Wind Turbine Rotor Speed Control for Gust Load Reduction
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Solution Overview
Problem
Existing wind turbine control methods fail to effectively manage short-term wind speed variations, leading to increased loads on the tower and reduced energy production due to oscillating rotor speeds and generator torque fluctuations.
Innovation Solution
A control method that adjusts the pitch angle and generator torque based on actual rotor speed deviations, using a main control for general power setting and an additional control to counteract fluctuations, ensuring the generator torque remains constant and reducing oscillatory loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If generator torque is adjusted to compensate for rotor speed changes during wind gusts, then output power can be kept constant, but rotor speed fluctuations increase leading to increased tower loads
Solution Approach 1:
The control system anticipates rotor speed changes by monitoring deviations from the reference rotor speed before they fully manifest. By applying torque adjustments in advance based on predicted speed deviations, the system cushions against the full impact of wind gusts, reducing the amplitude of rotor speed fluctuations and consequently decreasing oscillating tower loads while maintaining power output.
2Power
If pitch angle is adjusted frequently to maintain rated power during wind speed variations, then power output is stabilized, but mechanical stress on rotor blades increases
Solution Approach 1:
The control system continuously monitors actual rotor speed and compares it with the reference rotor speed, using this feedback to determine appropriate torque adjustments. This closed-loop feedback mechanism enables precise, minimal adjustments to generator torque that stabilize power output without requiring frequent pitch angle changes, thereby reducing mechanical stress on rotor blades while maintaining rated power output.
3Strength
If rotor speed is allowed to vary freely during wind gusts, then mechanical stress is reduced, but energy production decreases
Solution Approach 1:
The control system dynamically adjusts generator torque based on real-time rotor speed deviations from the reference value. By continuously adapting the torque setting to current wind conditions and rotor performance, the system optimizes the balance between maintaining rated power output for maximum energy production and allowing sufficient rotor speed variation to reduce mechanical stress, achieving both objectives simultaneously.
Data Source
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AI summary
Method for controlling a rotor speed of a rotor (106) of a wind turbine (100) at rated or curtailed operation conditions the rotor being an aerodynamic rotor having one or a plurality of rotor blades (108), and the wind turbine further having a tower and a generator wherein a pitch control (504) provides a pitch angle set value (α̇s) depending on an actual rotor speed (n) for setting a pitch angle of the rotor blades, a main control (506) provides a main power or torque set value (Ps) for controlling the power or torque of the generator, and an additional control (508) provides an additional power or torque set value (ΔP) depending on the actual rotor speed (ni) , wherein the additional power or torque set value (ΔP) is provided as an offset value and is added to the main power or torque set value (Ps) respectively, wherein the additional power or torque set value (Ps) is calculated depending on a control deviation (Δn) of the rotor speed, and optionally, in combination with the additional control, or instead of it, a maximum power control (540) provides a maximum power value (Pm) as a varying value for limiting an output power of the generator and the maximum power value (Pm) is calculated depending on a predetermined power limit value (PL) , and depending on a predetermined reference duration (T), in order to provide for the reference duration (T) an average power (Pa) reaching or at least not exceeding the predetermined power limit value.