Offshore wind farm seabed foundation real-time observation data transmission system and method

Abstract

A real-time observation and data transmission system and method for offshore wind farms based on the seabed is disclosed, belonging to the field of marine environmental monitoring technology. The system includes a seabed-based data aggregation terminal, a data transmission cable, and a sea surface data relay platform. It utilizes the existing single conductive cable of the offshore wind farm as the sole signal conductor, with seawater and double grounding electrodes forming the signal transmission loop. DC and power frequency interference are blocked by an isolation circuit, frame synchronization is achieved using a composite frequency preamble signal, and multi-carrier combinations are adaptively switched according to the signal-to-noise ratio. This invention eliminates the need for laying dedicated communication cables, significantly reducing costs, and enables stable, low-latency real-time transmission of multi-parameter data in complex marine electromagnetic environments, providing reliable data support for wind farm operation and maintenance.

Description

Technical Field

[0001] This invention relates to the field of marine environmental monitoring technology, specifically to a real-time observation and data transmission system and method for offshore wind farms based on the seabed. Background Technology

[0002] The offshore wind power industry is rapidly expanding into deep-sea areas, and the increasing size of wind turbines and the remoteness of sites pose serious challenges to their long-term safe operation and maintenance.

[0003] Traditional marine environmental monitoring relies on shipborne measurements or buoy observations, which suffer from drawbacks such as high cost, discontinuous data, and susceptibility to sea conditions. Existing online monitoring solutions mostly employ independently deployed dedicated communication optical cables or wireless transmissions. The former incurs huge deployment and maintenance costs, while the latter lacks reliability in the complex marine electromagnetic environment.

[0004] Therefore, there is an urgent need for a real-time marine environment perception solution that can be deeply integrated with wind farm infrastructure, and is stable, economical, and reliable in the long term. Summary of the Invention

[0005] In view of this, the main objective of the present invention is to provide a real-time observation and data transmission system and method for offshore wind farms based on the seabed, in order to at least partially solve the above-mentioned technical problems.

[0006] The following technical issues in real-time observation of seabed-based monitoring systems for offshore wind farms: 1. Transmission link cost and deployment issues: By directly utilizing the existing steel cables of the wind farm and seawater to form a signal loop, the high cost and easy-to-break communication optical cables are avoided, reducing system deployment costs and engineering complexity.

[0007] 2. Complex electromagnetic environment interference problem: Design a broadband carrier coding scheme and modulation / demodulation isolation circuit to effectively isolate DC potential and power frequency noise on the steel cable, and ensure stable and clean transmission of multi-parameter data in a strong interference environment.

[0008] 3. Data synchronization and identification reliability issues: A composite frequency preamble signal (such as 20KHz loaded on 1KHz) is used as the start identifier of the transmitted data frame, which realizes highly reliable and low-false-judgment frame synchronization in the background of noise, ensuring the integrity and real-time performance of data transmission.

[0009] This invention enables integrated real-time monitoring that is low-cost, highly reliable, and easy to deploy, significantly improving the safety and intelligence level of offshore wind farm operation and maintenance.

[0010] To achieve the above objectives, as a first aspect of the present invention, a real-time observation and data transmission system for seabed-based offshore wind farms is proposed, characterized in that it comprises: A seabed-based data aggregation terminal, a data transmission cable, and a sea surface data relay platform; wherein, the seabed-based data aggregation terminal includes: A multi-parameter sensor array is used to synchronously collect marine environmental parameters; A signal transmission modulation module is used to modulate the collected marine environmental parameters into a composite analog electrical signal; A first coupling isolation circuit is used to inject the composite analog electrical signal into the data transmission cable and block DC potential and low-frequency surges from the data transmission cable. The first grounding electrode is used to be buried in seabed sediment to form a low-impedance electrical connection with seawater; the data transmission cable is a single conductive cable that is currently used in offshore wind farms to connect the seabed foundation and the surface platform, and is used as the sole signal conductor to conduct the composite analog electrical signal. The sea surface data relay platform includes: The second coupling isolation circuit is used to extract the composite analog electrical signal from the data transmission cable and isolate interference on the platform side. The signal receiving and demodulation module is used to demodulate the extracted composite analog electrical signal to restore the marine environmental parameters; The second grounding electrode is used to contact the seawater and form the receiving end of the signal loop; the first grounding electrode, the seawater, the second grounding electrode, and the data transmission steel cable together form the signal transmission loop.

[0011] In one possible implementation, the signal transmission modulation module includes: A signal generating circuit is used to generate carrier signals having a first frequency, a second frequency, and a third frequency; A first-level modulation circuit is used to modulate the voltage range of the carrier signal to between a preset negative voltage and a preset positive voltage; The secondary modulation circuit is used to control the encoding of a preset carrier wave using the encoded control signal, and to superimpose and amplify the encoded signal with the carrier signal of the first frequency. The signal receiving and demodulation module includes: A signal receiving circuit, the signal receiving circuit including at least a filter circuit for separating different frequency components; and a shaping circuit for shaping the separated analog signal into a digital square wave signal.

[0012] In one possible implementation, both the first and second coupling isolation circuits are isolation transformers that only allow AC signals to pass through; the composite analog electrical signal uses a composite frequency signal as the start identifier of the data frame, and the composite frequency signal is a 20KHz carrier signal superimposed on a 1KHz carrier signal.

