半潛式浮動平台於拍頻波浪作用下之波浪負荷試驗

Abstract

浮動式風力發電平台之運動行為受波浪影響顯著，進而影響風力發電機之發電效率，以及整體系統的穩定性與安全性。本研究針對半潛式浮動平台進行縮尺模型試驗，以波浪激振力試驗探討平台在規則波與拍頻波作用下之波浪負荷，並分析波浪激振力。 本研究所使用之浮台外型，為臺灣大學團隊依據5 MW風力發電機所設計之半潛式平台（臺大浮台）的1/100幾何縮尺模型進行。由於試驗水槽尺寸及造波設備之限制，無法產生極低頻率波浪，因此除規則波試驗外，亦以兩組頻率接近之規則波疊加，使其相互干涉產生低頻拍頻波浪進行試驗。試驗條件涵蓋七種規則波頻率與二十一種拍頻波組合，分別分析一階波浪激振力及差頻波浪激振力。 此外，本研究亦將試驗結果與數值模擬進行比較以驗證數據之可靠性，並探討其中差異，分析非線性波浪效應對浮台行為之影響。結果顯示非線性效應在不同方向及不同頻率下具有不同影響程度，此外亦發現差頻波浪激振力對浮台所受激振力影響顯著。因此差頻波浪負荷應作為浮台設計與動態分析時的重要考量因素之一，有助於預估浮式風力發電系統於實海域中之受力狀況，進而提升整體系統之穩定性與可靠性。

The motion of floating offshore wind turbine platforms is strongly influenced by waves, which affect power generation efficiency, stability, and safety. This study investigates wave exciting forces of a 1/100 scaled semi-submersible platform, TaidaFloat, designed by National Taiwan University for a 5 MW turbine. Experiments are conducted under regular and bichromatic wave conditions to analyze the wave exciting force. The experiments include 7 regular wave frequencies and 21 combinations of bichromatic waves, with analyses focusing on first-order wave exciting forces and difference-frequency wave exciting forces induced by regular and bichromatic waves. The experimental results are compared with numerical simulations to compare the reliability of the data and to identify discrepancies. These comparisons are used to investigate the effects of nonlinear wave behavior on the motion of the platform. The results show that nonlinear wave effects vary depending on the degree of freedom and wave frequency, and that the difference-frequency components have a significant impact on the excitation forces acting on the platform. Therefore, the difference-frequency wave exciting forces should be regarded as a critical factor in the design and dynamic analysis of floating platforms, as it plays an essential role in predicting the wave-induced loads on floating offshore wind systems in real sea conditions, thereby enhancing the overall stability and reliability of the system.