Wind Turbine Blade Pitch Control for Tower Oscillation Damping
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Solution Overview
Problem
Wind turbine towers experience oscillations due to cyclic rotor forces and inhomogeneous wind fields, leading to wear and tear on the pitch system when using blade pitch adjustments for damping.
Innovation Solution
A method involving individually adjustable rotor blades with precursor signals containing periodic components at frequencies corresponding to the difference and sum of tower and rotor frequencies, generating tower damping pitch control signals to reduce the amplitude of the second frequency component, thereby minimizing pitching activity and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If blade pitch adjustments are used to damp tower oscillations, then the tower oscillation is damped, but wear and tear of the pitch system increases
Solution Approach 1:
The patent applies periodic pitch adjustments with specific frequencies (difference frequency and sum frequency between tower oscillation and rotor rotation) to damp tower oscillations. By using periodic action at optimized frequencies, the damping effect is achieved while minimizing the amplitude and duration of pitch movements, thereby reducing wear on pitch bearings and other components.
Solution Approach 2:
The patent changes the parameters of the pitch control signal by introducing two specific frequency components: the difference frequency (|ftow - f1P|) and the sum frequency (ftow + f1P). These parameter changes in frequency domain allow the system to achieve effective damping while controlling the magnitude of pitch actuations, thus reducing mechanical wear.
2Stability of the object's composition
If blade pitch adjustments are used to damp tower oscillations, then the tower oscillation is damped, but energy consumption increases
Solution Approach 1:
By using periodic pitch adjustments at specifically chosen frequencies (difference and sum frequencies), the system achieves damping with minimized energy input. The periodic nature allows the aerodynamic forces to work in conjunction with the pitch movements, reducing the total energy required compared to continuous or non-optimized periodic pitching.
Solution Approach 2:
The introduction of difference frequency and sum frequency components changes the temporal parameters of the pitch signal. This frequency-domain parameter optimization ensures that pitch actuations occur at moments when they are most effective, reducing unnecessary energy consumption while maintaining damping performance.
3Stability of the object's composition
If pitching activity is increased to improve damping, then tower oscillation damping improves, but wear and tear of blade bearings increases
Solution Approach 1:
The periodic pitch adjustments with optimized frequencies create a rhythm of actuation that achieves damping with minimal total movement. By spacing the pitch changes periodically at optimal intervals (determined by the frequency relationship), the system avoids continuous high-amplitude pitching that would rapidly degrade blade bearings.
Solution Approach 2:
Changing the frequency parameters to include difference and sum frequencies optimizes the timing and magnitude of pitch actuations. This parameter optimization ensures that each pitch movement is necessary and effective, minimizing redundant movements that would contribute to bearing wear while extending component service life.
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
This approach reduces the required pitching activity and wear on the pitch system by optimizing the amplitude of the tower damping pitch control signals, effectively damping tower oscillations with reduced energy consumption and increased system longevity.
Implementation Method 1
pitching the blades individually so that the resultant drag and aerodynamic forces act to dampen the oscillation of the tower
Data Source
AI summary
A method for damping an oscillation of a tower of a wind turbine is disclosed, wherein a pitch angle of each of the one or more rotor blades is individually adjustable, the method comprising damping the oscillation of the tower by pitching each rotor blade individually according to tower damping pitch control signals, wherein each tower damping pitch control signal comprises a first periodic component, where a first frequency of the first periodic component corresponds to a frequency difference between a tower frequency of the oscillation of the tower and a rotor frequency of a rotation of the rotor, and where a second periodic component has been reduced or removed. A second frequency of the second periodic component corresponds to a frequency sum of the tower frequency and the rotor frequency.