With the increase in size of wind turbine for larger energy capture, aeroelastic effects previously not seen in smaller rotors are beginning to surface as a result of increased blade flexibility. This has brought about new needs in terms of modelling requirements and methods of load control to improve the fatigue life of turbine blades. This dissertation presents an aeroservoelastic modelling approach for dynamic load alleviation in large wind turbines with trailing-edge aerodynamic surfaces. Time-domain aerodynamics are given by a linearised three-dimensional unsteady vortex-lattice method that allows better characterisation of aeroelastic responses under attached flow conditions and the direct modelling of lifting surfaces. The resulting unsteady aerodynamics is written in a state-space formulation suitable for model reductions and controller design. This approach does not rely on empirical corrections commonly found in Blade Element Momentum methods. Structural modules of the tower, potentially on a moving base, and the rotating blades are modelled using geometrically non-linear composite beams, which are linearised around reference conditions that have undergone arbitrarily-large structural displacements. \ud\udThe land-based NREL 5MW reference wind turbine is chosen to demonstrate the unified aeroelastic framework, in which the coupled rotor and tower description is modelled to examine both the aeroelastic effects and potential of load alleviation. In the presence of realistic wind fields, turbine blade root-bending moments and tower deflections can be reduced by 13% using active control methods. When combined with passive mechanisms through bend-twist coupling, performance can be improved to more than 40%. The baseline configuration is further extended to cover offshore floating wind turbine concepts. The focus of this dissertation is to provide higher-fidelity efficient numerical models for linear robust controller design (LQG and Hinf), to achieve load alleviation in larger and more flexible wind turbines.
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机译:随着风力涡轮机尺寸的增加以获取更大的能量,由于叶片灵活性的提高,以前在较小的转子中未见的气动弹性效应开始浮出水面。这在建模要求和载荷控制方法方面提出了新的需求,以改善涡轮叶片的疲劳寿命。本文提出了一种具有后缘空气动力学表面的大型风力发电机动态载荷减轻的气动弹性建模方法。时域空气动力学是通过线性化的三维非定常涡旋格子方法给出的,该方法可以更好地表征附加流动条件下的气动弹性响应,并可以直接对提升表面进行建模。产生的不稳定空气动力学以适合模型简化和控制器设计的状态空间公式编写。此方法不依赖于“叶片元素动量”方法中常见的经验校正。塔架的结构模块(可能位于移动基座上)和旋转叶片是使用几何非线性复合梁建模的,这些梁在经历了任意大结构位移的参考条件周围线性化。 \ ud \ ud选择了陆基NREL 5兆瓦参考风力涡轮机来演示统一的气动弹性框架,其中对转子和塔架的耦合描述进行了建模,以检验气动弹性效应和减轻负荷的潜力。在存在实际风场的情况下,使用主动控制方法可以将涡轮叶片根部弯矩和塔架挠度降低13%。当通过弯扭耦合与被动机构结合使用时,性能可以提高到40%以上。基线配置进一步扩展到涵盖海上浮动风力涡轮机概念。本文的重点是为线性鲁棒控制器设计(LQG和Hinf)提供高保真有效的数值模型,以实现更大,更灵活的风力涡轮机的负荷减轻。
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