Method and system for identifying and suppressing narrowband interference of power line

Abstract

The invention discloses a method and a system for identifying and suppressing narrowband interference of a power line, and belongs to the technical field of power line carrier communication. The method comprises the following steps: segmenting a power line signal output by an ADC (Analog to Digital Converter), and carrying out time-frequency conversion on each segment of power line signal; converting the amplitude of the frequency domain signal to obtain converted data and differential data; performing dual judgment to obtain a plurality of narrowband interference estimated frequency points; respectively calculating correlation ratios for the plurality of narrowband interference estimated frequency points, and when the maximum correlation ratio exceeds a correlation ratio threshold value, identifying the narrowband interference estimated frequency point corresponding to the maximum correlation ratio as a narrowband interference frequency point; based on the narrowband interference frequency point, performing single frequency point suppression on the power line signal to obtain a suppressed power line signal; and iteratively executing the steps on the suppressed power line signal to obtain a final suppressed power line signal. According to the method and the system, the influence of signal distortion, high bit error rate and stability reduction caused by narrowband interference on the transmission system is solved, and the reliability of the transmission system is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power line carrier communication, and particularly relates to a method and system for identifying and suppressing narrow-band interference of a power line. BACKGROUND

[0002] In a power line carrier communication system, since the power line is designed for power transmission, the channel characteristics thereof are complex, and there are a large number of sustained narrow-band interferences formed by power equipment harmonics, switching noise and the like. The narrow-band interferences are particularly sensitive to technologies such as OFDM (Orthogonal Frequency Division Multiplexing), which leads to a significant increase in system error rate. The performance of existing commercial power line carrier equipment is greatly reduced in the environment of strong narrow-band interference. Therefore, narrow-band interference suppression is one of the indispensable modules for improving the communication performance of the power line carrier system. In the process of implementing the present application, the inventors have found that the prior art has at least the following problems: first, the traditional method is difficult to accurately identify narrow-band interference in a low signal-to-noise ratio environment, especially when multiple narrow-band interferences with large energy differences exist simultaneously; second, the notch filter is usually fixed in parameters and cannot adapt to the dynamic changes of interference frequencies in the power line channel; and third, the power line communication is sensitive to processing delay, and many complex algorithms are difficult to meet the real-time processing requirements. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a method and system for identifying and suppressing narrow-band interference of a power line to overcome the deficiencies of the prior art.

[0004] To solve the above technical problems, in a first aspect, a method for identifying and suppressing narrow-band interference of a power line is disclosed, comprising:

[0005] Step 1: receiving a power line signal output by an ADC (Analog-to-Digital Converter);

[0006] Step 2: segmenting the power line signal, performing time-frequency transformation on each segment of the power line signal, obtaining multiple groups of frequency domain signals and averaging;

[0007] Step 3: converting the amplitude of the averaged frequency domain signal to obtain converted data; performing first-order difference on the converted data to obtain difference data; performing double judgment based on the converted data and the difference data to obtain multiple narrow-band interference estimated frequency points;

[0008] Step 4: calculating a correlation ratio for each of the multiple narrow-band interference estimated frequency points to obtain a maximum correlation ratio; when the maximum correlation ratio exceeds a correlation ratio threshold value, identifying the narrow-band interference estimated frequency point corresponding to the maximum correlation ratio as a narrow-band interference frequency point.

[0009] Step 5, based on the narrowband interference frequency point, the power line signal is suppressed by the notch filter to obtain the suppressed power line signal;

[0010] Step 6, iteratively performing steps 2 to 5 on the suppressed power line signal to obtain the final suppressed power line signal. Through iterative processing, multiple interference components are ensured not to be missed.

[0011] Further, it also includes: during the iteration of step 6 or after the iteration is completed, comparing and checking the ADC output power line signal and the suppressed power line signal to determine whether the identified narrowband interference frequency point still exists. If the identified narrowband interference frequency point does not exist, the notch filter stops suppressing the ADC output power line signal at the identified narrowband interference frequency point. When the notch filter suppresses the power line signal at a single frequency point, there is a limit to the number of single frequency points, and the iteration number is generally set according to the number of frequency points that can be suppressed by the notch filter. After the notch filter stops suppressing the ADC output power line signal at the identified narrowband interference frequency point, step 6 can continue to be executed until a new narrowband interference frequency point is identified and suppressed. This comparison and checking can continue to identify new narrowband interference frequency points, improve the real-time performance and accuracy of narrowband identification, and avoid the incomplete suppression or excessive suppression of effective signals caused by the same energy suppression of different energy narrowbands due to the fixed setting of the notch filter.

[0012] Further, if the narrowband interference frequency point identified in the subsequent iteration is within a preset threshold tolerance of the narrowband interference frequency point identified in the previous iteration, step 5 is skipped and step 6 is directly executed. That is, the notch filter does not suppress the suppressed power line signal at a single frequency point. If the narrowband interference frequency point identified in the subsequent iteration is within a preset threshold tolerance of the narrowband interference frequency point identified in the previous iteration, it is considered that the two narrowband interference frequency points belong to the same narrowband interference, and the notch filter does not suppress the suppressed power line signal at a single frequency point. This can avoid repeated counting and suppression of the same interference source.

