10kV medium-voltage distribution network power line carrier communication method and system based on adaptive OFDM (Orthogonal Frequency Division Multiplexing)

Abstract

The invention discloses a 10kV medium-voltage power distribution network power line carrier communication method and system based on adaptive OFDM (Orthogonal Frequency Division Multiplexing), and the method comprises the steps that a master station sends a detection frame to a slave station, and the slave station carries out the CE (Channel Estimation), and obtains the CSI (Channel State Information); the method comprises the following steps of: dividing a broadband channel into a plurality of parallel orthogonal subcarriers, and dynamically allocating a modulation mode, a modulation order and a forward error correction (FEC) coding rate for each subcarrier of OFDM (Orthogonal Frequency Division Multiplexing) by adopting a water injection algorithm based on channel state information (CSI); adopting two-stage automatic gain control (AGC) to condition a signal received from a power line; and carrying out dynamic frequency hopping between a frequency band with serious interference and an idle frequency band based on a continuous spectrum sensing result. Compared with the prior art, through the multi-dimensional adaptive technology, the communication system can sense the channel state in real time and dynamically adjust the communication strategy, so that a stable communication link is established in a severe power grid environment.

Description

Technical Field

[0001] This invention belongs to the field of power system communication technology, specifically relating to a power line carrier communication method and system for 10kV medium-voltage distribution networks based on adaptive OFDM. It is applicable to power line carrier communication (PLC) technology for 10kV medium-voltage distribution networks, and in particular, it is a carrier communication method and system that can adapt to channel conditions and has high anti-interference and high reliability. Background Technology

[0002] Distribution network automation (DAS) is a key component in realizing smart grids, relying on stable and reliable communication networks. 10kV medium-voltage power line carrier communication utilizes existing power lines as the transmission medium, eliminating the need for rewiring and offering inherent advantages such as low cost and wide coverage. However, the 10kV distribution network presents an open, time-varying, and challenging communication environment, posing the following main challenges: 1. Complex noise: Background noise (such as insulator corona discharge), periodic pulse noise (such as load switch operation), and random sudden noise (such as lightning and construction interference) coexist.

[0003] 2. Severe and time-varying signal attenuation: Signal attenuation varies drastically with line distance, branch nodes, and load switching (especially capacitive / inductive loads), and the communication channel has strong frequency selectivity.

[0004] 3. Impedance mismatch: Equipment such as transformers, capacitor banks, and load switches on the line cause a mismatch in the characteristic impedance of the line, resulting in signal reflection.

[0005] Traditional narrowband PLCs (such as BPSK and QAM modulation) and early OFDM PLC solutions suffer from problems such as low spectrum utilization, weak resistance to multipath effects and frequency-selective fading, and inability to effectively track rapid channel changes, making it difficult to meet the high requirements of distribution network automation for real-time performance and reliability. Summary of the Invention

[0006] Purpose of the invention: In order to overcome the shortcomings of the prior art, this invention provides a 10kV medium-voltage power line carrier communication method and system based on adaptive OFDM. Through multi-dimensional adaptive technology, the communication system can perceive the channel status in real time and dynamically adjust the communication strategy, thereby establishing a stable communication link in the harsh power grid environment.

[0007] Technical solution: This invention discloses a 10kV medium-voltage distribution network power line carrier communication method based on adaptive OFDM, comprising: The master station sends probe frames to the slave station, which then performs channel estimation (CE) and obtains channel state information (CSI). The broadband channel is divided into multiple parallel orthogonal subcarriers. Based on the channel state information (CSI), the water-filling algorithm is used to dynamically allocate the modulation scheme, modulation order, and coding rate of forward error correction (FEC) to each OFDM subcarrier. A two-stage automatic gain control (AGC) is used to condition the signal received from the power line; Based on continuous spectrum sensing results, dynamic frequency hopping is performed between heavily interfered frequency bands and idle frequency bands.

