A characteristic current communication method suitable for the electric power field

Abstract

The present invention relates to the field of power distribution automation technology, and discloses a characteristic current communication method applicable to the power field, and the steps are as follows: setting characteristic frequency, signal cycle and minimum signal transmission time; setting the single transmission time and total transmission time of characteristic sequence information bits, and designing characteristic sequence C0; the transmitting device transmits characteristic current; the receiving device detects the theoretical transmission signal characteristic frequency and sets the decoding sequence C1; the characteristic frequency of the received signal is detected to obtain Sc1' and Sc2'; Sc1' is judged to obtain C1'; the number of positions Ne where C1' and C1 have different values ​​is calculated; Sc2' is demodulated to obtain the trust degree En of C1'; if Ne≤En, the characteristic current reaches the receiving device; otherwise, it does not reach. The present invention is aimed at the current micro-current communication technology, and through the optimization of the transmission sequence and the improvement of the detection algorithm, the transmission power is reduced to 60% of the original scheme under the premise of not lower than the bit error rate of the current scheme, and the engineering practicability is strong.

Description

Technical Field

[0001] The present invention relates to the field of power distribution automation technology, and in particular to a characteristic current communication method applicable to the power field, mainly used for micro-current communication in a power distribution system. Background Art

[0002] In recent years, topology identification technology based on microcurrent communication has been widely used in power grids. This technology implements topology identification by injecting characteristic currents into the grid and using devices such as concentrators, intelligent circuit breakers, or LTUs to collect signals and detect the characteristic current components. Considering the impact of grid background noise on current detection accuracy, the current commonly used approach is to transmit interharmonic currents, requiring a current amplitude of 400mA. This high current amplitude results in high power consumption and also places high demands on the heat dissipation performance of the current transmitter. Therefore, further reducing the current amplitude while maintaining detection accuracy has become a key research priority. Summary of the Invention

[0003] In view of the shortcomings and defects of the prior art, the present invention provides a characteristic current communication method applicable to the electric power field.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A characteristic current communication method applicable to the electric power field comprises the following steps:

[0006] S1: Set the characteristic frequency F of the communication current signal, and calculate the signal period T = 1 / F and the minimum signal transmission time Tw based on F;

[0007] S2: Set the transmission time of a single information bit of the signature sequence Tc = 10*Tw and the total transmission time Ts, and design the signature sequence C0 based on Ts and Tc;

[0008] The characteristic sequence C0 consists of 1 and 0, and its number of bits N = Ts / Tc;

[0009] S3: The current switching module in the transmitting device modulates the PWM signal according to T and a duty cycle of 1 / 3 to generate a characteristic current and send it to the power line. When the value in the characteristic sequence C0 is 1, current switching is performed, and when the value in the characteristic sequence C0 is 0, current switching is not performed.

[0010] S4: For the theoretical transmitted signal, with Tw as the detection step size, the receiving device uses DFT windows of sizes Tw1 and Tw2 to detect the characteristic frequency of the current signal. The detection results are Sc1 and Sc2 respectively. The decoding sequence C1 is set according to the waveform trend of Sc1.

[0011] The decoding sequence C1 consists of 2, 1, and 0, Tw1 is the total time that the feature sequence C0 is continuously 1, and Tw2 is the total time from the starting 1 to the ending 1 in the feature sequence C0;

[0012] S5: For the received signal, with Tw as the detection step size, the receiving device uses DFT windows of sizes Tw1 and Tw2 to detect the characteristic frequency of the current signal, and the obtained detection results are Sc1' and Sc2' respectively;

[0013] S6: The receiving device makes a hard decision on Sc1' based on the numerical information in C1 to obtain C1'; compares the numerical values ​​of C1' and C1' at corresponding positions one by one, and calculates the number of positions Ne where the numerical values ​​of the two differ;

[0014] S7: Based on the waveform trend of Sc2, the receiving device soft-demodulates Sc2' and obtains the confidence level En of the current sequence C1', which is used as the fault tolerance number of C1';

[0015] S8: Compare Ne and En: If Ne≤En, it is determined that the characteristic current signal has reached the receiving device; otherwise, it is determined that the characteristic current signal has not reached the receiving device, and jump to S5.

