Deformation anomaly judgment and deformation value estimation method of isolated offshore wind turbine towers

Abstract

The present invention discloses a method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group, including: selecting a wind tower in the wind power tower group to mark the initial reference position, marking the installation position of the corner reflectors of the remaining wind towers, and installing the corner reflectors at the marked positions; performing radiation calibration, focusing, SAR image registration based on isolated points and geocoding according to the SAR image data acquired by the satellite for the corner reflectors; calculating the temporal phase change of a single wind tower relative to the wind power tower group using a deformation anomaly perception algorithm according to the SAR image data, and determining the distribution of wind towers with abnormal deformation; calculating the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and the wind power tower group using a deformation variable estimation method, and determining the cumulative deformation of each abnormally deformed wind tower. Through the technical solution of the present invention, high-frequency and large-scale monitoring of wind power tower groups is achieved with high accuracy and low equipment deployment and maintenance costs.

Description

Technical Field

[0001] The invention relates to the field of satellite remote sensing technology, and in particular to a method for determining deformation anomaly and estimating deformation values ​​of an isolated offshore wind power tower group. Background Art

[0002] Satellite remote sensing has the advantages of wide observation range, strong periodicity, all-day, all-weather, and not being affected by harsh ground environment. Currently, remote sensing technology has been successfully applied in the fields of landslides, mining subsidence, safety monitoring of important urban buildings, bridge deformation monitoring, etc., with very good results.

[0003] The corner reflector itself has a relatively stable radar cross-section that can be identified by the target SAR satellite. On the one hand, the corner reflector can be used as a reference point target for radiometric calibration of SAR images, and on the other hand, it can also be deployed on the target point for deformation measurement.

[0004] China's offshore wind power industry is developing rapidly. As of April 2021, offshore wind power projects have been connected to the grid in eight coastal provinces. Among them, the newly installed capacity in 2020 was 3.06 million kilowatts, accounting for about 50% of the world's new offshore wind power installed capacity that year.

[0005] At present, the common offshore wind tower deformation monitoring technologies on the market have the following difficulties: (1) Traditional manual surveying and mapping operations are difficult and inefficient; (2) Tilt sensors are not accurate enough and have large random errors; (3) GPS deployment is expensive and difficult to maintain. Summary of the invention

[0006] In response to the above problems, the present invention provides a method for determining deformation anomalies and estimating deformation values ​​of an isolated offshore wind tower group. SAR image data of the wind tower group is acquired based on a corner reflector, and the temporal phase change and phase difference characteristics of a single wind tower relative to adjacent wind towers and the entire wind tower group are calculated through the SAR images after data processing. The wind towers with abnormal deformation are determined and the cumulative deformation amount is calculated, thereby realizing high-frequency and large-scale monitoring of the wind tower group with high accuracy and low equipment deployment and maintenance costs.

[0007] To achieve the above object, the present invention provides a method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group, comprising:

[0008] Select a wind tower in the wind tower group to mark the initial reference position, and mark the installation positions of the corner reflectors of the remaining wind towers;

[0009] Install the corner reflector at the marked position of the wind tower;

[0010] According to the SAR image data acquired by the satellite for the corner reflector, radiation calibration, focusing, SAR image registration based on isolated points and geocoding data processing are performed;

[0011] According to the SAR image data after data processing, a deformation anomaly perception algorithm is used to calculate the time series phase change of a single wind tower relative to the wind tower group, and determine the distribution of wind towers with abnormal deformation;

[0012] According to the SAR image data, a deformation estimation method is used to calculate the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and the wind tower group, and the cumulative deformation of each abnormally deformed wind tower is determined.

[0013] In the above technical solution, preferably, the process of installing the corner reflector at the marked position of the wind tower also includes:

[0014] Collect historical data on the wave height of the sea where the wind turbine towers are located, and determine the 90% percentile height of the historical wave height as the installation height of the corner reflector;

[0015] The corner reflector is installed at a layout height corresponding to the marked position of the wind tower.

[0016] In the above technical solution, preferably, the step of calculating the time series phase change of a single wind tower relative to the wind tower group using a deformation anomaly perception algorithm based on the SAR image data after data processing, and determining the distribution of wind towers with abnormal deformation specifically includes:

[0017] Calculate the SAR image phase difference between adjacent time periods in the SAR images of each wind tower in each time period;

[0018] Calculate the mean and standard deviation of each phase difference in each time period in turn, preliminarily determine that the wind towers with phase differences exceeding the mean ± 2 times the standard deviation are abnormal wind towers, and count the number of times each wind tower is determined to be an abnormal wind tower;

[0019] According to the distribution position and abnormal number of abnormally deformed wind towers, a comprehensive judgment is made to obtain the distribution of the real abnormally deformed wind towers.

