Method for inhibiting interference of offshore wind driven generator on shipborne navigation radar echo

Abstract

The invention discloses a method for inhibiting interference of an offshore wind driven generator on a shipborne navigation radar echo, and relates to the technical field of radar signal processing and offshore traffic safety. The method comprises the following steps: S1, a radar system initialization and stable operation step; S2, a multi-coherence interval CPI echo power sequence acquisition and storage step; S3, a power echo reference signal construction step; and S4, an interference suppression and target echo extraction step. Through the characteristic that the echo sequence of the wind driven generator in the CPI has periodicity, the periodic interference characteristics of the wind driven generator are extracted through simple mean filtering, the echo interference of the offshore wind driven generator on the shipborne navigation radar is accurately learned and eliminated, the probability of occurrence of a false target is greatly reduced, and by means of collection and storage of the multi-CPI echo sequence, the accuracy of the detection result is improved. In combination with an interference rejection formula, a target echo signal is effectively extracted, and high-precision detection of a ship target can be further realized through a sea clutter and meteorological clutter suppression algorithm.

Description

Technical Field

[0001] This invention relates to the fields of radar signal processing and maritime traffic safety technology, specifically a method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes. Background Technology

[0002] With the increasing global demand for clean energy, offshore wind power, as a sustainable and environmentally friendly energy development method, has been rapidly developed worldwide.

[0003] The issue of echo interference from offshore wind turbines to shipborne navigation radar has not yet received sufficient attention or been addressed in relevant technologies and research. Technically, current marine radar clutter suppression capabilities only target sea clutter and meteorological clutter. Due to the inherent physical properties of offshore wind turbines, such as their materials, dimensions, and rotation, their power echo signals possess unique characteristics. Traditional methods for suppressing sea clutter and meteorological clutter in shipborne navigation radar, such as Fast Time Control (FTC) and Slow Time Control (STC) processing, cannot effectively suppress wind turbine power echoes. Furthermore, as the scale of near-shore offshore wind farms continues to increase, the distance between offshore wind turbines and traditional shipping lanes is gradually decreasing, increasing the potential risk of collisions between ships and between ships and wind turbines, especially when ships are navigating in busy or narrow waters near offshore wind farms. Shipborne navigation radar is an indispensable navigation tool for ships to avoid collisions.

[0004] In summary, traditional technologies are insufficient to effectively address the power echo interference from offshore wind turbines on shipborne navigation radar, making it difficult to effectively suppress or eliminate this interference and further improve the accuracy of maritime target detection to meet the application requirements of real-world scenarios. Therefore, developing a method to suppress the echo interference from offshore wind turbines on shipborne navigation radar is of paramount importance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for suppressing the echo interference of offshore wind turbines on shipborne navigation radar. It can effectively suppress and eliminate the echo interference generated by wind power in ship navigation radar by constructing interference feature processing and extraction, and significantly reduce the probability of false ship targets. At the same time, it further achieves high-precision detection of ship targets by shipborne navigation radar through sea clutter or meteorological clutter suppression algorithms.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes, the specific steps of which are as follows:

[0007] S1. Radar system initialization and stable operation steps: Warm up the shipborne navigation radar, turn it on, and enter a normal and stable working state. The shipborne navigation radar operates in the microwave X-band and uses mechanical scanning to achieve 360° scanning of the surrounding environment. Generally, the antenna has an adjustable rotation speed.

[0008] S2. Multiphase Interval CPI Echo Power Sequence Acquisition and Storage Steps: Record and store the N pulse echo powers of a specific distance gate RG in a certain azimuth within the first coherent processing interval, forming a time series S of length N. 1n Where N≥32; the power of the N pulse echoes of the distance gate RG in the same direction within the 2nd to Kth CPI are recorded and stored to form a time series S of length N. 2n To S kn The range of the number of CPIs K is 16 ≤ K ≤ 64; an interference feature extraction model is constructed, and interference feature signals are obtained by processing the time series of K CPIs. The formula for calculating the characteristic signal is: Where w i Here are the weighting coefficients for each CPI time series; values ​​w are taken under normal sea state and radar operating parameters. i =1, and the corresponding formula for calculating the interference characteristic signal is:

