Wind Turbine Speed Estimation Using Iterative Tip Speed Ratio
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Solution Overview
Problem
Existing methods for estimating wind speed at wind turbines are often inaccurate due to measurement points being behind the rotor, not reflecting wind speed in front of it, and failing to account for variations across the rotor area, leading to unstable control.
Innovation Solution
A method that involves obtaining the rotational speed and pitch angle of wind turbine blades, deriving a minimum tip speed ratio to define stable and unstable control regions, selecting an initial tip speed ratio above the minimum, and iteratively estimating wind speed using an initial estimate as a starting point to ensure stable and reliable estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wind speed is measured at a point behind the rotor, then the measurement is simple and direct, but the measured wind speed is affected by the rotor impact and does not reflect the wind speed in front of the rotor
Solution Approach 1:
The method performs preliminary estimation of wind speed using rotor speed and pitch angle data before the wind actually strikes the rotor. By calculating the tip speed ratio and using iterative estimation based on aerodynamic relationships, the system predicts the upstream wind conditions that will affect the rotor, rather than measuring after the wind has been disturbed.
Solution Approach 2:
The patent uses rotor speed and pitch angle as intermediary parameters to indirectly estimate the upstream wind speed. Instead of directly measuring the difficult-to-access upstream wind, the system measures easily obtainable rotor performance parameters and uses these as mediators to infer the upstream wind conditions through established aerodynamic relationships.
2Measurement precision
If wind speed is measured in a single point, then the measurement is simple, but it does not reflect variations in wind speed across the rotor area
Solution Approach 1:
The wind turbine's own operational parameters (rotor speed and pitch angle) serve the dual purpose of controlling the turbine and estimating the wind conditions. The system uses the turbine's self-generated data to infer upstream wind speed, eliminating the need for separate complex measurement systems while utilizing information already available from normal operation.
3Reliability
If iterative estimation is performed without proper initialization, then the estimation can adapt to changing conditions, but the estimation may become unstable and fail to converge
Solution Approach 1:
The patent performs preliminary determination of the minimum tip speed ratio before initiating the iterative estimation process. This preliminary calculation establishes a stable starting point and convergence criterion for the iteration, ensuring that the estimation process begins from a known stable state rather than attempting convergence from arbitrary initial conditions.
Solution Approach 2:
The iterative estimation process continuously compares the estimated wind speed with the measured rotor speed and pitch angle, using this feedback to adjust and refine the estimate. The feedback loop ensures that the estimation converges to a value consistent with the actual turbine performance, maintaining stability while adapting to changing wind conditions.
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 method provides a fast and reliable estimation of wind speed experienced by the wind turbine blades, ensuring accurate control even in unstable conditions like stalling or icing, by maintaining convergence within a stable control region.
Implementation Method 1
The wind turbine blades catch the wind, thereby causing the rotor to rotate, i.e. the energy of the wind is transformed into mechanical energy
Data Source
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AI summary
A method for iteratively estimating a wind speed at a wind turbine is disclosed, said wind turbine comprising a rotor carrying a set of wind turbine blades, each wind turbine blade having a variable pitch angle. A minimum tip speed ratio, λmin, is derived, based on an obtained pitch angle, θ. The minimum tip speed ratio, λmin, defines a limit between a stable and an unstable control region. An initial tip speed ratio, λinit> λmin, is selected, and an initial estimated wind speed, vinit, is derived based on the initial tip speed ratio, λint, and an obtained rotational speed, ω, of the rotor. An estimated wind speed, vest, is iteratively derived, based on the obtained rotational speed, ω, and the obtained pitch angle,ω, and using the derived initial estimated wind speed, vinit, as a starting point. The iterative process converges fast and reliably.