A real-time monitoring system and monitoring method for scour of offshore wind power pile foundations

Abstract

The present invention discloses a real-time monitoring system and a monitoring method for scour of an offshore wind power pile foundation. The data acquisition module, fiber Bragg grating acceleration sensors, fiber Bragg grating inclination sensors and wind speed sensors of the monitoring system are installed on the offshore wind power pile. The method includes: obtaining soil parameters and pile foundation parameters and inputting them into simulation software to output the response signal of the wind power pile foundation, and selecting a reference signal; performing frequency-domain and time-domain analyses to obtain the natural frequency-scour depth table and the inclination equilibrium position-wind speed-scour depth table; collecting the pile foundation vibration acceleration data, inclination data and ambient wind speed data; looking up the table to obtain the first and second scour depths; performing error judgment to determine the scour depth, and completing the continuous real-time monitoring of the scour of the offshore wind power pile foundation. The present invention can continuously and real-time monitor the scour condition of the offshore wind power pile foundation, has the characteristics of high precision, high durability and real-time monitoring, can effectively avoid accidents, and thus ensure the safe operation of the offshore wind turbine generator set.

Description

Technical Field

[0001] The present invention relates to a real-time monitoring system, and more particularly to a real-time monitoring system and method for scour of offshore wind turbine pile foundations. Background Art

[0002] Wind energy is currently the most mature renewable energy utilization technology. Due to the relatively richer wind resources offshore than on land and the easier transportation and deployment of large-scale units, large-scale development of offshore wind farms is underway. Among them, the monopile foundation has the advantages of simple structure, high bearing capacity, small floor area, small and uniform settlement, etc., and is the main foundation form of offshore wind turbines. However, the emergence of the wind turbine pile foundation has changed the original flow field and seabed boundary conditions. Under the combined action of waves and tides, the streamline of water flow particles near the wind turbine pile foundation will change, resulting in a sharp increase in the shear stress on the seabed soil particles, causing scour of the seabed soil. With the development of the scour pit, seabed scour will have the following adverse effects on the wind turbine pile foundation: 1) The embedment depth of the wind turbine pile foundation decreases, and part of the pile foundation is exposed above the seabed, reducing the bearing capacity of the pile foundation; 2) The cantilever length of the wind turbine pile foundation increases, increasing the overturning moment of the pile foundation; 3) The natural vibration frequency of the wind turbine unit decreases, increasing the fatigue stress amplitude and the number of stress cycles of the wind turbine pile foundation and reducing the fatigue life of the wind turbine unit.

[0003] Based on the above adverse effects of scour on wind turbine pile foundations, some scour monitoring systems and methods for wind turbine pile foundations based on acoustic, optical, and mechanical principles have been proposed. For example, monitoring the scour of wind turbine pile foundations based on schemes such as acoustic echo signals, lidar, cameras, and water and soil pressure signals. Although some of the above-mentioned scour monitoring systems and methods for wind turbine pile foundations have been proposed, these methods still have deficiencies: For example, the signal quality of acoustic and optical monitoring methods is very susceptible to the influence of sediment particles or aquatic plants. When the sea current is strong, a large amount of sediment and other suspended substances in the seawater cause serious attenuation of the monitored signals, greatly reducing the measurement accuracy; The scheme based on monitoring water and soil pressure generally requires the use of many sensors, and the sensors are located underwater, with weak reliability, high maintenance costs, and great difficulty; The existing schemes based on monitoring the acceleration signal of the pile foundation generally obtain the scour depth through empirical formulas, and their accuracy has not been verified. Summary of the Invention

[0004] To solve the problems existing in the background art, the present invention provides a real-time monitoring system for scour of an offshore wind power pile foundation and a monitoring method thereof. After the wind power pile is scoured, the vibration balance position of the wind power pile foundation changes, and the inclination time history curve of the pile foundation vibrates at the balance position, and the vibration balance position is related to the wind speed and the scour pit depth. Therefore, it is a feasible solution to judge the scour pit depth by monitoring the wind speed and the inclination balance position of the pile foundation. The present invention performs continuous time monitoring based on a time domain and frequency domain coupling method, can monitor the scour development of the offshore wind power pile foundation in real time, accurately and reliably, and has the advantages of simple operation process, stable performance, high precision, high durability and real-time monitoring, can effectively avoid the occurrence of accidents, and thus ensure the safe operation of the offshore wind turbine unit.