[0009] S3. Power Echo Reference Signal Construction: Record and store the power of N pulse echoes from the range gate RG at the same azimuth within the (K+1)th CPI, forming a time series S of length N. (k+1)n ;

[0010] S4. Interference Suppression and Target Echo Extraction Steps: Using time series S (k+1)n As a reference signal, the radar echo power signal ΔS after suppressing / removing wind turbine interference is calculated using the interference removal formula, which is: in The characteristic signal of interference echo from offshore wind turbines extracted from S2;

[0011] S5. Subsequent clutter suppression and high-precision detection of ship targets: Utilize the existing clutter suppression function of the marine radar to further suppress sea clutter or meteorological clutter in ΔS, thereby improving the detection accuracy of ship targets at sea.

[0012] Furthermore, in step S2, the value of N satisfies N≥32. The determination of the value of N comprehensively considers common value ranges such as the pulse repetition frequency of the shipborne navigation radar and the rotation period of the wind turbine blades. Through extensive simulation verification, when N is larger, the power echo time series is longer, and the characterization of the periodicity of the wind turbine echo becomes more obvious. However, it will also increase the radar data storage and processing pressure. In practical applications, the value of N can be dynamically adjusted within the allowable range of computing resources, combined with the specific parameters of the wind turbine, such as the typical value of the rotation period of the wind turbine under regional wind farms.

[0013] Furthermore, in step S2, the number of CPI intervals K in the coherent processing intervals ranges from 16 to K and from 64. This range is determined by considering multiple factors, including the correlation time T of sea clutter. sea The correlation time of sea clutter is affected by sea state, radar operating frequency, etc. By using the measured values ​​of shipborne navigation radar under different sea states, the range of sea clutter correlation time is estimated. Combined with the value of N in claim 1, the sea clutter is decorrelated in the time series within K CPI, thereby ensuring the accuracy and effectiveness of the algorithm. Through simulation experiments, combined with the value of N in claim 1, and comparing the interference suppression effect under different values ​​of K, when the value of K is in the range of 16 to 64, it can effectively extract the interference features of wind turbines through the interference feature model, and can also better avoid the presence of residual parts of other clutter or target information in the interference features of wind turbines, thus ensuring the accuracy and effectiveness of the algorithm.

[0014] Furthermore, when the mechanical scanning speed of the shipborne navigation radar antenna is within the range of 20-45 rpm, the algorithm accuracy and performance are better. This is because the lower the antenna scanning speed, the longer the antenna points to the same azimuth distance gate RG per unit time, resulting in more thorough sampling and accumulation of the wind turbine power echo within each CPI, and a more efficient time series S. in (i = 1, 2, ..., K) can more accurately present and characterize the periodicity of wind turbine echoes; at the same time, a lower antenna rotation speed can better ensure that the correlation between sea clutter and other targets in the pulse echo within each acquired CPI is low, which is beneficial to ensuring the effectiveness and accuracy of the algorithm; in addition, at a lower antenna rotation speed, the time interval between adjacent CPIs is relatively stable, reducing the complexity of the interference feature extraction model, that is, the weight can be taken as w under normal sea conditions. i =1; however, in practical applications, the antenna rotation speed also needs to be adjusted in conjunction with the radar scan refresh rate requirements of ship navigation. If the ship is navigating in a complex navigation environment, it needs to quickly scan the radar to update the surrounding target information, thus increasing the antenna rotation speed. In this case, a trade-off needs to be made between algorithm accuracy and scan refresh rate, by adjusting the weighting coefficient w. iThe method was re-optimized to ensure its adaptability under different antenna rotation speeds.

[0015] Furthermore, the method is designed to suppress the interference of a single, rotating offshore wind turbine on the echo signal of shipborne navigation radar. It is also applicable to scenarios involving interference from multiple wind turbines, because in most cases, the rotational speeds of multiple wind turbines in the same wind field are almost the same, exhibiting similar or identical periodic characteristics. The method can also achieve the same suppression effect on the periodic characteristics of multiple wind turbines with different rotational speeds.

[0016] Furthermore, in step S5, when further suppressing sea clutter or meteorological clutter on ΔS, the clutter suppression function of current maritime radar can be used to suppress sea clutter or meteorological clutter, thereby further improving and achieving high-precision detection of maritime targets.

