IEA 15 MW離岸浮動半潛式浮台結合雙饋式感應風力發電機之數位孿生系統及控制之研究

Abstract

本研究使用IEA15MW風力發電機結合UMaine VolturnUS-S reference platform半潛式浮台，以台灣海峽水深作為主要深度條件來進行全機組系統動態整合模擬分析及控制器設計測試，發展IEA15MW 半潛浮動式風機數位孿生系統，藉由MATLAB/SIMULINK結合SIMPACK整合AeroDyn、HydroDyn、WAMIT、MAP++四個模組進行氣動力-水動力-伺服-彈性的全機組系統整合模擬實現主要風機模型架構在SIMPACK中建立，包含葉片、機艙、塔柱、浮台及錨定繫泊系統。AeroDyn提供對葉片及塔柱的空氣動力計算，HydroDyn透過WAMIT提供的水動力係數、設定波浪計計算浮動平台的負載與運動，MAP++則負責繫泊系統的參數設定。整合上述四項，並在MATLAB/SIMULINK中建立雙饋式感應發電機控制系統、併網側轉換器、功率控制系統、閥控液壓式葉片變旋角系統等全機組主要控制系統，並透過連結介面SIMAT與SIMPACK進行資訊傳遞以完成此動態整合模擬。 過去風機動態系統模擬皆以PI控制器為主，但隨著風機大型化及離岸浮動式風機的趨勢，使原先PI控制器越來越難達成所設想的控制目標。故本研究設計一模糊滑動式控制器與PI控制器進行比較，在正常運轉風速下進行控制器效能分析。但浮動式平台的縱搖是影響風力發電機發電功率穩定的主要因素，因此設計一回授給功率控制器來減小縱搖的影響。接著以實際運作環境條件配合紊流強度設定來進行風機效能測試及在不同變旋角控制器之比較。同時也以全域風速進行測試。此外，本研究更發展極端條件功率控制以提升風力發電機系統之運轉發電性能，風速超過切出風速時本應停機，而本研究嘗試在極端風速下進行降載控制測試，以調控葉片旋角方式進行發電功率追蹤控制五階曲線及線性曲線，由額定功率逐漸降載至停機，使風機在極端條件下仍可在安全狀態下持續發電，也測試風機在五十年迴歸週期環境條件下停機之情形。 由於浮動式發電機會因受到波浪及風力的影響使之產生多餘的運動，對風力發電機的效能有負面的影響。故此研究嘗試以調整壓載改變吃水方式，探討在不同的吃水情況下是否能改善風力發電機的運動，便能有效減少外力對風機結構上的傷害。 本研究所使用的風機模擬軟體是SIMPACK，相較於由NREL所研發的Openfast是目前廣為人知的風力發電機模擬套件。但基於SIMPACK的各項優點，舉例來說，方便使用者的圖形化使用介面以及能快速且自由修改模型的能力，故本篇論文將風機模型建立在SIMPACK當中。因此，本研究也在正常運轉條件下比較在不同的模型架構下風力發電機組的表現。

This study aims to develop a digital twins system for analyzing the IEA 15MW semi-submersible floating wind turbine with a doubly-fed induction generator under Taiwan Strait. The IEA 15MW wind turbine is mounted on a UMaine VolturnUS-S reference platform. This digital twins system combines MATALB/SIMULINK with SIMPACK, including AeroDyn, HydroDyn, WAMIT, MAP++, to operate an aero-hydro-servo-elastic simulation. The floating wind turbine model is mainly built in SIMPACK, including blades, nacelle, tower, floating platform. AeroDyn provides aerodynamic to blades and tower. HydroDyn is responsible for hydrodynamic calculation of floating platform by hydrodynamic parameters and design wave condition provided by WAMIT. MAP++ is for the setting of mooring system. Together, the four modules and the control system which is built in MATLAB/SIMULINK includes rotor speed control system, power control system to complete the co-simulation via the interface, SIMAT. In the past, the traditional wind turbine system for power control uses a PI controller. Due to the large-scale wind turbine, the control performance by PI controller cannot reach our goal. Therefore, in this research, the PI controller is replaced by fuzzy sliding mode controller. Fuzzy sliding mode controller has an ability to cancel out the nonlinear term. This controller improves the disadvantages of the traditional PI controller in transient time. This study compares the simulation result of traditional PI controller with fuzzy sliding mode controller in power control system with different operating wind and wave. Besides, motions of floating platform, especially pitching motion, contribute to unstable power performance. Therefore, the power control system is added pitching rate feedback aiming to cancel out the floating platform rotation. These controllers and control strategies are tested in normal and extreme condition. Apart from the power control system, the study also proposed innovative ballast control strategy to reduce the platform displacement and mitigate the structural load by draft adjustment. Openfast is the most common wind turbine analysis software, which is developed by NREL. Due to the advantage of SIMPACK, including graphic user interface and easily modified the model, the wind turbine model in this study is still built in SIMPACK. Thus, this study shows the comparison between Openfast and SIMPACK. All the simulations are tested in a normal condition.