[0016] Furthermore, C0 in S2 is [1 1 1 0 0 0 1 1 1 0 0 0 1 1 1].

[0017] Furthermore, in S4, Tw1=3*Tc, Tw2=15*Tc.

[0018] Furthermore, the specific process of performing hard decision on Sc1' according to the numerical information in C1 in S6 to obtain C1' is as follows:

[0019] S61: extracting data from Sc1' according to a preset step size, and composing the extracted data into a new sequence C11;

[0020] S62: Extract the data at the corresponding position in C11 according to the positions of 0 and 2 in C1;

[0021] S63: Calculate the minimum value MinValue2 among the values ​​of all 2s in C1 at the corresponding positions in C11, and the maximum value MaxValue0 among the values ​​of all 0s in C1 at the corresponding positions in C11;

[0022] S64: Calculate the difference between the value of the corresponding position of 2 in each C1 in C11 and the value of the corresponding position of 0 adjacent to 2 in each C1 in C11, and record the difference as Err1 to Err6;

[0023] S65: Calculate MinValue2 - MaxValue0 = ErrValue and the number N20 of values greater than 0.05 among Err1 to Err6;

[0024] S66: If any of the following conditions is satisfied:

[0025] (1) ErrValue > 0.03 and MinValue2 > 0.07;

[0026] (2) ErrValue > 0 and N20 > 3;

[0027] Then it is considered that the values at the corresponding positions of all 2s and 0s in C1 at this time in C1' are accurate, and jump to the next step; otherwise, it is determined that the characteristic current signal has not reached the receiving device;

[0028] S67: Denote the position of 1 in C1 as d

[0032] ,

[0035] ,

[0034] ,

[0033] , , , , and the positions of the adjacent 0s and 2s are d i0 and d i2 ;

[0029] If the value at position d in C11 i0 < the value at position d in C11 i < the value at position d in C11 i2 < the value at position d in C11 i < the value at position d in C11 i < the value at position d in C11

[0030] Furthermore, the length of Sc1' in S61 is 195, and the length of C11 is 13.

[0031] Furthermore, the preset step size in S61 is 15, and one data is extracted from Sc1' every 15 step sizes, and the average value of this data and the two data before and after it is used as a component value of C11.

[0032] Furthermore, the soft demodulation in S7 is specifically as follows:

[0033] S71: Obtain the highest point position p of the Sc2 waveform;

[0034] S72: Obtain the average values a1 to a5 of the data at position p of Sc2' and the nine positions before and after it, the average values of the data at position p - 70 and the nine positions before and after it, the average values of the data at position p - 140 and the nine positions before and after it, the average values of the data at position p + 70 and the nine positions before and after it, and the average values of the data at position p + 140 and the nine positions before and after it;

[0035] S73: Calculate the intensity of the characteristic frequency m=a1 / P based on a1 and the proportion P of 1 in C0;

[0036] S74: When the characteristic frequency intensity m meets the preset value and a1>a2>a3 and a1>a4>a5, the confidence En of the current sequence is calculated; otherwise, it is determined that the characteristic current signal has not reached the receiving device.

[0037] Furthermore, the calculation method of En is as follows: the following three conditions exist:

[0038] (1) a1>1.1a2 and a1>1.1a4;

[0039] (2) a1>1.7a3 and a1>1.7a5;

[0040] (3) a1 / maxV>0.8;

[0041] If (1) and (2) are satisfied, then En = 2;

[0042] If (1) or (2) and (3) are satisfied, then En = 1;

[0043] Otherwise En=0;

[0044] Where maxV is the maximum value of Sc2' in the data of the 70 positions before and after position p.

[0045] Preferably, the sending device may be an HPLC module, an intelligent circuit breaker, or a line terminal unit (LTU).

