Offshore wind power cathodic protection real-time monitoring system and method

Abstract

This invention provides a real-time monitoring system and method for cathodic protection of offshore wind power. The system includes: an ultrasonic excitation module, a thickness measurement module, a host computer, a sacrificial anode shape fitting module, and a real-time cathodic protection level monitoring module. The ultrasonic excitation module is connected to the thickness measurement module, which measures the thickness of the sacrificial anode. The thickness measurement module is connected to the host computer, which is equipped with the sacrificial anode shape fitting module and the real-time cathodic protection level monitoring module. The sacrificial anode shape fitting module is used to fit the overall shape of the sacrificial anode at a specific time point using the thickness at multiple points on the sacrificial anode. The real-time cathodic protection level monitoring module is used to monitor the corrosion status of the sacrificial anode. The real-time monitoring system and method for cathodic protection of offshore wind power provided by this invention can achieve monitoring of the cathodic protection level of offshore wind power with small errors, high sensitivity, no need for manual intervention, and ease of use.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power cathodic protection technology, and in particular to a real-time monitoring system and method for offshore wind power cathodic protection. Background Technology

[0002] With the development and application of marine resources in my country, offshore wind energy resources are abundant and stable, and global wind power development is showing a trend of shifting from onshore to nearshore. The principle of wind power is to use wind to drive the rotation of wind turbine blades, which in turn generates electricity. Therefore, the local wind speed has a significant impact on power generation. Compared to onshore wind power, offshore wind energy resources are abundant and stable, and coastal areas have large power grid capacity and good wind power grid connection conditions, making offshore wind power more advantageous. However, this also brings the problem of corrosion of offshore wind turbines. Corrosion detection is delayed, and once corrosion occurs, it damages marine structures. Therefore, corrosion protection for offshore wind power is usually prevention-oriented, i.e., detecting the degree of cathodic protection. National standards indicate the degree of cathodic protection by detecting the potential difference between the reference electrode and the protected metal. However, current cathodic protection detection requires divers to carry specialized camera equipment, cleaning tools, and measuring tools to the site for cleaning and testing, necessitates stopping the normal operation of the wind power equipment, and is susceptible to electromagnetic interference during the measurement process. Therefore, it is essential to design a real-time monitoring system and method for offshore wind power cathodic protection. Summary of the Invention

[0003] The purpose of this invention is to provide a real-time monitoring system and method for cathodic protection of offshore wind power, which can monitor the degree of cathodic protection of offshore wind power with small error, high sensitivity, no need for manual intervention, and is easy to use.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A real-time monitoring system for cathodic protection of offshore wind power includes: an ultrasonic excitation module, a thickness measurement module, a host computer, a sacrificial anode shape fitting module, and a real-time monitoring module for cathodic protection level. The ultrasonic excitation module is connected to the thickness measurement module and is used to achieve multi-point ultrasonic excitation. The thickness measurement module is used to measure the thickness of the sacrificial anode. The thickness measurement module is connected to the host computer, which is equipped with the sacrificial anode shape fitting module and the real-time monitoring module for cathodic protection level. The sacrificial anode shape fitting module is used to fit the overall shape of the sacrificial anode at a certain time point using the multi-point thickness of the sacrificial anode. The real-time monitoring module for cathodic protection level is used to monitor the corrosion status of the sacrificial anode.

[0006] Optionally, the ultrasonic excitation module includes a laser seed source, a high-power optical amplifier, a high-power optical isolator, and an encapsulation array. The laser seed source is connected to the high-power optical amplifier, the high-power optical amplifier is connected to the high-power optical isolator, the high-power optical isolator is connected to the encapsulation array, and the encapsulation array is connected to the thickness measurement module. The encapsulation array includes a string of tilted gratings and an acoustic coupling cone. The string of tilted gratings includes a series of tilted gratings with different phantom mode operating wavelengths. The tilted gratings are arranged sequentially from upstream to downstream of the optical fiber link according to the operating wavelength from shortest to longest. Each tilted grating is encapsulated with an acoustic coupling cone.

[0007] The laser seed source is used to generate pulsed light signals based on the principle of frequency-modulated continuous wave.

[0008] The high-power optical amplifier is used to amplify the power of the generated pulsed optical signal;

[0009] The high-power optical isolator is used to prevent the generated pulsed light from damaging the light source;

[0010] The tilted grating string is used to convert the received optical signal into ultrasonic waves through an ultrasonic excitation material;

[0011] The acoustic coupling cone is used to focus the generated ultrasonic waves and propagate them from the lower right to the upper right.