[0020] In the above technical solution, preferably, the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and the wind tower group are calculated using a deformation estimation method based on the SAR image data, and the cumulative deformation of each abnormally deformed wind tower is determined specifically including:

[0021] Calculating the cumulative phase difference of each wind tower according to the SAR image data;

[0022] The accumulated phase differences of all wind towers are sorted first in the north-south direction and then in the east-west direction, and the distribution law is statistically analyzed;

[0023] Determining phase ambiguity according to phase differences of the wind tower relative to adjacent wind towers and the wind turbine tower group at different time periods;

[0024] The actual cumulative deformation of each abnormally deformed wind tower is obtained by using the phase conversion deformation method.

[0025] In the above technical solution, preferably, the data processing process of the SAR image registration based on isolated points includes:

[0026] Counting the scattering intensity values ​​of the pixels in the SAR image, and calculating the average value of the scattering intensity values;

[0027] Performing mask processing on the SAR image to retain strong pixels whose scattering intensity values ​​exceed the average value;

[0028] The strong pixels are precisely aligned using a precise alignment algorithm, wherein the precise alignment algorithm includes a coherence coefficient method, a correlation coefficient method, a maximum interference spectrum method, a phase difference image average fluctuation function method and a least squares method.

[0029] In the above technical solution, preferably, the maximum correlation coefficient method is used to accurately align the strong pixels, and the specific formula is:

[0030]

[0031] Among them, S l (i, j), S2(i+u, j+v) are the complex values ​​of the main image at the pixel coordinate (i, j) and the auxiliary image at the pixel coordinate (i+u, j+v), * represents the complex conjugate, r is the correlation function value, when r is the maximum value, u and v are the azimuth and distance offsets obtained by aligning the two images at the pixel (i, j).

[0032] In the above technical solution, preferably, the selecting a wind tower in the wind tower group to mark the initial reference position and marking the installation positions of the corner reflectors of the remaining wind towers specifically includes:

[0033] Marking the installation position of the corner reflector on a wind tower located relatively in the center of the wind tower group as an initial reference position;

[0034] Based on the initial reference position, the installation positions of the corner reflectors of the remaining wind towers are marked using a laser device.

[0035] In the above technical solution, preferably, the statistical analysis of historical wave height data of the sea surface where the wind turbine tower group is located and determining the 90% percentile height of the historical wave height as the layout height of the corner reflector specifically includes:

[0036] The statistical historical data of the water level of the sea surface where the wind power tower group is located relative to the wind tower;

[0037] Obtaining historical statistical data of the height of wind and waves on the current sea surface relative to the wind tower for more than one year;

[0038] The 90% percentile height of the wind tower that is not affected by waves is calculated as the installation height of the corner reflector on the wind tower.

[0039] In the above technical solution, preferably, the method of installing the corner reflector at the marked position of the wind tower includes:

[0040] confirming the type of the corner reflector;

[0041] Calculating the pitch angle of the corner reflector according to the shape and specifications of the corner reflector;

[0042] According to the satellite orbit inclination α of the satellite and the latitude ε of the corner reflector, the formula Calculate and obtain the bottom edge azimuth angle β of the corner reflector;

[0043] The difference between the bottom edge azimuth and the magnetic declination is used as the bottom edge installation direction of the corner reflector;

[0044] According to the pitch angle and the bottom edge installation direction, the corner reflector is installed at a layout height corresponding to the marked position.

[0045] In the above technical solution, preferably, the data processing process of the geocoding includes:

[0046] Based on the nearby coastline, the deformation results in the radar coordinate system are geocoded into the external DEM coordinate system using a lookup table generated by the correspondence between the SAR image coordinates and the external DEM coordinates.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: SAR image data of a wind tower group is obtained based on a corner reflector, and the temporal phase change and phase difference characteristics of a single wind tower relative to adjacent wind towers and the entire wind tower group are calculated through the SAR images after data processing, the wind tower with abnormal deformation is judged and the cumulative deformation is calculated, so as to realize high-frequency and large-scale monitoring of the wind tower group with high accuracy and low equipment deployment and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A schematic flow chart of a method for determining deformation anomalies and estimating deformation values ​​of an isolated offshore wind power tower group disclosed in an embodiment of the present invention;

[0049] Figure 2A schematic diagram of the distribution of a group of wind power towers disclosed in an embodiment of the present invention;

