本篇論文研究直接甲醇燃料電池之阻抗分析與控制設計問題。藉由使用氯化銀參考電極，即時的量測直接甲醇燃料電池在不同的空氣流量、甲醇流量、甲醇濃度、溫度與電流密度操作下，其陽極、陰極以及全電池之電化學阻抗頻譜，並將其結果對應於極化曲線 (polarization curve) 進行有系統之比較。再者，針對陰極溢流 (water flooding) 問題進行詳細研究。為了能更清楚的解析在直接甲醇燃料電池中陽極內部的所有反應，提出有效的等效電路選取規則，能分別針對於穩定操作以及質傳限制 (mass transport limitation) 下的陽極阻抗頻譜進行模擬，並以合適之等效電子元件進行陽極內部反應分析。除此之外，並使用上述之分析結果,導入阻抗頻譜分析之高頻阻抗 (high frequency resistance) 與電荷轉移阻抗 (charge transfer resistance) 為控制輸入變數，設計一模糊控制器來有效的調整陰極空氣量大小，以維持直接甲醇燃料電池之功率輸出穩定度。藉由本論文中有層次漸進的討論證明阻抗分析可以提供對於甲醇燃料電池內部反應之了解，並可藉此發展出燃料電池系統之最佳化控制設計，以利於未來商業化發展。 This dissertation proposes the impedance based analysis and control design for an operating direct methanol fuel cell (DMFC) system. By using a silver/silver chloride electrode as the extended reference electrode, the electrochemical impedance spectroscopy (EIS) response of the real anode, real cathode, and full-cell impedance, corresponding to the polarization curves, are systematically investigated as a function of air and methanol flow rates, methanol concentrations, cell temperatures, and current densities. Water flooding in the cathode was also examined. For clearly interpreting each physic-chemical phenomenon in a DMFC anode, the selection of electrical equivalent circuits (EECs) of the anode impedance response at the stable operation and the mass transport limitation are developed. The suitable electrical elements of different EEC models can provide a clearly understanding of a DMFC during various operations. Furthermore, by applying the impedance characteristic of high frequency resistance (HFR) and charge transfer resistance (CTR) as the control input, the control strategy, based on the fuzzy logic, is designed to adjust the cathodic air stoichiometric flow for preventing the performance drops of a DMFC caused by flooding and drying. It is sufficient to assist the stack in reacting at an optimal operating state and can reduce the measuring time of impedance during the real-time control process. Although the influences of operating temperature on the state of system are not accounted, this fuzzy controller has the adaptability to run even if the stack is operated at various temperatures. The series of proposed work in this dissertation indicates that the EIS technique is a powerful to understand the operating and failure mechanism in view of the performance and durability of DMFC under the practical application and thus to develop an optimal control for preventing the deterioration of DMFC.
