Wind Turbine Cable Pitch Control for Lightweight Rotors
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Solution Overview
Problem
Small to medium-sized structurally optimized wind turbines face challenges in implementing effective pitch control systems due to mechanical complexity and instability, particularly when transferring blade loads through tethers to the tower, leading to issues like deviating pitch angles and flutter behavior.
Innovation Solution
A coordinated movement system using first and second displaceable pitch control cables, attached to blades at a substantial distance from the hub, and controlled by pitch control members on the main boom, achieves simple and optimized pitch control without the need for complex electric connections or additional mass on the blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual blade pitch control servos are installed on each blade, then pitch control precision is improved, but device complexity and mass on blades increase
Solution Approach 1:
The patent merges the pitch control function from individual blade-mounted servos to a centralized hub-mounted servo that controls all blades simultaneously through a common pitch control cable system. This eliminates the need for multiple separate servos on each blade, reducing overall system complexity while maintaining pitch control capability.
Solution Approach 2:
The single pitch control cable serves multiple blades simultaneously, making the control system universal rather than individual-specific. The hub-mounted servo controls the pitch of all blades through the shared cable system, achieving multi-functionality with reduced component count.
2Device complexity
If pitch control cables are attached close to the hub, then mechanical simplicity is improved, but pitch control effectiveness deteriorates
Solution Approach 1:
The patent transitions from attaching pitch control cables at the hub (radial dimension) to attaching them at the blade tip (longitudinal dimension). This dimensional change allows the cables to effectively control blade pitch while maintaining mechanical simplicity through the hub-mounted servo design.
3Weight of moving object
If the rotor inner part is made lightweight, then weight is reduced, but torsional stiffness deteriorates causing pitch angle deviations
Solution Approach 1:
The patent introduces a blade torsion beam as an intermediary element between the blade root and the pitch control cable attachment point at the blade tip. This torsion beam provides the necessary torsional stiffness to maintain accurate pitch angles while allowing the overall rotor structure to remain lightweight.
Data Source
AI summary
The wind turbine (1) includes a tower (2) supporting a main boom (3) carrying a rotor (4) of the axial flow type having a main rotation axis and including a hub (5) carrying a number of blades (6) being supported by blade lines (7, 8). A pitch angle of each blade about its pitch axis is controllable by coordinated movement of a set of at least a first displace-able pitch control cable (10) and a second displaceable pitch control cable (11) acting on said blade. Each pitch control cable has a blade end (12) being attached to the respective blade at a longitudinal position more than ⅓ of the total blade length away from the main rotation axis and has a boom end (13) being attached to a pitch control mem-ber (14) arranged rotatably on the main boom and being adapted to displace the pitch control cable.