[0005] The technical solution adopted by the present invention is as follows:

[0006] I. A real-time monitoring system for scour of an offshore wind power pile foundation:

[0007] The monitoring system includes a data acquisition module, a fiber Bragg grating acceleration sensor, a fiber Bragg grating inclination sensor and a wind speed sensor. The data acquisition module, the fiber Bragg grating acceleration sensor, the fiber Bragg grating inclination sensor and the wind speed sensor are all installed on the surface of the wind turbine tower of the offshore wind power pile above the water surface; the data acquisition module is electrically connected or wirelessly connected to an external upper computer, and the data acquisition module is connected to the fiber Bragg grating acceleration sensor and the fiber Bragg grating inclination sensor through an optical fiber data line, and the data acquisition module is electrically connected to the wind speed sensor.

[0008] The data acquisition module includes a multi-channel fiber Bragg grating demodulator and a wind speed data acquisition unit. The multi-channel fiber Bragg grating demodulator and the wind speed data acquisition unit are both electrically connected or wirelessly connected to an external upper computer. The multi-channel fiber Bragg grating demodulator is connected to the fiber Bragg grating acceleration sensor and the fiber Bragg grating inclination sensor through an optical fiber data line. The pile foundation vibration acceleration data of the offshore wind power pile collected in real time by the fiber Bragg grating acceleration sensor and the inclination data of the offshore wind power pile collected in real time by the fiber Bragg grating inclination sensor are transmitted to the external upper computer through the multi-channel fiber Bragg grating demodulator; the wind speed data acquisition unit is electrically connected to the wind speed sensor, and the environmental wind speed data at the position of the offshore wind power pile collected in real time by the wind speed sensor is transmitted to the external upper computer through the wind speed data acquisition unit.

[0009] II. A monitoring method for a real-time monitoring system for scour of an offshore wind power pile foundation:

[0010] The method includes the following steps:

[0011] 1) Obtain the soil parameters and the offshore wind turbine pile foundation parameters at the buried position of the offshore wind turbine pile foundation. There is simulation software installed in the external host computer. Input the soil parameters and the offshore wind turbine pile foundation parameters at the buried position of the offshore wind turbine pile foundation into the simulation software. The simulation software outputs the response signals of the wind turbine pile foundation under different simulated environmental wind speeds and different simulated scour depths. Select a signal segment with a duration of ten minutes in the response signals of the wind turbine pile foundation as the reference signal.

[0012] 2) After the external host computer performs frequency-domain and time-domain analysis and processing on the reference signal, it obtains the natural frequency - scour depth table and the inclination equilibrium position - wind speed - scour depth table of the offshore wind turbine respectively.

[0013] 3) The pile foundation vibration acceleration data and inclination data of the offshore wind turbine within the current ten minutes are respectively collected in real time through a fiber Bragg grating acceleration sensor and a fiber Bragg grating inclination sensor, and are transmitted to the external host computer through a multi-channel fiber Bragg grating demodulator; the environmental wind speed data at the position of the offshore wind turbine within the current ten minutes are collected in real time through a wind speed sensor and are transmitted to the external host computer through a wind speed data acquisition unit; the acquisition frequencies of the fiber Bragg grating acceleration sensor, the fiber Bragg grating inclination sensor, and the wind speed sensor can be 50 Hz.

[0014] 4) The external host computer looks up the table according to the pile foundation vibration acceleration data of the offshore wind turbine within the current ten minutes and the natural frequency - scour depth table in step 2) to obtain the first scour depth D1 of the offshore wind turbine within the current ten minutes; the external host computer looks up the table according to the inclination data of the offshore wind turbine within the current ten minutes, the environmental wind speed data at the position of the offshore wind turbine, and the inclination equilibrium position - wind speed - scour depth table in step 2) to obtain the second scour depth D2 of the offshore wind turbine within the current ten minutes.

