Wind Turbine Rotor Blade Control for Edgewise Vibration Avoidance
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Solution Overview
Problem
Wind turbines experience oscillations in rotor blades due to edgewise vibrations, which can lead to damage and resonate with structural frequencies, especially when the vibration frequency matches the rotational frequency, posing a challenge in maintaining reliable operation without significantly increasing manufacturing costs through reinforcement with carbon fibers.
Innovation Solution
A method to control wind turbine rotor blades by determining the whirling mode frequency and adjusting the rotational speed to create a divergence between this frequency and the rotational frequency, thereby preventing resonant conditions that cause excessive edgewise vibrations, using sensors to measure wind conditions and blade dynamics for accurate threshold determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor blade structure is strengthened and stiffened with carbon fibres to modify structural frequencies, then the resonant edgewise vibrations are avoided, but the manufacturing cost significantly increases
Solution Approach 1:
The patent changes the operational parameters (rotational speed) of the wind turbine to avoid resonant conditions. By dynamically adjusting the rotational speed to keep it away from the blade's natural frequency, the system avoids resonant edgewise vibrations without requiring structural modifications or carbon fiber reinforcement, thus resolving the contradiction between reliability and manufacturing cost.
2Reliability
If the speed of the rotor blade is reduced to create frequency divergence, then resonant conditions are avoided, but the power output decreases
Solution Approach 1:
The patent implements dynamic speed adjustment rather than a fixed speed reduction. The control system continuously monitors the rotational speed and blade frequency characteristics, adjusting the speed dynamically to maintain frequency divergence only when necessary to avoid resonance. This allows the turbine to operate at optimal speeds most of the time, minimizing impact on power output while ensuring reliability when resonant conditions are detected.
Solution Approach 2:
The system uses feedback control by monitoring the rotational speed and comparing it with the blade's natural frequency characteristics. When the rotational frequency approaches the natural frequency, the control system provides feedback to reduce speed, creating frequency divergence. This feedback mechanism ensures that speed reduction occurs only when necessary to avoid resonance, thereby minimizing the impact on overall power output while maintaining reliability.
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 approach effectively reduces the likelihood of resonant conditions and subsequent damage by ensuring the whirling mode frequency exceeds the threshold, maintaining operational reliability without the need for costly structural reinforcement, and can be applied in both full and partial load operation modes.
Implementation Method 1
the frequency of the oscillations coincides with resonant frequencies of the wind turbine components
Implementation Method 2
Edgewise vibrations at certain amplitudes can cause damage to the blades
Data Source
AI summary
A method of controlling a wind turbine for the avoidance of edgewise vibrations. The method comprises the steps of determining a whirling mode frequency of a rotor blade of the wind turbine; determining a rotational frequency of the rotor blade corresponding to the speed of the rotor blade; determining a threshold value for the whirling mode frequency based on the rotational frequency; and, reducing the speed of the rotor blade if the whirling mode frequency substantially equals or is less than the threshold value.