[0013] Further, step 3 includes: excluding zero values from the amplitude of the averaged frequency domain signal, converting the amplitude into a power spectral density to obtain converted data;

[0014] Taking the maximum value of the converted data, marking it as , the position is recorded as P_top_idx1, and the current point frequency is recorded as , and the estimated current point is the first narrowband interference estimated frequency point.

[0015] Further, the step 3 further comprises: first-order difference processing on the converted data to obtain difference data, taking the maximum value of the difference data, and marking the position point corresponding to the maximum value as P_diff_idx, taking the front N position point values and the rear N position point values of the position point P_diff_idx from the difference data, and taking the maximum value from the 2N+1 position point values as , and marking the current point frequency as , and estimating the current point as the second narrowband interference estimation frequency point; the N is set according to the narrowband interference frequency band width.

[0016] The operation purpose is mainly because the narrowband interference usually has a relatively obvious energy change in the frequency domain signal, so the first-order difference method is considered to identify the narrowband interference, but in actual application, considering the ADC sampling rate and the limited length of time-frequency transformation (FFT length) processing, the maximum value of the first-order difference may be a point near the maximum value of the narrowband interference, so in the case of considering the actual example, the positions of the actual maximum values are determined by taking the front and rear N points, so as to avoid the frequency judgment deviation.

[0017] Further, the step 4 of calculating the correlation ratio of the plurality of narrowband interference estimation frequency points respectively to obtain the maximum correlation ratio comprises: designing an average sampling length L, taking the first narrowband interference estimation frequency point and the position P_top_idx1, taking the average value of the data of the first narrowband interference estimation frequency point from the converted data, and marking the average value as ;

[0018] taking the second narrowband interference estimation frequency point and the position P_top_idx2, taking the average value of the data of the second narrowband interference estimation frequency point from the converted data, and marking the average value as ;

[0019] the correlation ratio of the first narrowband interference estimation frequency point is ,

[0020] the correlation ratio of the second narrowband interference estimation frequency point is ,

[0021] if , the maximum correlation ratio is ; if , the maximum correlation ratio is .

[0022] Step 3 employs a dual detection strategy: absolute peak detection of the averaged frequency domain signal (directly finding the maximum power spectrum point) and first-order differential peak detection (identifying the edge points where power spectrum changes most drastically). Step 4 uses the correlation ratio between peak power and the average power of the neighborhood as the interference criterion, improving detection reliability. An adaptive threshold mechanism is set up for more accurate identification of narrowband interference frequencies. Introducing first-order differential features into narrowband interference detection solves the problem of insufficient sensitivity for weak interference detection in the context of OFDM signals using traditional methods.

[0023] Furthermore, during or after the iteration in step 6, the power line signal output by the ADC and the suppressed power line signal are compared and verified to determine whether the identified narrowband interference frequency points still exist, including:

[0024] The power line signal and the suppressed power line signal output by the ADC are subjected to time-frequency transformation to obtain the frequency domain signal before suppression and the frequency domain signal after suppression.

[0025] The frequency domain signals before and after suppression are compared. If a certain narrowband interference frequency point is found to have no difference in energy between the frequency domain signals before and after suppression, it is determined that the identified narrowband interference frequency point no longer exists.

[0026] Furthermore, step 2 involves segmenting the power line signal, including: dividing it into segments. The length divides the power line signal into multiple segments. The time-frequency transformation is performed on each segment of the time-domain signal. Traditional methods usually perform FFT (Fast Fourier Transform) on the entire signal. This step can effectively suppress the random spikes caused by Gaussian white noise by segmenting the signal, thereby improving the reliability of subsequent detection.

[0027] Secondly, a system for identifying and suppressing narrowband interference on power lines is disclosed, comprising a narrowband interference identification module and a narrowband interference suppression module. The narrowband interference identification module includes a data acquisition unit, a time-frequency conversion unit, a narrowband interference prediction unit, and a narrowband interference identification unit.

[0028] The data acquisition unit is used to receive the power line signal output by the ADC;

[0029] The time-frequency conversion unit is used to segment the power line signal, perform time-frequency conversion on each segment of the power line signal, obtain multiple sets of frequency domain signals, and average them.

[0030] The narrow-band interference estimation unit is configured to convert the amplitude of the averaged frequency domain signal to obtain converted data, perform first-order differentiation on the converted data to obtain differentiated data, and perform double judgment based on the converted data and the differentiated data to obtain a plurality of narrow-band interference estimation frequency points.

[0031] The narrow-band interference identification unit is configured to calculate a correlation ratio for each of the plurality of narrow-band interference estimation frequency points to obtain a maximum correlation ratio, and identify the narrow-band interference estimation frequency point corresponding to the maximum correlation ratio as a narrow-band interference frequency point when the maximum correlation ratio exceeds a correlation ratio threshold value.