[0015] 5) Make an error judgment based on the first scour depth D1 and the second scour depth D2 to determine the scour depth of the offshore wind turbine within the current ten minutes, and complete the real-time monitoring of the scour of the offshore wind turbine pile foundation within the current ten minutes; every ten minutes hereafter, repeat steps 3) - 5) to complete the continuous real-time monitoring of the scour of the offshore wind turbine pile foundation.

[0016] In the above step 1), the soil parameters at the buried position of the offshore wind turbine pile foundation include but are not limited to tensile strength, Poisson's ratio, Young's modulus, dilatancy angle, and unit weight parameters; the offshore wind turbine pile foundation parameters include but are not limited to diameter, length, buried depth, Young's modulus, and Poisson's ratio parameters.

[0017] In the above step 1), the simulation software is ABAQUS software or ANSYS software.

[0018] In the described step 1), the foundation response signals of the offshore wind power pile under different simulated environmental wind speeds and different simulated scouring depths include the pile foundation vibration acceleration signals and inclination signals of the offshore wind power pile under different simulated environmental wind speeds and different simulated scouring depths; a signal segment with a length of ten minutes in the foundation response signals of the wind power pile is selected as the reference signal, that is, a signal segment with a length of ten minutes in the pile foundation vibration acceleration signals and inclination signals of the offshore wind power pile under different simulated environmental wind speeds and different simulated scouring depths is respectively selected and used as the pile foundation vibration acceleration reference signal and the inclination reference signal.

[0019] In the described step 2), the external host computer performs frequency-domain and time-domain analysis and processing on the reference signals respectively. Specifically, the external host computer performs frequency-domain analysis and processing on the pile foundation vibration acceleration reference signal, that is, after performing fast Fourier transform processing on the pile foundation vibration acceleration reference signal, the natural frequencies of the offshore wind power pile under different simulated scouring depths are obtained, and then the natural frequency - scouring depth table of the offshore wind power pile is obtained; after the external host computer performs time-domain analysis and processing on the inclination reference signal, the simulated inclination balance positions and the average value of the simulated environmental wind speed of the offshore wind power pile under different simulated scouring depths are obtained, and then the inclination balance position - wind speed - scouring depth table of the offshore wind power pile is obtained.

[0020] In the described step 4), the external host computer looks up the table according to the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes and the natural frequency - scouring depth table in step 2) to obtain the first scouring depth D1 of the offshore wind power pile in the current ten minutes. Specifically, the external host computer performs frequency-domain analysis and processing on the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes, that is, after performing fast Fourier transform processing on the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes, the measured natural frequency of the offshore wind power pile in the current ten minutes is obtained, and then the first scouring depth D1 of the offshore wind power pile in the current ten minutes is obtained by looking up the table in the natural frequency - scouring depth table.

[0021] The external host computer looks up the table according to the inclination data of the offshore wind power pile in the current ten minutes, the environmental wind speed data at the position of the offshore wind power pile, and the inclination balance position - wind speed - scouring depth table in step 2) to obtain the second scouring depth D2 of the offshore wind power pile in the current ten minutes. Specifically, the external host computer calculates the average values of the inclination data of the offshore wind power pile in the current ten minutes and the environmental wind speed data at the position of the offshore wind power pile respectively, and then obtains the measured inclination balance position and the measured average environmental wind speed of the offshore wind power pile in the current ten minutes respectively, and then obtains the second scouring depth D2 of the offshore wind power pile in the current ten minutes by looking up the table in the inclination balance position - wind speed - scouring depth table.

[0022] In step 5), error judgment is performed based on the first scour depth D1 and the second scour depth D2 to determine the scour depth of the offshore wind turbine pile within the current ten minutes. Specifically, the error between the first scour depth D1 and the second scour depth D2 is calculated. If the error is less than the preset threshold, the larger value of the first scour depth D1 and the second scour depth D2 is selected as the scour depth of the offshore wind turbine pile within the current ten minutes. If the error is greater than or equal to the preset threshold, the first scour depth D1 and the second scour depth D2 within the current ten minutes are discarded, and the real-time monitoring of the scour of the offshore wind turbine pile foundation is continued for the next ten minutes.

