Wind Turbine Blade Tip Clearance Control Using Strain Feedback
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Solution Overview
Problem
Existing methods for determining rotor blade tip to tower clearance in wind turbines are unreliable, require complex measurement systems, and increase pitch bearing load, leading to increased costs and potential collisions.
Innovation Solution
A method and arrangement that estimate and correct the distance between a rotor blade tip and a wind turbine tower using strain measurements, combining estimated and measured distances to improve accuracy and reliability, and adjust blade pitch angles to maintain safe clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blade is stiffened by introducing carbon into the blade beams, then the blade tip to tower clearance is improved, but the manufacturing cost and complexity increase
Solution Approach 1:
The patent replaces the mechanical approach of stiffening blades with carbon materials with a control-based solution. A controller receives signals from strain sensors measuring blade root strain, calculates blade deflection using a Coleman transformation, and actuates pitch actuators to adjust blade pitch angles. This substitutes mechanical reinforcement with active control to maintain blade tip to tower clearance.
Solution Approach 2:
The patent changes the operational parameters of the blade by adjusting the pitch angle dynamically. Instead of modifying the physical stiffness of the blade, the system varies the pitch angle parameter in response to measured strain and calculated deflection, thereby controlling the blade tip position relative to the tower while maintaining the original blade structure.
2Productivity
If the tower diameter is increased, then the wind turbine can capture more wind, but the blade tip to tower clearance is reduced
Solution Approach 1:
The patent introduces dynamic adjustment of blade pitch angles based on real-time strain measurements and calculated deflection. The system continuously monitors blade root strain, computes blade deflection, and adjusts pitch angles to maintain safe clearance from the tower, allowing the tower diameter to be optimized for wind capture without compromising blade safety.
Solution Approach 2:
The patent implements a feedback control system where strain sensors continuously measure blade root strain, the controller calculates blade deflection using a Coleman transformation, and pitch actuators adjust blade pitch angles in response to the calculated deflection. This closed-loop feedback enables dynamic maintenance of blade tip to tower clearance regardless of tower diameter.
3Reliability
If additional pitching is applied to increase clearance, then the blade tip to tower clearance is improved, but the pitch bearing load increases
Solution Approach 1:
The patent applies partial pitching action only when and where needed. The controller calculates blade deflection from strain measurements and actuates pitch actuators only when the blade approaches the tower clearance limit, rather than continuously pitching. This partial action reduces unnecessary pitch bearing load while maintaining adequate clearance.
Solution Approach 2:
The system uses the blade's own strain sensors and structural properties to self-diagnose its deflection state and automatically adjust its pitch angle accordingly. The blade essentially controls its own clearance through the feedback loop, reducing the need for excessive external pitching intervention and thereby reducing pitch bearing load.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the reliability and accuracy of rotor blade tip to tower clearance determination, reducing the complexity of measurement systems and pitch bearing load, while allowing for a more flexible and cost-effective blade design.
Implementation Method 1
estimating the distance based on a strain measurement
Implementation Method 2
estimate the blade deflection in front of the tower using a Coleman transformation
Data Source
AI summary
A method of determining a distance between a rotor blade tip and a tower of a wind turbine includes: estimating the distance based on a strain measurement; measuring the distance; correcting an estimation procedure based on the estimated distance and the measured distance; and deriving a corrected distance based on the corrected estimation procedure.