[0032] The narrow-band interference suppression module is configured to perform single-frequency point suppression on the power line signal output by the ADC using a notch filter based on the narrow-band interference frequency point to obtain a suppressed power line signal.

[0033] The narrow-band interference identification module is further configured to input the suppressed power line signal into the time-frequency conversion unit, the narrow-band interference estimation unit and the narrow-band interference identification unit iteratively to obtain a new narrow-band interference frequency point, and the narrow-band interference suppression module is configured to perform single-frequency point suppression on the suppressed power line signal using the notch filter based on the new narrow-band interference frequency point to obtain a final suppressed power line signal.

[0034] Further, the narrow-band interference identification module further comprises a comparison and verification module configured to compare and verify the power line signal output by the ADC and the suppressed power line signal during the iteration process of the narrow-band interference identification module or after the iteration is completed to determine whether the identified narrow-band interference frequency point still exists, and if the identified narrow-band interference frequency point does not exist, the notch filter stops suppressing the identified narrow-band interference frequency point of the power line signal output by the ADC.

[0035] Further, the narrow-band interference identification module further comprises a tolerance unit configured to determine whether the narrow-band interference frequency point identified after iteration and the narrow-band interference frequency point identified before iteration are within a preset threshold value, and if the narrow-band interference frequency point identified after iteration is within the preset threshold value, the narrow-band interference frequency point identified after iteration is not sent to the notch filter, and the iteration inside the narrow-band interference identification module is continued.

[0036] Beneficial effects: The correlation ratio threshold value is set to identify the specific frequency point of the multi-frequency point narrow-band interference with uneven energy in the frequency domain, and the notch filter is used for narrow-band interference suppression, thereby solving the influence of the narrow-band interference on the signal distortion, high error rate and stability decline of the signal transmission system, and improving the reliability of the signal transmission system. Without the need to increase the hardware cost, the communication performance is greatly improved without a large increase in cost. BRIEF DESCRIPTION OF DRAWINGS

[0037] The above and / or other aspects of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings in which:

[0038] Figure 1 A flow chart of a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0039] Figure 2 A system block diagram of a system for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0040] Figure 3 A structure diagram of a narrowband interference identification module in a system for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0041] Figure 4 A comparison diagram before and after suppression of 1 MHz, -20 dBm narrowband interference using a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0042] Figure 5 A comparison diagram before and after suppression of 1 MHz (-20 dBm), 3 MHz (-30 dBm), 6 MHz (-30 dBm) multiple narrowband interference using a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0043] Figure 6 A comparison diagram before and after suppression of 1 MHz narrowband interference (low out-of-band) + OFDM effective signal using a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0044] Figure 7 A comparison diagram before and after suppression of 3 MHz narrowband interference (in-band) + OFDM effective signal using a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0045] Figure 8 A comparison diagram before and after suppression of 6 MHz narrowband interference (high out-of-band) + OFDM effective signal using a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application.

[0046] Figure 9 A comparison diagram before and after suppression of multiple narrowband interference + OFDM effective signal using a method for identifying and suppressing narrowband interference on a power line according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] Embodiments of the present application will be described below with reference to the accompanying drawings.

[0048] The raw data processing can be categorized into the following schemes: 1. Directly perform time-frequency transformation on a single segment of the raw signal to obtain frequency domain information; 2. Perform two time-domain samplings on the raw signal, design delays for the two information streams, and apply different windowing methods, then superimpose them after time-frequency transformation to obtain the frequency domain signal; 3. Sample the raw signal multiple times, and accumulate the samples after time-frequency transformation to obtain the frequency domain signal. Methods for narrowband identification in power line carrier communication can be broadly categorized as follows: 1. Use subcarrier SINR (Signal-to-Interference-plus-Noise Ratio) to determine narrowband interference. SINR values ​​below a threshold are identified as narrowband. For similar SINR values, standard deviation is used for fine decomposition. The advantage of this method is accurate identification of narrowband interference in different subcarriers. However, its disadvantages include the need for extremely accurate channel estimation to obtain SINR values ​​and the inability to accurately determine the precise frequency of narrowband interference. If the narrowband frequency is between adjacent subcarriers, this method requires suppressing two subcarrier segments, wasting significant spectrum resources and impacting communication performance. 2. A method based on the highest amplitude of the frequency domain signal exceeding a threshold value is used, employing the difference between the highest value and the average of nearby spectra. This method can resolve most interference with obvious narrowband characteristics. However, under OFDM signals and in situations with uneven background noise, false alarms and misjudgments may occur with single amplitude detection. 3. A method that normalizes by dividing the entire frequency range by its magnitude and identifies narrowbands through a threshold value suffers from computational complexity and requires precise threshold setting; otherwise, false alarms and misjudgments will still occur.