[0013] In one possible implementation, the seabed-based data aggregation terminal further includes a main control module configured to perform an adaptive channel matching operation, the adaptive channel matching operation including: The pilot sequence is transmitted via the data transmission steel cable; Based on the channel state information returned from the sea surface data relay platform, the frequency modulation scheme and transmission power of the subcarrier are dynamically selected; The channel state information includes at least the signal-to-noise ratio.

[0014] In one possible implementation, the main control module has a preset signal-to-noise ratio (SNR)-modulation-coding mapping table for selecting the corresponding carrier combination method based on the real-time measured SNR. When the signal-to-noise ratio is lower than the first threshold, a carrier combination of the first frequency and the second frequency is used; When the signal-to-noise ratio is between the first threshold and the second threshold, a carrier combination of the first frequency, the second frequency, and the third frequency is used; When the signal-to-noise ratio is higher than the second threshold, a carrier combination of the first and third frequencies is used.

[0015] As a second aspect of the present invention, a method for real-time observation data transmission of offshore wind farms based on the seabed is proposed, comprising: The sea surface data relay platform transmits command signals via data transmission steel cables; The seabed-based data aggregation terminal receives the command signal through the data transmission steel cable, which wakes up the multi-parameter sensor array to synchronously collect marine environmental parameters. The seabed-based data aggregation terminal modulates the collected marine environmental parameters into composite analog electrical signals; The composite analog electrical signal is injected into the data transmission steel cable through a first coupling isolation circuit, and the data transmission steel cable is a conductive steel cable. The composite analog electrical signal uses seawater as the return point and is transmitted to the sea surface through a loop consisting of a first grounding electrode, seawater, a second grounding electrode, and the data transmission steel cable. The sea surface data relay platform extracts the composite analog electrical signal from the data transmission steel cable through a second coupling isolation circuit; The extracted composite analog electrical signal is demodulated to restore the marine environmental parameters, and then forwarded to the shore-based monitoring center via a communication network.

[0016] In one possible implementation, the step of modulating the marine environmental parameters into a composite analog electrical signal specifically includes: Generate a carrier signal with a first frequency, a second frequency, and a third frequency; The voltage range of the carrier signal is modulated to be between a preset negative voltage and a preset positive voltage; The preset carrier wave is controlled by the encoded control signal; The encoded signal is superimposed and amplified with the carrier signal of the first frequency to generate the composite analog electrical signal; The specific steps for demodulating the extracted composite analog electrical signal include: Different frequency components are separated from the extracted composite analog electrical signal through filtering; The separated analog signal is shaped into a digital square wave signal.

[0017] One possible implementation also includes an adaptive channel matching step: The seabed-based data aggregation terminal transmits pilot sequences via the data transmission steel cable; The sea surface data relay platform receives the pilot sequence, estimates the frequency response and signal-to-noise ratio of the current channel on each subcarrier, and generates channel state information. Based on the channel state information and the preset signal-to-noise ratio-modulation-coding mapping table, the frequency modulation scheme and transmission power of the subcarrier are dynamically selected; The determined frequency modulation parameters are sent to the seabed-based data aggregation terminal for subsequent data modulation.

[0018] In one possible implementation, the adaptive channel matching step is triggered by periodic timing or by a signal-to-noise ratio (SNR) abrupt change event; the SNR-modulation coding map includes: When the signal-to-noise ratio is lower than the first threshold, a carrier combination of the first frequency and the second frequency is used; when the signal-to-noise ratio is between the first threshold and the second threshold, a carrier combination of the first frequency, the second frequency and the third frequency is used. When the signal-to-noise ratio is higher than the second threshold, a carrier combination of the first frequency and the third frequency is used.

[0019] One possible implementation also includes error control steps: The sea surface data relay platform performs frame verification on the demodulated and restored data packets; If the verification fails, a negative response signal is sent to the seabed-based data aggregation terminal via the data transmission cable to trigger the selective retransmission mechanism.

[0020] Based on the above technical solution, it can be seen that the real-time observation and data transmission system and method for offshore wind farms based on seabed foundations of the present invention has at least one of the following beneficial effects compared with the prior art: 1. By using the existing single conductive steel cable of the offshore wind farm as the sole signal conductor, and combining it with seawater, the first grounding electrode, and the second grounding electrode to form a complete signal transmission loop, there is no need to lay expensive and easily damaged dedicated communication optical cables or signal lines. The existing infrastructure of the wind farm can be directly reused, saving material, engineering, and subsequent maintenance costs. The pure analog signal coupling and transmission method does not require complex digital packaging and protocol stack processing, and the signal transmission delay is negligible, meeting the high real-time application requirements such as scour early warning and earthquake and tsunami monitoring.

[0021] 2. By setting up specific first-level modulation circuits, second-level modulation circuits, filtering circuits, and shaping circuits, and using multi-frequency carriers for signal superposition, modulation, and separation, and by modulating different sensor data onto carriers of different frequencies such as 1KHz, 20KHz, and 40KHz, parallel transmission of multiple data streams on the same steel cable is achieved, improving channel utilization. Through the coding switch control and signal superposition in the second-level modulation, as well as the multi-level filtering processing at the receiving end, the power frequency interference, surge noise, and DC potential drift present in the steel cable-seawater channel are effectively suppressed, ensuring the purity and recognizability of the signal in complex electromagnetic environments.

