Wind Turbine Rotor Asymmetric Load Compensation
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Solution Overview
Problem
Large wind turbines experience significant asymmetrical loadings due to spatial wind distribution, leading to pulsating or oscillating rotor loads known as 3p loads, which contribute to fatigue and reduce the turbine's operational lifespan.
Innovation Solution
A method and system that determine mechanical loads on wind turbine blades, calculate asymmetric load moments, and generate individual pitch control signals for each blade to compensate for high-order harmonics, specifically 3p loads, by using sensors and control algorithms to adjust the pitch angle dynamically, thereby minimizing these loads without requiring hardware changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual pitch control is implemented to compensate for asymmetric load moments, then fatigue loads and asymmetrical loadings are reduced, but device complexity and control system complexity increase
Solution Approach 1:
The control system is segmented into multiple independent pitch control channels, one for each blade. Each channel processes load measurements and generates individual pitch commands independently, allowing targeted compensation of asymmetric loads without requiring complete system redesign. This segmentation reduces the complexity burden by distributing control functions across modular units.
Solution Approach 2:
The system implements closed-loop feedback control where load measurements from sensors are continuously fed back to the pitch control system. The feedback signal includes asymmetric load moment components that trigger corrective pitch adjustments. This automatic feedback mechanism reduces reliance on complex open-loop calculations and simplifies the overall control architecture while maintaining effectiveness.
2Object-affected harmful factors
If cyclic pitching is used to compensate for 3p loads, then high-order harmonics are minimized, but the complexity of determining individual pitch control signals increases
Solution Approach 1:
The system applies periodic cyclic pitching commands at the 3p frequency (three times per rotor revolution) to counteract the oscillating asymmetric loads. By synchronizing the pitch adjustments with the rotational frequency and its harmonics, the system effectively minimizes high-order harmonics through constructive interference cancellation, reducing the need for overly complex continuous control algorithms.
Solution Approach 2:
The control system dynamically adjusts pitch angle parameters based on detected load conditions and rotor position. By changing the pitch parameter in a controlled cyclic manner rather than requiring complex real-time optimization, the system achieves effective compensation of 3p loads while keeping the control algorithm complexity manageable through parameter-based control rather than full dynamic optimization.
Data Source
AI summary
A method of operating a wind turbine is provided. The wind turbine comprises a turbine rotor with at least two blades, each blade having a variable pitch angle. The method comprises determining mechanical loads on the blades, determining an asymmetric load moment experienced by the turbine rotor based on the mechanical loads on the blades, determining high order harmonics from the asymmetric load moment, and determining an individual pitch control signal for each of the blades for varying the pitch angle of each blade to compensate for the asymmetric load moment. The individual pitch control signal for each blade is determined at least based on the high order harmonics.