[0008] Furthermore, based on Channel State Information (CSI), a water-filling algorithm is used to dynamically allocate modulation scheme, modulation order, and coding rate to each OFDM subcarrier, and to calculate bit allocation. The number of bits b_k allocated on the k-th subcarrier is determined by its signal-to-noise ratio (SNR). The simplified algorithm based on the water-filling algorithm is as follows: b_k = floor(log2(1+SNR_k / Γ)) Where: SNR_k is the signal-to-noise ratio of the kth subcarrier, Γ is the signal-to-noise ratio gap (SNR gap), which is related to the target bit error rate (BER) and the modulation and coding scheme, Γ=-ln(5*BER) / 1.5, and floor() is the floor function to ensure that the number of allocated bits is an integer.

[0009] Furthermore, the dynamic allocation modulation method is specifically as follows: 1) The subcarrier threshold range (dB) is < 2 - 5 dB; 2) The threshold range (dB) of the binary phase shift keying (BPSK) modulation method is 5 - 8 dB; 3) The threshold range (dB) of the quadrature phase shift keying (QPSK) modulation method is 8 - 11 dB; 4) The threshold range (dB) of the high-order quadrature amplitude modulation 16QAM modulation method is 14 - 17 dB; 5) The threshold range (dB) of the high-order quadrature amplitude modulation (64QAM) modulation method is 20 - 23 dB; 6) The threshold range (dB) of the high-order quadrature amplitude modulation 256QAM modulation method is 26 - 29 dB.

[0010] Furthermore, the two-stage automatic gain control (AGC) conditions the signal received from the power line, specifically as follows: 1) At the receiver front end, a two-stage AGC circuit is used, with the following adjustments made: Coarse AGC: Performs wide-range analog-level gain adjustment based on Received Signal Strength Indication (RSSI); Fine AGC: At the digital level, fine-tuning is performed based on the pilot signal power in the OFDM symbol to ensure stable signal power input to the demodulator; The formula for calculating gain update is: G_new=G_old*(P_target / P_measured) Where P_target is the target power level, P_measured is the measured power level, and G_old is the gain before the update; 2) A frequency domain equalizer based on the least mean square (LMS) or recursive least squares (RLS) algorithm is used to continuously update the equalizer coefficients using pilot signals to compensate for channel distortion and multipath effects.

[0011] Furthermore, during the communication process, after forward error correction (FEC) coding, the bit stream is frequency-domain interleaved, distributing continuous bit errors into multiple forward error correction (FEC) blocks, thus transforming burst noise errors into random errors.

[0012] Furthermore, during communication, if the master station carrier fails to decode, it sends a NACK signal, triggering the slave station carrier to perform a HARQ process. Instead of directly discarding the data, it requests the sending end to retransmit part of the information and merges it with the previously received erroneous data before decoding.

[0013] Furthermore, the specific process of dynamic frequency hopping between heavily interfered frequency bands and idle frequency bands is as follows: The broadband channel is divided into multiple parallel orthogonal subcarriers, and some subcarriers are reserved as "sentinel carriers" to monitor the SNR in real time. When the SNR of a certain working frequency band drops below the threshold, the system automatically switches the data service to the pre-identified clean frequency band, realizing "unobtrusive" smooth frequency hopping.

[0014] Furthermore, if the average SNR calculated by the "sentinel carrier" remains below a preset threshold for T seconds, a decision-making process for switching frequency bands is triggered. The preset SNR threshold is set to 1 second when the average SNR drops to a position 2dB higher than the minimum SNR required by the current MCS.

[0015] This invention also discloses a 10kV medium-voltage distribution network power line carrier communication system based on adaptive OFDM, comprising: a master station concentrator and slave station nodes, wherein both the master station concentrator and the slave station nodes include: Coupling circuit, used to couple communication signals to a 10kV power line; An adaptive impedance matching network is used to dynamically adjust the output impedance of the coupled device to match the characteristic impedance of the power line that changes in real time. The modulation and demodulation module is used to dynamically allocate modulation scheme, modulation order and coding rate of forward error correction (FEC) to each subcarrier of OFDM based on channel state information (CSI) and using a water-filling algorithm. A digital signal processor (DSP) is used for signal conditioning to perform channel estimation and two-stage automatic gain control (AGC). The central processing unit (CPU) is used to control the entire communication process and make dynamic frequency hopping decisions.

