Wind Turbine Speed and Pitch Control Under Rotor Thrust Limits
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Solution Overview
Problem
Wind turbines in partial load situations face challenges in reducing rotor thrust while maintaining optimal power production, particularly when operating in close proximity to other turbines, leading to increased turbulence and reduced efficiency.
Innovation Solution
A method for controlling wind turbine operation using variable rotor speed and adjustable pitch angles, incorporating a curtailment speed control and pitch angle to manage rotor thrust, allowing for optimized power generation even in reduced thrust conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the rotor thrust is reduced by pitching rotor blades out of the wind, then the turbulence produced by the rotor is reduced, but the rotor speed is reduced according to the rotor speed curve leading to a non-optimal tip speed ratio
Solution Approach 1:
The patent changes the operational parameters by using a different rotor speed curve specifically designed for curtailment mode. Instead of following the normal rotor speed curve that would result in non-optimal tip speed ratios, the system transitions to an alternative rotor speed curve that maintains optimal tip speed ratio even when rotor thrust is reduced through blade pitching. This parameter change allows the wind turbine to operate efficiently under curtailment conditions.
2Reliability
If the rotor thrust is reduced to protect downstream wind turbines, then the stress on downstream rotors is reduced, but less power is produced than could be possible even with reduced rotor thrust
Solution Approach 1:
The patent implements a dynamic control system that automatically switches between normal operation mode and curtailment mode based on real-time conditions. When downstream turbines are affected by turbulence, the system dynamically transitions to curtailment mode using the alternative rotor speed curve, and can switch back when conditions improve. This dynamic adaptation ensures optimal power production is maintained whenever possible while providing protection when needed.
3Device complexity
If a single rotor speed curve is used for all operating conditions, then the control system is simple, but the tip speed ratio is not optimal when rotor thrust needs to be limited
Solution Approach 1:
The patent segments the operational characteristics by creating distinct rotor speed curves for different operating modes. Instead of using a single universal rotor speed curve, the system divides operation into normal mode and curtailment mode, each with its own optimized rotor speed curve. The control system selects the appropriate curve based on operational requirements, providing optimal performance for each specific condition while maintaining manageable system complexity through clear segmentation.
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
The method stabilizes rotor speed and maximizes electrical power production by adjusting generator torque and pitch angles, reducing rotor thrust and turbulence, and enhancing overall wind farm efficiency.
Implementation Method 1
The wind causes a rotor thrust acting on the rotor depending on the rotor speed and depending on the pitch angle
Implementation Method 2
the wind turbine produces electrical power from wind
Data Source
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AI summary
The invention relates to a method for operating a wind turbine (100), the wind turbine (100) comprising a rotor (106) operable with variable rotor speed, and the rotor (106) having rotor blades (108) with adjustable pitch angles, wherein the wind turbine (100) produces electrical power from wind, the wind causes a rotor thrust acting on the rotor (106) depending on the rotor speed (n) and depending on the pitch angle (α), in a partial load situation, when the wind is below rated wind speed (VWN), the wind turbine (100) is controlled by means of a speed control for controlling the rotor speed (n) depending on a given pitch angle (α), wherein in a normal operational mode when the operation of the wind turbine (100) is not in a curtailment mode, a normal speed control is used controlling the rotor speed (n) in combination with an optimal pitch angle (α), and in a curtailment mode when the rotor thrust is to be limited, a curtailment speed control, different to the normal speed control, in combination with a curtailment pitch angle, different to the optimal pitch angle, is used in order to reduce the rotor thrust.