[0023] The beneficial effects of the present invention are as follows:

[0024] Based on the time-domain and frequency-domain coupling method, the present invention conducts continuous time monitoring, and the results are relatively accurate. The sensors and the data acquisition module are all located above the water surface, with strong reliability and convenient maintenance. The fiber Bragg grating sensor is used, which has the advantages of adaptability, strong corrosion resistance, high precision, and anti-interference. Generally speaking, the present invention can monitor the scour development of the offshore wind turbine pile foundation in real time, accurately, and reliably, and has the advantages of simple operation process and stable performance, which can effectively avoid accidents and ensure the safe operation of the offshore wind turbine. Description of the Drawings

[0025] Figure 1 It is the overall schematic diagram of the system of the present invention;

[0026] Figure 2 It is the overall flow chart of the present invention;

[0027] In the figure: 1. Data acquisition module, 2. Fiber Bragg grating acceleration sensor, 3. Fiber Bragg grating inclination sensor, 4. Wind speed sensor. Specific Embodiments

[0028] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0029] As Figure 1 shown, the real-time monitoring system for the scour of the offshore wind turbine pile foundation includes a data acquisition module 1, a fiber Bragg grating acceleration sensor 2, a fiber Bragg grating inclination sensor 3, and a wind speed sensor 4. The data acquisition module 1, the fiber Bragg grating acceleration sensor 2, the fiber Bragg grating inclination sensor 3, and the wind speed sensor 4 are all installed on the surface of the wind turbine tower of the offshore wind turbine pile above the water surface. The data acquisition module 1 is electrically connected or wirelessly connected to an external host computer. The data acquisition module 1 is connected to the fiber Bragg grating acceleration sensor 2 and the fiber Bragg grating inclination sensor 3 through an optical fiber data line, and the data acquisition module 1 is electrically connected to the wind speed sensor 4.

[0030] The data acquisition module 1 includes a multi-channel fiber Bragg grating demodulator and a wind speed data acquisition unit. Both the multi-channel fiber Bragg grating demodulator and the wind speed data acquisition unit are electrically or wirelessly connected to an external host computer. The multi-channel fiber Bragg grating demodulator is connected to a fiber Bragg grating acceleration sensor 2 and a fiber Bragg grating inclination sensor 3 through fiber optic data lines. The pile foundation vibration acceleration data of the offshore wind turbine pile collected in real time by the fiber Bragg grating acceleration sensor 2 and the inclination data of the offshore wind turbine pile collected in real time by the fiber Bragg grating inclination sensor 3 are transmitted to the external host computer through the multi-channel fiber Bragg grating demodulator; the wind speed data acquisition unit is electrically connected to a wind speed sensor 4, and the environmental wind speed data at the position of the offshore wind turbine pile collected in real time by the wind speed sensor 4 is transmitted to the external host computer through the wind speed data acquisition unit.

[0031] As Figure 2 shown, the monitoring method of the real-time monitoring system for the scour of the offshore wind turbine pile foundation includes the following steps:

[0032] 1) Obtain the soil parameters and the offshore wind turbine pile foundation parameters at the buried position of the offshore wind turbine pile foundation. There is simulation software installed in the external host computer. Input the soil parameters and the offshore wind turbine pile foundation parameters at the buried position of the offshore wind turbine pile foundation into the simulation software. The simulation software outputs the pile foundation response signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths. Select a signal segment with a duration of ten minutes in the pile foundation response signals as the reference signal.

[0033] In step 1), the soil parameters at the buried position of the offshore wind turbine pile foundation include, but are not limited to, tensile strength, Poisson's ratio, Young's modulus, dilatancy angle, and unit weight parameters; the offshore wind turbine pile foundation parameters include, but are not limited to, diameter, length, buried depth, Young's modulus, and Poisson's ratio parameters.

[0034] In step 1), the simulation software is ABAQUS software or ANSYS software.