[0016] Preferably, the coupling circuit is a capacitive coupling circuit, and the adaptive impedance matching network is composed of an adjustable capacitor and inductor array controlled by an MCU.

[0017] Preferably, the specific execution process of the system is as follows: When sending data: The central processing unit (CPU) generates data frames, which are then conditioned by the digital signal processor (DSP) and input to the modulation and demodulation module. The modulation and demodulation module performs digital-to-analog conversion and dynamically allocates the modulation mode, modulation order, and forward error correction (FEC) coding rate. The data is then injected into the power line via an adaptive matching network to adjust the impedance. When receiving data: the power line transmission signal is first extracted by the coupling circuit and then input to the adaptive matching network to dynamically adjust the output impedance and maximize energy reception. After two-stage automatic gain control (AGC) and digital-to-analog conversion by the modulation and demodulation module, the data frame is synchronized, equalized, demodulated, and decoded by the digital signal processor (DSP). Finally, the data frame is processed by the central processing unit (CPU).

[0018] Beneficial effects

[0019] 1. This invention divides a broadband channel into multiple parallel orthogonal subcarriers, each of which can be modulated independently, thereby effectively combating frequency-selective fading. Through dynamic modulation and coding (AMC), adaptive gain control (AGC), adaptive equalization algorithms, frequency domain interleaving coding, and a high-frequency automatic retransmission (HARQ) mechanism, the success rate and stability of communication under harsh noise and time-varying channel conditions are greatly improved.

[0020] 2. The dynamic modulation and coding (AGC) of this invention selects different modulation methods according to the subcarrier threshold range. Subcarriers with good channel conditions use high-order QAM (such as 64QAM) to improve the data rate; subcarriers with poor conditions use robust BPSK or QPSK to ensure reliability; and subcarriers with deep fading are turned off (allocated 0 bits).

[0021] 3. Automatic gain control adopts a two-stage control method and a two-stage architecture: the analog stage is responsible for handling large dynamics and pulses, and performs a wide range of analog gain adjustment based on the received signal strength indicator RSSI to prevent saturation; the digital stage is responsible for fine adjustment to provide the best signal for demodulation; the two stages work together through feedback, which is a classic and effective solution for dealing with the harsh environment of power lines.

[0022] 4. The adaptive bit allocation and "water injection" principle of this invention maximizes spectrum utilization, and can achieve a higher data transmission rate under the same bandwidth.

[0023] 5. The dynamic frequency hopping and spectrum sensing functions of this invention enable the system to actively avoid sudden interference. When the SNR of a certain working frequency band drops below the threshold, the system automatically switches the data service to the pre-identified clean frequency band, realizing "unobtrusive" smooth frequency hopping, avoiding communication interruption, and having "self-healing" capability. It is particularly suitable for complex interference distribution network environments.

[0024] 6. The adaptive impedance matching and other designs of this invention are closely integrated with the actual working conditions of medium-voltage power grids, solving key pain points in engineering applications. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the overall communication method of the present invention. Figure 2 This is a diagram illustrating the network architecture and communication flow of the system of this invention; Figure 3 This is a schematic diagram of the OFDM subcarrier adaptive bit allocation of the present invention; Figure 4 This is a timing diagram for the dynamic frequency hopping switching of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0027] This invention discloses a power line carrier communication method for 10kV medium-voltage distribution networks based on adaptive OFDM, which is implemented through the following technical solution: The master station sends probe frames to the slave station, which then performs channel estimation (CE) and obtains channel state information (CSI). The broadband channel is divided into multiple parallel orthogonal subcarriers. Based on the channel state information (CSI), the water-filling algorithm is used to dynamically allocate the modulation scheme, modulation order, and coding rate of forward error correction (FEC) to each OFDM subcarrier. A two-stage automatic gain control (AGC) is used to condition the signal received from the power line; Based on continuous spectrum sensing results, dynamic frequency hopping is performed between heavily interfered frequency bands and idle frequency bands.

[0028] I. System Overall Architecture, see Figure 2 The system architecture diagram of this invention is shown, mainly including a master station carrier and slave station carriers deployed in power distribution terminals (FTU / DTU / TTU). The communication process is as follows: 1. Data transmission between the master station and the slave station is carried out via a 10kV power line.