[0012] Optionally, the thickness measurement module includes an FPGA modulation module, an adder, a signal generator, a DFB laser, a first coupler, a second coupler, a circulator, a DUS-FBG array, and a photodetector. The FPGA modulation module and the signal generator are connected to the adder. The adder is connected to the input terminal of the DFB laser. The output terminal of the DFB laser is connected to the input terminal of the first coupler. The output terminal of the first coupler is connected to the circulator. The circulator is connected to the DUS-FBG array. The first coupler and the circulator are connected to the second coupler. The second coupler is connected to the photodetector. The photodetector is connected to the host computer. The packaging array and the DUS-FBG array are combined and packaged. The DUS-FBG array is disposed in close contact with the sacrificial anode.

[0013] The FPGA modulation module is used to linearly modulate the DFB laser so that it outputs linearly swept frequency light;

[0014] The signal generator is used to provide an electrical signal with a fixed frequency and amplitude;

[0015] The adder is used to superimpose the electrical signals generated by the DFB laser and the signal generator;

[0016] The DFB laser is used to generate modulated linearly swept light;

[0017] The first coupler and the second coupler are used for beam splitting and coupling beat frequency of the two beams;

[0018] The circulator is used for bidirectional optical signal transmission on a single optical fiber;

[0019] The photodetector is used to convert beat frequency optical signals into electrical signals;

[0020] The DUS-FBG array is used for sensing fiber optic gratings after being modulated by ultrasonic waves.

[0021] This invention also provides a real-time monitoring method for offshore wind power cathodic protection, applied to the aforementioned real-time monitoring system for offshore wind power cathodic protection, comprising the following steps:

[0022] Step 1: Encapsulate the tilted grating string and acoustic coupling cone one by one, and set the top of the acoustic coupling cone to be tightly attached to the corresponding DUS-FBG array. Adjust the optical path and circuit of the ultrasonic excitation module.

[0023] Step 2: Arrange the DUS-FBG array in a serpentine pattern and place it close to the bottom surface of the sacrificial anode. Adjust the monitoring optical path and fix the sacrificial anode at a position 20m below sea level. Set the host computer at a certain point on the shore.

[0024] Step 3: Turn on the laser seed source so that the tilted grating string receives the pulse light signal to excite the ultrasound. At the same time, turn on the DFB laser, monitor the change of the beat frequency signal in real time, and transmit the beat frequency signal to the host computer for real-time demodulation. The thickness is calculated by the echo method and the addition of a window function algorithm.

[0025] Step 4: The sacrificial anode shape fitting module summarizes the thickness data measured by the DUS-FBG array at different locations, establishes a three-dimensional coordinate system, and uses the least squares method to fit the overall shape of the sacrificial anode.

[0026] Step 5: The real-time monitoring module for the degree of cathodic protection compares the overall shape of the sacrificial anode with the original shape of the sacrificial anode.

[0027] According to specific embodiments provided by the present invention, the following technical effects are disclosed: The real-time monitoring system and method for offshore wind power cathodic protection provided by the present invention includes an ultrasonic excitation module, a thickness measurement module, a host computer, a sacrificial anode shape fitting module, and a real-time monitoring module for the degree of cathodic protection. The method includes encapsulating tilted grating strings and acoustic coupling cones one by one, attaching the top of the acoustic coupling cones to the corresponding DUS-FBG array, adjusting the optical path and circuit of the ultrasonic excitation module, arranging the DUS-FBG arrays in a serpentine pattern and attaching them to the bottom surface of the sacrificial anode, adjusting the monitoring optical path, fixing the sacrificial anode 20m below sea level, setting the host computer at a certain point on the shore, turning on the laser seed light source, and causing the tilted grating strings to connect... The system receives a pulsed light signal to excite ultrasound, simultaneously activating a DFB laser. It monitors changes in the beat frequency signal in real time and transmits the beat frequency signal to a host computer for real-time demodulation. Thickness is calculated using the echo method and a window function algorithm. The sacrificial anode shape fitting module summarizes the thickness data measured by the DUS-FBG array at different locations, establishes a three-dimensional coordinate system, and fits the overall shape of the sacrificial anode using the least squares method. The real-time cathodic protection monitoring module compares the obtained overall shape of the sacrificial anode with its original shape. This system and method can monitor the cathodic protection level of offshore wind power with small errors, high sensitivity, no need for manual intervention, ease of use, and advantages such as resistance to electromagnetic interference and low transmission loss. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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.

