A current carrier communication method based on pulse modulation technology

Abstract

The present invention discloses a current carrier communication method based on pulse modulation technology. The technical solution comprises the following steps: step 1: using a pseudo-random algorithm and a Manchester coding algorithm to generate a leading sequence; step 2: using a pseudo-random algorithm and a Manchester coding algorithm to generate a forward information coding sequence; step 3: inverting the forward information coding sequence in step 2 to generate a reverse information coding sequence; step 4: performing Manchester coding on the original information and then modulating the information coding sequence; step 5: combining the leading sequence and the information sequence into a complete transmission sequence, using the sequence to perform current switching control, and generating a pulse width modulation current signal of a specific order; step 6: sampling and filtering the current signal; step 7: performing a sliding correlation operation on the leading sequence and the sampled data to perform synchronous detection; and step 8: performing a correlation operation on the sampled data segmentation and the forward information coding sequence to demodulate the information.

Description

Technical Field

[0001] The present invention relates to the field of current communication technology, and in particular to a current carrier communication method based on pulse modulation technology. Background Art

[0002] Current carrier communication is a communication technology that transmits information by superimposing tiny distortions on the grid current. It has the characteristics of unidirectional transmission and low signal attenuation, and has great benefits in the field of distribution line topology identification. However, due to the complex structure of distribution lines and the diversity of power loads, there is a large amount of current noise in the power grid, which has a significant impact on current carrier communication.

[0003] Currently, current carrier communications mostly use the OOK modulation and demodulation method. The transmitter uses a current signal of a specific frequency to modulate the information and demodulate it at the receiver. This method has poor anti-interference performance, high current signal transmission power, and low information transmission efficiency. Summary of the Invention

[0004] The present invention addresses the shortcomings and defects of existing technologies and provides a current carrier communication method based on pulse modulation technology. The information transmitter generates a pulse width modulation signal in a specific sequence by controlling the switching of the current signal. The information receiver samples, filters, and demodulates the current signal to achieve information transmission.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] Step 1: Generate an M-bit pseudo-random sequence and perform Manchester encoding on the pseudo-random sequence to obtain a 2M-bit preamble sequence.

[0007] Step 2: Generate an N-bit pseudo-random sequence and perform Manchester encoding on the pseudo-random sequence to obtain a 2N-bit forward information coding sequence.

[0008] Step 3: Invert the forward information coding sequence described in step 2 to obtain a 2N-bit reverse information coding sequence.

[0009] Step 4: Manchester encode the K-bit original information to obtain 2K-bit encoded information. In the encoded information, 1'b is modulated using the forward information encoding sequence, and 0'b is modulated using the reverse information encoding sequence to generate an information sequence.

[0010] Step 5: The preamble sequence generated in step 1 and the information sequence generated in step 4 form a complete transmission sequence with a total sequence length of (2*M+4*K*N) bits. This sequence is used for current switching control to generate a pulse width modulated current signal in a specific sequence and inject it into the power line.

[0011] Step 6: Sample the current signal on the power line and perform digital filtering on the sampled data.

[0012] Step 7: Perform sliding correlation operation on the leading sequence and the sampled data. When the correlation value meets the set threshold S, the signal synchronization is successful.

[0013] Step 8: After the signal synchronization is successful, the sampled data segments are correlated with the forward information coding sequence to obtain 2K correlation values. The difference between every two correlation values can obtain K bits of information.

[0014] Furthermore, in steps 1 and 2, the pseudo-random sequence is usually generated by a PN sequence. The values of M and N are selected according to the current channel parameters of the application scenario, and the value range is 16~8192. The signal strength of the preamble sequence is higher than that of the information sequence, so the value of N is usually smaller than M.

[0015] Furthermore, in step 3, the reverse information coding sequence is the inverse of the forward information coding sequence in step 2.

[0016] Furthermore, in step 4, the signal transmission process is affected by the frequency deviation of the device, so the original information length is usually less than 256 bits.

[0017] Furthermore, in step 4, the K bits of original information may include checksum and error correction information to ensure the validity of the transmitted information.