[0049] This application embodiment is based on the frequency domain signal obtained after segmented time-frequency transformation processing of the received ADC raw data information. It performs accurate identification of narrowband interference and achieves effective identification and suppression of narrowband interference through a three-level thickening of "dual detection - precise positioning - adaptive filtering". It can be applied to power line carrier communication SOC (System on Chip) in various environments, and is particularly suitable for power line communication application scenarios with high requirements for communication reliability, such as smart grids and industrial automation.

[0050] The first embodiment of this application discloses a method for identifying and suppressing narrowband interference on power lines, such as... Figure 1 As shown, it includes:

[0051] Step 1: Receive the power line signal output by the ADC;

[0052] Step 2: Segment the power line signal, perform time-frequency transformation on each segment of the power line signal to obtain multiple sets of frequency domain signals, and then average them.

[0053] Segmenting the power line signal, including: according to each segment The length divides the power line signal into multiple segments. .

[0054] Step 3, converting the amplitude of the averaged frequency domain signal to obtain converted data; first-order difference is performed on the converted data to obtain difference data; double judgment is performed based on the converted data and the difference data to obtain a plurality of narrowband interference estimated frequency points; specifically, including:

[0055] After excluding the zero value of the amplitude of the averaged frequency domain signal, the amplitude is converted to power spectral density to obtain converted data;

[0056] Let the averaged frequency domain signal be X, and the converted data be Y, then the conversion formula is as follows:

[0057]

[0058] The unit of the converted data Y obtained by the above formula is dBm / Hz, the communication module impedance is 50 ohms, the communication module refers to the chip plus peripherals and PCB (Printed Circuit Board) as a whole, and the method and system provided in the embodiment are integrated in the chip.

[0059] Taking the maximum value of the converted data, marking it as , the position is recorded as P_top_idx1, and the current point frequency is recorded as , and the estimated current point is the first narrowband interference estimated frequency point.

[0060] In an actual signal transmission system, the power spectral density of the OFDM effective signal can be greater than the narrowband interference of the weak energy out of the band. Such interference still has an impact on the transmission system, resulting in a decrease in the transmission rate and stability of the transmission system. Considering that the above method cannot identify the narrowband interference of this kind, first-order difference is performed on the converted data to obtain difference data, the maximum value of the difference data is taken, the position point corresponding to the maximum value is recorded as P_diff_idx, the values of the N position points before and after the position point P_diff_idx are taken from the difference data, and the maximum value is taken from the 2N+1 position points, marked as , the corresponding position is recorded as P_top_idx2, and the current point frequency is recorded as , and the estimated current point is the second narrowband interference estimated frequency point; the N is set according to the narrowband interference frequency band width, for example: if the narrowband interference strong energy bandwidth is 250 KHz, and the width of each subcarrier is 24 KHz, then N is set to 5.

[0061] Step 4, calculating the correlation ratio of each of the plurality of narrowband interference estimated frequency points to obtain the maximum correlation ratio; when the maximum correlation ratio exceeds the correlation ratio threshold value, identifying the narrowband interference estimated frequency point corresponding to the maximum correlation ratio as the narrowband interference frequency point, and continuing to perform step 5; when the maximum correlation ratio is lower than the correlation ratio threshold value, performing step 1.

[0062] calculating correlation ratios of multiple narrowband interference estimation frequency points respectively, and obtaining a maximum correlation ratio, comprising: designing a mean sampling length L, taking a first narrowband interference estimation frequency point and a position P_top_idx1, and taking average values of two pieces of data with a length of L before and after the first narrowband interference estimation frequency point from the converted data, denoted as

[0063]

[0064] wherein, P_top_idx1 represents a position index of the two pieces of data with a length of L before and after the first narrowband interference estimation frequency point, i P_top_idx1 represents converted data at the position. i taking a second narrowband interference estimation frequency point and a position P_top_idx2, and taking average values of two pieces of data with a length of L before and after the second narrowband interference estimation frequency point from the converted data, denoted as

[0065]

[0066]

[0067] wherein, P_top_idx2 represents a position index of the two pieces of data with a length of L before and after the second narrowband interference estimation frequency point, j P_top_idx2 represents converted data at the position. j a correlation ratio of the first narrowband interference estimation frequency point

[0068] a correlation ratio of the second narrowband interference estimation frequency point

[0069]

[0070] if , the maximum correlation ratio is , and the narrowband interference frequency point is ; if , the maximum correlation ratio is , and the narrowband interference frequency point is .

[0071] when the maximum correlation ratio is , the corresponding frequency point is identified as a narrowband interference frequency point.

[0072] The embodiment is tested in a large number of laboratories, and it is found that when the narrowband interference energy is greater than the energy value in the adjacent frequency band by more than 20 dB, the bit error rate of the system will greatly increase, and the stability will sharply decrease, so the embodiment sets the correlation ratio threshold value to​​​​​​​​​​​​ .

[0073] The narrowband interference, after sampling and time-frequency conversion, is not a single frequency point jump, but gradually decreases to both sides with the frequency point as the center, and the influence range is from 500 kHz to 1 MHz. For example, if the power line signal bandwidth is 12.5 MHz and the number of subcarriers is 512, 1 MHz bandwidth covers 41 subcarriers, and L is 20, the energy mean value in the range can be obtained more rigorously.