[0029] 2. The master station initiates communication by first sending probe frames (Chirp signals or known training sequences) for channel estimation (CE).

[0030] 3. The slave station receives probe frames, performs channel estimation, and feeds back Channel State Information (CSI) to the master station.

[0031] 4. The master station constructs a "channel quality map" for the entire network based on feedback information from all slave stations, and dynamically selects the optimal parameters for each communication based on this map. It dynamically adjusts the transmitter parameters according to real-time changing channel conditions (such as signal-to-noise ratio (SNR), signal strength, interference level, etc.) to maximize spectral efficiency or throughput under current constraints (such as target bit error rate). Specific parameters are as follows: Modulation method and modulation order: Modulation determines how many bits of information each symbol can carry. The higher the modulation order, the more bits each symbol carries, the higher the spectral efficiency, but the worse the anti-interference ability.

[0032] Coding scheme and coding rate: Coding combats channel errors by adding redundant information. Coding rate = number of useful information bits / total number of encoded bits. The lower the coding rate, the more redundancy and the stronger the error correction capability, but the lower the effective throughput.

[0033] Power control: Dynamically adjust the transmit power, not always transmitting at maximum power. When channel conditions are good, the power can be appropriately reduced to decrease interference and power consumption; when channel conditions are poor, the power can be increased to ensure connectivity. This is an important parameter for optimizing energy efficiency and overall network performance.

[0034] II. The core technical solutions are as follows: 1. Adaptive multi-mode modulation technology (dynamic switching between OFDM / BPSK / QAM) This invention adopts a multi-mode modulation architecture with OFDM as the main modulator and BPSK and QAM as auxiliary modulators.

[0035] OFDM (Orthogonal Frequency Division Multiplexing) is a core technology that divides a broadband channel into multiple parallel orthogonal subcarriers, each of which can be modulated independently, thereby effectively combating frequency-selective fading.

[0036] Dynamic Modulation and Coding (AMC): Based on real-time acquired Channel State Information (CSI), the system independently selects the optimal modulation scheme (BPSK, QPSK, 16QAM, 64QAM) and forward error correction (FEC) coding rate for each subcarrier or a group of subcarriers, as detailed below: 1) Bit allocation calculation: The number of bits b_k allocated on the k-th subcarrier is determined by its signal-to-noise ratio (SNR), using a simplified algorithm based on the water-filling theorem: b_k = floor(log2(1+SNR_k / Γ)) Where: SNR_k is the signal-to-noise ratio of the kth subcarrier, Γ is the signal-to-noise ratio gap (SNR gap), which is related to the target bit error rate (BER) and the modulation and coding scheme, Γ=-ln(5*BER) / 1.5, and floor() is the floor function.

[0037] 2) Determine the application scenario: Subcarriers with good channel conditions use high-order QAM (such as 64QAM) to improve the data rate; subcarriers with poor conditions use robust BPSK or QPSK to ensure reliability; subcarriers with deep fading are turned off (allocated 0 bits).

[0038] In this embodiment, the dynamic allocation modulation method is specifically as follows: 1) Disable subcarrier threshold range (dB) < 2 - 5 dB.

[0039] 2) The threshold range (dB) of the binary phase shift keying (BPSK) modulation method is 5 - 8 dB.

[0040] 3) The threshold range (dB) of the quadrature phase shift keying (QPSK) modulation method is 8 - 11 dB.

[0041] 4) The threshold range (dB) of the high-order quadrature amplitude modulation 16QAM modulation method is 14 - 17 dB.

[0042] 5) The threshold range (dB) of the high-order quadrature amplitude modulation 64QAM modulation method is 20 - 23 dB.

[0043] 6) The threshold range (dB) of the high-order quadrature amplitude modulation 256QAM modulation method is 26 - 29 dB.

[0044] See Figure 3 , Figure 3 The subcarrier bit allocation is shown, demonstrating that different subcarriers are assigned different modulation orders based on their SNR levels.

[0045] 2. Internal Automatic Gain Control (AGC) and Adaptive Equalization Algorithm 1) Adaptive Gain Control (AGC): A two-stage AGC circuit is used at the receiver front end.