[0046] Preferably, the receiving device may be an intelligent circuit breaker, a line terminal unit (LTU), a data collection terminal, or a fusion terminal.

[0047] The beneficial effects of the present invention are as follows: for the current micro-current communication technology, under the premise of ensuring the recognition accuracy, an effective new solution is proposed, including the optimization of the transmission sequence and the improvement of the detection algorithm, so that the transmission power can be reduced to 62.5% of the original without being lower than the bit error rate of the current communication scheme, and the engineering practicability is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the overall flow chart of the present invention.

[0049] Figure 2 1 is a time domain waveform diagram of the transmission current of two schemes in the embodiments of the present invention.

[0050] Figure 3 This is a diagram showing the detection results of the signal sent by this solution in an embodiment of the present invention.

[0051] Figure 4This is a diagram showing the detection results of the received signal of this solution in an embodiment of the present invention.

[0052] Figure 5 2 is a comparison chart of the bit error rates of the two solutions in the embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0054] like Figure 1 As shown, a characteristic current communication method applicable to the power field is as follows:

[0055] S1: Set the characteristic frequency F of the communication current signal to 833.33 Hz, and calculate the signal period T = 1 / F = 1.2 ms and the minimum signal transmission time Tw = 60 ms based on F.

[0056] S2: Set the transmission time of a single information bit of the signature sequence Tc = 10*Tw = 600ms and the total transmission time Ts = 9s. Based on Ts and Tc, design the signature sequence C0 = [1 1 1 0 0 0 1 1 1 0 0 0 1 1 1];

[0057] The characteristic sequence C0 consists of 1 and 0, and its bit number N = Ts / Tc.

[0058] S3: The current switching module in the sending device (intelligent circuit breaker) modulates the PWM signal according to T and a duty cycle of 1 / 3 to generate a characteristic current and send it to the power line. When the value in the characteristic sequence C0 is 1, current switching is performed; when the value in the characteristic sequence C0 is 0, current switching is not performed.

[0059] like Figure 2 As shown, the upper figure shows the time-domain waveform of the transmitted current of an existing microcurrent communication solution, and the lower figure shows the time-domain waveform of the transmitted current of this solution. The number of points in each characteristic code is 3000. It can be seen that the characteristic sequences of the two solutions are different, but the time it takes to transmit a "1" is the same, 5.4s (i.e., 27,000 points). The bottom of the figure also shows a partial zoom of the time-domain waveform of the transmitted current of this solution.

[0060] S4: For the theoretical transmitted signal, with Tw as the detection step size, the characteristic frequency of the current signal is detected at the receiving device (line terminal unit LTU) using DFT windows of Tw1 = 3 * Tc = 1.8s and Tw2 = 15 * Tc = 9s. The detection results are Sc1 and Sc2, respectively. The decoding sequence C1 is set to [0 1 2 1 0 1 2 1 0 1 21 0] according to the waveform trend of Sc1.

[0061] The decoding sequence C1 consists of 2, 1, and 0, Tw1 is the total time that the feature sequence C0 is continuously 1, and Tw2 is the total time from the starting 1 to the ending 1 in the feature sequence C0.

[0062] like Figure 3 As shown in the figure, a sliding Fourier transform (SDFT) algorithm is used to extract the characteristic frequency signal, with a sliding step of Tw. The upper figure shows the detection results using the Tw1 window. It can be seen that the detection result using the Tw1 window is a straight line with six rising and falling segments. Due to the misidentification of short sequences, a midpoint is added between the high and low points as the sequence standard. The corresponding C1 is also set to [0 1 2 1 0 1 2 1 0 1 2 1 0], and the sequence length is 13, which is similar to the 16-bit length of the existing solution. The lower figure shows the detection results using the Tw2 window. It can be seen that the detection signal strength using the Tw2 window is a segmented rising process lasting 150Tw and a segmented falling process lasting 150Tw. The 150Tw period corresponds exactly to the total transmission time of the characteristic sequence of 9 seconds. The segmented rising and falling processes each have two flat periods, corresponding to the process when three consecutive zeros in the characteristic sequence C0 enter and leave the detection window. The basis for the demodulation, judgment and position selection of Sc1' and Sc2' mentioned later in this solution all comes from this.