[0074] Step 5, based on the narrowband interference frequency point, the notch filter performs single frequency point suppression on the power line signal to obtain the suppressed power line signal;

[0075] Step 6, iteratively performing steps 2 to 5 on the suppressed power line signal to obtain the final suppressed power line signal. The iteration period is set according to the configuration of the notch filter, specifically, according to the number of narrowband interference frequency points that the notch filter can suppress.

[0076] In the iteration process of step 6 or after the iteration is completed, the ADC output power line signal and the suppressed power line signal are compared and verified to determine whether the identified narrowband interference frequency point still exists. If the identified narrowband interference frequency point does not exist, the notch filter stops suppressing the ADC output power line signal at the identified narrowband interference frequency point. The comparison and verification of the ADC output power line signal and the suppressed power line signal to determine whether the identified narrowband interference frequency point still exists includes:

[0077] The ADC output power line signal and the suppressed power line signal are respectively subjected to time-frequency conversion to obtain the pre-suppression frequency domain signal and the post-suppression frequency domain signal;

[0078] The energy of the identified narrowband interference frequency point of the pre-suppression frequency domain signal and the post-suppression frequency domain signal is compared. If there is no energy difference, it is determined that the identified narrowband interference frequency point does not exist, and the parameters of the notch filter for the narrowband interference frequency point are reset for subsequent new narrowband interference frequency point parameter setting. The energy refers to the value obtained by converting the amplitude of the identified narrowband interference frequency point of the frequency domain signal into power spectral density.

[0079] When step 6 is performed, if the narrowband interference frequency point identified in the subsequent iteration is within a preset threshold tolerance of the narrowband interference frequency point identified in the previous iteration, step 5 is skipped and step 6 is directly performed, i.e. the notch filter does not perform single frequency point suppression on the suppressed power line signal. In the specific implementation process, the preset threshold can be set to 100 KHz. Generally, the interference within 100 KHz is considered to come from a single narrowband frequency point. If another narrowband interference is identified within 100 KHz, it is considered that the data processing is abnormal with a high probability, and the data needs to be reprocessed or the hardware is abnormal.

[0080] The first embodiment of the present application sets a threshold value after algorithm processing of a frequency domain signal, and accurately identifies narrowband interference through a double comparison mode, and adjusts a narrowband suppression frequency point in real time through dynamic notch filter parameter adjustment, thereby solving the influence of narrowband interference on signal transmission system, such as signal distortion, high bit error rate, and stability decline, and improving the reliability of the signal transmission system.

[0081] The second embodiment of the present application discloses a narrowband interference identification and suppression system for power lines, as shown in the figure, which comprises a narrowband interference identification module and a narrowband interference suppression module (notch filter). Figure 2 As shown in the figure, the narrowband interference identification module comprises a data acquisition unit, a time-frequency conversion unit, a narrowband interference estimation unit, and a narrowband interference identification unit. Figure 3 The data acquisition unit is configured to receive an ADC output power line signal or a narrowband interference suppression module output power line signal.

[0082] The time-frequency conversion unit is configured to segment the power line signal, perform time-frequency conversion on each segment of the power line signal, and obtain multiple groups of frequency domain signals and average them.

[0083] The narrowband interference estimation unit is configured to convert the amplitude of the averaged frequency domain signal to obtain converted data, perform first-order difference on the converted data to obtain difference data, and perform double judgment based on the converted data and the difference data to obtain multiple narrowband interference estimation frequency points.

[0084] The narrowband interference identification unit is configured to calculate a correlation ratio for each of the multiple narrowband interference estimation frequency points to obtain a maximum correlation ratio, and identify the narrowband interference estimation frequency point corresponding to the maximum correlation ratio as a narrowband interference frequency point when the maximum correlation ratio exceeds a correlation ratio threshold value.

[0085] The narrowband interference suppression module is configured to use a notch filter to perform single-frequency point suppression on the ADC output power line signal based on the narrowband interference frequency point to obtain a suppressed power line signal.

[0086] The narrowband interference identification module is further configured to iteratively input the suppressed power line signal into the time-frequency conversion unit, the narrowband interference estimation unit, and the narrowband interference identification unit to obtain a new narrowband interference frequency point, and the narrowband interference suppression module uses a notch filter to perform single-frequency point suppression on the suppressed power line signal based on the new narrowband interference frequency point to obtain a final suppressed power line signal.

[0087] The identification and suppression system of the narrowband interference of the power line further comprises a comparison and verification module, which is configured to compare and verify the power line signal output by the ADC and the power line signal after suppression in the iteration process of the narrowband interference identification module or after the iteration, to determine whether the identified narrowband interference frequency point still exists, and if the identified narrowband interference frequency point does not exist, the notch filter stops suppressing the narrowband interference frequency point of the power line signal output by the ADC.