[0022] 3. By using a composite frequency signal as the start identifier of the data frame, even under strong background noise, the receiver can accurately identify the start position of the frame by detecting a specific frequency combination, which greatly reduces the probability of misjudgment and missed judgment and ensures the integrity of the data structure. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention; Figure 2 This is a schematic diagram of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention. Figure 3 This is a schematic diagram of the signal generation circuit of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention. Figure 4 This is a schematic diagram of the first-stage modulation circuit of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention. Figure 5 This is a schematic diagram of the secondary modulation circuit of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention. Figure 6 This is a schematic diagram of the signal receiving circuit of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention. Figure 7 This is a schematic diagram of the signal shaping circuit of a real-time observation and data transmission system for seabed-based offshore wind farms according to the present invention. Figure 8 This is a flowchart illustrating a method for real-time observation and data transmission of offshore wind farms based on the seabed. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0026] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of the invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0027] The present invention will be further illustrated below through specific embodiments. It should be noted that the following embodiments are merely illustrative and not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments shown below without inventive effort are within the scope of protection of the embodiments of the present invention.

[0028] Therefore, as Figure 1 As shown, this application proposes a real-time observation and data transmission system for seabed-based offshore wind farms, characterized by comprising: The system comprises a seabed-based data aggregation terminal, a data transmission cable, and a sea surface data relay platform. The seabed-based data aggregation terminal is responsible for data sensing and information exchange with the sea surface data relay platform, and is permanently deployed on the seabed in the offshore wind farm area. Its main functions are to receive command signals from the sea surface data relay platform, synchronously collect various marine environmental parameters, and transmit the data to the transmission cable in real time. The seabed-based data aggregation terminal includes: A multi-parameter sensor array is used to simultaneously acquire marine environmental parameters. This array integrates various hydrological sensors for simultaneous observation. Specifically, it includes an Acoustic Doppler Current Profiler (ADCP) for measuring water column velocity and direction, and a Temperature, Salinity, and Depth (CTD) sensor for acquiring temperature, salinity, and depth data. All sensor outputs are standard analog voltages or digital signals.

[0029] A signal transmission modulation module is used to modulate the collected marine environmental parameters into a composite analog electrical signal; A first coupling isolation circuit is used to inject the composite analog electrical signal into the data transmission cable and block DC potential and low-frequency surges from the data transmission cable. The first grounding electrode is used to bury itself in seabed sediment to form a low-impedance electrical connection with seawater. The data transmission cable is an existing single conductive cable from the offshore wind farm, connecting the seabed foundation and the surface platform, used as the sole signal conductor to transmit the composite analog electrical signal. The data transmission cable is the physical transmission channel of the system, directly utilizing existing high-strength composite steel cables (such as wind turbine anchor cables and structural support cables) from the wind farm to provide a robust physical channel for transmitting the modulated analog electrical signal. There is no need to add dedicated signal lines or optical cables within the cable; its metal armor or core steel wires serve as the sole signal conductor. The electrical characteristics of the cable (resistance, inductance, and distributed capacitance to seawater) and the conductivity of seawater together determine the frequency response characteristics of the channel. The system learns and adapts to these characteristics in advance through an algorithm.

[0030] The marine data relay platform is typically fixedly installed on the surface support structure of the offshore wind farm, such as the wind turbine foundation platform, booster station platform, or dedicated monitoring buoy. This platform serves as the signal receiving, processing, and remote forwarding node for the entire system. It is responsible for extracting weak uplink composite analog electrical signals from the data transmission cable, demodulating and restoring them, and then pushing the data in real time to the shore-based monitoring center via the existing communication network. The shore-based monitoring center is a central control platform located on land, used for receiving, storing, displaying, and analyzing marine environmental data from the offshore wind farm.

[0031] The sea surface data relay platform includes a second coupling isolation circuit for extracting the composite analog electrical signal from the data transmission cable and isolating interference from the platform side. The second coupling isolation circuit is a broadband high-pass coupling isolation transformer (in principle, it is the same as the first coupling isolation circuit of the seabed-based data aggregation terminal, but the turns ratio can be optimized according to the signal transmission direction). One end of this circuit is directly electrically connected to the top of the data transmission cable, and the other end is connected to the input of the signal receiving and demodulation module. Its core functions are twofold: first, to extract the upstream composite analog electrical signal from the cable without loss, while completely isolating the receiving circuit from the DC potential of the cable, preventing stray currents or lightning surges from the wind turbine platform from entering the receiving circuit; second, to utilize the common-mode rejection characteristics of the transformer to suppress potential interference between the cable and the platform's seawater grounding electrode, ensuring the purity of the extracted signal.

[0032] The signal receiving and demodulation module, as the core unit for performing signal restoration, is used to demodulate the extracted composite analog electrical signal to restore the marine environmental parameters. The second grounding electrode is used to contact seawater and form the receiving end of the signal loop; The first grounding electrode, seawater, the second grounding electrode, and the data transmission steel cable together constitute a signal transmission loop.

[0033] In this embodiment, the seabed-based data aggregation terminal receives command signals from the surface platform via a steel cable. Data collected by multi-parameter sensors is modulated by the transmitting circuit and injected into the steel cable conductor as a composite analog electrical signal. The signal is transmitted along the steel cable, forming a loop through seawater to reach the surface platform. The platform's receiving circuit extracts and demodulates the signal from the steel cable, recovers the data, and forwards it to the shore via existing communication methods, thereby achieving real-time, stable, and low-cost observation of marine environmental parameters.