[0050] Figure 3 A schematic diagram of an installation method of a corner reflector disclosed in an embodiment of the present invention;

[0051] Figure 4 A schematic diagram of a phase difference sequence corresponding to a group of wind power towers disclosed in an embodiment of the present invention;

[0052] Figure 5 A schematic diagram of the phase distribution of a wind tower showing obvious deformation anomaly disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0055] like Figure 1 and Figure 2 As shown, a method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to the present invention includes:

[0056] Step 1, select a wind tower in the wind tower group to mark the initial reference position, and mark the installation positions of the corner reflectors of the remaining wind towers;

[0057] Step 2, install the corner reflector at the marked position of the wind tower;

[0058] Step 3, according to the SAR image data acquired by the satellite for the corner reflector, perform radiation calibration, focusing, SAR image registration based on isolated points and geocoding data processing;

[0059] Step 4: Based on the processed SAR image data, a deformation anomaly perception algorithm is used to calculate the temporal phase change of a single wind tower relative to the wind tower group, and determine the distribution of wind towers with abnormal deformation;

[0060] Step 5: Based on the SAR image data, the deformation estimation method is used to calculate the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and wind tower groups, and the cumulative deformation of each abnormally deformed wind tower is determined.

[0061] In this embodiment, SAR image data of a group of wind turbines is acquired based on a corner reflector. The time-series phase change and phase difference characteristics of a single wind tower relative to adjacent wind towers and the entire group of wind turbines are calculated through the SAR images after data processing. The wind towers with abnormal deformation are judged and the cumulative deformation is calculated, thereby realizing high-frequency and large-scale monitoring of the wind turbine group with high accuracy and low equipment deployment and maintenance costs.

[0062] In step 1 of the above embodiment, preferably, selecting a wind tower in the wind tower group to mark the initial reference position, and marking the installation positions of the corner reflectors of the remaining wind towers specifically include:

[0063] Mark the installation position of the corner reflector on the wind tower in the center of the wind tower group as the initial reference position;

[0064] Based on the initial reference position, laser equipment is used to mark the installation positions of the corner reflectors of the remaining wind towers. This is because there is a lack of DEM data for isolated points at sea, and a unified layout can be free from the influence of errors such as terrain, which facilitates the estimation of the deformation values ​​of the wind towers.

[0065] Specifically, when the above-mentioned deformation abnormality judgment method of a wind power tower group is applied to an offshore wind power tower, in order to avoid the influence of offshore wind and waves on devices such as corner reflectors, it is also necessary to set the installation height of the corner reflectors, specifically including:

[0066] Collect historical data on the wave height of the sea where the wind turbine towers are located, and determine the 90% percentile height of the historical wave height as the layout height of the corner reflector, including:

[0067] Collect historical data on the water level of the sea surface where the wind turbine towers are located relative to the wind towers;

[0068] Obtain the statistical historical data of the height of wind and waves on the current sea surface relative to the wind tower for more than one year;

[0069] Calculate the 90% percentile height of the wind tower that is not affected by waves, which will be used as the installation height of the corner reflector on the wind tower;

[0070] Install the corner reflector at the installation height corresponding to the marked position of the wind tower.

[0071] like Figure 3 As shown, in step 2 of the above embodiment, preferably, the method of installing the corner reflector at the marked position of the wind tower includes:

[0072] Confirm the type of corner reflector;

[0073] Calculate the elevation angle of the corner reflector according to its shape and specifications;

[0074] According to the satellite orbit inclination α and the latitude ε of the corner reflector, the formula The bottom azimuth angle β of the corner reflector (the angle between the bottom of the corner reflector and the meridian direction (north-south direction)) is calculated; if the acquired data is ascending orbit data, cosε takes a positive value, and if it is descending orbit data, it takes a negative value.

[0075] The difference between the bottom azimuth and the magnetic declination is used as the bottom installation direction of the corner reflector;

[0076] According to the pitch angle and bottom installation direction, install the corner reflector at the layout height corresponding to the marked position.

[0077] In step 3 of the above embodiment, preferably, the data processing process of SAR image registration based on isolated points includes:

[0078] During the registration process, coarse registration and fine registration are performed in sequence. Finally, the registration accuracy between SAR complex images should reach the sub-pixel level, which should reach 1 / 8 pixel.