[0063] S5: For the received signal, with Tw as the detection step, the line terminal unit LTU uses DFT windows of sizes Tw1=3*Tc=1.8s and Tw2=15*Tc=9s to detect the characteristic frequency of the current signal. The detection results are Sc1' and Sc2', both of which have a length of 195.

[0064] like Figure 4 As shown, the received signal in this scheme is the signal after the transmission signal is superimposed with the background noise. The peak value of the background noise is 250A. From the detection results of the Tw1 window and the Tw2 window, it can be seen that although the characteristic current signal is only 0.25A, it is still clearly analyzed. Figure 3 It can be seen that Figure 4The signal intensity error obtained is small. This is because the time of Tw1 and Tw2 is long and the spectrum leakage is very weak. Since the characteristic frequency content in the background current is very low, the error obtained by detection is small, which further illustrates the feasibility of the practical application of this scheme.

[0065] S6: The line terminal unit LTU performs a hard decision on Sc1' based on the numerical information in C1 to obtain C1'; compares the numerical values ​​of C1' and C1' at corresponding positions one by one, and calculates the number of positions Ne where the numerical values ​​of the two positions are different.

[0066] The specific process of making a hard decision on Sc1' based on the numerical information in C1 to obtain C1' is as follows:

[0067] S61: extract data from Sc1' according to the preset step size of 15, calculate the average value of the data and the two data before and after it as a component value of C11, and finally form a new sequence C11 with a length of 13;

[0068] S62: Extract the data at the corresponding position in C11 according to the positions of 0 and 2 in C1;

[0069] S63: Calculate the minimum value MinValue2 among the values ​​of all 2s in C1 at the corresponding positions in C11, and the maximum value MaxValue0 among the values ​​of all 0s in C1 at the corresponding positions in C11;

[0070] S64: Calculate the difference between the value of the corresponding position of 2 in each C1 in C11 and the value of the corresponding position of 0 adjacent to 2 in each C1 in C11, and record the difference as Err1 to Err6;

[0071] S65: Calculate MinValue2-MaxValue0=ErrValue and the number N20 of values ​​greater than 0.05 in Err1-Err6;

[0072] S66: If any of the following conditions are met:

[0073] (1)ErrValue>0.03 and MinValue2>0.07;

[0074] (2) ErrValue>0 and N20>3;

[0075] It is considered that the values ​​of all 2s and 0s in C1 at the corresponding positions in C1' are accurate, and the process goes to the next step; otherwise, it is determined that the characteristic current signal has not reached the line terminal unit LTU;

[0076] S67: Note that the position of 1 in C1 is d i , the adjacent 0 and 2 positions are d i0 and d i2 ;

[0077] If the value at the position in C11 is d i0 The value at the position < the value of d in C11 i The value at the position < the value of d in C11 i2 The value at the position, then the decision d i The value at the corresponding position in C1’ is 1, otherwise the decision d i The value at the corresponding position in C1’ is 0; thus, the complete C1’ is obtained.

[0078] S7: According to the waveform trend of Sc2, the line terminal unit LTU performs soft demodulation on Sc2’ to obtain the confidence En of the current sequence C1’, which is used as the error tolerance count of C1’.

[0079] The specific process of the soft demodulation is as follows:

[0080] S71: Obtain the highest point position p of the Sc2 waveform;

[0081] S72: Obtain the average values of the data at the p position and the 9 positions before and after it, the average values of the data at the p - 70 position and the 9 positions before and after it, the average values of the data at the p - 140 position and the 9 positions before and after it, the average values of the data at the p + 70 position and the 9 positions before and after it, and the average values of the data at the p + 140 position and the 9 positions before and after it, namely a1 to a5;

[0082] S73: According to a1 and the proportion P of 1 in C0, calculate the intensity m of the characteristic frequency as m = a1 / P;

[0083] S74: When the characteristic frequency intensity m meets the preset value and a1 > a2 > a3 and a1 > a4 > a5, calculate the confidence En of the current sequence, otherwise determine that the characteristic current signal has not reached the line terminal unit LTU.

