Integrated wind-wave control of semi-submersible floating offshore wind turbine platforms (FOWT-Control)

随着未来在深水领域的扩张，海上风能正在成为主要的电力供应商。浮动平台可以进入通常大于30米的水深，但由于组合波浪和涡轮机运动时变的推力，平台存在运动的缺点。平台稳定性对于提高性能、减少停机时间和实现安全访问至关重要。按照今天的价格，仅一台拟议的15兆瓦机器的电力输出损失就可以达到每天2万GB。此外，由于偏航和俯仰导致涡轮轴与风向不对齐，会导致功率损失和不希望看到的叶片应力。由于多向波浪场的作用，在波浪方向上除纵摇和涌浪外，还可能出现横摇和偏航交错波。因此，该项目有两个截然不同的目标，这两个目标都影响整个生命周期成本：目标1：通过对平台和涡轮机上的海浪和风的影响进行集成(整体)预览控制，最大限度地减少发电过程中平台的运动。一个关键的可靠性目标是确保机舱因俯仰和浪涌而产生的加速度小于推荐的0.2-0.3g，并将破坏性电涌和结构部件的疲劳降至最低。目标2：在乘船或直升机运送人员和物资时，绝对减少平台运动，以确保安全维护，并将维护工作期间对人员的运动影响降至最低。所采用的说明性案例是流行的半潜式浮子概念，它具有较浅的吃水和简单的部署。平台稳定将通过组合实现：(I)半分柱之间的抽油箱控制，以最大限度地减少船舶上使用的俯仰和横摇；(Ii)叶片螺距控制，已用于风力涡轮机控制；以及(Iii)偏航控制，以与风向对齐。这一多目标非因果控制问题需要未来对波浪和风的强迫函数的了解，以实现最优。

Offshore wind energy is becoming a major electricity provider with future expansion in deep water. Floating platforms can access water depths typically greater than 30 m, but have the disadvantage of platform motions due to combined waves and time varying thrust from turbine motion. Platform stabilisation is critically important for improving performance, reducing downtime and enabling safe access. Lost electrical output alone for a proposed 15 MW machine can be £20k per day at today's prices. Moreover, misalignment of the turbine axis with wind direction due to yaw and pitch causes power loss and undesirable blade stresses. In addition to pitch and surge in the wave direction, roll and yaw cross wave may occur due to multi-directional wave fields. Thus this project has two distinct aims both impacting on through life cost: Aim 1: to optimally minimise platform motion during power production by integrated (holistic) preview control of wave and wind effects on platform and turbines. A key reliability goal is to ensure acceleration at the nacelle due to pitch and surge is less than the recommended 0.2-0.3g, and to minimise damaging electrical surges and fatigue of structural components. Aim 2: to absolutely minimise platform motion for safe maintenance during personnel and material transfers by boat or helicopter and minimise debilitating motion effects on personnel during maintenance work. The illustrative case employed is the popular semi-sub floater concept which has comparatively shallow draft and simple deployment. Platform stabilisation will be achieved by combining: (i) pumped tank control between semi-sub columns to minimise pitch and roll as employed in ships, (ii) blade pitch control, already used in wind turbine control and (iii) yaw control for alignment with the wind direction. This multi-objective non-causal control problem requires future knowledge of both wave and wind forcing functions to achieve optimality.