[0088] The narrowband interference identification module further comprises a tolerance unit, which is configured to determine whether the narrowband interference frequency point identified in the later iteration and the narrowband interference frequency point identified in the previous iteration are within a preset threshold, if the narrowband interference frequency point identified in the later iteration is within the preset threshold, the narrowband interference frequency point identified in the later iteration is not sent to the notch filter, and the iteration inside the narrowband interference identification module is continued. The iteration period is set according to the configuration of the notch filter.

[0089] The signal transmission system comprises the identification and suppression system of the narrowband interference of the power line, a PGA (Programmable Gain Amplifier), an ADC and an AGC (Auto-Gain Control), the signal to be transmitted enters the ADC under the gain of the PGA, the power line signal output by the ADC is identified and suppressed by the narrowband interference identification module and the narrowband interference suppression module, and the signal after suppression is sent to a subsequent digital system for signal processing. The signal after completion of the narrowband interference suppression is subjected to gain value calculation again by the AGC to correct the influence of the deviation of the gain value caused by the excessive narrowband interference energy, and is fed back to the PGA for correct gain adjustment. The PGA, the ADC and the AGC and the connection relationship thereof belong to the prior art, and the embodiments of the present application are not limited herein.

[0090] Embodiment:

[0091] Step 1, receiving the power line signal output by the ADC, the sampling rate of the ADC is 50 MHz, the bandwidth of the power line signal is 12.5 MHz, and the number of time domain signal sampling points is 16384;

[0092] Step 2, segmenting the power line signal, each segment has a length of , and a total of 4 segments.

[0093] Performing time-frequency transformation on each segment of the power line signal to obtain a plurality of groups of frequency domain signals and averaging to obtain the averaged frequency domain signal X;

[0094] Step 3, excluding zero value from the current frequency domain signal X and converting it into PSD, denoted as Y,

[0095]

[0096] The PSD unit derived from the above formula is dBm / Hz, and the impedance of the communication module is 50 ohms.

[0097] We will process Y in two ways:

[0098] 1. Take the maximum PSD of the current frequency domain signal Y and mark it as... The position is denoted as P_top_idx1, and the frequency of the current point is denoted as... The current location is estimated to be a narrowband interference frequency point;

[0099] 2. In practical signal transmission systems, the PSD of the effective OFDM signal may exceed that of weak out-of-band interference. However, this interference still affects the transmission system, leading to a decrease in transmission rate and stability. Considering that the first processing method cannot identify this type of narrowband interference, we consider performing a first-order difference on the frequency domain signal Y, taking the position point corresponding to the maximum PSD after the difference, denoted as P_diff_idx. We then compare the maximum PSD among the eleven points (five points before and five points after this point) to find the maximum PSD, marking it as... The position is denoted as P_top_idx2, and the frequency of the current point is denoted as... The purpose of this operation is mainly because narrowband interference usually exhibits significant energy changes in the frequency domain signal. Therefore, a one-stage differential method is considered to identify narrowband interference. However, in practical applications, considering the ADC sampling rate and the finite length of the time-frequency transform (FFT length), the maximum value of the first-order differential may be a point near the maximum value of the narrowband interference. Therefore, considering the example, five points before and after are taken to determine the actual location of the maximum PSD (50MHz sampling rate, FFT length 4096, 11 points cover an area of ​​approximately 100KHz, which can basically cover most of the narrowband interference frequency band width) to avoid frequency judgment deviation.

[0100] Step 4: Calculate the correlation ratio for each of the multiple narrowband interference prediction frequency points to obtain the maximum correlation ratio; when the maximum correlation ratio exceeds the correlation ratio threshold, identify the narrowband interference prediction frequency point corresponding to the maximum correlation ratio as the narrowband interference frequency point.

[0101] For the two known sets of narrowband interference prediction markers P_top_idx1, as well as P_top_idx2, The design sampling length is L=20. The average of two data segments of length L before and after the narrowband interference prediction frequency point is taken as the standard for judging the mean. The narrowband interference prediction frequency point is then calculated. correlation ratio and narrowband interference prediction frequency points the correlation ratio of the relevant .

[0102] If , the maximum correlation ratio , the narrowband interference frequency point ; if , the maximum correlation ratio , the narrowband interference frequency point .

[0103] When the maximum correlation ratio , the corresponding frequency point is identified as a narrowband interference frequency point.

[0104] Step 5, based on the narrowband interference frequency point, the notch filter performs single-frequency point suppression on the power line signal to obtain a suppressed power line signal;

[0105] Step 6, iteratively performing steps 2 to 5 on the suppressed power line signal to obtain a final suppressed power line signal. This embodiment can suppress up to five different frequency points based on the hardware configuration of the notch filter, so the iteration period can be set to 5. If a frequency point is deleted through comparison and verification later, step 6 can be continued to identify and suppress a new frequency point.