[0084] The calculation method of En is as follows: There are the following three conditions:

[0085] (1) a1 > 1.1a2 and a1 > 1.1a4;

[0086] (2) a1 > 1.7a3 and a1 > 1.7a5;

[0087] (3) a1 / maxV > 0.8;

[0088] If (1) and (2) are satisfied, then En = 2;

[0089] If (1) or (2) is satisfied and (3) is satisfied, then En = 1;

[0090] Otherwise, En = 0;

[0091] Where maxV is the maximum value of Sc2' in the data of the 70 positions before and after position p.

[0092] S8: Compare Ne and En: If Ne≤En, it is determined that the characteristic current signal has reached the line terminal unit LTU; otherwise, it is determined that the characteristic current signal has not reached the line terminal unit LTU, and jump to S5.

[0093] like Figure 5 As shown, based on the detection of this sequence C1, under the existing communication scheme, there is a 3dB performance difference when the sending current is 250mA and when the sending current is 400mA. The adoption of this scheme can make up for this 3dB performance difference and obtain a bit error rate performance similar to that of the existing communication scheme. This proves that this scheme can reduce the transmission signal power while ensuring the bit error rate performance.

[0094] The above embodiments are illustrations of specific implementation methods of the present invention, rather than limitations of the present invention. Technicians in the relevant technical fields may make various transformations and changes 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 scope of patent protection of the present invention.

Claims

1. A characteristic current communication method applicable to the electric power field, characterized in that: The following steps are involved: S1: Set the characteristic frequency F of the communication current signal, and calculate the signal period T=1 / F and the minimum signal transmission time Tw according to F; S2: Set the transmission time of a single information bit of the feature sequence Tc=10*Tw and the total transmission time Ts, and design the feature sequence C0 according to Ts and Tc; The characteristic sequence C0 consists of 1 and 0, and its number of bits N = Ts / Tc; S3: The current switching module in the transmitting device modulates the PWM signal according to T and a duty cycle of 1 / 3 to generate a characteristic current and send it to the power line, wherein the current switching is performed when the value in the characteristic sequence C0 is 1, and the current switching is not performed when the value in the characteristic sequence C0 is 0; S4: For the theoretical transmission signal, Tw is used as the detection step size, and the characteristic frequency of the current signal is detected by using DFT windows of sizes Tw1 and Tw2 in the receiving device, and the detection results are Sc1 and Sc2 respectively; the decoding sequence C1 is set according to the waveform trend of Sc1; The decoding sequence C1 is composed of 2, 1, and 0, Tw1 is the total time of continuous 1 in the feature sequence C0, and Tw2 is the total time from the starting 1 to the ending 1 in the feature sequence C0; S5: With respect to the received signal, the receiving device uses a DFT window with sizes of Tw1 and Tw2 to detect the characteristic frequency of the current signal, with Tw as the detection step size, and the obtained detection results are Sc1' and Sc2' respectively; S6: The receiving device makes a hard decision on Sc1' according to the numerical information in C1 to obtain C1'; compares the numerical values ​​of C1' and C1' at the corresponding positions one by one, and calculates the number of positions Ne where the numerical values ​​of the two are different; S7: According to the waveform trend of Sc2, the receiving device soft-demodulates Sc2' to obtain the trustworthiness En of the current sequence C1' as the fault tolerance number of C1'; S8: Compare Ne and En: If Ne≤En, it is determined that the characteristic current signal has reached the receiving device; otherwise, it is determined that the characteristic current signal has not reached the receiving device, and jump to S5.

2. A characteristic current communication method applicable to the electric power field according to claim 1, characterized in that: C0 in S2 is [1 1 1 0 0 0 1 1 1 0 0 0 1 1 ].

