-sequence is provided, which generates an m-sequence to counter power line noise, searches for correlation peaks by combining threshold judgment and peak-to-average ratio judgment for the processed correlation sequence, and performs two correlation peak searches to determine the first correlation peak. By utilizing a complete interaction of the transceiver device, the time difference between the host sending time and the receiving time is calculated to determine the distance of the carrier communication line, which has the advantages of high ranging accuracy and low implementation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the overall flow chart of the present invention.

[0022] Figure 2 This is a functional block diagram of the test platform of the present invention.

[0023] Figure 3 This is a test sequence waveform diagram of the present invention.

[0024] Figure 4 This is the correlation calculation result of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0026] Combined with Figure 1 , a low voltage line distance measurement method based on m-sequence, comprising the following steps:

[0027] Step 1: The carrier communication line distance measurement host and slave are installed at both ends of the low-voltage line, and GPS modules are installed on the distance measurement test host and test equipment slave to ensure that the test equipment master and slave are synchronized through satellite timing. The functional block diagram of the test platform is as follows: Figure 2 shown.

[0028] Step 2: Send the m-sequence to the low-voltage power line channel through the test equipment host at one end of the line to be tested, and record the time T0 when the last data is sent; the tested m-sequence is a sequence of 255-length m-sequence upsampled by 2 times, and the sending sequence waveform is as follows: Figure 3 shown.

[0029] Step 3: Through GPS timing synchronization, the other end of the line to be tested turns on the test equipment slave in advance and starts receiving power line signals.

[0030] Step 4: Perform a correlation operation on the collected sequence and the symbol sequence corresponding to the m sequence stored locally in the test device slave to obtain a correlation sequence, such as Figure 4As shown. The maximum correlation peak position is determined by combining threshold judgment and peak-to-average ratio judgment. Among them, the method for determining the synchronization position is that the value in the correlation sequence satisfies the following formula y(n-n0)<y(n)>y(n+n0), and y(n)>R, where y(n) is the value at a certain moment in the correlation sequence; n0=500; R is the preset peak-to-average ratio judgment threshold value In the formula, N=512~1024, A=8~15.

[0031] Step 5: After the second search, determine the synchronization time of the first correlation peak. The method for determining the synchronization time of the first correlation peak is to multiply the maximum peak result by the threshold coefficient G, that is, G = 0.1-0.3. The result is used as the threshold condition for whether there is a first correlation peak before the maximum correlation peak, and the position of the correlation peak greater than the threshold is marked. If there are one or more correlation peaks, the first correlation peak time is used as the synchronization time. If there is no correlation peak, the maximum correlation peak is used as the synchronization time.

[0032] Step 6: Based on the synchronization time of the first correlation peak, the test device slave adds a fixed delay time T on the basis of the synchronization time. delay After that, the same m sequence is sent to the low-voltage power line, and the host of the test equipment obtains the synchronization time T1 in the same manner as steps 3, 4, and 5.

[0033] Step 7: Calculate the single line transmission delay T tran , and calculate the distance L between the two ends of the test point based on the signal transmission rate in the power line. The specific formula for L is:

[0034]

[0035] L=T tran *V p

[0036] Among them, T a is the fixed transmission delay of the transceiver system, which is determined by the digital and analog components of the transceiver. p is the transmission speed of the signal in the power line; finally T tran The error accuracy is related to the data processing working frequency, and the transmission delay error does not exceed plus or minus one data processing working cycle.

[0037] Use this transceiver to measure the distance of a 100-meter cable. p =1.8*10^8 meters per second to calculate the length of the power line. After multiple calculations, the final result is L=97.5 meters.

[0038] The above embodiments are descriptions of specific implementation methods of the present invention rather than limitations of the present invention. Technical personnel in the relevant technical field may make various changes and modifications to obtain corresponding equivalent technical solutions without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should be included in the patent protection scope of the present invention.

Claims

1. A low voltage line distance measurement method based on m-sequence, characterized in that: The following steps are involved: Step 1: Send the m sequence to the low-voltage power line channel through the test equipment host at one end of the line to be tested, and record the time T0 when the last data is sent; Step 2: Through timing synchronization, the other end of the line to be tested turns on the test equipment slave in advance and starts receiving power line signals; Step 3: perform a correlation operation on the collected sequence and the symbol sequence corresponding to the m-sequence stored locally in the test equipment slave to obtain a correlation sequence; Step 4: Search for correlation peaks by combining threshold judgment and peak-to-average ratio. First, search for the maximum correlation peak time. After determining the maximum correlation peak time, perform a second search a period of time in the past to find the first correlation peak time, thereby reducing the impact of multipath channels on the measurement results. Step 5: After the second search, determine the synchronization time of the first correlation peak. The method for determining the first correlation peak is to multiply the maximum correlation peak value result by the threshold coefficient, and use the result as the threshold condition for whether there is a first correlation peak before the maximum correlation peak. Mark the position of the correlation peak that is greater than the threshold. If there are one or more correlation peaks, the first correlation peak time is used as the synchronization time. If there is no correlation peak, the maximum correlation peak is used as the synchronization time. Step 6: Based on the synchronization time of the first correlation peak, the test device slave adds a fixed delay time T on the basis of the synchronization time. delay After that, the same m sequence is sent to the low-voltage power line, and the host of the test equipment obtains the synchronization time T1 in the same manner as steps 3, 4, and 5; Step 7: Calculate the single line transmission delay T tran , and calculate the distance L between the two ends of the test point according to the signal transmission rate in the power line. The specific formula is: L=T tran *V p , where T a is the fixed transmission delay of the transceiver system, which is determined by the digital and analog components of the transceiver. p It is the speed at which signals travel in power lines.

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