[0029] Figure 1 This is a schematic diagram of the structure of the real-time monitoring system for cathodic protection of offshore wind power according to an embodiment of the present invention;

[0030] Figure 2 Diagram showing the arrangement of the sacrificial anode and DUS-FBG array;

[0031] Figure 3 This is a schematic diagram of the DUS-FBG array layout;

[0032] Figure 4 This is a schematic diagram of ultrasound excited by a tilted grating.

[0033] Figure 5 This is a schematic diagram of the ultrasonic excitation module structure;

[0034] Figure 6This is a schematic diagram of the real-time monitoring method for offshore wind power cathodic protection according to an embodiment of the present invention.

[0035] Figure reference numerals: 1. FPGA modulation module; 2. Adder; 3. Signal generator; 4. DFB laser; 5. First coupler; 6. Second coupler; 7. Circulator; 8. Sacrificial anode; 9. DUS-FBG array; 10. Photodetector; 11. Host computer; 12. Package array; 13. High-power optical isolator; 14. High-power optical amplifier; 15. Laser seed source; 16. Acoustic coupling cone; 17. Tilted grating. Detailed Implementation

[0036] The purpose of this invention is to provide a real-time monitoring system and method for cathodic protection of offshore wind power, which can monitor the degree of cathodic protection of offshore wind power with small error, high sensitivity, no need for manual intervention, and is easy to use.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1 As shown in the embodiment of the present invention, the real-time monitoring system for offshore wind power cathodic protection includes: an ultrasonic excitation module, a thickness measurement module, a host computer 11, a sacrificial anode shape fitting module, and a real-time monitoring module for cathodic protection level. The ultrasonic excitation module is connected to the thickness measurement module and is used to realize multi-point ultrasonic excitation. The thickness measurement module is used to measure the thickness of the sacrificial anode. The thickness measurement module is connected to the host computer 11. The host computer 11 is equipped with the sacrificial anode shape fitting module and the real-time monitoring module for cathodic protection level. The sacrificial anode shape fitting module is used to fit the overall shape of the sacrificial anode 8 at a certain time point using the multi-point thickness of the sacrificial anode. The real-time monitoring module for cathodic protection level is used to monitor the corrosion of the sacrificial anode.

[0039] like Figure 4 and Figure 5As shown, the ultrasonic excitation module includes a laser seed source 15, a high-power optical amplifier 14, a high-power optical isolator 13, and an encapsulation array 12. The laser seed source 15 is connected to the high-power optical amplifier 14, the high-power optical amplifier 14 is connected to the high-power optical isolator 13, the high-power optical isolator 13 is connected to the encapsulation array 12, and the encapsulation array 12 is connected to the thickness measurement module. The encapsulation array 12 includes a series of tilted grating strings and an acoustic coupling cone 16. The tilted grating string includes a series of tilted gratings 17 with different phantom mode operating wavelengths. The tilted gratings 17 are arranged sequentially from upstream to downstream of the optical fiber link according to the working wavelength from shortest to longest. The laser energy in the phantom mode of the tilted grating 17 is used as the energy source for ultrasonic excitation. A section of the fiber cladding in the optical fiber link in front of each tilted grating 17 is partially removed and filled with absorbing material to release and absorb the energy of the phantom mode in the fiber cladding and to excite ultrasonic waves using the thermoelastic expansion effect. Each tilted grating 17 is encapsulated with an acoustic coupling cone 16.

[0040] The laser seed light source 15 is used to generate pulsed light signals based on the principle of frequency-modulated continuous wave.

[0041] The high-power optical amplifier 14 is used to amplify the power of the generated pulsed optical signal;

[0042] The high-power optical isolator 13 is used to prevent the generated pulsed light from damaging the light source;

[0043] The tilted grating string is used to convert the received optical signal into ultrasonic waves through an ultrasonic excitation material;

[0044] The acoustic coupling cone 16 is used to converge the generated ultrasonic waves and propagate them from the lower right to the upper right, and to converge the ultrasonic waves excited by the tilted grating to enhance the intensity of the ultrasonic signal.

[0045] The present invention provides an embodiment: the total length of the tilted grating string is 2.4m, with a total of 1200 gratings engraved. Each tilted grating has 17 grating areas with a length of 1cm. A grating is engraved every 1cm. The minimum sensing unit spatial resolution is 1cm.

