Sliding Mode Extremum Seeking Control for Wind Turbine Torque Fatigue
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Solution Overview
Problem
Existing maximum wind energy tracking methods for wind turbine generators face challenges such as mechanical fatigue due to rapid torque changes, require accurate wind speed measurements, and increase system complexity and cost, especially in turbulent wind fields.
Innovation Solution
A sliding mode extremum seeking-based control method that uses closed-loop feedback mechanisms to adjust rotating speed and control mechanical torque without real-time wind speed measurement, stabilizing torque variations and reducing mechanical load by employing sign functions, WCES images, and PI proportional differential steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mechanical torque changes fast to keep the optimal tip speed ratio in turbulent wind field, then the maximum wind energy tracking is improved, but the mechanical load increases and vibration is enhanced, increasing the risk of fatigue damage
Solution Approach 1:
The patent implements dynamic control of the mechanical torque by using a sliding mode extremum seeking algorithm that continuously adapts the torque changes based on real-time wind conditions. The control method dynamically adjusts the tip speed ratio reference value and mechanical torque according to wind speed variations, enabling the system to respond to turbulent wind fields while limiting excessive torque fluctuations. This dynamic approach allows the system to track maximum wind energy without subjecting the mechanical structure to excessive loads and vibrations.
2Device complexity
If the optimal tip speed ratio method is used to perform maximum wind energy tracking, then the control structure is simple and easy to implement, but real-time accurate wind speed measurement is required which is hard to realize in the actual wind field
Solution Approach 1:
The patent employs a feedback-based extremum seeking control mechanism that uses the measured output power and rotating speed to infer wind conditions and adjust the tip speed ratio reference value. Instead of directly measuring wind speed, the system uses power feedback from the generator and rotating speed measurements to create a closed-loop control system that automatically adjusts operating parameters to maximize power extraction. This feedback approach eliminates the need for complex wind speed sensors while maintaining simple control structure.
3Difficulty of detecting and measuring
If the hill climbing method is used to avoid wind speed measurement, then the control is simplified, but gradient sensors make louder noise and are unstable at high frequency, and the time for measuring and judging affects the accuracy of algorithm
Solution Approach 1:
The patent replaces the mechanical gradient sensing approach with an extremum seeking control algorithm that uses electrical measurements (power and rotating speed) to determine the optimal operating point. Instead of using gradient sensors that are prone to noise and instability, the system uses a computational algorithm that processes electrical signals to infer the direction toward maximum power extraction. This substitution of mechanical sensing with electrical measurement and computational processing improves reliability while eliminating the noise and stability issues of gradient sensors.
4Reliability
If the power feedback method is used to control electromagnetic torque, then the output power fluctuation is avoided and wind speed detection is not required, but simulation and experiment are required to obtain the power-wind speed curve with different curves for different wind wheels
Solution Approach 1:
The patent implements a self-adaptive control system that automatically generates the appropriate power-wind speed characteristics through real-time extremum seeking optimization. Instead of requiring pre-established power curves for different wind conditions, the system uses the extremum seeking algorithm to continuously identify and track the optimal operating point based on actual system response. The control method adapts to different wind wheel characteristics and wind conditions automatically through on-line optimization, eliminating the need for extensive simulation and experimentation to create lookup tables or control maps.
Data Source
AI summary
The present invention discloses an extremum seeking-based control method for maximum output tracking of a wind turbine generator, mainly comprising three steps of first closed-loop feedback, second closed-loop feedback, and third closed-loop feedback. The method for resisting mechanical fatigue of a double-fed variable speed constant frequency wind turbine generator by controlling mechanical torque while capturing maximum wind energy provided in the present invention is applied to a double-fed variable speed constant frequency wind turbine system by improving the control based on sliding mode extremum seeking with the following effects that, with regard to the maximum wind energy tracking effect, the rotating speed can be quickly adjusted to keep the tip speed ratio λ as its optimum value after the wind speed changes, so that the wind energy utilization coefficient is restored to the maximum value.