Wind Turbine Rotor Blade Eigenmode Detection via Tower Clearance Sensors
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Solution Overview
Problem
Existing systems for determining the Eigenmode of a wind turbine rotor blade during operation are complex, difficult to maintain, and vulnerable to damage from lightning, making them unreliable for health monitoring and risk assessment.
Innovation Solution
A system using blade clearance sensors to measure the distance between the rotor blade and the tower, with a control unit that determines the Eigenmode by comparing sensor signals to predetermined sets of reference data, allowing for estimation of the blade clearance profile and identification of the corresponding Eigenmode, potentially using artificial intelligence, least squares methods, or spline functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic sensors are installed directly in the rotor blades for Eigenmode monitoring, then health monitoring capability is improved, but device complexity increases and reliability decreases due to vulnerability to lightning damage
Solution Approach 1:
The sensor system is extracted from the rotor blade structure and relocated to the tower. Blade clearance sensors measure the distance between the tower and rotor blade, obtaining Eigenmode information without requiring sensors to be installed inside the rotor blades. This eliminates the vulnerability to lightning damage while maintaining health monitoring capability.
Solution Approach 2:
The blade clearance serves as an intermediary measurement parameter. Instead of directly measuring blade properties with sensors in the blade, the system measures the clearance between tower and blade, then derives Eigenmode information from this indirect measurement. This intermediary approach improves reliability while simplifying the overall system.
2Ease of repair
If sensors are installed in the rotor blades for health monitoring, then Eigenmode information is obtained, but ease of repair deteriorates as damaged sensors cannot be easily replaced
Solution Approach 1:
The sensor system is extracted from the difficult-to-access rotor blade locations and relocated to the tower where sensors are easily accessible for maintenance and replacement. This dramatically improves serviceability while maintaining the ability to obtain Eigenmode information through blade clearance measurements.
3Measurement precision
If multiple blade clearance sensors are used to measure blade clearance profile, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The tower is divided into multiple sensor locations at different heights, with each sensor measuring clearance at its specific position. This segmentation approach improves measurement precision by capturing the blade clearance profile at multiple points, while the modular nature of adding sensors at discrete locations keeps system complexity manageable.
Data Source
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AI summary
There is described a system for determining an Eigenmode of a rotor blade of a wind turbine during operation, the wind turbine comprising a tower and at least one rotor blade. The system comprises (a) a plurality of blade clearance sensors, each blade clearance sensor being arranged and configured to provide a sensor signal indicative of a distance between the rotor blade and a corresponding predetermined position on the tower surface, and (b) a control unit coupled to receive the sensor signal from each of the blade clearance sensors and configured to determine the Eigenmode of the rotor blade based on the sensor signals and a plurality of predetermined sets of reference data, each predetermined set of reference data being representative of one corresponding Eigenmode. Furthermore, a wind turbine comprising such a system and a corresponding method are described.