3. A characteristic current communication method applicable to the electric power field according to claim 1, characterized in that: In S4, Tw1=3*Tc, Tw2=15*Tc.

4. A characteristic current communication method applicable to the electric power field according to claim 1, characterized in that: The specific process of making a hard decision on Sc1' according to the numerical information in C1 in S6 to obtain C1' is: S61: extracting data from Sc1' according to a preset step length, and composing the extracted data into a new sequence C11; S62: extracting data at corresponding positions in C11 according to the positions of 0 and 2 in C1; S63: Calculate the minimum value MinValue2 among the values ​​of all 2s in C1 at the corresponding positions in C11, and the maximum value MaxValue0 among the values ​​of all 0s in C1 at the corresponding positions in C11; S64: Calculate the difference between the value of the corresponding position of 2 in each C1 in C11 and the value of the corresponding position of 0 adjacent to 2 in each C1 in C11, and record the difference as Err1 to Err6; S65: Calculate MinValue2-MaxValue0=ErrValue and the number N20 of values ​​greater than 0.05 in Err1-Err6; S66: If any of the following conditions are met: (1)ErrValue>0.03 and MinValue2>0.07; (2) ErrValue>0 and N20>3; It is considered that the values ​​of all 2s and 0s in C1 at the corresponding positions in C1' are accurate, and the next step is jumped; otherwise, it is determined that the characteristic current signal has not reached the receiving device; S67: Let the position of 1 in C1 be d i , the positions of the adjacent 0 and 2 are d i0 and d i2 ; If the value at the position d in C11 i0 is less than the value at the position d in C11 i is less than the value at the position d in C11 i2 then the decision d i has a corresponding value of 1 in C1', otherwise the decision d i has a corresponding value of 0 in C1'; thus the complete C1' is obtained.

5. A characteristic current communication method applicable to the electric power field according to claim 4, characterized in that: The length of Sc1' in S61 is 195, and the length of C11 is 13.

6. A characteristic current communication method applicable to the electric power field according to claim 4, characterized in that: The preset step length in S61 is 15, and one data is extracted from Sc1' every 15 steps, and the average value of the data and the two data before and after it is calculated as a component element value of C11.

7. A characteristic current communication method applicable to the electric power field according to claim 1, characterized in that: The soft demodulation in S7 is as follows: S71: Obtain the highest point position p of the Sc2 waveform; S72: Obtain the average value of the data of Sc2' at the p position and the 9 positions before and after it, the average value of the data of the p-70 position and the 9 positions before and after it, the average value of the data of the p-140 position and the 9 positions before and after it, the average value of the data of the p+70 position and the 9 positions before and after it, and the average values ​​a1-a5 of the data of the p+140 position and the 9 positions before and after it; S73: Calculate the intensity of the characteristic frequency m=a1 / P according to a1 and the proportion P of 1 in C0; S74: When the characteristic frequency intensity m meets the preset value and a1>a2>a3 and a1>a4>a5, the confidence En of the current sequence is calculated, otherwise it is determined that the characteristic current signal has not reached the receiving device.

8. A characteristic current communication method applicable to the electric power field according to claim 7, characterized in that: The calculation method of En is as follows: There are three conditions: (1) a1>1.1a2 and a1>1.1a4; (2) a1>1.7a3 and a1>1.7a5; (3) a1 / maxV>0.8; If (1) and (2) are satisfied, then En = 2; If (1) or (2) and (3) are satisfied, then En = 1; Otherwise En=0; Where maxV is the maximum value of Sc2' in the data of the 70 positions before and after position p.

9. A characteristic current communication method applicable to the electric power field according to claim 1, characterized in that: The sending device may be an HPLC module or an intelligent circuit breaker or a line terminal unit LTU.

10. A characteristic current communication method applicable to the electric power field according to claim 1, characterized in that: The receiving device may be an intelligent circuit breaker, a line terminal unit LTU, a collection terminal, or a fusion terminal.

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