[0046] During the fiber drawing process, a tilted grating 17 with a center wavelength ranging from 1540nm to 1564nm at intervals of 0.02nm is dynamically written using the phase mask method, arranged in a sequential serpentine pattern, and then encapsulated and fixed with an acoustic coupling cone.

[0047] When in use, the laser seed light source 15 generates a pulsed light signal after being powered on. The pulsed light signal is amplified by the high-power amplifier 14 and then enters the tilted grating 17 through the isolator. The laser energy in the phantom mode of the tilted grating 17 is used as the energy source for ultrasonic excitation.

[0048] The thickness measurement module includes an FPGA modulation module 1, an adder 2, a signal generator 3, a DFB laser 4, a first coupler 5, a second coupler 6, a circulator 7, a DUS-FBG array 9, and a photodetector 10. It utilizes the OFDR principle to achieve ultrasonic modulation sensing of the DUS-FBG array 9. The FPGA modulation module 1 and the signal generator 3 are connected to the adder 2. The adder 2 is connected to the input terminal of the DFB laser 4. The output terminal of the DFB laser 4 is connected to the input terminal of the first coupler 5. The output terminal of the first coupler 5 is connected to the circulator 7. The circulator 7 is connected to the DUS-FBG array 9. The first coupler 5 and the circulator 7 are connected to the second coupler 6. The second coupler 6 is connected to the photodetector 10. The photodetector 10 is connected to the host computer 11. The encapsulation array 12 is combined and encapsulated with the DUS-FBG array 9. The DUS-FBG array 9 is positioned close to the sacrificial anode 8.

[0049] The FPGA modulation module 1 is used to linearly modulate the DFB laser so that it outputs linearly swept frequency light.

[0050] The signal generator 3 is used to provide an electrical signal with a fixed frequency and amplitude;

[0051] The adder 2 is used to superimpose the electrical signals generated by the DFB laser and the signal generator;

[0052] The DFB laser 4 is used to generate modulated linear sweep light;

[0053] The first coupler 5 and the second coupler 6 are used for beam splitting and coupling beat frequency of the two beams;

[0054] The circulator 7 is used for bidirectional optical signal transmission on a single optical fiber;

[0055] The photodetector 10 is used to convert the beat frequency optical signal into an electrical signal;

[0056] The DUS-FBG array 9 is used for sensing fiber optic gratings after being modulated by ultrasonic waves.

[0057] like Figure 2 and Figure 3 As shown, the present invention provides an embodiment: the DUS-FBG array 9 has a total length of 2.4m and is engraved with 1200 gratings, with one grating engraved at every 1cm interval, and the minimum sensing unit spatial resolution is 1cm;

[0058] During the fiber drawing process, a DUS-FBG with a center wavelength of 1550nm is dynamically written using the phase mask method and arranged in a sequential serpentine pattern.

[0059] In operation, the FPGA modulation module 1 generates a voltage signal, which is then connected to adder 2 via a DAC digital-to-analog converter module. Another signal generator 3 is connected to adder 2. The two signals are combined and superimposed before being input to DFB laser 4. DFB laser 4 performs a linear frequency sweep, using the OFDR principle for vibration sensing. The output of DFB laser 4 is connected to the input of the first coupler 5. The first coupler 5 outputs two optical signals: one as a reference signal entering the second coupler 6, and the other as a sensing optical signal entering the circulator 7. The first output of the first coupler 5 is connected to the circulator 7, used to input the sensing optical signal to the DUS-FBG array 9. The DUS-FBG array 9 is attached to the surface of the sacrificial anode 8. The ultrasonic excitation module is combined and packaged with the corresponding DUS-FBG array 9. The ultrasonic excitation module is used to generate high-frequency ultrasonic signals to stimulate the DUS-FBG array 8. The wavelength of the US-FBG array 9 is modulated and the thickness of the sacrificial anode 8 is monitored by ultrasound. Due to the modulation of the ultrasonic signal, the wavelength of the reflected light of the DUS-FBG array 9 changes periodically, resulting in a change in the intensity of the reflected light. The reflected light signal enters the second coupler 6 after passing through the circulator 7. The original reference light signal and the reflected light signal are coupled and beat at the second coupler 6. Due to the modulation of the ultrasonic wave, the reflected light signal is different from the unmodulated reflected light signal, resulting in a change in the frequency of the beat signal. The DUS-FBG array 9 is modulated twice, from the emission of the ultrasonic signal to the return of the ultrasonic signal, and both can be observed through the beat signal. The output of the second coupler 6 is connected to the input of the photodetector 10. The photodetector 10 is used to convert the beat light intensity signal generated by the sensor into an electrical signal and transmit it back to the host computer 11. The host computer 11 performs demodulation and processing of the signal.