[0017] Compared with existing technologies, this method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes has the following advantages:

[0018] First, this method, through interference feature extraction and processing, can accurately eliminate and suppress power echo interference from offshore wind turbines on shipborne navigation radar, significantly reducing the probability of false targets. By collecting and storing multiple CPI power echo sequences, combined with interference feature extraction and elimination formulas, the method effectively suppresses the power echo signal of wind turbines. Furthermore, by utilizing existing sea clutter and meteorological clutter suppression algorithms for shipborne navigation radar, it achieves high-precision detection of maritime targets. This series of processing steps greatly improves the target detection capability of shipborne navigation radar in the context of navigation in the vicinity of offshore wind farms, enhancing maritime traffic safety and the accuracy of target detection.

[0019] Second, this method employs flexible and adjustable parameter settings, such as the number K of coherent interval CPIs and antenna scanning speed. These parameters can be dynamically adjusted according to different sea conditions, radar operating parameters, and wind turbine characteristics (such as the number of turbines), ensuring optimal interference suppression. In particular, regarding antenna rotation speed, a balance can be found between algorithm accuracy and detection backgrounds such as special sea conditions by further optimizing the weighting coefficients, enabling the radar system to maintain stable and efficient operation under different detection scenarios. Furthermore, this method is scalable and can handle scenarios where multiple wind turbines simultaneously generate interference, further enhancing the adaptability and robustness of the shipborne navigation radar system.

[0020] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0022] Figure 1 This is a schematic diagram illustrating the functional implementation process of a method for suppressing the echo interference of offshore wind turbines on shipborne navigation radar. Detailed Implementation

[0023] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0024] Example 1

[0025] Radar system initialization and stable operation steps: When the ship is sailing smoothly, start the shipborne navigation radar and allow it to warm up fully. After all indicators stabilize, it will enter normal operation. The radar operates in the microwave X-band and relies on mechanical rotation to achieve a comprehensive scan of the surrounding environment within a 360° range. The antenna rotation speed can be adjusted according to actual needs. Considering the current open sea area and simple ship navigation environment, in order to ensure more sufficient sampling of wind turbine echoes, the antenna rotation speed is set to the lower value of 20rpm between 20-45rpm. This allows the antenna to point to the same direction at a specific distance RG for a longer period of time, so as to more accurately capture the significant periodic characteristics of wind turbine power echoes, which can be eliminated in the interference feature model.

[0026] Multi-CPI echo sequence acquisition and storage steps: The radar begins scanning the surrounding environment. When a single rotating wind turbine is detected in a certain azimuth, for a specific range gate in that azimuth, multiple pulse echo powers of that range gate are continuously recorded within the first coherent processing interval (CPI). These power data form a time series S. 1n Subsequently, following the same method, the pulse echo power of the same distance gate within the 2nd to 64th CPIs was recorded and stored, with each CPI forming a corresponding time series S. 2nTo S 64N Using the collected time series data of 64 CPIs, an interference feature extraction and processing model was constructed. By processing the power echo time series data of the 64 CPIs, an interference feature benchmark was obtained. The model calculation formula is: Where w i The weighting coefficients for each CPI time series are as follows: In this embodiment, there are no special detection background situations such as high sea states, so the weight values ​​are as described above and conform to the general situation in most cases. i =1.

[0027] Reference power echo signal construction steps: After completing the echo sequence acquisition of the first 64 CPIs, continue to monitor the distance gate in the same direction. When entering the 65th (64+1)th CPI, record the echo power of multiple pulses in the CPI, and organize these power data into a new time series to prepare for subsequent interference suppression.

[0028] Interference suppression and target echo extraction steps: The time series generated by the 65th CPI is used as the power echo reference signal. The interference removal formula ΔS is applied to process this signal. The formula is: ΔS 65N -S; Since the wind turbine signal is periodic and the sea clutter component and related target component in each power echo signal within each CPI are not correlated, the radar echo power signal ΔS after suppressing / removing wind turbine power echo interference can be obtained by formula.