[0034] The communication component consists of a main control module and a remote communication module (such as a 4G / 5G DTU, a BeiDou short message terminal, or a fiber optic Ethernet interface). The main control module timestamps multiple sensor data streams from the signal receiving and demodulation module and performs data fusion, compression, and temporary storage. Then, the data is transmitted to the shore-based monitoring center via the remote communication module. If the platform already has an existing fiber optic network (such as a submarine fiber optic cable ring network between wind turbines), wired transmission is preferred to achieve higher bandwidth and stability.

[0035] In one possible implementation, the signal transmission modulation module includes: A signal generating circuit is used to generate carrier signals having a first frequency, a second frequency, and a third frequency; Figure 3 The signal generation circuit consists of Y100 and IC105 generating the clock signal. IC104, IC106, and IC107 generate 1kHz, 20kHz, and 40kHz analog signals SIG_VOUT, SIG_VOUT_1, and SIG_VOUT_2, respectively, with a signal range of 0V to 0.66V. Y100 and IC105 form a stable clock source, providing a precise time reference for the entire modulation process. IC104, IC106, and IC107 generate 1kHz, 20kHz, and 40kHz analog carrier signals SIG_VOUT, SIG_VOUT_1, and SIG_VOUT_2, respectively, with an output range of 0V to 0.66V. The function of this circuit is to generate multiple clean carriers with separated frequencies and uniform amplitudes, providing a clear and stable signal source for subsequent modulation circuits. The effect is that by limiting the amplitude of different frequency carriers to the same low voltage range, it is easier for subsequent circuits to perform unified level shifting and superposition processing, reducing circuit complexity. At the same time, it avoids nonlinear distortion caused by excessive differences in carrier amplitude, thereby ensuring the signal fidelity and stability of the entire modulation link.

[0036] A first-level modulation circuit is used to modulate the voltage range of the carrier signal to between a preset negative voltage and a preset positive voltage; Figure 4This is a first-stage modulation circuit. The input signals are SIG_VOUT, SIG_VOUT_1, and SIG_VOUT_2. IC103A and IC103B provide a reference voltage of -0.33V to the first-stage modulation circuit, modulating the output voltage of the first-stage modulation circuit to -0.33V to 0.33V, resulting in analog signals SIG_V1K, SIG_V20K, and SIG_V40K. The core function of the first-stage modulation circuit is to convert the unipolar carrier (0V to 0.66V) output by the signal generation circuit into a bipolar carrier to meet the AC coupling transmission requirements of the steel cable-seawater channel. Specifically, IC103A and IC103B provide a reference voltage of -0.33V to the circuit, shifting the input SIG_VOUT, SIG_VOUT_1, and SIG_VOUT_2 to the voltage range of -0.33V to 0.33V, and outputting analog signals SIG_V1K, SIG_V20K, and SIG_V40K. The effect of this circuit is to eliminate the DC component in the carrier signal, giving the signal positive and negative symmetrical AC characteristics, so that it can be smoothly coupled to the steel cable through the subsequent isolation transformer. At the same time, it avoids the risk of electrochemical corrosion of the steel cable and seawater circuit caused by DC potential, and significantly improves the long-term working stability and safety of the system.

[0037] The secondary modulation circuit is used to control the encoding of a preset carrier wave using the encoded control signal, and to superimpose and amplify the encoded signal with the carrier signal of the first frequency. Figure 5 The circuit is a two-stage modulation circuit. SIG_V20K and SIG_V40K are input to IC305, which is an encoding switch. IC305's control input is the CRL_OUT signal, which is the output signal of IC304 after being encoded by the FPGA. IC303 and IC304 are square wave shaping circuits that convert the analog signal SIG_V1K into a digital square wave signal. The output signals SIG_F and SIG_V1K from the encoding switch IC305 enter the two-stage modulation circuit. IC300A adds the two signals, and IC300B inverts the signal. After amplification by IC302A, and according to the control switch command of IC306, the signal is output to the data transmission cable through the isolation circuit. T300 is the isolation circuit, which plays a crucial role in isolation, allowing only AC signals to pass through while blocking any DC potential or low-frequency surges that may exist on the cable, protecting the downstream circuitry. The control switch of IC306 is controlled by the STM32 via the F_ONOFF signal to avoid signal interference between the transmit and receive signals on the data transmission cable.

[0038] The signal receiving and demodulation module includes: A signal receiving circuit, the signal receiving circuit including at least a filter circuit for separating different frequency components; and a shaping circuit for shaping the separated analog signal into a digital square wave signal.

[0039] In the embodiments of this application, the signal receiving circuit is as follows: Figure 6 As shown, its function is to extract weak signals from the steel cable and perform analog domain preprocessing. Specifically, T400 is a receiving signal isolation circuit used to block DC and low-frequency surges; after amplification by IC401A, it enters the filter circuit, which is composed of a second-order low-pass filter circuit consisting of IC402A and IC402B connected in series with a second-order high-pass filter circuit consisting of IC403A and IC403B, used to separate components of different frequencies from the composite analog electrical signal (for example, extracting signal components carrying low-frequency data and high-frequency data respectively). The circuit outputs SIG_LK_S and SIG_FK_S, both of which are analog signals.

[0040] Shaping circuits such as Figure 7 As shown, its input is Figure 6 The output analog signals SIG_LK_S and SIG_FK_S are shaped into digital square wave signals SIG_FK and SIG_LK by IC400 and IC404, respectively, and then output to the main control module (or FPGA). The digital demodulation unit in the main control module decodes and parses the digital square wave signals to ultimately reconstruct the original marine environmental parameter data. Therefore, the signal receiving circuit, the shaping circuit, and the digital demodulation unit in the main control module together constitute the complete function of the signal receiving and demodulation module.