[0106] The narrowband interference frequency points identified in subsequent iterations are evaluated with the narrowband interference frequency points identified in previous iterations, with a tolerance of within 100 KHz. This avoids repeated counting of the same interference source while also adjusting some filter parameters to make the notch depth deeper and increase the suppression of narrowband energy. This avoids the incomplete suppression or excessive suppression of different energy narrowbands caused by the fixed setting of the notch filter, which affects the energy of the effective signal. In addition, after five iterations, the system does not stop detecting. During the entire system operation, the detection mechanism remains in a continuously open state. At this time, the system will simultaneously monitor and compare the frequency domain signals of the ADC data and the data after the notch filter, and real-time feedback the real-time changing narrowband interference frequency points in the line. If it is found that there is no obvious difference between the energy of the ADC data and the data after the notch filter for a detected narrowband interference frequency point, it means that the narrowband interference corresponding to the narrowband interference frequency point no longer exists. Therefore, the suppression function of the narrowband interference frequency point can be turned off, and step 6 can be continued until a new narrowband interference frequency point is identified for suppression. This improves the real-time performance and accuracy of narrowband identification of the system.

[0107] Figures 4 to 9 In the above embodiment, the upper part of the figure represents the original frequency domain signal diagram, and the lower part of the figure represents the narrowband suppressed frequency domain signal diagram. Figure 4The single narrowband suppression result is shown, freq_nbi represents the identified narrowband interference frequency point, and R_nbi represents the correlation ratio calculated at the frequency point. Due to the ADC itself, the system will introduce some 1MHz main frequency harmonics, such as the 3rd and 5th harmonic energy in this embodiment, but compared with the fundamental wave, the energy of the two harmonics is still very low. The traditional identification method is difficult to identify such low-energy harmonics, but the results of this embodiment show that the two harmonics can still be identified and suppressed, greatly improving the communication performance. Figure 5 The multi-narrowband suppression result is shown. When different energy and different frequency narrowband interference is introduced, the interference can be accurately identified and suppressed. Figure 6 、 Figure 7 and Figure 8 The identification and suppression of low-frequency out-of-band narrowband, in-band narrowband and high-frequency out-of-band narrowband with OFDM effective signal are shown respectively. It can be seen that the out-of-band narrowband interference is completely suppressed and has no effect on the effective spectrum of OFDM. The in-band narrowband is also significantly suppressed, and the influence frequency band width is about 200kHz, which has almost no effect on the effective information frequency band of this embodiment. Figure 9 The multi-narrowband suppression result with OFDM effective signal is shown. It can be seen that it completely suppresses each frequency point narrowband while having almost no effect on the effective information frequency band, and has a performance comparable to that of single frequency point narrowband suppression.

[0108] In the specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and the computer program can run the invention content of a narrowband interference identification and suppression method for power lines and part or all steps in each embodiment of the present application when executed by the data processing unit. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0109] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present application can be realized by means of a computer program and its corresponding general hardware platform. Based on such understanding, the technical solutions in the embodiments of the present application can be embodied in the form of a computer program, i.e. a software product, which can be stored in a storage medium, including a plurality of instructions for causing a device (which can be a personal computer, a server, a single-chip microcomputer, a MUU or a network device, etc.) containing a data processing unit to execute the method described in each embodiment or some parts of the embodiments of the present application.

[0110] The application provides a method and system for identifying and inhibiting narrow-band interference of a power line. The above description is only the preferred embodiment of the application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principle of the application, and these improvements and refinements should also be considered as the protection scope of the application. The components not explicitly described in the embodiment can be realized by using the prior art.

Claims

1. A method for identifying and suppressing narrowband interference on power lines, characterized in that, include: Step 1: Receive the power line signal output by the ADC; Step 2: Segment the power line signal, perform time-frequency transformation on each segment of the power line signal to obtain multiple sets of frequency domain signals, and then average them. Step 3: Convert the amplitude of the averaged frequency domain signal to obtain the converted data; Perform first-order differencing on the transformed data to obtain the differencing data; Multiple narrowband interference prediction frequency points are obtained by making dual judgments based on the transformed data and differential data; Step 4: Calculate the correlation ratio for each of the multiple narrowband interference prediction frequency points to obtain the maximum correlation ratio; When the maximum correlation ratio exceeds the correlation ratio threshold, the narrowband interference prediction frequency corresponding to the maximum correlation ratio is identified as the narrowband interference frequency. Step 5: Based on the narrowband interference frequency, the notch filter performs single-frequency suppression on the power line signal to obtain the suppressed power line signal; Step 6: Iteratively execute steps 2 to 5 on the suppressed electric field signal to obtain the final suppressed electric field signal.

2. The method for identifying and suppressing narrowband interference on power lines according to claim 1, characterized in that, Also includes: During or after the iteration in step 6, the power line signal output by the ADC and the suppressed power line signal are compared and verified to determine whether the identified narrowband interference frequency point still exists. If the identified narrowband interference frequency point does not exist, the notch filter stops suppressing the identified narrowband interference frequency point on the power line signal output by the ADC.