[0029] Subsequent clutter suppression and high-precision target detection steps: The echo power signal ΔS obtained after the above steps may still contain sea clutter or meteorological clutter, therefore, it needs to be suppressed. Utilizing the existing sea clutter and meteorological clutter suppression functions of ship navigation radar, and adjusting knobs as needed, more accurate detection of surrounding ship targets can be achieved, providing safe and reliable navigation information for ships navigating in the vicinity of offshore wind farms. In this example, the sea state is calm and the weather is clear. The power of the ΔS signal obtained according to the above steps is approximately -25dB, which is negligible and cannot be displayed on the PPI screen; this indicates that the wind turbine power echo within this bearing and range has been effectively suppressed.

[0030] Example 2

[0031] Radar system initialization and stable operation steps: The ship gradually approaches an offshore wind farm area containing multiple offshore wind turbines. The navigation environment is relatively complex, requiring the radar to quickly update surrounding target information. The shipborne navigation radar is activated and, after warm-up, enters a stable operating state. The radar also operates in the microwave X-band, performing a 360° scan using mechanical scanning. Due to the current environment requiring rapid radar refresh of scan information, the antenna rotation speed is appropriately increased from 20-45 rpm to 40 rpm. Simultaneously, the weighting coefficients of each CPI time series are re-optimized, with a value of w. i =1 / 32; to ensure that the model for processing and eliminating interference features can still work accurately at higher rotation speeds, in order to balance the needs of algorithm accuracy and special sea state detection background.

[0032] Multi-CPI echo sequence acquisition and storage steps: When the radar scans the wind farm area, echo sequences are acquired for the range gates of multiple wind turbine locations within the area. Multiple pulse echo power is recorded within the first CPI to form a time series. Then, multiple pulse echo power of the same range gate within the second to 32nd CPIs are recorded and stored sequentially to obtain their respective time series. Using the interference feature extraction and processing model, combined with weighting coefficients, the corresponding interference feature benchmark within the range gate is calculated.

[0033] Construction of power echo reference signal: After completing the echo sequence acquisition from the 2nd to the 32nd CPI, continue to monitor the azimuth range gate. When entering the 33rd CPI, record the power of multiple pulse echoes of the range gate in the 33rd CPI to form a new time series.

[0034] Interference suppression and target echo extraction steps: Using the time series formed by its 33rd CPI as a reference signal, the echo power signal after suppressing the wind turbine interference is calculated using the interference elimination formula; the radar power echo signal ΔS after suppressing the echo interference of multiple wind turbines within the range gate is obtained.

[0035] Subsequent clutter suppression and high-precision target detection steps: The fused echo signal is processed to suppress not only sea clutter but also potential meteorological clutter; the inherent sea clutter and meteorological clutter suppression of the ship's radar is utilized, and the suppression intensity is selected by adjusting the knob according to the sea conditions; after clutter suppression is completed, a constant false alarm rate (CFAR) detection algorithm is used, combined with the relevant characteristics of the ship target echo, to detect ship targets around the wind farm area with high precision, ensuring the navigation safety of ships in this complex area.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes, characterized in that, The specific steps of this method are as follows: S1. Radar system initialization and stable operation steps: Warm up the shipborne navigation radar, turn it on, and enter a normal and stable working state. The shipborne navigation radar operates in the microwave X-band and uses mechanical scanning to achieve 360° scanning of the surrounding environment. Generally, the antenna has an adjustable rotation speed. S2. Multiphase Interval CPI Echo Power Sequence Acquisition and Storage Steps: Record and store the N pulse echo powers of a specific distance gate RG in a certain azimuth within the first coherent processing interval, forming a time series S of length N. 1n Where N≥32; the power of the N pulse echoes of the distance gate RG in the same direction within the 2nd to Kth CPI are recorded and stored to form a time series S of length N. 2n To S kn The number of CPIs K ranges from 16 to K and from 64. An interference feature extraction model is constructed. By processing the time series of K CPIs, the interference feature signal S is obtained. The feature signal is calculated as follows: Where w i Here are the weighting coefficients for each CPI time series; values ​​w are taken under normal sea state and radar operating parameters. i =1, and the corresponding formula for calculating the interference characteristic signal is: S3. Power Echo Reference Signal Construction: Record and store the power of N pulse echoes from the range gate RG at the same azimuth within the (K+1)th CPI, forming a time series S of length N. (k+1)n ; S4. Interference Suppression and Target Echo Extraction Steps: Using time series S (k+1)n As a reference signal, the radar echo power signal ΔS after suppressing / removing wind turbine interference is calculated using the interference removal formula, which is: in The characteristic signal of interference echo from offshore wind turbines extracted from S2; S5. Subsequent clutter suppression and high-precision detection of ship targets: Utilize the existing clutter suppression function of the marine radar to further suppress sea clutter or meteorological clutter in ΔS.