[0046] Coarse AGC: Performs a wide range of gain adjustments based on Received Signal Strength Indication (RSSI) to prevent ADC saturation.

[0047] Fine AGC: In the digital domain, fine-tuning is performed based on the pilot signal power in the OFDM symbol to ensure that the signal power input to the demodulator is stable.

[0048] The formula for calculating gain update is: G_new=G_old*(P_target / P_measured) Where P_target is the target power level, P_measured is the measured power level, and G_old is the gain before the update.

[0049] 2) Adaptive equalization: A frequency domain equalizer based on the least mean square (LMS) or recursive least square (RLS) algorithm is used to continuously update the equalizer coefficients using pilot signals to compensate for channel distortion and multipath effects.

[0050] 3. Anti-interference and communication stability enhancement technologies 1) Frequency domain interleaving coding: After forward error correction (FEC) coding, the bit stream is interleaved in the frequency domain, which distributes continuous bit errors into multiple forward error correction FEC blocks, so that burst noise errors are transformed into random errors, greatly improving the decoding success rate of FEC.

[0051] 2) Retransmission Mechanism (HARQ): Employs Hybrid Automatic Repeat Request (HARQ) technology. If decoding fails at the receiving end, it does not discard the data directly, but requests the sending end to retransmit part of the information (incremental redundancy), and merges it with the previously received erroneous data before decoding, significantly reducing retransmission overhead and improving transmission efficiency.

[0052] 4. Automatic frequency hopping and spectrum sensing technology 1) Perception and avoidance: The system periodically goes silent, listens to the background noise of the power grid, draws a "noise spectrum diagram", and identifies the frequency bands with severe interference ("spectral holes").

[0053] 2) Dynamic frequency hopping: Not all subcarriers are used for data transmission. Some subcarriers are reserved as "sentinel carriers" to monitor their SNR in real time. When the SNR of a certain operating frequency band drops below the threshold, the system automatically switches data services to the pre-identified clean frequency band, achieving "seamless" smooth frequency hopping and avoiding communication interruptions.

[0054] In this embodiment, if the average SNR calculated by the "sentinel carrier" remains below a preset threshold for T seconds, a decision-making process for switching frequency bands is triggered. The preset SNR threshold is set to 1 second when the average SNR drops to a position 2dB higher than the minimum SNR required by the current MCS.

[0055] See Figure 4 , Figure 3This is a dynamic frequency hopping timing diagram, showing the process from monitoring to decision-making and then to switching.

[0056] 5. Special design for medium-voltage power grid environments 1) Zero-crossing transmission technology: Data transmission is synchronized with the zero-crossing point of the power frequency voltage. At this time, the grid voltage is at its lowest, the instantaneous interference caused by load switching and other operations is minimal, the signal-to-noise ratio is highest, and the communication success rate can be effectively improved.

[0057] 2) Impedance matching network: Design a wide-range adaptive impedance matching circuit. Through an adjustable capacitor and inductor array, dynamically adjust the output impedance of the coupling device to match the real-time changing characteristic impedance of the electric field line, maximize signal injection efficiency and reduce reflection.

[0058] This embodiment takes the FTU (Distribution Automation Monitoring Terminal) of a pole-mounted switch and the main station carrier communication as an example: S1. The main station carrier transmits a channel probe frame within a microsecond window before the voltage crosses zero.

[0059] The S2.FTU receives probe frames from the carrier, performs CE, calculates the SNR of each subcarrier, and feeds it back to the master carrier.

[0060] S3. The master station carrier generates a modulation and coding scheme (MCS) table for the FTU link and transmits it through the downlink channel.

[0061] S4. Formal data transmission begins. The FTU sends data from the carrier in the uplink channel according to the MCS table.

[0062] S5. If the master station carrier fails to decode, it sends a NACK signal, and the FTU triggers the HARQ process from the carrier.

[0063] S6. At the same time, the system background continuously performs spectrum sensing. If it finds that the interference in the current frequency band continues to worsen, the master station makes a carrier decision and notifies all nodes to switch to the backup frequency band in the next communication cycle.

