Wind Turbine Blade Pitch Control to Reduce Tower-Passage Deflection
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Solution Overview
Problem
Existing wind turbine control methods either increase blade stiffness to prevent collisions with the tower, leading to increased weight and potential breakage, or introduce rotor design changes that increase loads on the main shaft and drive train.
Innovation Solution
A method that involves measuring and estimating blade flap moments and rotor tilt moments to determine when to apply a pitch offset at specific azimuth angles, reducing blade deflection during tower passage without increasing wear on pitch bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wind turbine blades are designed with high stiffness to prevent collisions with the tower, then collision risk is reduced, but blade weight increases and the blades cannot deflect to avoid loads
Solution Approach 1:
The patent applies dynamic pitch angle adjustment during tower passage to control blade deflection in real-time. The pitch angle is modified based on the blade's azimuth position, allowing flexible blades to maintain safety clearance through active control rather than static stiffness design. This resolves the contradiction by enabling flexible blades (lower weight) to prevent collisions through dynamic adjustment.
Solution Approach 2:
The patent changes the pitch angle parameter cyclically during tower passage to control blade deflection. By adjusting the pitch angle in response to the blade's position relative to the tower, the system enables flexible blades to maintain safe clearance without requiring increased stiffness or weight.
2Reliability
If the rotor is designed with large coning angle, overhang, or tilt angle to prevent collisions, then collision risk is reduced, but loads on the main shaft and drive train increase
Solution Approach 1:
The patent uses dynamic pitch angle adjustment during tower passage rather than static rotor design modifications. This dynamic control approach prevents collisions through real-time blade positioning while maintaining the rotor's original design parameters, thereby avoiding increased loads on the main shaft and drive train.
3Reliability
If the pitch angle is adjusted cyclically to decrease blade deflection during tower passage, then collision risk is reduced, but wear on pitch bearings increases
Solution Approach 1:
The patent applies partial pitch angle adjustment only during the specific azimuth range corresponding to tower passage, rather than continuous cyclic adjustment. By limiting the pitch modification to the critical region where collision risk exists, the system prevents collisions while minimizing unnecessary pitch bearing wear during other operational phases.
Solution Approach 2:
The patent implements periodic pitch angle adjustment synchronized with the rotor's rotation, applying modifications only during tower passage azimuth angles. This periodic action maintains collision prevention while reducing overall bearing wear compared to continuous cyclic adjustment, as the pitch system remains idle during non-critical phases.
Data Source
AI summary
A method for controlling a wind turbine to decrease blade deflection during tower passage is disclosed. A blade flap moment of the wind turbine blades is measured. A blade flap moment of the wind turbine blades and a rotor tilt moment in a situation where the pitch offset has not been added are estimated, based on the measured blade flap moment. In the case that the estimated blade flap moment exceeds a first activation threshold value and the estimated rotor tilt moment exceeds a second activation threshold value, individual pitch angle adjustment of the wind turbine blades is initiated by adding a pitch offset, at azimuth angles within an azimuth adjustment region corresponding to tower passage of the wind turbine blades.