Wind Turbine Thrust Control with Doppler Lidar for Turbulent Loads
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Solution Overview
Problem
Modern wind turbines face high aerodynamic thrust and resulting structural loads, particularly in turbulent conditions, leading to reduced fatigue life and energy output inefficiencies due to the reliance on theoretical thrust limits without precise turbulence measurement.
Innovation Solution
Implementing a Doppler lidar system to actively measure wind turbulence upstream of the rotor, allowing for continuous calculation of wind speed variations and defining site-specific thrust limits using quantile-based regression to manage rotor thrust within defined turbulence ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If theoretical thrust limits are used without precise turbulence measurement, then the control system is simple, but structural loads are high and fatigue life is reduced
Solution Approach 1:
The Doppler lidar system performs preliminary measurement of wind turbulence conditions upstream of the rotor before the wind reaches the turbine. This advance measurement allows the control system to prepare appropriate thrust limits in advance, reducing structural loads before high-load conditions occur, rather than reacting after damage has already been incurred.
Solution Approach 2:
The patent replaces traditional mechanical turbulence measurement methods (such as physical anemometers that directly experience turbulent loads) with optical measurement using Doppler lidar. This non-contact optical system measures wind velocity fluctuations upstream without being subjected to the same mechanical stresses, providing more accurate turbulence data while reducing measurement system complexity.
2Strength
If thrust limits are reduced to accommodate turbulence, then structural loads are reduced, but energy production is negatively affected
Solution Approach 1:
The control system dynamically adjusts thrust limits based on real-time turbulence measurements rather than using fixed, conservative limits. When turbulence is low, higher thrust limits are permitted to maximize energy production. When turbulence increases, thrust limits are reduced to protect structural integrity. This dynamic adaptation resolves the contradiction by allowing the system to optimize for energy production when safe and protect structural safety when necessary.
Solution Approach 2:
The system changes the thrust limit parameter based on measured turbulence intensity. By continuously monitoring wind speed variations and adjusting the thrust limit parameter accordingly, the system optimizes the balance between structural safety and energy production. Higher thrust limits are applied when turbulence is low, and lower limits are applied when turbulence is high, maximizing productivity while maintaining strength.
3Device complexity
If fixed thrust limits are used, then the control strategy is simple, but it does not account for varying turbulence conditions
Solution Approach 1:
The control system implements feedback by continuously measuring wind turbulence with the Doppler lidar and using this information to adjust thrust limits. The measured wind speed variations are fed back to the control system, which automatically adapts the thrust limits to current turbulence conditions. This feedback loop provides adaptability to varying turbulence conditions while keeping the control strategy relatively simple through automated adjustment.
Solution Approach 2:
The control system is designed to handle multiple operating conditions universally through a single adaptive framework. The same control system uses turbulence measurements to adjust thrust limits across all wind speed ranges and turbulence conditions, rather than requiring separate control strategies for different scenarios. This multi-functionality provides adaptability while maintaining control strategy simplicity.
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
Enhances structural safety by reducing high loads while optimizing energy production, particularly in turbulent conditions, by dynamically adjusting thrust limits based on real-time turbulence measurements.
Implementation Method 1
a Doppler lidar system, to generate multiple fixed measurement beams upwind of the wind turbine to detect wind speed of an incoming wind flow
Data Source
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AI summary
A wind turbine and method are provided for defining a plurality of thrust limits for the wind turbine located at a site and having a rotor with rotor blades, wherein the thrust limits define values of aerodynamic thrust on the rotor not to be exceeded in operation. The method includes providing a wind speed distribution representative for the site and defining one or more isolines of constant turbulence probability representing a turbulence parameter as a function of wind speed. The isolines correspond to quantile levels of turbulence of the wind speed distribution and the turbulence parameter is indicative of wind speed variation. The turbulence parameter is determined by continuously measuring wind speed upstream of the rotor with an active sensing system and calculating the wind speed variations from the measured wind speed. Turbulence ranges are defined with respect to the isolines and thrust limits are defined for the turbulence ranges.