Wind Turbine Idling Speed Control via Pitch and Torque
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Solution Overview
Problem
Wind turbines face issues during idling due to mechanical vibrations, bearing damage, and insufficient lubrication, which can lead to costly repairs and fatigue damage, especially in offshore environments where wind-wave misalignment exacerbates these problems.
Innovation Solution
A method and control device that adjust the rotational speed of the rotor hub during idling by controlling the pitch angle of the rotor blades and generator torque, using an active feedback system to maintain a minimum idling speed within defined allowed rotational speed ranges, thereby minimizing loads and avoiding damaging frequencies and misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rotor hub is allowed to idle at extremely low rotational speeds (around 0.2 rpm) during stopped conditions, then the wind turbine can remain in a stopped state without active control, but mechanical vibrations and harmonic vibrations collocate at certain frequencies causing higher loads on the generator and gearbox
Solution Approach 1:
The patent applies dynamics by transitioning from a static idling approach (fixed low speed) to a dynamic controlled approach. The control device actively adjusts the rotational speed of the rotor hub during idling based on detected vibration frequencies, ensuring the speed remains within allowed ranges that avoid resonant frequencies. This dynamic adjustment prevents collocation of mechanical and harmonic vibrations while maintaining the stopped condition benefits.
Solution Approach 2:
The patent implements feedback by using vibration sensors to detect mechanical and harmonic vibration frequencies during idling, then feeding this information back to the control device. The control device processes this feedback and adjusts the rotational speed accordingly to avoid resonant conditions. This closed-loop feedback system ensures the rotor hub operates at safe speeds without requiring continuous active pitch control.
2Ease of operation
If the rotor hub is allowed to rock between two positions at low to medium wind speeds, then the wind turbine remains in stopped condition, but this rocking motion causes damage to the bearings of the rotor hub
Solution Approach 1:
The patent applies dynamics by maintaining a minimum rotational speed during idling to prevent the rotor hub from rocking between positions. By keeping the rotor hub rotating at a controlled speed within the allowed range, the dynamic motion prevents the static rocking phenomenon that causes bearing damage, while still maintaining the stopped condition operational state.
Solution Approach 2:
The patent applies preliminary anti-action by proactively preventing the rocking motion before it can cause bearing damage. The control device detects when the rotor hub approaches rocking conditions and adjusts the rotational speed in advance to maintain it within the allowed range, thereby preventing the harmful rocking motion from occurring in the first place.
3Ease of operation
If the rotational speed during idling is too low, then the wind turbine remains in stopped condition, but sufficient rotation speed is not obtained for proper lubrication of the main bearing
Solution Approach 1:
The patent applies dynamics by establishing a dynamic balance between maintaining stopped condition and ensuring adequate lubrication. The control device maintains the rotational speed within an allowed range that is high enough to provide sufficient lubrication to the main bearing while low enough to preserve the benefits of stopped condition operation. This dynamic speed control resolves the contradiction between operational simplicity and bearing protection.
4Ease of operation
If the rotor hub idles at low speed in offshore conditions, then the wind turbine operates in stopped condition, but misalignment of wind and wave introduces additional damage to the tower
Solution Approach 1:
The patent applies dynamics by using rotational speed as a control parameter to mitigate wind-wave misalignment effects. By maintaining the rotor hub within allowed speed ranges during offshore idling, the dynamic rotation provides damping that reduces the impact of wind-wave misalignment on the tower, while still maintaining the operational simplicity of stopped condition.
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 ensures controlled idling speeds, reduces mechanical wear, and prevents damage to bearings and towers, leading to cost savings and extended turbine life by maintaining a stable idling speed and effective lubrication.
Implementation Method 1
Moving air like, e.g., wind, impacting onto the at least one rotor blade transfers a part of its kinetic energy to the rotor blades causing rotation of the rotor blades and the rotor hub
Implementation Method 2
a pitch angle of zero degree causes the blade or blade chord to be pitched in a way to be essential parallel to a plane of rotation of the rotor blades, whereas a pitch angle approaching 90 degrees results in pitching the blade in a way to be essential perpendicular to the plane of rotation
Data Source
Figure 1
Figure 2
AI summary
A method is proposed for operating a wind turbine (140) during idling, comprising a rotor hub, thereby controlling a rotational speed of the rotor hub during idling of the wind turbine (140) based on a determined rotational speed (150) of the rotor hub. Further a wind turbine, a control device and a computer program product are suggested.