本論文研究基於模組化多階轉換器之多饋入式高壓直流輸電系統，整合了離岸風場以及海洋溫差發電系統併入電網之穩定度改善分析。本論文前半部於不同工作條件下，探討所研究系統之小訊號穩定度分析，後半部則針對系統中低頻振盪模態，提出了模組化多階轉換器之阻尼控制器，即比例-積分-微分以及超前-落後型式之阻尼控制器。藉由頻域分析方法，評估所設計控制器參數之有效性，再將控制器代入非線性系統中，以動暫態等時域模擬方法驗證控制器在系統遭遇各種干擾時之性能。文中對控制器在改善系統穩定度、輸出波形以及增加阻尼特性等方面，均有進行比較。由模擬結果得知，比例-積分-微分型式之控制器對於輸出波形具有最佳的改善效果。本論文同時也探討實際風場之風速加入所研究系統，以分析長時間之系統動態特性。

This thesis investigates stability-improvement analysis of multi-infeed high-voltage direct current transmission systems based on modular multi-level converters, integrating offshore wind farms and ocean thermal energy conversion systems into the grid. The first half of this thesis examines the studied system's small-signal stability analysis under various operating conditions. The latter half proposes damping controllers for low-frequency oscillation modes in the system, namely proportional-integral-derivative (PID) and lead-lag controllers based on modular multi-level converters. Through frequency domain analysis methods, the effectiveness of the designed controller parameters is evaluated. This is followed by validating the controller's performance under various disturbances using time-domain simulation methods in nonlinear systems. Comparative studies are conducted on the controllers to improve system stability, and output waveforms, and enhance damping characteristics. Simulation results indicate that the PID controller shows the most significant improvement in the output waveform. This thesis also explores the incorporation of actual wind speeds from real wind farms into the studied system to analyze its long-term dynamic characteristics.

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