[0035] In step 1), the pile foundation response signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths include the pile foundation vibration acceleration signals and inclination signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths; select a signal segment with a duration of ten minutes in the pile foundation response signals as the reference signal, that is, respectively select a signal segment with a duration of ten minutes in the pile foundation vibration acceleration signals and inclination signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths and use them as the pile foundation vibration acceleration reference signal and the inclination reference signal respectively.

[0036] 2) The external host computer performs frequency-domain and time-domain analysis and processing on the reference signal to obtain the natural frequency - scour depth table and the inclination equilibrium position - wind speed - scour depth table of the offshore wind turbine respectively.

[0037] In step 2), the external host computer performs frequency-domain and time-domain analysis on the reference signals respectively. Specifically, the external host computer performs frequency-domain analysis on the pile foundation vibration acceleration reference signal, that is, performs fast Fourier transform on the pile foundation vibration acceleration reference signal to obtain the natural frequencies of the offshore wind power pile at different simulated scour depths, and then obtains the natural frequency-scour depth table of the offshore wind power pile; the external host computer performs time-domain analysis on the inclination reference signal to obtain the simulated inclination balance positions and the average simulated environmental wind speed of the offshore wind power pile at different simulated scour depths, and then obtains the inclination balance position-wind speed-scour depth table of the offshore wind power pile.

[0038] 3) The fiber Bragg grating acceleration sensor 2 and the fiber Bragg grating inclination sensor 3 are used to respectively collect the pile foundation vibration acceleration data and the inclination data of the offshore wind power pile in the current ten minutes in real time, and transmit them to the external host computer through a multi-channel fiber Bragg grating demodulator; the environmental wind speed data at the position of the offshore wind power pile in the current ten minutes is collected in real time by the wind speed sensor 4 and transmitted to the external host computer through the wind speed data acquisition unit; the acquisition frequencies of the fiber Bragg grating acceleration sensor 2, the fiber Bragg grating inclination sensor 3 and the wind speed sensor 4 can be 50 Hz.

[0039] 4) The external host computer looks up the table according to the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes and the natural frequency-scour depth table in step 2) to obtain the first scour depth D1 of the offshore wind power pile in the current ten minutes; the external host computer looks up the table according to the inclination data of the offshore wind power pile in the current ten minutes, the environmental wind speed data at the position of the offshore wind power pile and the inclination balance position-wind speed-scour depth table in step 2) to obtain the second scour depth D2 of the offshore wind power pile in the current ten minutes.

[0040] In step 4), the external host computer looks up the table according to the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes and the natural frequency-scour depth table in step 2) to obtain the first scour depth D1 of the offshore wind power pile in the current ten minutes. Specifically, the external host computer performs frequency-domain analysis on the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes, that is, performs fast Fourier transform on the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes to obtain the measured natural frequency of the offshore wind power pile in the current ten minutes, and then looks up the table through the natural frequency-scour depth table to obtain the first scour depth D1 of the offshore wind power pile in the current ten minutes.

[0041] The external host computer obtains the second scour depth D2 of the offshore wind power pile within the current ten minutes according to the inclination angle data of the offshore wind power pile within the current ten minutes, the environmental wind speed data at the position of the offshore wind power pile, and the inclination angle balance position - wind speed - scour depth table in step 2). Specifically, the external host computer calculates the average values of the inclination angle data of the offshore wind power pile and the environmental wind speed data at the position of the offshore wind power pile within the current ten minutes respectively, and then obtains the measured inclination angle balance position and the measured average environmental wind speed of the offshore wind power pile within the current ten minutes respectively. Furthermore, the second scour depth D2 of the offshore wind power pile within the current ten minutes is obtained by looking up the inclination angle balance position - wind speed - scour depth table.

[0042] 5) Perform error judgment based on the first scour depth D1 and the second scour depth D2 to determine the scour depth of the offshore wind power pile within the current ten minutes, and complete the real-time monitoring of the scour of the offshore wind power pile foundation within the current ten minutes; every ten minutes hereafter, repeat steps 3)-5) to complete the continuous real-time monitoring of the scour of the offshore wind power pile foundation.