2. The method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes according to claim 1, characterized in that, In step S2, the value of N satisfies N≥32, and the determination of the value of N comprehensively considers common value ranges such as the pulse repetition frequency of the shipborne navigation radar and the rotation period of the wind turbine blades. Through extensive simulation verification, when N is larger, the power echo time series is longer, and the characterization of the periodicity of the wind turbine echo becomes more obvious. However, it will also increase the radar data storage and processing pressure. In practical applications, the value of N can be dynamically adjusted within the allowable computing resources, combined with the specific parameters of the wind turbine, such as the typical value of the rotation period of the wind turbine under regional wind farms.

3. The method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes according to claim 1, characterized in that, In step S2, the number of CPI intervals K in the coherent processing intervals ranges from 16 to K and from 64. This range is determined by considering multiple factors, including the correlation time T of sea clutter. sea The correlation time of sea clutter is affected by sea state, radar operating frequency, etc. By using the measured values ​​of shipborne navigation radar under different sea states, the range of sea clutter correlation time is estimated. Combined with the value of N in claim 1, the sea clutter is decorrelated in the time series within K CPI, thereby ensuring the accuracy and effectiveness of the algorithm. Through simulation experiments, combined with the value of N in claim 1, and comparing the interference suppression effect under different values ​​of K, when the value of K is in the range of 16 to 64, it can effectively extract the interference features of wind turbines through the interference feature model, and can also better avoid the presence of residual parts of other clutter or target information in the interference features of wind turbines, thus ensuring the accuracy and effectiveness of the algorithm.

4. The method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes according to claim 1, characterized in that, When the mechanical scanning speed of the shipborne navigation radar antenna is within the range of 20-45 rpm, the algorithm achieves better accuracy and performance. This is because a lower antenna scanning speed results in a longer time interval between antennas pointing to the same azimuth distance gate RG, leading to more thorough sampling and accumulation of wind turbine power echoes within each CPI, and a better time series S. in (i = 1, 2, ..., K) can more accurately represent the periodic characteristics of wind turbine echoes; at the same time, a lower antenna rotation speed can better ensure that the correlation between sea clutter and other target echoes in the pulse echoes within each acquired CPI is low, which is beneficial to ensuring the effectiveness and accuracy of the algorithm; in addition, at a lower antenna rotation speed, the time interval between adjacent CPIs is relatively stable, reducing the complexity of the interference feature extraction model, that is, the weight can be taken as w under normal sea conditions. i =1; however, in practical applications, the antenna rotation speed also needs to be adjusted in conjunction with the radar scan refresh rate requirements of ship navigation. For example, if a ship is navigating in a complex navigation environment, it needs to quickly scan with radar to update surrounding target information, thus increasing the antenna rotation speed. In this case, a trade-off needs to be made between algorithm accuracy and scan refresh rate, which can be achieved by adjusting the weighting coefficient w. i The method has been re-optimized and adjusted to ensure its adaptability under different antenna rotation speeds.

5. The method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes according to claim 1, characterized in that, The method described herein is designed to suppress the interference of a single, rotating offshore wind turbine on the echo signal of a shipborne navigation radar. It is also applicable to scenarios involving interference from multiple wind turbine echoes. This is because, in most cases, the rotational speeds of multiple wind turbines in the same wind field are usually quite similar, exhibiting similar periodic characteristics. The method's interference feature extraction and processing approach also achieves the same suppression effect for the different periodic characteristics of multiple wind turbines with different rotational speeds.

6. The method for suppressing the interference of offshore wind turbines on shipborne navigation radar echoes according to claim 1, characterized in that, In step S5, when further suppressing sea clutter or meteorological clutter in ΔS, the clutter suppression function of the current maritime radar can be used to suppress sea clutter or meteorological clutter, thereby further improving and achieving high-precision detection of maritime targets.

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