[0018] Furthermore, in step 5, each bit of information 1'b in the transmission sequence represents a pulse with a width of T0 and an intensity of A0, the transmission signal sequence controls the transmission of current pulses with two widths of T0 and 2T0, and the center frequency of the transmission signal sequence is f0≈1 / (2T0).

[0019] Furthermore, in step 5, the current channel has a better frequency response characteristic below 10,000 Hz, so the value range of f0 is 50-10,000 Hz, the value range of T0 is 0.05-10 milliseconds, and the value range of pulse intensity A0 is 10-800 mA depending on the application scenario.

[0020] Furthermore, in step 6, to ensure accurate sampling, the sampling frequency f of the receiving end is s It should be higher than 4 times f0, with an accuracy of no less than 12 digits.

[0021] Furthermore, in step 6, the digital filter selects an FIR bandpass filter, the passband frequency is set to f0±1 / 3f0, the lower limit cutoff frequency is 1 / 3f0, and the upper limit cutoff frequency is 5 / 3f0. The filter parameters can be adjusted according to the channel parameters.

[0022] Furthermore, in step 7, the correlation value is the leading sequence according to f sThe sampling is quantized and multiplied and accumulated with the current sampling data. When the correlation value meets the set threshold S, the synchronization is successful. When the correlation value is positive, the current direction is positive, and when the correlation value is negative, the current direction is reverse.

[0023] Furthermore, in step 8, the correlation value is the forward information encoding according to f s The quantized samples are multiplied and accumulated with the sampled data. The difference between the 2K correlation values is multiplied by the current direction bit. If the result is greater than zero, it is the information bit 1'b; if it is less than zero, it is the information bit 0'b.

[0024] The beneficial technical effects of the present invention are as follows: the method provides a current carrier communication method based on pulse modulation technology, which has greatly improved the anti-interference ability and transmission efficiency compared with OOK modulation technology. At the same time, it can realize the identification of the current direction, and then determine the power consumption relationship between the sending end and the receiving end, which is of great significance in the field of digitalization of distribution line structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the overall flow chart of the current carrier communication method of the present invention.

[0026] Figure 2 It is a diagram of the structure of a signal frame sent in an embodiment of the present invention.

[0027] Figure 3 1 is a spectrum diagram of a transmitted signal in an embodiment of the present invention.

[0028] Figure 4 is a frequency response curve of the digital filter in an embodiment of the present invention.

[0029] Figure 5 It is the sliding correlation result of the leading sequence in the embodiment of the present invention.

[0030] Figure 6 It is the information demodulation result in the embodiment of the present invention. DETAILED DESCRIPTION

[0031] 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.

[0032] Combined with attachment Figure 1 , a current carrier communication method based on pulse modulation technology, comprising the following steps:

[0033] Step 1: Generate a 1024-bit PN sequence and perform Manchester encoding on the PN sequence to obtain a 2048-bit preamble sequence.

[0034] Step 2: Generate a 32-bit PN sequence, perform Manchester encoding on the PN sequence, and obtain a 64-bit forward information coding sequence.

[0035] Step 3: Invert the forward information encoding sequence to obtain a 64-bit reverse information encoding sequence.

[0036] Step 4: Generate 64-bit information 0x00278CDCB6B05655. When transmitting, the low-order information comes first. Manchester encoding is performed on the information to obtain 128-bit information. 0'b is modulated using the reverse information coding sequence, and 1'b is modulated using the forward information coding sequence, to obtain an 8192-bit information sequence.

[0037] Step 5: The 2048-bit preamble sequence is combined with the 8192-bit information sequence to obtain a 10240-bit transmission sequence. The width of each information bit, T0, is set to 400 microseconds, the intensity, A0, is set to 100 mA, and the signal is transmitted at the end user's electricity meter in the 400V low-voltage power supply area. The total signal transmission time is 4096 milliseconds, and the center frequency, f0, of the transmission signal is approximately 1250 Hz. The transmission signal frame structure is as follows: Figure 2 As shown, the signal spectrum is Figure 3 shown.

