Wind Turbine Rotor Blade Extreme Load Envelope Control
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Solution Overview
Problem
Existing wind turbines face challenges in effectively controlling extreme loads on rotor blades due to fluctuating environmental conditions, which can lead to component damage and failure, and current sensor systems are complex, expensive, and prone to inaccuracies.
Innovation Solution
A method and system utilizing a processor to calculate flapwise and edgewise bending moments, along with an average and overall load envelope, to implement control actions when loads exceed a threshold, including pitching the rotor blades, through an envelope-based control algorithm that filters unwanted frequencies and predicts future loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensor systems are used to measure loads on wind turbine components, then measurement accuracy may be improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent uses a computational model (copy) of the load calculation based on thrust measurements and aerodynamic relationships, rather than directly installing complex sensor systems on the blade roots. The model replicates the load measurement function using existing sensors and mathematical relationships, thereby avoiding the complexity and cost of direct measurement sensors while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical sensor system (strain gauges, load cells) with a computational approach using aerodynamic models and thrust measurements. The mechanical measurement system is substituted with an information-processing system that calculates loads from readily available operational parameters, reducing device complexity while providing load information
2Reliability
If more sensors are installed to improve load measurement reliability, then measurement accuracy improves, but device complexity and failure risk increase
Solution Approach 1:
The patent makes the existing thrust measurement system serve multiple functions: it provides both the primary control feedback for pitch regulation and the basis for calculating blade root loads. This multi-functionality eliminates the need for separate dedicated load sensors, maintaining reliability while reducing system complexity and the number of potential failure points
Solution Approach 2:
The control system uses its own existing measurements (thrust, pitch angle, power output) to calculate loads autonomously without requiring external sensor systems. The system serves its own measurement needs by processing data already collected for control purposes, thereby improving reliability without adding vulnerable external components
3Reliability
If control actions are taken to reduce extreme loads on rotor blades, then component reliability improves, but energy production may be reduced
Solution Approach 1:
The patent calculates and predicts future load envelopes in advance, allowing the control system to prepare for upcoming extreme loads before they occur. By using look-ahead prediction based on wind speed forecasts and aerodynamic models, the system can proactively adjust pitch angles to prevent load exceedances rather than reacting after damage occurs, thereby maintaining reliability while minimizing production losses
Solution Approach 2:
The control system dynamically adjusts pitch angles based on real-time thrust measurements and predicted load envelopes, rather than using fixed conservative limits. This dynamic control allows the system to operate at optimal pitch angles during normal conditions (maximizing energy production) and automatically reduce loads only when and where extreme conditions are predicted, thereby balancing productivity and reliability
4Device complexity
If thrust-based control strategies are used to estimate loads, then device complexity is reduced, but measurement precision and reliability may be compromised
Solution Approach 1:
The patent implements a feedback mechanism where the calculated load estimates are continuously compared against predicted load envelopes, and the pitch control is adjusted based on the difference. This closed-loop feedback ensures that even though the load estimation uses simplified thrust-based calculations rather than direct measurements, the control system compensates by actively regulating pitch to maintain loads within acceptable limits, thereby achieving both simplicity and accuracy
Data Source
AI summary
A method for reducing extreme loads acting on at least one rotor blade of a wind turbine includes calculating, via a processor, a flapwise bending moment of the rotor blade(s). Further, the method includes calculating, via the processor, an edgewise bending moment of the rotor blade(s). The method also includes calculating, via the processor, an average load envelope of a blade root bending moment of the rotor blade(s) as a function of the flapwise bending moment and the edgewise bending moment of the rotor blade(s). Moreover, the method includes calculating, via the processor, an overall load envelope of the blade root bending moment of the rotor blade(s) as a function of the average load envelope and a future load estimation of the blade root bending moment of the rotor blade(s). As such, the method also includes implementing, via the processor, a control action when the overall load envelope is above a certain threshold.