[0041] In one possible implementation, both the first and second coupling isolation circuits are isolation transformers that only allow AC signals to pass through; the composite analog electrical signal uses a composite frequency signal as the start identifier of the data frame, wherein the composite frequency signal is a 20KHz carrier signal superimposed on a 1KHz carrier signal, and once detected, the start of a data frame is confirmed.

[0042] In one possible implementation, the seabed-based data aggregation terminal further includes a main control module configured to perform an adaptive channel matching operation, the adaptive channel matching operation including: The pilot sequence is transmitted via the data transmission steel cable; Based on the channel state information returned from the sea surface data relay platform, the frequency modulation scheme and transmission power of the subcarrier are dynamically selected; The channel state information includes at least the signal-to-noise ratio.

[0043] In one possible implementation, the main control module has a preset signal-to-noise ratio (SNR)-modulation-coding mapping table for selecting the corresponding carrier combination method based on the real-time measured SNR. When the signal-to-noise ratio is lower than the first threshold, a carrier combination of the first frequency and the second frequency is used; When the signal-to-noise ratio is between the first threshold and the second threshold, a carrier combination of the first frequency, the second frequency, and the third frequency is used; When the signal-to-noise ratio is higher than the second threshold, a carrier combination of the first and third frequencies is used.

[0044] As a second aspect of the present invention, a method for real-time observation data transmission of offshore wind farms based on the seabed is proposed, such as... Figure 8 As shown, it includes: The sea surface data relay platform transmits command signals via data transmission steel cables; The seabed-based data aggregation terminal receives the command signal through the data transmission cable, waking up the multi-parameter sensor array to synchronously collect marine environmental parameters. The power supply of the seabed-based data aggregation terminal is provided by the main power source of the seabed-based data aggregation terminal (battery or submarine cable) through a high-efficiency DC-DC converter to provide a stable operating voltage for each module. At the same time, the power module realizes the system's sleep and wake-up control, so that the terminal enters a low-power sleep state when not transmitting data, thereby extending the working time under battery power.

[0045] In this embodiment, the complete operation of the sea surface data relay platform is as follows: when real-time data needs to be acquired or acquisition parameters need to be modified, the shore-based control center sends instructions to the platform via remote communication. The platform's data processing unit packages the instructions, modulates them digitally, and then injects them back into the steel cable through a second coupling isolation circuit, transmitting them down to the seabed-based data aggregation terminal. This downlink uses the same physical channel and modulation method as the uplink, but uses a different carrier frequency (e.g., a 5kHz carrier) to avoid collisions. After responding to the instructions, the seabed-based data aggregation terminal uploads the acquired sensor data. The platform extracts the uplink analog signal from the steel cable through the second coupling isolation circuit, and then sequentially passes it through the front-end receiving circuit, shaping circuit, and digital demodulation unit to reconstruct the original data. The main control module packages the multi-parameter data, adds time stamps, and forwards it to the shore-based monitoring center in real time through the remote communication module, completing one complete observation and transmission cycle.

[0046] The seabed-based data aggregation terminal modulates the collected marine environmental parameters into composite analog electrical signals; The composite analog electrical signal is injected into the data transmission steel cable through a first coupling isolation circuit, and the data transmission steel cable is a conductive steel cable. The composite analog electrical signal uses seawater as the return point and is transmitted to the sea surface through a loop consisting of a first grounding electrode, seawater, a second grounding electrode, and the data transmission cable. The terminal shell of the first grounding electrode is connected to a large-area titanium alloy electrode, which is buried in seabed sediment to form a low-impedance electrical connection with the seawater, providing a return path for the signal.

[0047] In this embodiment, the second grounding electrode is a large-area titanium alloy plate or copper-based antifouling electrode, firmly installed on the underwater part of the platform, maintaining continuous, low-impedance electrical contact with seawater. This electrode serves as the grounding of the receiving end of the signal loop, providing a return path for the weak signal current transmitted from the steel cable. The complete signal current loop is: first grounding electrode of the seabed-based data aggregation terminal → seabed sediment → seawater → second grounding electrode of the platform → input terminal of the signal receiving and demodulation module (via the second coupling isolation circuit) → steel cable conductor → output terminal of the signal transmitting module of the seabed-based data aggregation terminal. This loop ensures that even if the steel cable is several kilometers long, the signal current can form a closed loop, thereby achieving stable transmission.

[0048] The sea surface data relay platform extracts the composite analog electrical signal from the data transmission steel cable through a second coupling isolation circuit; The extracted composite analog electrical signal is demodulated to restore the marine environmental parameters, and then forwarded to the shore-based monitoring center via a communication network.

[0049] In one possible implementation, the step of modulating the marine environmental parameters into a composite analog electrical signal specifically includes: Generate a carrier signal with a first frequency, a second frequency, and a third frequency; The voltage range of the carrier signal is modulated to be between a preset negative voltage and a preset positive voltage; The preset carrier wave is controlled by the encoded control signal; The encoded signal is superimposed and amplified with the carrier signal of the first frequency to generate the composite analog electrical signal; The specific steps for demodulating the extracted composite analog electrical signal include: Different frequency components are separated from the extracted composite analog electrical signal through filtering; The separated analog signal is shaped into a digital square wave signal.