3. The method for identifying and suppressing narrowband interference on power lines according to claim 2, characterized in that, If the tolerance between the narrowband interference frequency points identified in subsequent iterations and those identified in previous iterations is within a preset threshold when performing step 6, then step 5 is skipped and step 6 is executed directly.

4. The method for identifying and suppressing narrowband interference on power lines according to claim 3, characterized in that, Step 3 includes: after removing zero values ​​from the amplitude of the averaged frequency domain signal, converting the amplitude into power spectral density to obtain the converted data; Take the maximum value from the transformed data and mark it as... The position is denoted as P_top_idx1, and the frequency of the current point is denoted as... The current location is estimated to be the first narrowband interference frequency.

5. The method for identifying and suppressing narrowband interference on power lines according to claim 4, characterized in that, Step 3 also includes: performing first-order differencing on the transformed data to obtain differencing data; taking the maximum value from the differencing data, and denoting the position point corresponding to the maximum value as P_diff_idx; taking the first N position point values ​​and the last N position point values ​​from the differencing data P_diff_idx; and taking the maximum value from the 2N+1 position point values, marking it as... The corresponding position is recorded as P_top_idx2, and the frequency of the current point is recorded as... The current location is estimated to be the second narrowband interference estimated frequency point; N is set according to the narrowband interference frequency band width.

6. The method for identifying and suppressing narrowband interference on power lines according to claim 5, characterized in that, Step 4 involves calculating the correlation ratio for multiple narrowband interference prediction frequency points to obtain the maximum correlation ratio. This includes: designing the mean sampling length L for the first narrowband interference prediction frequency point. And position P_top_idx1, take the average of two data segments of length L before and after the first narrowband interference prediction frequency point from the transformed data, and denot it as ; Frequency prediction for the second narrowband interference And position P_top_idx2, take the average of two data segments of length L before and after the second narrowband interference prediction frequency point from the transformed data, and denot it as ; First narrowband interference predicted frequency correlation ratio , Second narrowband interference predicted frequency correlation ratio , like Then the maximum correlation ratio ;like Then the maximum correlation ratio .

7. The method for identifying and suppressing narrowband interference on power lines according to claim 6, characterized in that, During or at the end of step 6, the power line signal output by the ADC and the suppressed power line signal are compared and verified to determine whether the identified narrowband interference frequency points still exist, including: The power line signal and the suppressed power line signal output by the ADC are subjected to time-frequency transformation to obtain the frequency domain signal before suppression and the frequency domain signal after suppression. Energy comparison is performed on the identified narrowband interference frequency points of the pre-suppression frequency domain signal and the post-suppression frequency domain signal. If there is no energy difference, it is determined that the identified narrowband interference frequency points no longer exist.

8. The method for identifying and suppressing narrowband interference on power lines according to claim 7, characterized in that, Step 2 involves segmenting the power line signal, including: dividing it into segments. The length divides the power line signal into multiple segments. .

9. A system for identifying and suppressing narrowband interference on power lines, characterized in that, It includes a narrowband interference identification module and a narrowband interference suppression module. The narrowband interference identification module includes a data acquisition unit, a time-frequency conversion unit, a narrowband interference prediction unit, and a narrowband interference identification unit. The data acquisition unit is used to receive the power line signal output by the ADC. The time-frequency conversion unit is used to segment the power line signal, perform time-frequency conversion on each segment of the power line signal, obtain multiple sets of frequency domain signals, and average them. The narrowband interference prediction unit is used to convert the amplitude of the averaged frequency domain signal to obtain the converted data. Perform first-order differencing on the transformed data to obtain the differencing data; Multiple narrowband interference prediction frequency points are obtained by making dual judgments based on the transformed data and differential data; The narrowband interference identification unit is used to calculate the correlation ratio for multiple narrowband interference prediction frequency points respectively, and obtain the maximum correlation ratio; When the maximum correlation ratio exceeds the correlation ratio threshold, the narrowband interference prediction frequency corresponding to the maximum correlation ratio is identified as the narrowband interference frequency. The narrowband interference suppression module is used to suppress the electric line signal output by the ADC at a single frequency point using a notch filter based on the narrowband interference frequency point, so as to obtain the suppressed electric line signal. The narrowband interference identification module is also used to iteratively input the suppressed power line signal into the time-frequency conversion unit, the narrowband interference prediction unit, and the narrowband interference identification unit to obtain new narrowband interference frequency points. The narrowband interference suppression module uses a notch filter to perform single-frequency suppression on the suppressed power line signal based on the new narrowband interference frequency point, thereby obtaining the final suppressed power line signal.

10. The identification and suppression system for narrowband power line interference according to claim 9, characterized in that, It also includes a comparison and verification module, which is used to compare and verify the power line signal output by the ADC and the suppressed power line signal during or after the iteration of the narrowband interference identification module, and to determine whether the identified narrowband interference frequency point still exists. If the identified narrowband interference frequency point does not exist, the notch filter stops suppressing the identified narrowband interference frequency point on the power line signal output by the ADC.

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