Wind Turbine Cyclic Pitch Control for Blade-Tower Clearance
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Solution Overview
Problem
The increase in blade length for wind turbines leads to flexibility issues, causing deflection towards the tower, which can result in collisions and energy loss due to non-optimal pitch angle adjustments, particularly in high wind regimes.
Innovation Solution
A cyclic pitch control method that adjusts blade pitch angles based on wind speed and azimuthal position to maintain optimal energy capture while preventing collisions, using a control term that varies with wind speed and azimuthal angle to minimize energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blade pitch angle is increased to prevent blade-tower collision, then the distance between blade tip and tower increases, but the annual power production decreases due to non-optimal aerodynamic positions
Solution Approach 1:
The patent applies periodic cyclic pitch control where the blade pitch angle is oscillated at the first harmonic frequency of blade rotation. This periodic action creates time-varying pitch angles that increase blade-tower separation during critical azimuth positions while maintaining optimal aerodynamic performance during power-generating positions, thus resolving the contradiction between collision prevention and power production
Solution Approach 2:
The invention transitions from static pitch control to dynamic pitch control by introducing time-varying pitch angles through cyclic modulation. The dynamic pitch control system adjusts blade pitch in real-time based on azimuth position and wind conditions, enabling optimal performance across different operational phases and resolving the trade-off between safety margins and aerodynamic efficiency
2Weight of moving object
If blades are made more flexible to reduce weight, then the weight and cost of components decrease, but blade deflection towards the tower increases causing collision risk
Solution Approach 1:
The patent applies preliminary anti-action by using active pitch control to counteract the natural deflection of flexible blades before collision can occur. The cyclic pitch control anticipates blade-tower proximity and preemptively adjusts pitch angles to increase separation, compensating for the increased flexibility and allowing lightweight blade design without compromising safety
3Weight of moving object
If the rotor shaft tilt angle is increased to separate blade tips from the tower, then blade flexibility and weight are improved, but the effective rotor surface area is reduced
Solution Approach 1:
The invention replaces the static geometric solution (fixed tilt angle) with a dynamic control solution (cyclic pitch adjustment). This allows the system to maintain maximum rotor surface area while actively managing blade-tower separation through real-time pitch control, eliminating the need to reduce effective area for safety margins
4Weight of moving object
If the hub coning angle is increased to prevent blade-tower impact, then blade flexibility is improved, but the area swept by the rotor is reduced
Solution Approach 1:
The patent uses preliminary anti-action through active pitch control to prevent blade-tower impact without requiring increased coning angle. The cyclic pitch modulation anticipates and counteracts blade deflection, maintaining full rotor swept area while preventing collision, thus resolving the contradiction between blade flexibility and rotor area
Data Source
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AI summary
Control method for a wind turbine which comprises the steps of obtaining a first signal regarding the azimuthal position (θ) for each blade, obtaining at least one signal indicative of wind speed (v), and calculating a blade pitch angle control term (Δβ). The step of calculating the blade pitch angle control term (Δβ) comprises the use of at least one function dependent on the at least one signal indicative of wind speed (v) and the at least one function dependent on the at least one signal indicative of wind speed (v) includes a rising trend within a range of wind speed values below a nominal wind speed (vnom).