Floating Wind Turbine Control for Multi-Frequency Motion Damping
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Solution Overview
Problem
Floating wind turbines experience complex oscillations due to rigid body motions, leading to negative damping and excessive structural stresses, which existing control systems fail to effectively address.
Innovation Solution
A controller with separate control loops for different frequency ranges, using low pass filters tailored to dampen both high-frequency pitch motions and low-frequency surge motions, reducing loads on the turbine structure and mooring system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single control loop is used for blade pitch control, then the control system is simple, but it cannot effectively dampen both high-frequency pitch motions and low-frequency surge motions simultaneously
Solution Approach 1:
The control system is segmented into multiple independent control loops, each targeting specific frequency ranges. A first control loop handles high-frequency pitch motions while a second control loop addresses low-frequency surge motions. This segmentation allows each loop to be optimized for its specific frequency range, effectively resolving the contradiction between system simplicity and damping effectiveness.
2Power
If blade pitch is increased to reduce thrust above rated wind speed, then power output is controlled, but negative damping occurs and structural stresses increase
Solution Approach 1:
The control system dynamically adjusts blade pitch based on real-time motion characteristics and frequency content. Rather than using static pitch increases for power control, the system actively modulates pitch in response to measured motions, applying damping forces that are adaptive to current operating conditions. This dynamic approach maintains power control while preventing negative damping effects.
Solution Approach 2:
The system implements feedback control by continuously measuring turbine motions, analyzing their frequency content, and adjusting blade pitch accordingly. The control loops use feedback from motion sensors to generate corrective pitch commands that actively dampen oscillations. This closed-loop feedback mechanism ensures power control is achieved without inducing harmful negative damping or excessive structural stresses.
3Power
If conventional pitch control is used for power regulation, then power output is maintained, but low-frequency rigid body motions are exacerbated
Solution Approach 1:
The control architecture segments power control functions from motion damping functions. The first control loop specifically targets low-frequency surge motions with appropriate pitch adjustments, while maintaining overall power output through coordinated control. This segmentation allows independent optimization of power regulation and motion stability, resolving the contradiction between maintaining power and stabilizing rigid body motions.
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
Effectively damps multiple frequency oscillations, enhancing structural stability and extending mooring system lifetime while maintaining power output efficiency.
Implementation Method 1
A second low pass filter frequency for the second control loop is set lower than a first low pass filter frequency for the first control loop
Implementation Method 2
calculating one or more outputs for damping both a first motion of the floating wind turbine in a first frequency range and a second motion of the floating wind turbine in a second frequency range
Data Source
Figure 1~2
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AI summary
A controller for a floating wind turbine comprising a rotor with a plurality of rotor blades connected to a generator is provided. The controller comprises: an active damping controller for calculating one or more outputs for damping both a first motion of the floating wind turbine in a first frequency range and a second motion of the floating wind turbine in a second frequency range based on an input of the first motion and an input of the second motion; wherein the controller is arranged to calculate an output for controlling a blade pitch of one or more of the plurality of rotor blades and/or for controlling a torque of the generator based on an actual rotor speed, a target rotor speed, and the one or more outputs from the active damping controller such that both the first motion and the second motion will be damped. A method of controlling a floating wind turbine is also provided.