[0043] In step 5), perform error judgment based on the first scour depth D1 and the second scour depth D2 to determine the scour depth of the offshore wind power pile within the current ten minutes. Specifically, calculate the error between the first scour depth D1 and the second scour depth D2. If the error is less than the preset threshold, select the larger value between the first scour depth D1 and the second scour depth D2 as the scour depth of the offshore wind power pile within the current ten minutes; if the error is greater than or equal to the preset threshold, discard the first scour depth D1 and the second scour depth D2 within the current ten minutes, and continue the real-time monitoring of the scour of the offshore wind power pile foundation within the next ten minutes.

[0044] In terms of the monitoring principle of the present invention, once the soil around the foundation of the wind power pile is scoured by the fluid, the buried depth of the pile decreases, resulting in a change in its natural frequency. On the other hand, the vibration balance position of the wind power pile foundation changes after scouring. The inclination angle time history curve of the pile foundation vibrates at the balance position, and the vibration balance position is related to the wind speed and the depth of the scour pit. Based on the above principles, monitor the natural frequency of the wind power pile foundation in the frequency domain, monitor the wind speed and the inclination angle balance position of the pile foundation in the time domain, and perform continuous time monitoring through the time domain and frequency domain coupling method, so as to monitor the development of the scour of the offshore wind power pile foundation in real time, accurately and reliably, and can play a substantial role in the scour monitoring of the offshore wind power pile foundation.

[0045] In terms of sensor selection, this monitoring system uses fiber Bragg grating sensors. Fiber Bragg grating sensors are the most widely used type of fiber optic sensors. The principle is that changes in temperature, strain, and stress will cause changes in the grating pitch and refractive index of the fiber Bragg grating, thereby changing the reflection and transmission spectra of the fiber Bragg grating. When a broadband light beam passes through the fiber Bragg grating, the wavelength that satisfies the Bragg condition of the fiber Bragg grating will be reflected, and the remaining wavelengths will pass through the fiber Bragg grating and continue to propagate. By monitoring the changes in the reflection spectrum or transmission spectrum of the fiber Bragg grating, the corresponding temperature, strain, and pressure information can be obtained. Fiber Bragg grating sensors have the advantages of adaptability, strong corrosion resistance, high precision, and anti-interference. Therefore, based on the monitoring principle, this invention selects fiber Bragg grating acceleration sensors and fiber Bragg grating inclination sensors.

[0046] Aiming at the disadvantages of the current offshore wind turbine pile foundation scour monitoring system and its monitoring method, this invention proposes a real-time monitoring system and its monitoring method for offshore wind turbine pile foundation scour, which can monitor the scour development of offshore wind turbine pile foundation in real time, accurately, and reliably, without affecting the normal operation of wind turbine units, and has the advantages of simple operation process and stable performance.

[0047] This monitoring system uses fiber Bragg grating sensors. Fiber Bragg grating sensors are the most widely used type of fiber optic sensors. The principle is that changes in temperature, strain, and stress will cause changes in the grating pitch and refractive index of the fiber Bragg grating, thereby changing the reflection and transmission spectra of the fiber Bragg grating. When a broadband light beam passes through the fiber Bragg grating, the wavelength that satisfies the Bragg condition of the fiber Bragg grating will be reflected, and the remaining wavelengths will pass through the fiber Bragg grating and continue to propagate. By monitoring the changes in the reflection spectrum or transmission spectrum of the fiber Bragg grating, the corresponding temperature, strain, and pressure information can be obtained. Currently, many types of fiber Bragg grating sensors have been developed and applied, such as fiber Bragg grating acceleration sensors, fiber Bragg grating inclination sensors, etc.