[0060] Each DUS-FBG corresponds to a beat frequency signal. By performing FFT on the original time domain signal, the position of each DUS-FBG can be located based on the frequency domain diagram.

[0061] The thickness is calculated using the echo method and an algorithm that adds a window function.

[0062] Sacrificial anode shape fitting module: Each grating in the DUS-FBG array corresponds to an xy plane coordinate in a three-dimensional coordinate system. When measuring the thickness at each grating, the sacrificial anode surface is fitted using the least squares algorithm on 1200 data points.

[0063] Real-time monitoring module for cathodic protection level: After the sacrificial anode shape fitting module fits the shape, a three-dimensional sacrificial anode can be obtained. By comparing it with the original sacrificial anode shape, real-time monitoring can be achieved.

[0064] like Figure 6As shown, the present invention also provides a real-time monitoring method for offshore wind power cathodic protection, applied to the above-mentioned real-time monitoring system for offshore wind power cathodic protection, comprising the following steps:

[0065] Step 1: Encapsulate the tilted grating string and acoustic coupling cone one by one, and set the top of the acoustic coupling cone to be tightly attached to the corresponding DUS-FBG array. Adjust the optical path and circuit of the ultrasonic excitation module.

[0066] Step 2: Arrange the DUS-FBG array in a serpentine pattern and place it close to the bottom surface of the sacrificial anode. Adjust the monitoring optical path and fix the sacrificial anode at a position 20m below sea level. Set the host computer at a certain point on the shore.

[0067] Step 3: Turn on the laser seed source so that the tilted grating string receives the pulse light signal to excite the ultrasound. At the same time, turn on the DFB laser, monitor the change of the beat frequency signal in real time, and transmit the beat frequency signal to the host computer for real-time demodulation. The thickness is calculated by the echo method and the addition of a window function algorithm.

[0068] Step 4: The sacrificial anode shape fitting module summarizes the thickness data measured by the DUS-FBG array at different locations, establishes a three-dimensional coordinate system, and uses the least squares method to fit the overall shape of the sacrificial anode.

[0069] Step 5: The real-time monitoring module for the degree of cathodic protection compares the overall shape of the sacrificial anode with the original shape of the sacrificial anode.

[0070] The present invention provides a real-time monitoring system and method for cathodic protection of offshore wind power. The system includes an ultrasonic excitation module, a thickness measurement module, a host computer, a sacrificial anode shape fitting module, and a real-time monitoring module for the degree of cathodic protection. The method includes encapsulating tilted grating strings and acoustic coupling cones one by one; attaching the top of the acoustic coupling cone to the corresponding DUS-FBG array; adjusting the optical path and circuitry of the ultrasonic excitation module; arranging the DUS-FBG array in a serpentine pattern and attaching it tightly to the bottom surface of the sacrificial anode; adjusting the monitoring optical path; fixing the sacrificial anode 20m below sea level; setting the host computer at a fixed point on shore; and turning on the laser seed source to allow the tilted grating strings to receive pulsed light signals, thereby exciting the ultrasonic excitation. Simultaneously, the DFB laser is activated to monitor changes in the beat frequency signal in real time, and the beat frequency signal is transmitted to the host computer for real-time demodulation. The thickness is calculated using the echo method and the addition of a window function algorithm. The sacrificial anode shape fitting module summarizes the thickness data measured by the DUS-FBG array at different locations, establishes a three-dimensional coordinate system, and fits the overall shape of the sacrificial anode using the least squares method. The real-time cathodic protection degree monitoring module compares the obtained overall shape of the sacrificial anode with the original shape of the sacrificial anode. This system and method can realize the monitoring of the cathodic protection degree of offshore wind power with small error, high sensitivity, no need for manual intervention, and easy use. It also has the advantages of anti-electromagnetic interference and low transmission loss.