[0038] Step 6: Receive the signal on the transformer side of the 400V low-voltage power supply station, with a sampling frequency of 5000 Hz, a sampling accuracy of 16 bits, a measurement range of ±500 amps, and a current resolution of 15 mA. The digital filter passband frequency is 833-1666 Hz, the lower cutoff frequency is 400 Hz, the upper cutoff frequency is 2000 Hz, and the out-of-band attenuation is greater than 70 dB. The digital filter frequency response curve is as follows: Figure 4 shown.

[0039] Step 7: Sample the leading sequence at 5000 Hz. The length of the sequence after sampling is 4096. Use this sequence with the current sampling data after filtering by the digital filter. Sample(i) Perform sliding correlation operation, the formula is , the correlation peak threshold S is set to 150. The sliding operation result of the leading code sequence is as follows Figure 5 As shown, the correlation peak is 284.5, the synchronous identification is successful, the current direction is positive, and the current sampling point is recorded as the information start index.

[0040] Step 8: The current sampling data after the information start index is grouped into 128 points per group, and 128 groups of data are continuously collected. The forward information coding sequence is sampled at 5000 Hz. The length of the sequence after sampling is 128. Correlation operations are performed with the 128 groups of current sampling data respectively. The 128 groups of correlation results are subtracted from each other and multiplied with the leading direction bit to obtain 64 groups of operation results, such as Figure 6As shown, after decoding, the information 0x00278CDCB6B05655 can be obtained.

[0041] 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 current carrier communication method based on pulse modulation technology, characterized in that: The following steps are involved: Step 1: Generate an M-bit pseudo-random sequence and perform Manchester encoding on the pseudo-random sequence to obtain a 2M-bit preamble sequence; Step 2: Generate an N-bit pseudo-random sequence, and perform Manchester encoding on the pseudo-random sequence to obtain a 2N-bit forward information coding sequence; Step 3: Invert the forward information encoding sequence described in step 2 to obtain a 2N-bit reverse information encoding sequence; Step 4: Manchester encode the K-bit original information to obtain 2K-bit encoded information. In the encoded information, 1'b is modulated using the forward information encoding sequence, and 0'b is modulated using the reverse information encoding sequence to generate an information sequence. Step 5: The preamble sequence generated in step 1 and the information sequence generated in step 4 form a complete transmission sequence with a total sequence length of (2*M+4*K*N) bits. This sequence is used to control current switching and generate a pulse width modulated current signal in a specific sequence to be injected into the power line. Step 6: Sample the current signal on the power line and perform digital filtering on the sampled data; Step 7: Perform sliding correlation operation on the leading sequence and the sampled data. When the correlation value meets the set threshold S, the signal synchronization is successful. Step 8: After the signal is synchronized successfully, the sampled data segments are correlated with the forward information coding sequence to obtain 2K correlation values. The difference between every two correlation values is used to obtain K bits of information.

2. The current carrier communication method based on pulse modulation technology according to claim 1, characterized in that: In steps 1 and 2, the pseudo-random sequence is usually generated by a PN sequence. The values of M and N are selected according to the current channel parameters of the application scenario, and the value range is 16 to 8192. The pseudo-random sequence generation algorithm is not limited to the PN sequence.

3. The current carrier communication method based on pulse modulation technology according to claim 1, characterized in that: In step 5, each information bit 1'b of the transmission sequence represents a pulse with a width of T0 and an intensity of A0. The signal transmitted by the transmission signal sequence control contains current pulses with two widths of T0 and 2T0. The center frequency f0 of the transmission signal sequence is ≈1 / (2T0). The frequency response characteristics of the current channel are stable below 10,000 Hz. Therefore, the value range of f0 is 50-10,000 Hz, the value range of T0 is 0.05-10 milliseconds, and the value range of the pulse intensity A0 is 10-800 mA depending on the application scenario.

4. The current carrier communication method based on pulse modulation technology according to claim 1, characterized in that: In step 8, the difference between the two 2K correlation values is multiplied by the current direction bit. If the result is greater than zero, it is the information bit 1'b; if it is less than zero, it is the information bit 0'b.

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