[0048] Fiber Bragg grating sensors have the following advantages: First, they have strong adaptability and corrosion resistance and can work for a long time in complex working environments. Second, because the length of the grating is small, only in millimeters, the spatial resolution of the measured value is high, that is, fiber Bragg grating sensors have high precision. Third, fiber Bragg grating sensors have strong anti-electromagnetic interference and anti-interference from the external environment. However, fiber Bragg grating sensors have not been applied to the existing offshore wind turbine pile foundation scour monitoring. This monitoring system uses fiber Bragg grating acceleration sensors and fiber Bragg grating inclination sensors at the same time. Based on a reliable monitoring principle and making full use of the above advantages of fiber Bragg grating sensors, it can play a substantial role in the scour monitoring of offshore wind turbine pile foundations.

[0049] The present invention conducts continuous-time monitoring based on the time-domain and frequency-domain coupling method, and the results are relatively accurate; both the sensor and the data acquisition module are located above the water surface, with strong reliability and convenient maintenance; the fiber Bragg grating sensor is used, which has advantages such as adaptability, strong corrosion resistance, high precision, and anti-interference. Generally speaking, the present invention can monitor the scour development of the offshore wind turbine pile foundation in real time, accurately and reliably, and has the advantages of simple operation process and stable performance, which can effectively avoid accidents and ensure the safe operation of the offshore wind turbine unit.

[0050] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. Monitoring method of a real-time monitoring system for scour of an offshore wind power pile foundation. The real-time monitoring system for scour of the offshore wind power pile foundation includes a data acquisition module (1), a fiber Bragg grating acceleration sensor (2), a fiber Bragg grating inclination sensor (3), and a wind speed sensor (4). The data acquisition module (1), the fiber Bragg grating acceleration sensor (2), the fiber Bragg grating inclination sensor (3), and the wind speed sensor (4) are all installed on the surface of the wind turbine tower above the water level of the offshore wind power pile. The data acquisition module (1) is electrically connected or wirelessly connected to an external host computer. The data acquisition module (1) is connected to the fiber Bragg grating acceleration sensor (2) and the fiber Bragg grating inclination sensor (3) through an optical fiber data line, and the data acquisition module (1) is electrically connected to the wind speed sensor (4). It is characterized in that: The method includes the following steps: 1) Obtain the soil parameters and the offshore wind turbine pile foundation parameters at the buried position of the offshore wind turbine pile foundation. There is simulation software installed in the external host computer. Input the soil parameters and the offshore wind turbine pile foundation parameters at the buried position of the offshore wind turbine pile foundation into the simulation software. The simulation software outputs the wind turbine pile foundation response signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths. Select a signal segment with a duration of ten minutes in the wind turbine pile foundation response signals as the reference signal. 2) The external host computer respectively obtains the natural frequency - scour depth table and the inclination equilibrium position - wind speed - scour depth table of the offshore wind turbine after performing frequency domain and time domain analysis and processing on the reference signal. 3) Respectively and real - time collect the pile foundation vibration acceleration data and inclination data of the offshore wind turbine within the current ten minutes through the fiber Bragg grating acceleration sensor (2) and the fiber Bragg grating inclination sensor (3), and transmit them to the external host computer through the multi - channel fiber Bragg grating demodulator; real - time collect the environmental wind speed data at the position of the offshore wind turbine within the current ten minutes through the wind speed sensor (4) and transmit it to the external host computer through the wind speed data acquisition unit. 4) The external host computer looks up the table according to the pile foundation vibration acceleration data of the offshore wind turbine within the current ten minutes and the natural frequency - scour depth table in step 2) to obtain the first scour depth D1 of the offshore wind turbine within the current ten minutes; the external host computer looks up the table according to the inclination data of the offshore wind turbine within the current ten minutes, the environmental wind speed data at the position of the offshore wind turbine, and the inclination equilibrium position - wind speed - scour depth table in step 2) to obtain the second scour depth D2 of the offshore wind turbine within the current ten minutes. 5) Perform error judgment based on the first scour depth D1 and the second scour depth D2 to determine the scour depth of the offshore wind turbine within the current ten minutes, and complete the real - time monitoring of the offshore wind turbine pile foundation scour within the current ten minutes; subsequently, repeat steps 3) - 5) every ten minutes to complete the continuous real - time monitoring of the offshore wind turbine pile foundation scour.