[0050] One possible implementation also includes an adaptive channel matching step: The seabed-based data aggregation terminal transmits pilot sequences via the data transmission steel cable; The sea surface data relay platform receives the pilot sequence, estimates the frequency response and signal-to-noise ratio of the current channel on each subcarrier, and generates channel state information. According to the channel state information and a preset signal-to-noise ratio - modulation coding mapping table, dynamically select the frequency modulation scheme and transmission power of subcarriers; Send the determined frequency modulation parameters to the seabed-based data aggregation terminal for subsequent data modulation.

[0051] In a possible implementation manner, the adaptive channel matching step is triggered by periodic timing or by a signal-to-noise ratio mutation event; specifically, the adaptive process can be triggered by a timer (such as every 10 minutes) or an abnormal event (such as continuous reception failure, SNR mutation); after being awakened, the seabed-based data aggregation terminal first sends a known pilot sequence and a composite frequency preamble signal (for example, a 20KHz signal loaded on a 1KHz signal as the frame start identifier). After the sea surface platform receives it, by comparing the received pilot with the original sequence, accurately estimate the frequency response and signal-to-noise ratio (SNR) of the current channel on subcarriers of 1KHz, 20KHz, and 40KHz; according to the real-time measured SNR, referring to the preset "signal-to-noise ratio - modulation coding scheme" mapping table (for example: SNR < 10dB uses 1K + 20K carriers; 10dB < SNR < 20dB uses 1K + 20K + 40K carriers; SNR > 20dB uses 1K + 40K carriers), dynamically select the optimal carrier combination and modulation method. Send the decision result to the seabed-based data aggregation terminal, and the terminal updates its internal communication parameter table accordingly.

[0052] In a time-varying channel composed of a steel cable and seawater, signal attenuation and noise interference will change dynamically with factors such as sea conditions, sediment coverage, and steel cable aging. To achieve reliable and efficient transmission, this application pre-constructs a signal-to-noise ratio - modulation coding mapping table and stores it in the non-volatile memories of the seabed-based data aggregation terminal and the sea surface data relay platform. This mapping table divides the real-time measured signal-to-noise ratio (SNR) into multiple intervals, and each interval corresponds to an optimal carrier combination scheme. The signal-to-noise ratio - modulation coding mapping table includes: When the signal-to-noise ratio is lower than the first threshold, use a carrier combination of the first frequency and the second frequency; when the signal-to-noise ratio is between the first threshold and the second threshold, use a carrier combination of the first frequency, the second frequency, and the third frequency; When the signal-to-noise ratio is higher than the second threshold, use a carrier combination of the first frequency and the third frequency.

[0053] In this embodiment, firstly, three carrier frequencies are defined: the first frequency f1 is 1 kHz, the second frequency f2 is 20 kHz, and the third frequency f3 is 40 kHz. Two signal-to-noise ratio (SNR) thresholds are set: the first threshold TH1 = 10 dB and the second threshold TH2 = 20 dB. The mapping table details are as follows: When the signal-to-noise ratio (SNR) is < 10dB, the carrier combination is f1 + f2 (1kHz + 20kHz), resulting in poor channel quality. The highest frequency, 40kHz, is abandoned to avoid excessive attenuation. When the SNR is 10dB ≤ SNR ≤ 20dB, the carrier combination is f1 + f2 + f3 (1kHz + 20kHz + 40kHz), resulting in moderate channel quality. All three carriers can be used to achieve maximum data throughput. When the SNR is > 20dB, the carrier combination is f1 + f3 (1kHz + 40kHz), resulting in excellent channel quality. Only the low-frequency and highest-frequency combinations can be used to ensure data rate while reducing multi-carrier interference. It should be noted that the thresholds of 10dB and 20dB and their corresponding frequency combinations are empirical values ​​obtained through extensive field measurements in typical application scenarios of this invention (steel cable length 1–3km, seawater conductivity 3–5S / m). In actual deployment, engineers can calibrate and modify the thresholds through on-site pre-commissioning based on the water depth, electrical characteristics of the steel cables, and the environmental noise spectrum of the specific wind farm.

[0054] The adaptive workflow based on the mapping table is as follows: the system initiates the adaptive process after startup or periodically (e.g., every 10 minutes) by a timer. The main control module of the seabed-based data aggregation terminal generates a known pilot sequence, which sequentially transmits test signals at three frequencies of 1kHz, 20kHz, and 40kHz in single-carrier form, with each frequency continuously transmitted for 10 symbol cycles.

[0055] The sea-based data relay platform receives pilot signals at various frequencies and calculates the received signal power and background noise power at each carrier frequency, thereby obtaining the signal-to-noise ratio (SNR) of each subcarrier: SNR1k, SNR20k, and SNR40k. Since the fading characteristics of the channel may differ at the three frequencies, this system adopts the worst-case subcarrier dominance principle: taking min(SNR1k, SNR20k, SNR40k) as the overall SNR of the current channel to ensure that the selected scheme covers the minimum passability conditions for all enabled carriers.

[0056] The calculated SNR is compared with two pre-stored thresholds (10dB, 20dB): If SNR < 10dB, the decision result is a low signal-to-noise ratio mode, and the carrier combination is {1KHz, 20KHz}, discarding the 40KHz carrier; If 10dB ≤ SNR ≤ 20dB, the decision result is medium signal-to-noise ratio mode, and the carrier combination is {1KHz, 20KHz, 40KHz}, enabling all carriers; If SNR>20dB, the decision result is a high signal-to-noise ratio mode, and the carrier combination is {1KHz, 40KHz}. The 20KHz carrier is discarded because the channel is good enough at this time, and the highest frequency can be used to increase the equivalent code rate directly. At the same time, reducing one carrier can reduce the transmission power consumption.