[0064] Based on the above communication method, this invention also discloses a 10kV medium-voltage distribution network power line carrier communication system based on adaptive OFDM, comprising: a master station concentrator and slave station nodes, wherein both the master station concentrator and the slave station nodes include: A coupling circuit is used to couple communication signals to a 10kV power line.

[0065] An adaptive impedance matching network is used to dynamically adjust the output impedance of a coupled device to match the characteristic impedance of the power line in real time.

[0066] The modulation and demodulation module is used to dynamically allocate modulation scheme, modulation order and coding rate of forward error correction (FEC) to each subcarrier of OFDM based on channel state information (CSI) and using a water-filling algorithm.

[0067] A digital signal processor (DSP) is used for signal conditioning to perform channel estimation and two-stage automatic gain control (AGC).

[0068] The central processing unit (CPU) is used to control the entire communication process and make dynamic frequency hopping decisions.

[0069] The coupling circuit is a capacitive coupling circuit, and the adaptive impedance matching network is composed of an adjustable capacitor and inductor array controlled by the MCU.

[0070] The specific execution process of the system is as follows: When sending data: The central processing unit (CPU) generates data frames, which are then conditioned by the digital signal processor (DSP) and input to the modulation and demodulation module. The modulation and demodulation module performs digital-to-analog conversion and dynamically allocates the modulation mode, modulation order, and forward error correction (FEC) coding rate. The data is then injected into the power line via an adaptive matching network to adjust the impedance.

[0071] When receiving data: the power line transmission signal is first extracted by the coupling circuit and then input to the adaptive matching network to dynamically adjust the output impedance and maximize energy reception. After two-stage automatic gain control (AGC) and digital-to-analog conversion by the modulation and demodulation module, the data frame is synchronized, equalized, demodulated, and decoded by the digital signal processor (DSP). Finally, the data frame is processed by the central processing unit (CPU).

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A power line carrier communication method for 10kV medium-voltage distribution networks based on adaptive OFDM, characterized in that, include: The master station sends probe frames to the slave station, which then performs channel estimation (CE) and obtains channel state information (CSI). The broadband channel is divided into multiple parallel orthogonal subcarriers. Based on the channel state information (CSI), the water-filling algorithm is used to dynamically allocate the modulation scheme, modulation order, and coding rate of forward error correction (FEC) to each OFDM subcarrier. A two-stage automatic gain control (AGC) is used to condition the signal received from the power line; Based on continuous spectrum sensing results, dynamic frequency hopping is performed between heavily interfered frequency bands and idle frequency bands.

2. A method for power line carrier communication in a 10kV medium-voltage distribution network based on adaptive OFDM according to claim 1, characterized in that, Based on Channel State Information (CSI), a water-filling algorithm is used to dynamically allocate modulation scheme, modulation order, and coding rate to each OFDM subcarrier. Bit allocation is calculated, and the number of bits b_k allocated to the k-th subcarrier is determined by its Signal-to-Noise Ratio (SNR). A simplified algorithm based on the water-filling algorithm is as follows: b_k = floor(log2(1+SNR_k / Γ)) Where: SNR_k is the signal-to-noise ratio of the kth subcarrier, Γ is the signal-to-noise ratio gap (SNR gap), which is related to the target bit error rate (BER) and the modulation and coding scheme, Γ=-ln(5*BER) / 1.5, and floor() is the floor function to ensure that the number of allocated bits is an integer.

3. The method for 10kV medium-voltage distribution network power line carrier communication based on adaptive OFDM according to claim 2, characterized in that, The dynamic allocation modulation method is as follows: 1) The subcarrier threshold range (dB) is < 2 - 5 dB; 2) The threshold range (dB) of the binary phase shift keying (BPSK) modulation method is 5 - 8 dB; 3) The threshold range (dB) of the quadrature phase shift keying (QPSK) modulation method is 8 - 11 dB; 4) The threshold range (dB) of the high-order quadrature amplitude modulation 16QAM modulation method is 14 - 17 dB; 5) The threshold range (dB) of the high-order quadrature amplitude modulation (64QAM) modulation method is 20 - 23 dB; 6) The threshold range (dB) of the high-order quadrature amplitude modulation 256QAM modulation method is 26 - 29 dB.