2. The monitoring method of the real-time monitoring system for scour of offshore wind power pile foundation according to claim 1, characterized in that: In the said step 1), the soil parameters at the buried position of the offshore wind turbine pile foundation include tensile strength, Poisson's ratio, Young's modulus, dilatancy angle, and unit weight parameters; the offshore wind turbine pile foundation parameters include diameter, length, buried depth, Young's modulus, and Poisson's ratio parameters.

3. The monitoring method of the real - time monitoring system for offshore wind turbine pile foundation scour according to claim 1, characterized in that: In the said step 1), the simulation software is ABAQUS software or ANSYS software.

4. The monitoring method of the real-time monitoring system for scour of offshore wind power pile foundation according to claim 1, characterized in that: In the said step 1), the wind turbine pile foundation response signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths include the pile foundation vibration acceleration signals and inclination signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths; select a signal segment with a duration of ten minutes in the wind turbine pile foundation response signals as the reference signal, that is, respectively select a signal segment with a duration of ten minutes in the pile foundation vibration acceleration signals and inclination signals of the offshore wind turbine under different simulated environmental wind speeds and different simulated scour depths and respectively use them as the pile foundation vibration acceleration reference signal and the inclination reference signal.

5. The monitoring method of the real-time monitoring system for scour of offshore wind power pile foundation according to claim 4, characterized in that: In step 2), the external host computer performs frequency-domain and time-domain analysis and processing on the reference signals respectively. Specifically, the external host computer performs frequency-domain analysis and processing on the pile foundation vibration acceleration reference signal, that is, performs fast Fourier transform processing on the pile foundation vibration acceleration reference signal to obtain the natural frequencies of the offshore wind power pile at different simulated scour depths, and then obtains the natural frequency - scour depth table of the offshore wind power pile; the external host computer performs time-domain analysis and processing on the inclination reference signal to obtain the simulated inclination balance position and the average value of the simulated environmental wind speed of the offshore wind power pile at different simulated scour depths, and then obtains the inclination balance position - wind speed - scour depth table of the offshore wind power pile.

6. The monitoring method of the real-time monitoring system for scour of offshore wind power pile foundation according to claim 1, characterized in that: In step 4), the external host computer looks up the first scour depth D1 of the offshore wind power pile in the current ten minutes according to the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes and the natural frequency - scour depth table in step 2). Specifically, the external host computer performs frequency-domain analysis and processing on the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes, that is, performs fast Fourier transform processing on the pile foundation vibration acceleration data of the offshore wind power pile in the current ten minutes to obtain the measured natural frequency of the offshore wind power pile in the current ten minutes, and then looks up the first scour depth D1 of the offshore wind power pile in the current ten minutes through the natural frequency - scour depth table. The external host computer looks up the second scour depth D2 of the offshore wind power pile in the current ten minutes according to the inclination data of the offshore wind power pile in the current ten minutes, the environmental wind speed data at the location of the offshore wind power pile, and the inclination balance position - wind speed - scour depth table in step 2). Specifically, the external host computer calculates the average value of the inclination data of the offshore wind power pile in the current ten minutes and the environmental wind speed data at the location of the offshore wind power pile respectively, and then obtains the measured inclination balance position and the measured average environmental wind speed of the offshore wind power pile in the current ten minutes respectively, and then looks up the second scour depth D2 of the offshore wind power pile in the current ten minutes through the inclination balance position - wind speed - scour depth table.

7. The monitoring method of the real-time monitoring system for scour of offshore wind power pile foundation according to claim 1, characterized in that: In step 5), error judgment is performed according to the first scour depth D1 and the second scour depth D2 to determine the scour depth of the offshore wind power pile in the current ten minutes. Specifically, calculate the error between the first scour depth D1 and the second scour depth D2. If the error is less than the preset threshold, select the larger value of the first scour depth D1 and the second scour depth D2 as the scour depth of the offshore wind power pile in the current ten minutes; if the error is greater than or equal to the preset threshold, discard the first scour depth D1 and the second scour depth D2 in the current ten minutes, and continue the real-time monitoring of the scour of the offshore wind power pile foundation in the next ten minutes.

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