Wind Turbine Rotational Speed Limit Control
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Solution Overview
Problem
Existing wind turbine systems face inefficiencies and increased mechanical stress due to forced braking when rotational speeds exceed a fixed limit, leading to unnecessary shutdowns and delayed restarts, which disrupt energy feeding into the grid and incur additional costs.
Innovation Solution
The method involves dynamically adjusting the rotational speed limit as a function of the blade pitch angle movement rate, allowing for temporary changes and incorporating additional braking mechanisms independent of pitch angle, to reduce unnecessary shutdowns and optimize operational ranges based on real-time data and power changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed rotational speed limit is used for forced braking, then mechanical stress from high rotational speed is avoided, but unnecessary shutdowns occur and energy feeding into the grid is interrupted
Solution Approach 1:
The rotational speed limit is changed from a fixed static value to a dynamic value that varies as a function of the blade pitch angle movement rate. The control dynamically adjusts the rotational speed limit nlim based on the current blade pitch angle movement rate ω, allowing the limit to adapt to real-time operational conditions. This resolves the contradiction by enabling forced braking only when necessary (high pitch rate indicating active speed reduction) while maintaining higher limits when pitch adjustment is insufficient, thus avoiding unnecessary shutdowns while protecting against mechanical stress.
Solution Approach 2:
The patent changes the parameter of rotational speed limit from a constant fixed value to a variable parameter that depends on the blade pitch angle movement rate. The control continuously monitors the pitch rate and adjusts the rotational speed limit accordingly, creating a functional relationship nlim=f(ω). This parameter transformation allows the system to distinguish between normal speed fluctuations and critical conditions requiring forced braking, thereby maintaining productivity while ensuring reliability.
2Reliability
If forced braking is applied frequently to maintain rotational speed limits, then mechanical stress is reduced, but shutdown duration increases and restart delays occur
Solution Approach 1:
The dynamic rotational speed limit based on blade pitch angle movement rate allows the system to avoid forced braking when the pitch mechanism is already actively reducing speed. By monitoring the pitch rate, the control can distinguish between situations where forced braking would be redundant (pitch already moving at high rate) versus situations where it is necessary (low pitch rate). This reduces unnecessary shutdowns and associated time losses while maintaining mechanical stress protection.
Solution Approach 2:
The control uses feedback from the blade pitch angle movement rate sensor to continuously adjust the rotational speed limit. This feedback mechanism allows the system to respond to actual operational conditions rather than applying fixed threshold-based braking. When the pitch rate indicates active speed reduction is occurring, the feedback loop raises the rotational speed limit, preventing redundant forced braking and reducing shutdown frequency and duration.
3Stability of the object's composition
If a static rotational speed limit is enforced, then operational range is clearly defined, but the system lacks adaptability to real-time wind conditions and control capacity
Solution Approach 1:
The rotational speed limit transforms from a static fixed value to a dynamic value that adapts to real-time wind conditions through its functional relationship with blade pitch angle movement rate. The control continuously adjusts the limit based on current operational context, maintaining clear operational boundaries while enabling adaptability to varying wind conditions and turbine control capacity.
Solution Approach 2:
The patent changes the rotational speed limit parameter from a constant to a variable that reflects real-time turbine state. By making the limit dependent on the blade pitch angle movement rate, the system gains adaptability to different wind conditions and control scenarios while maintaining a well-defined operational range through the functional relationship nlim=f(ω).
Data Source
AI summary
The invention relates to a method for operating a wind turbine (10) comprising a rotor (12) and a generator (18), connected to said rotor (12), for outputting electrical power to an electrical grid, said rotor (12) comprising rotor blades (14) whose blade pitch angles (α) may be moved during operation in order to control the rotational speed (n) of the rotor (12). Upon reaching a rotational speed (n) higher than a rotational speed limit (nlim) that delimits an operational range (34, 34′, 34″) of said wind turbine (10), the rotor (12) is forcibly braked by increasing the blade pitch angle (α) at a predefined positive blade pitch angle movement rate (ωr). According to the invention, the rotational speed limit (nlim) is altered as a function of a blade pitch angle movement rate (ω) set by the control. The invention also relates to a corresponding wind turbine (10).