4. The method for 10kV medium-voltage distribution network power line carrier communication based on adaptive OFDM according to claim 1, characterized in that, The two-stage automatic gain control (AGC) conditions the signal received from the power line, specifically as follows: 1) At the receiver front end, a two-stage AGC circuit is used, with the following adjustments made: Coarse AGC: Performs wide-range analog-level gain adjustment based on Received Signal Strength Indication (RSSI); Fine AGC: At the digital level, fine-tuning is performed based on the pilot signal power in the OFDM symbol to ensure stable signal power input to the demodulator; The formula for calculating gain update is: G_new=G_old*(P_target / P_measured) Where P_target is the target power level, P_measured is the measured power level, and G_old is the gain before the update; 2) A frequency domain equalizer based on the least mean square (LMS) or recursive least squares (RLS) algorithm is used to continuously update the equalizer coefficients using pilot signals to compensate for channel distortion and multipath effects.

5. The method for 10kV medium-voltage distribution network power line carrier communication based on adaptive OFDM according to claim 1, characterized in that, During communication, if the master station carrier fails to decode, it sends a NACK signal. The slave station carrier triggers the HARQ process, but does not directly discard the data. Instead, it requests the sender to retransmit part of the information and merges it with the previously received erroneous data before decoding.

6. The method for power line carrier communication in a 10kV medium-voltage distribution network based on adaptive OFDM according to claim 1, characterized in that, The specific process of dynamic frequency hopping between heavily interfered frequency bands and idle frequency bands is as follows: The broadband channel is divided into multiple parallel orthogonal subcarriers, and some subcarriers are reserved as "sentinel carriers" to monitor the SNR in real time. When the SNR of a certain working frequency band drops below the threshold, the system automatically switches the data service to the pre-identified clean frequency band, realizing "unobtrusive" smooth frequency hopping.

7. A method for power line carrier communication in a 10kV medium-voltage distribution network based on adaptive OFDM according to claim 6, characterized in that, If the average SNR calculated by the "sentinel carrier" remains below a preset threshold for T seconds, a decision-making process for switching frequency bands is triggered. The preset SNR threshold is set to 1 second when the average SNR drops to a position 2dB higher than the minimum SNR required by the current MCS.

8. A 10kV medium-voltage distribution network power line carrier communication system based on adaptive OFDM, characterized in that, include: Master concentrator and slave nodes, each comprising: Coupling circuit, used to couple communication signals to a 10kV power line; An adaptive impedance matching network is used to dynamically adjust the output impedance of the coupled device to match the characteristic impedance of the power line that changes in real time. The modulation and demodulation module is used to dynamically allocate modulation scheme, modulation order and coding rate of forward error correction (FEC) to each subcarrier of OFDM based on channel state information (CSI) and using a water-filling algorithm. A digital signal processor (DSP) is used for signal conditioning to perform channel estimation and two-stage automatic gain control (AGC). The central processing unit (CPU) is used to control the entire communication process and make dynamic frequency hopping decisions.

9. A 10kV medium-voltage distribution network power line carrier communication system based on adaptive OFDM according to claim 8, characterized in that, The coupling circuit is a capacitive coupling circuit, and the adaptive impedance matching network is composed of an adjustable capacitor and inductor array controlled by the MCU.

10. A 10kV medium-voltage distribution network power line carrier communication system based on adaptive OFDM according to claim 8, characterized in that, The specific execution process of the system is as follows: When sending data: The central processing unit (CPU) generates data frames, which are then conditioned by the digital signal processor (DSP) and input to the modulation and demodulation module. The modulation and demodulation module performs digital-to-analog conversion and dynamically allocates the modulation mode, modulation order, and forward error correction (FEC) coding rate. The data is then injected into the power line via an adaptive matching network to adjust the impedance. When receiving data: the power line transmission signal is first extracted by the coupling circuit and then input to the adaptive matching network to dynamically adjust the output impedance and maximize energy reception. After two-stage automatic gain control (AGC) and digital-to-analog conversion by the modulation and demodulation module, the data frame is synchronized, equalized, demodulated, and decoded by the digital signal processor (DSP). Finally, the data frame is processed by the central processing unit (CPU).

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