Floating offshore wind turbines are a novel technology, which has reached, with the first wind farm in operation, an advanced state of development. The question of how floating wind systems can be optimized to operate smoothly in harsh wind and wave conditions is the subject of the present work. An integrated optimization was conducted, where the hull shape of a semi-submersible, as well as the wind turbine controller were varied with the goal of finding a cost-efficient design, which does not respond to wind and wave excitations, resulting in small structural fatigue and extreme loads. The optimum design was found to have a remarkably low tower-base fatigue load response and small rotor fore-aft amplitudes. Further investigations showed that the reason for the good dynamic behavior is a particularly favorable response to first-order wave loads: The floating wind turbine rotates in pitch-direction about a point close to the rotor hub and the rotor fore-aft motion is almost unaffected by the wave excitation. As a result, the power production and the blade loads are not influenced by the waves. A comparable effect was so far known for Tension Leg Platforms but not for semi-submersible wind turbines. The methodology builds on a low-order simulation model, coupled to a parametric panel code model, a detailed viscous drag model and an individually tuned blade pitch controller. The results are confirmed by the higher-fidelity model FAST. A new indicator to express the optimal behavior through a single design criterion has been developed.

中文翻译：

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半潜式风力涡轮机船体形状设计，具有良好的系统响应行为

浮动式海上风力涡轮机是一项新技术，随着第一个风电场的投入运行，它已经达到了先进的发展状态。如何优化浮动风力系统以在恶劣的风浪条件下平稳运行是当前工作的主题。进行了综合优化，其中半潜水器的船体形状以及风力涡轮机控制器发生变化，目的是找到一种具有成本效益的设计，该设计不会对风和波浪的激励做出响应，从而导致较小的结构疲劳和极端负载。发现最佳设计具有非常低的塔基疲劳载荷响应和较小的旋翼前后振幅。进一步的调查表明，良好的动态行为的原因是对一阶波浪载荷的特别有利的响应：浮动式风力机围绕靠近转子轮毂的一点沿桨距方向旋转，转子前后运动几乎不受波浪激励的影响。因此，发电量和叶片负载不受波浪的影响。迄今为止，张力腿平台具有类似的效果，但半潜式风力涡轮机却没有。该方法建立在低阶仿真模型上，耦合到参数面板代码模型、详细的粘性阻力模型和单独调整的叶片桨距控制器。结果得到了更高保真度模型 FAST 的证实。已开发出一种新指标，可通过单一设计标准来表达最佳行为。