[0079] In the process of precise registration, the scattering intensity values ​​of the pixels in the SAR image are first counted, and the average value M of the scattering intensity value is calculated. P ;

[0080] Mask the SAR image and retain the strong pixels M whose scattering intensity values ​​exceed the average value. P ;

[0081] The strong pixels are precisely registered using a precise registration algorithm, wherein the precise registration algorithm includes a coherence coefficient method, a correlation coefficient method, a maximum interference spectrum method, a phase difference image average fluctuation function method and a least squares method.

[0082] In the above embodiment, preferably, the maximum correlation coefficient method is used to accurately align strong pixels, and the specific formula is:

[0083]

[0084] Among them, S l (i, j), S2(i+u, j+v) are the complex values ​​of the main image at the pixel coordinate (i, j) and the auxiliary image at the pixel coordinate (i+u, j+v), * represents the complex conjugate, r is the correlation function value, when r is the maximum value, u and v are the azimuth and distance offsets obtained by aligning the two images at the pixel (i, j).

[0085] In the above embodiment, preferably, the data processing process of geocoding includes:

[0086] Based on the nearby coastline, the deformation results in the radar coordinate system are geocoded into the external DEM coordinate system using the lookup table generated by the correspondence between the SAR image coordinates and the external DEM coordinates.

[0087] like Figure 4 and Figure 5 As shown, in step 4 of the above embodiment, preferably, according to the SAR image data after data processing, the deformation anomaly perception algorithm is used to calculate the time series phase change of a single wind tower relative to the wind tower group, and the distribution of wind towers with abnormal deformation is determined to specifically include:

[0088] Calculate the phase difference of the SAR images of each wind tower in each time period between adjacent time periods, and record it as The superscript indicates the phase difference between SAR images of different periods, and the subscript refers to the number of the corner reflector. Due to the special arrangement of the corner reflector, the interference of most non-deformed phases (such as terrain phase) in the phase difference can be effectively reduced, and the phase differences obtained by different corner reflectors without deformation in the same time period are extremely similar.

[0089] Calculate the mean and standard deviation of each phase difference in each time period in all time periods, and preliminarily determine that the wind tower with a phase difference exceeding the mean ± 2 times the standard deviation is an abnormal wind tower, record the number of abnormalities as 1, complete all deformation calculations in the time period in turn, and count the number of times each wind tower is determined to be an abnormal wind tower;

[0090] Extract wind towers with abnormal deformation and their corresponding times, and pay special attention to wind towers with times greater than 2 or more;

[0091] A comprehensive judgment is made based on the distribution position and abnormal number of abnormally deformed wind towers. Through the comprehensive judgment, the single overall phase anomaly caused by abnormal conditions can be excluded, and the distribution of the real abnormally deformed wind towers can be obtained.

[0092] In step 5 of the above embodiment, preferably, according to the SAR image data, the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and wind turbine tower groups are calculated using a deformation estimation method, and the cumulative deformation of each abnormally deformed wind tower is determined, specifically including:

[0093] Based on the SAR image data, the cumulative phase difference of each wind tower is calculated;

[0094] The accumulated phase differences of all wind towers are sorted first in the north-south direction and then in the east-west direction to statistically analyze the distribution law. Generally, when the distribution distance is close, it fluctuates within a certain limit around a specific value. When the distribution distance is far, the influence of the earth's curvature and the environment may cause a certain error to increase, and the phase may show a slight trend of increasing or decreasing.

[0095] According to the phase difference of the wind tower relative to the adjacent wind towers and wind turbine tower groups in different time periods, specifically the deviation degree between the current wind tower and the overall wind tower, the deviation degree from the adjacent wind towers, and the phase deviation degree from the adjacent wind towers in different time periods, the phase ambiguity is confirmed using the idea of ​​phase gradual change;

[0096] The actual cumulative deformation of each abnormally deformed wind tower is obtained by using the phase conversion deformation method.

[0097] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group, characterized in that: include: Select a wind tower in the wind tower group to mark the initial reference position, and mark the installation positions of the corner reflectors of the remaining wind towers; Install the corner reflector at the marked position of the wind tower; According to the SAR image data acquired by the satellite for the corner reflector, radiation calibration, focusing, SAR image registration based on isolated points and geocoding data processing are performed; According to the SAR image data after data processing, a deformation anomaly perception algorithm is used to calculate the time series phase change of a single wind tower relative to the wind tower group, and determine the distribution of wind towers with abnormal deformation; According to the SAR image data, a deformation estimation method is used to calculate the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and the wind tower group, and the cumulative deformation of each abnormally deformed wind tower is determined.

2. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 1, characterized in that: The process of installing the corner reflector at the marked position of the wind tower also includes: Collect historical data on the wave height of the sea where the wind turbine towers are located, and determine the 90% percentile height of the historical wave height as the installation height of the corner reflector; The corner reflector is installed at a layout height corresponding to the marked position of the wind tower.

3. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 1, characterized in that: The method of calculating the time-series phase change of a single wind tower relative to the wind tower group using a deformation anomaly perception algorithm based on the SAR image data after data processing to determine the distribution of wind towers with abnormal deformation specifically includes: Calculate the SAR image phase difference between adjacent time periods in the SAR images of each wind tower in each time period; Calculate the mean and standard deviation of each phase difference in each time period in turn, preliminarily determine that the wind towers with phase differences exceeding the mean ± 2 times the standard deviation are abnormal wind towers, and count the number of times each wind tower is determined to be an abnormal wind tower; According to the distribution position and abnormal number of abnormally deformed wind towers, a comprehensive judgment is made to obtain the distribution of the real abnormally deformed wind towers.

4. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 3, characterized in that: The method of calculating the phase gradient characteristics of a single wind tower and the phase difference characteristics of the current wind tower relative to adjacent wind towers and the wind tower group using a deformation estimation method based on the SAR image data to determine the cumulative deformation of each abnormally deformed wind tower specifically includes: Calculating the cumulative phase difference of each wind tower according to the SAR image data; The accumulated phase differences of all wind towers are sorted first in the north-south direction and then in the east-west direction, and the distribution law is statistically analyzed; Determining phase ambiguity according to phase differences of the wind tower relative to adjacent wind towers and the wind turbine tower group at different time periods; The actual cumulative deformation of each abnormally deformed wind tower is obtained by using the phase conversion deformation method.

5. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 1, characterized in that: The data processing process of the isolated point-based SAR image registration includes: Counting the scattering intensity values ​​of the pixels in the SAR image, and calculating the average value of the scattering intensity values; Performing mask processing on the SAR image to retain strong pixels whose scattering intensity values ​​exceed the average value; The strong pixels are precisely aligned using a precise alignment algorithm, wherein the precise alignment algorithm includes a coherence coefficient method, a correlation coefficient method, a maximum interference spectrum method, a phase difference image average fluctuation function method and a least squares method.

6. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 5, characterized in that: The maximum correlation coefficient method is used to accurately align the strong pixels. The specific formula is: Among them, S l (i, j), S2(i+u, j+v) are the complex values ​​of the main image at the pixel coordinate (i, j) and the auxiliary image at the pixel coordinate (i+u, j+v), * represents the complex conjugate, r is the correlation function value, when r is the maximum value, u and v are the azimuth and distance offsets obtained by aligning the two images at the pixel (i, j).

7. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 1, characterized in that: The step of selecting a wind tower from the wind power tower group to mark an initial reference position and marking the installation positions of the corner reflectors of the remaining wind towers specifically includes: Marking the installation position of the corner reflector on a wind tower located relatively in the center of the wind tower group as an initial reference position; Based on the initial reference position, the installation positions of the corner reflectors of the remaining wind towers are marked using a laser device.

8. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 2, characterized in that: The statistical analysis of the historical data of wave height on the sea surface where the wind turbine towers are located and determining the 90% percentile height of the historical wave height as the installation height of the corner reflector specifically includes: Count historical data of the water level of the sea surface where the wind turbine tower group is located relative to the wind turbine tower; Obtaining historical statistical data of the height of wind and waves on the current sea surface relative to the wind tower for more than one year; The 90% percentile height of the wind tower that is not affected by waves is calculated as the installation height of the corner reflector on the wind tower.

9. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 1 or 2, characterized in that: The method of installing the corner reflector at the marked position of the wind tower comprises: confirming the type of the corner reflector; Calculating the pitch angle of the corner reflector according to the shape and specifications of the corner reflector; According to the satellite orbit inclination α of the satellite and the latitude ε of the corner reflector, the formula Calculate and obtain the bottom edge azimuth angle β of the corner reflector; The difference between the bottom edge azimuth and the magnetic declination is used as the bottom edge installation direction of the corner reflector; According to the pitch angle and the bottom edge installation direction, the corner reflector is installed at a layout height corresponding to the marked position.

10. The method for determining deformation anomaly and estimating deformation value of an isolated offshore wind power tower group according to claim 1, characterized in that: The data processing process of geocoding includes: Based on the nearby coastline, the deformation results in the radar coordinate system are geocoded into the external DEM coordinate system using a lookup table generated by the correspondence between the SAR image coordinates and the external DEM coordinates.

Images