[0071] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A real-time monitoring system for offshore wind farm cathodic protection, characterized in that, The application relates to a sacrificial anode thickness measurement system, which comprises an ultrasonic excitation module, a thickness measurement module, a host computer, a sacrificial anode shape fitting module and a cathode protection degree real-time monitoring module. The ultrasonic excitation module is connected with the thickness measurement module, the ultrasonic excitation module is used for realizing ultrasonic excitation of multiple points, the thickness measurement module is used for measuring the thickness of a sacrificial anode, the thickness measurement module is connected with the host computer, the host computer is provided with the sacrificial anode shape fitting module and the cathode protection degree real-time monitoring module, the sacrificial anode shape fitting module is used for fitting the overall shape of the sacrificial anode at a certain time point by using the thickness of the sacrificial anode at multiple points, and the cathode protection degree real-time monitoring module is used for monitoring the corrosion condition of the sacrificial anode.

2. The offshore wind farm cathodic protection real-time monitoring system according to claim 1, characterized in that, The ultrasonic excitation module comprises a laser seed light source, a high-power light amplifier, a high-power light isolator and a packaging array, the laser seed light source is connected with the high-power light amplifier, the high-power light amplifier is connected with the high-power light isolator, the high-power light isolator is connected with the packaging array, the packaging array comprises an inclined grating string and an acoustic coupling cone, the thickness measurement module comprises a DUS-FBG array, the packaging array and the DUS-FBG array are combined and packaged, and the DUS-FBG array is arranged close to the sacrificial anode, the inclined grating string is used for converting the received optical signals into ultrasonic waves through ultrasonic excitation materials, and the acoustic coupling cone is used for converging the generated ultrasonic waves and transmitting the ultrasonic waves to the DUS-FBG array, so that the DUS-FBG array senses the fiber Bragg grating under ultrasonic wave modulation and outputs signals used for measuring the thickness of the sacrificial anode. The inclined grating string comprises a series of inclined gratings with different working wavelengths, and the inclined gratings are arranged in sequence from upstream to downstream of a fiber link according to the working wavelengths from short to long. The laser seed light source is used for generating pulse optical signals through the principle of frequency-modulated continuous wave. The high-power light amplifier is used for power amplifying the generated pulse optical signals.

3. The offshore wind farm cathodic protection real-time monitoring system of claim 2, wherein, The high-power light isolator is used for preventing the generated pulse optical signals from damaging the light source. The thickness measurement module comprises an FPGA modulation module, a signal generator, a DFB laser, a first coupler, a second coupler, a circulator, a DUS-FBG array and a photodetector, the FPGA modulation module and the signal generator are connected with the adder, the adder is connected with the input end of the DFB laser, the output end of the DFB laser is connected with the input end of the first coupler, the output end of the first coupler is connected with the circulator, the circulator is connected with the DUS-FBG array, the first coupler and the circulator are connected with the second coupler, the second coupler is connected with the photodetector, and the photodetector is connected with the host computer. The FPGA modulation module is used for linearly modulating the DFB laser to make the DFB laser output linear sweep light. The signal generator is used for providing an electrical signal with a fixed frequency and amplitude. The adder is used for superimposing the electrical signals generated by the DFB laser and the signal generator; The DFB laser is used for generating the linear sweep light after modulation; The first coupler and the second coupler are used for splitting light and coupling beat frequency of two beams of light; The circulator is used for bidirectional optical signal transmission on a single optical fiber; The photodetector is used for converting the beat frequency optical signal into an electrical signal.

4. A real-time monitoring method for offshore wind power cathodic protection, applied to the offshore wind power cathodic protection real-time monitoring system of any one of claims 1-3, characterized in that, The method comprises the following steps: Step 1: encapsulate the tilted grating string and the acoustic coupling cone one by one, set the top of the acoustic coupling cone close to the corresponding DUS-FBG array, and adjust the optical path and the circuit of the ultrasonic excitation module; Step 2: arrange the DUS-FBG arrays in a serpentine shape close to the bottom surface of the sacrificial anode in sequence, adjust the monitoring optical path, fix the sacrificial anode at a position 20 m below the sea level, and set the upper computer at a certain point on the shore; Step 3: turn on the laser seed light source, make the tilted grating string receive the pulsed light signal to excite ultrasonic, turn on the DFB laser at the same time, monitor the change of the beat frequency signal in real time, transmit the beat frequency signal to the upper computer for real-time demodulation, and calculate the thickness by using the echo method and adding the window function algorithm; Step 4: the sacrificial anode shape fitting module collects the thickness data measured by the DUS-FBG arrays at different positions, establishes a three-dimensional coordinate system, and fits the overall shape of the sacrificial anode by using the least square method; Step 5: the cathodic protection degree real-time monitoring module compares the overall shape of the sacrificial anode with the original shape of the sacrificial anode.

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