5MW浮動半潛式離岸風力發電機整合直驅式永磁同步發電機與併網之全機組運轉控制研究

Abstract

本論文旨在發展浮動半潛式離岸風力發電機全系統動態模擬分析與控制，風力發電機以美國國家再生能源實驗室NREL提供的5MW風機為主體進行探討，結合OC4半潛式載台及錨碇系統，整合波浪力、空氣動力、風機系統動態及控制系統動態分析。本文以軟體FAST結合軟體WAMIT以及軟體MATLAB/ SIMULINK進行全系統動態模擬與分析。浮動式風力發電機模型以軟體FAST建立，包含浮台、錨碇系統、塔架、葉片及機艙模型，葉片氣動力分析(Aerodynamic Analysis)以AeroDyn進行計算，由軟體WAMIT預先計算取得的浮台水動力係數在HydroDyn下進行水動力分析(Hydrodynamic Analysis)及進行浮動式風力發電機組的全機動態模擬，將自行發展的子系統動態模型在MATLAB/SIMULINK環境下建模，包含發電機系統的直驅式永磁同步發電機(Direct-Drive Permanent Magnet Synchronous Generator)結合磁場導向控制(Field-Oriented Control)及電網側變流器控制(Grid-Side Converter Control)，其他子系統含葉片變旋角系統以及交流感應馬達驅動的機艙轉向(yaw)系統等，並進行浮式風機閉迴路控制系統的設計及分析。最後於不同風況及海況下，整合浮式風機之運轉控制策略與控制理論，進行浮動半潛式離岸風力發電機全系統動態模擬與控制。當風機運轉於切入風速與額定風速之間時，利用直驅式永磁同步發電機的變轉速控制系統，控制發電機轉速追蹤最佳葉尖速比，保持在最大功率係數即維持最佳的發電功率輸出。而當風機運轉於額定風速之上，葉片變旋角系統開始作動，調控葉片旋角以降低葉片轉子對風能擷取效率，使風機發電功率輸出穩定在額定值。本研究所發展之動態模擬，可分析浮動半潛式載台受波浪力及風力之作用產生運動，以及風力發電機之操控及發電功率之影響。

This study aims to investigate dynamic simulation and analysis for a NREL OC4 5MW semi-submersible floating wind turbine by combining the software of WAMIT, FAST and MATLAB/SIMULINK. FAST serves to build the motion models of floater, mooring system, tower, blades, nacelle of wind turbine, aerodynamic analysis of blade, dynamic simulation of wind turbines and hydrodynamic analysis, in which the hydrodynamic coefficients of floater is obtained from the preprocessing of WAMIT. MATLAB/SIMULINK is used to establish the subsystem dynamic models for analysis and design of floating wind turbines. The subsystems comprise the direct-drive permanent magnet synchronous generator mathematical model with the magnetic field oriented control and grid-side converter control, the blade pitch control system, the AC induction motor driving nacelle yaw system. Finally, through combining the models of WAMIT、FAST and MATLAB/SIMULINK, the floating wind turbine operation and control strategies can be implemented and verified in the different wind and wave conditions. As the wind turbine operates between the cut-in speed and the rated wind speed, the variable speed control of direct drive permanent magnet synchronous generator is performed to make the wind turbine rotor tracking the desired rotor speed calculated by the optimal tip speed ratio strategy for maintaining the maximum power coefficient and optimum power output. As the wind turbine operates above the rated wind speed, the blade pitch control is implemented to adjust the pitch angle of the blades and maintain the rated power output. Different wind and wave conditions are given for verifying the developed overall dynamic simulation of floating offshore wind turbines. The motion of the floating platform can be analyzed that influence the output power seriously.