[0057] The sea surface data relay platform transmits the decision result (i.e., the selected carrier combination mode) to the seabed-based data aggregation terminal via a steel cable downlink in the form of a command frame. This command frame uses low-order modulation (e.g., BPSK on 1kHz) and includes a CRC checksum to ensure reliable reception of the decision result. Upon receiving the command, the seabed-based data aggregation terminal updates its local transmission parameter table and sends a confirmation reply. Both parties simultaneously switch to the new carrier combination mode at the start of the next synchronization time slot. Based on the updated carrier combination, the seabed-based data aggregation terminal allocates the collected multi-parameter data to the corresponding carriers for modulation. For example, if the current mode is {1kHz, 40kHz}, parameters with slow changes, such as temperature and salinity, are assigned to the 1kHz carrier, while dynamic parameters, such as current velocity and waves, are assigned to the 40kHz carrier. After transmission, continuous monitoring is maintained for subsequent received ACK / NACK feedback or re-triggered channel probing. If multiple consecutive NACKs are received or an increase in the bit error rate is detected, the adaptive process is immediately re-triggered, the SNR is measured again, and the mapping mode is adjusted.

[0058] In this embodiment, during a field test at an offshore wind farm with a water depth of 28m and a steel cable length of approximately 350m, the background noise primarily consisted of power frequency harmonics (50Hz and its multiples) and broadband interference generated by the wind turbine inverter. During initial deployment, the system first performed channel detection, measuring a combined SNR of 12dB (between 10 and 20dB). Based on the mapping table, the system automatically selected a "1K+20K+40K" three-carrier fully open mode for data transmission, achieving a data success rate of 99.7% over 72 consecutive hours of testing.

[0059] Two days later, a storm surge occurred, causing seabed sediment to resuspend and reducing the insulation impedance of the steel cable, resulting in a signal-to-noise ratio (SNR) drop to 8 dB. The system periodically detected an SNR below 10 dB and automatically downgraded to a "1K+20K" dual-carrier mode. After the switch, although the equivalent data rate decreased by approximately 30%, the bit error rate decreased from 1.2 × 10⁻⁶. -3 Restored to 1.5×10 -5 The transmission success rate rose back to 99.9%. After the storm, the channel recovered, the SNR rose back to 18dB, and the system was upgraded to three-carrier full-on mode again.

[0060] This example verifies the effectiveness of the signal-to-noise ratio-modulation coding mapping table and adaptive switching mechanism in harsh real-world environments, achieving a dynamic balance between reliability and transmission efficiency.

[0061] One possible implementation also includes error control steps: The sea surface data relay platform performs frame verification on the demodulated and restored data packets; If the verification fails, a negative response signal is sent to the seabed-based data aggregation terminal via the data transmission cable to trigger the selective retransmission mechanism.

[0062] In this embodiment, the receiving end performs forward error correction (FEC) decoding on the data and then performs frame verification. If the verification is successful, the data is forwarded normally; if the verification fails (e.g., a CRC check error), a negative acknowledgment (NACK) signal is sent to the seabed-based data aggregation terminal via a steel cable, triggering selective retransmission of specific data packets. This constitutes a closed-loop reliability assurance mechanism.

[0063] A method and device for real-time marine environment observation and data transmission based on seabed-based multi-parameter integrated technology for offshore wind farms is disclosed. The core technology utilizes a single steel cable currently in use at the offshore wind farm as the sole signal conductor, with seawater and dual grounding electrodes deployed on the seabed and surface forming a closed-loop return path, eliminating the need for expensive dedicated communication optical cables or independent signal lines found in traditional solutions. Furthermore, a dedicated isolation coupling circuit blocks DC potential and power frequency interference coupled to the steel cable, and a composite frequency preamble signal is used to achieve highly reliable frame synchronization under strong noise conditions. Simultaneously, the system detects the channel signal-to-noise ratio in real time and dynamically switches multi-carrier combinations (such as 1K+20K, 1K+20K+40K, 1K+40K) according to a preset signal-to-noise ratio-modulation coding mapping table to achieve adaptive transmission. This invention significantly reduces the engineering deployment and long-term operation and maintenance costs of the seabed observation system for offshore wind farms. It ensures continuous, stable, and low-latency transmission of multi-parameter data in complex marine electromagnetic environments. Through intelligent channel matching and error correction mechanisms, it provides high-precision and high-completeness real-time data support for key operation and maintenance decisions such as wind turbine foundation scour early warning and cable status monitoring, thus comprehensively improving the safety and intelligence level of wind farm operation.

[0064] The foregoing has described specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0065] In the description of the embodiments of the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In the embodiments of the present invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in the embodiments of the present invention, as well as the features of the different embodiments or examples.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of embodiments of the present invention, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A real-time observation and data transmission system for seabed-based offshore wind farms, characterized in that, include: A seabed-based data aggregation terminal, a data transmission cable, and a sea surface data relay platform; wherein, the seabed-based data aggregation terminal includes: A multi-parameter sensor array is used to synchronously collect marine environmental parameters; A signal transmission modulation module is used to modulate the collected marine environmental parameters into a composite analog electrical signal; A first coupling isolation circuit is used to inject the composite analog electrical signal into the data transmission cable and block DC potential and low-frequency surges from the data transmission cable. The first grounding electrode is used to be buried in seabed sediment to form a low-impedance electrical connection with seawater; the data transmission cable is a single conductive cable that is currently used in offshore wind farms to connect the seabed foundation and the surface platform, and is used as the sole signal conductor to conduct the composite analog electrical signal. The sea surface data relay platform includes: The second coupling isolation circuit is used to extract the composite analog electrical signal from the data transmission cable and isolate interference on the platform side. The signal receiving and demodulation module is used to demodulate the extracted composite analog electrical signal to restore the marine environmental parameters; The second grounding electrode is used to contact the seawater and form the receiving end of the signal loop; the first grounding electrode, the seawater, the second grounding electrode, and the data transmission steel cable together form the signal transmission loop.

