Wind Turbine Shutdown Pitch Angle Alignment Control
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Solution Overview
Problem
In pitch-controlled wind turbines with individually pitched blades, shutdown processes often result in asymmetric loads on blades and towers, as existing methods either exacerbate or fail to adequately address these imbalances, leading to increased stress on the rotor and tower during shutdown.
Innovation Solution
A method for controlling wind turbines during shutdown that involves measuring misalignment of pitch angles, calculating the time and azimuth angle required for alignment, and employing a two-stage shutdown strategy: an initial high-speed phase to minimize tower loads followed by a phase that aligns pitch angles to reduce asymmetric loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If all wind turbine blades are moved quickly to the feathered position during shutdown, then the shutdown time is reduced, but asymmetric loads on the wind turbine blades increase
Solution Approach 1:
The control unit calculates in advance the time required to align pitch angles and determines an azimuth angle position for alignment before the blades reach the feathered position. This preliminary calculation allows the system to plan the alignment action in advance, ensuring that pitch angles are aligned at the optimal moment during the shutdown process, thereby reducing asymmetric loads while maintaining efficient shutdown timing.
Solution Approach 2:
The control unit dynamically adjusts the pitch angles of individual blades during shutdown based on real-time conditions. Instead of applying a static shutdown strategy to all blades, the system continuously monitors and adjusts each blade's pitch angle individually, allowing for adaptive alignment that reduces asymmetric loads while accommodating the dynamic nature of the shutdown process.
2Object-affected harmful factors
If pitch angles are aligned during shutdown, then asymmetric loads on blades are reduced, but loads on the tower may increase
Solution Approach 1:
The control unit calculates in advance the optimal azimuth angle position for pitch angle alignment, taking into account the rotor's current azimuth angle and the time required for alignment. By determining this optimal position beforehand, the system can align pitch angles at the most favorable moment, minimizing the impact on tower loads while still achieving the goal of reducing asymmetric blade loads.
Solution Approach 2:
The control unit changes the pitch angle parameters of individual blades during shutdown based on calculated optimal values. By adjusting pitch angles to specific target values at calculated optimal times and positions, the system optimizes the balance between reducing asymmetric blade loads and minimizing tower loads, effectively managing the trade-off between these two objectives.
3Object-affected harmful factors
If individual pitch control is used during operation, then asymmetric loads are reduced, but pitch angle misalignment occurs during shutdown
Solution Approach 1:
The control unit calculates in advance the time required to align pitch angles and the optimal azimuth angle position for alignment during shutdown. By performing these calculations before the shutdown process begins, the system can plan and execute pitch angle alignment at the optimal moment, ensuring that the benefits of individual pitch control during operation are maintained while achieving proper alignment during shutdown.
Solution Approach 2:
The control unit dynamically adjusts pitch angles during shutdown based on real-time rotor position and calculated optimal alignment parameters. Instead of using a fixed shutdown strategy, the system continuously adapts the pitch angle adjustments to maintain alignment, effectively bridging the transition from individual pitch control during operation to aligned shutdown conditions.
Data Source
AI summary
A method for controlling a wind turbine during shutdown is disclosed, said wind turbine comprising a rotor carrying at least three wind turbine blades adapted to be pitched individually. A first shutdown strategy is initially selected, and subsequently a second shutdown strategy is selected, the second shutdown strategy ensuring alignment of the pitch angles of the wind turbine blades. The time for switching from the first shutdown strategy to the second shutdown strategy is calculated on the basis of a misalignment of the pitch angles, and in order to align the pitch angles before an estimated point in time where the pitch angles must be aligned, in order to avoid excessive asymmetric loads on the wind turbine blades and/or on the rotor. According to an alternative embodiment, the first shutdown strategy includes moving the wind turbine blades towards a feathered position at identical pitch rates.