While detailed aero-servo-hydro-elastic simulation codes for modelling floating wind turbines (FWTs) are available, they achieve high accuracy at the expense of calculation speed. For conceptual design and optimisation, fast solutions are needed, and equivalent linearisation techniques combined with frequency-domain analysis offers to capture the complex behaviour of FWTs in fast, approximate models. The main aim of this paper is to apply a harmonic linearisation approach to model the aerodynamic loading within a complete coupled model of a FWT, quantifying its performance, and where accuracy is unsatisfactory, to give insight into the causes. Two linearised models are derived from a coupled nonlinear aero-hydro-servo-elastic model, using the OC3-Hywind FWT as a test case: the typical tangent linearisation derived by numerical perturbation of the nonlinear model and the harmonic linearisation yielding improved representation of the aerodynamic loads. Comparisons against nonlinear time-domain simulations from Bladed show that it is possible to create a frequency-domain model of a FWT, including a flexible structure, aeroelastic rotor loads and the effect of the control system, with reasonable accuracy. The biggest source of errors is the presence of additional harmonics caused by nonlinear interactions between loads at different frequencies, rather than inaccurate linearisation of the magnitudes of forces. The computational cost of the harmonic linearisation implemented varies, but in most cases is ∼10× slower than the tangent linearisation and ∼100× faster than the time domain solution.

中文翻译：

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浮动风力涡轮机频域模型中气动载荷的谐波线性化

虽然可以使用用于建模浮动风力涡轮机 (FWT) 的详细气动伺服水弹性仿真代码，但它们以计算速度为代价实现了高精度。对于概念设计和优化，需要快速解决方案，等效线性化技术与频域分析相结合，可以在快速、近似模型中捕获 FWT 的复杂行为。本文的主要目的是应用谐波线性化方法对 FWT 的完整耦合模型内的空气动力学载荷进行建模，量化其性能，并在精度不令人满意的情况下深入了解原因。使用 OC3-Hywind FWT 作为测试案例，从耦合非线性气动-液压-伺服-弹性模型导出两个线性模型：通过非线性模型的数值扰动导出的典型切线线性化和产生改进的空气动力载荷表示的谐波线性化。与来自 Bladed 的非线性时域仿真的比较表明，可以以合理的精度创建 FWT 的频域模型，包括柔性结构、气动弹性转子载荷和控制系统的影响。最大的误差来源是由不同频率负载之间的非线性相互作用引起的额外谐波的存在，而不是力大小的不准确线性化。实现的谐波线性化的计算成本各不相同，但在大多数情况下，比切线线性化慢 10 倍，比时域解决方案快 100 倍。