2. The system according to claim 1, characterized in that, The signal transmission modulation module includes: A signal generating circuit is used to generate carrier signals having a first frequency, a second frequency, and a third frequency; A first-level modulation circuit is used to modulate the voltage range of the carrier signal to between a preset negative voltage and a preset positive voltage; The secondary modulation circuit is used to control the encoding of a preset carrier wave using the encoded control signal, and to superimpose and amplify the encoded signal with the carrier signal of the first frequency. The signal receiving and demodulation module includes: A signal receiving circuit, the signal receiving circuit including at least a filter circuit for separating different frequency components; and a shaping circuit for shaping the separated analog signal into a digital square wave signal.

3. The system according to claim 2, characterized in that, Both the first and second coupling isolation circuits are isolation transformers that only allow AC signals to pass through; the composite analog electrical signal uses a composite frequency signal as the start identifier of the data frame, and the composite frequency signal is a 20KHz carrier signal superimposed on a 1KHz carrier signal.

4. The system according to claim 1, characterized in that, The seabed-based data aggregation terminal also includes a main control module, which is configured to perform adaptive channel matching operations, including: The pilot sequence is transmitted via the data transmission steel cable; Based on the channel state information returned from the sea surface data relay platform, the frequency modulation scheme and transmission power of the subcarrier are dynamically selected; The channel state information includes at least the signal-to-noise ratio.

5. The system according to claim 4, characterized in that, The main control module has a preset signal-to-noise ratio (SNR)-modulation-coding mapping table, which is used to select the corresponding carrier combination method based on the real-time measured SNR. When the signal-to-noise ratio is lower than the first threshold, a carrier combination of the first frequency and the second frequency is used; When the signal-to-noise ratio is between the first threshold and the second threshold, a carrier combination of the first frequency, the second frequency, and the third frequency is used; When the signal-to-noise ratio is higher than the second threshold, a carrier combination of the first and third frequencies is used.

6. A method for real-time observation and data transmission of offshore wind farms based on the seabed, applied to the system described in any one of claims 1 to 5, characterized in that, include: The sea surface data relay platform transmits command signals via data transmission steel cables; The seabed-based data aggregation terminal receives the command signal through the data transmission steel cable, which wakes up the multi-parameter sensor array to synchronously collect marine environmental parameters. The seabed-based data aggregation terminal modulates the collected marine environmental parameters into composite analog electrical signals; The composite analog electrical signal is injected into the data transmission steel cable through a first coupling isolation circuit, and the data transmission steel cable is a conductive steel cable. The composite analog electrical signal uses seawater as the return point and is transmitted to the sea surface through a loop consisting of a first grounding electrode, seawater, a second grounding electrode, and the data transmission steel cable. The sea surface data relay platform extracts the composite analog electrical signal from the data transmission steel cable through a second coupling isolation circuit; The extracted composite analog electrical signal is demodulated to restore the marine environmental parameters, and then forwarded to the shore-based monitoring center via a communication network.

7. The method according to claim 6, characterized in that, The specific steps of modulating the marine environmental parameters into a composite analog electrical signal include: Generate a carrier signal with a first frequency, a second frequency, and a third frequency; The voltage range of the carrier signal is modulated to be between a preset negative voltage and a preset positive voltage; The preset carrier wave is controlled by the encoded control signal; The encoded signal is superimposed and amplified with the carrier signal of the first frequency to generate the composite analog electrical signal; The specific steps for demodulating the extracted composite analog electrical signal include: Different frequency components are separated from the extracted composite analog electrical signal through filtering; The separated analog signal is shaped into a digital square wave signal.

8. The method according to claim 6, characterized in that, It also includes an adaptive channel matching step: The seabed-based data aggregation terminal transmits pilot sequences via the data transmission steel cable; The sea surface data relay platform receives the pilot sequence, estimates the frequency response and signal-to-noise ratio of the current channel on each subcarrier, and generates channel state information. Based on the channel state information and the preset signal-to-noise ratio-modulation-coding mapping table, the frequency modulation scheme and transmission power of the subcarrier are dynamically selected; The determined frequency modulation parameters are sent to the seabed-based data aggregation terminal for subsequent data modulation.

9. The method according to claim 8, characterized in that, The adaptive channel matching step is triggered by periodic timing or by a signal-to-noise ratio (SNR) mutation event; the SNR-modulation coding mapping table includes: When the signal-to-noise ratio is lower than the first threshold, a carrier combination of the first frequency and the second frequency is used; when the signal-to-noise ratio is between the first threshold and the second threshold, a carrier combination of the first frequency, the second frequency and the third frequency is used. When the signal-to-noise ratio is higher than the second threshold, a carrier combination of the first frequency and the third frequency is used.

10. The method according to claim 6, characterized in that, It also includes error control steps: The sea surface data relay platform performs frame verification on the demodulated and restored data packets; If the verification fails, a negative response signal is sent to the seabed-based data aggregation terminal via the data transmission cable to trigger the selective retransmission mechanism.

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