Wind Turbine Rotor Speed Control via Generator Torque
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Solution Overview
Problem
As wind turbines increase in size, the pitch drive system faces challenges with increased friction, gear backlash, and parasitic power losses, making it difficult to accurately control rotor blade pitch and potentially damaging components due to higher torque and cooling requirements.
Innovation Solution
A method that controls rotor speed by adjusting generator torque and alternating between changing and maintaining the pitch angle of rotor blades, reducing the need for frequent pitch adjustments and minimizing wear on pitch system components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If rotor blade length increases to increase electrical power output, then power output is improved, but friction within the pitch drive system increases and manufacturing precision deteriorates
Solution Approach 1:
The patent replaces continuous mechanical pitch adjustments with a hybrid control system that uses generator torque control for primary speed regulation and only makes discrete pitch adjustments when necessary. This substitution reduces the reliance on the mechanical pitch drive system, thereby reducing the impact of friction and gear backlash on control accuracy for larger rotor blades.
Solution Approach 2:
The patent changes the control parameter from continuous pitch angle adjustment to alternating between torque control and discrete pitch adjustments. By modifying how the system controls rotor speed (switching between torque-based and pitch-based control), it reduces the frequency and magnitude of pitch drive system operations, thereby mitigating the effects of increased friction and backlash in larger turbines.
2Manufacturing precision
If pitch drive system performs more pitching operations to accurately control rotor blade pitch, then control accuracy is improved, but parasitic power losses increase and reliability deteriorates
Solution Approach 1:
The patent implements periodic action by alternating between two control modes: generator torque control and discrete pitch adjustments. Instead of continuous pitch adjustments, the system switches between torque-based control (which has no parasitic losses from pitch mechanics) and occasional pitch adjustments, thereby reducing overall parasitic power losses while maintaining control accuracy.
Solution Approach 2:
The patent extracts the speed control function from the pitch drive system and relocates it to the generator torque control system. By separating the speed control function from the pitch mechanism, the system reduces the burden on the pitch drive system, thereby reducing parasitic power losses and improving reliability while maintaining the ability to make precise pitch adjustments when needed.
3Force
If pitch drive motor increases torque to pitch larger rotor blades, then control capability is improved, but device complexity increases and reliability deteriorates
Solution Approach 1:
The patent replaces high-torque mechanical pitch operations with electrical torque control of the generator. By using generator torque to control rotor speed and reduce aerodynamic torque, the system decreases the torque requirements for the pitch drive motor, thereby reducing mechanical stress and improving the reliability of the pitch drive system for larger rotor blades.
4Speed
If rotor speed is controlled by pitching rotor blades, then speed control is achieved, but tower oscillations increase and harmful factors increase
Solution Approach 1:
The patent replaces pitch-based speed control with generator torque-based speed control. By controlling rotor speed through electrical torque rather than mechanical pitch adjustments, the system reduces the frequency and magnitude of pitch movements, thereby reducing the aerodynamic thrust variations that cause tower oscillations and other harmful effects.
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 reduces parasitic power losses, minimizes wear on pitch system components, and decreases the interaction between blade pitch movements and rotor thrust-induced tower oscillations, enhancing the efficiency and reliability of wind turbine operation.
Implementation Method 1
controlling a torque of the generator rotor shaft to thereby control a torque of the rotor shaft
Implementation Method 2
rotor blades extending radially outwardly from hub for converting wind energy into rotational energy
Data Source
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AI summary
A method for controlling a rotational speed of a rotor having at least one rotor blade, a rotor shaft, and an electrical generator coupled thereto. The method includes controlling a torque of the rotor shaft by controlling a torque of the electrical generator, alternating between changing an angle of pitch of the at least one rotor blade and maintaining the angle of pitch of the at least one rotor blade substantially constant, and maintaining a substantially constant rotational speed of the rotor during variable wind speeds above a predetermined rated wind speed.