直接甲醇燃料電池之無感測濃度控制

Sensor-less concentration control for direct methanol fuel cells

徐偉倫(Wei-Lun Hsu)

指導教授 ： 練光祐

國立臺北科技大學/電資學院/電機工程系研究所/碩士(2009年)

摘要

近年來，由於能源短缺的問題日益嚴重，各種替代能源的方案都備受重視。在各種新能源中，氫能算是最理想的能源，它的產物為水及少量的二氧化碳。而燃料電池就是其中一種利用氫能透過化學反應轉化成電能的電池。在各種燃料電池中，以直接甲醇燃料電池最為熱門，多數用在可攜式3C設備上。本論文的主旨以直接甲醇燃料電池電源管理系統為主體，提出一套有效的電源管理方法－電壓雙次核對濃度控制方法Voltage Double-Check Concentration Control，決定是否供應甲醇以維持其濃度於適當範圍。這裡所謂的電壓雙次核對有兩層意思：(i)量測電壓與預測電壓的核對;(ii)經多次的核對電壓發生偏差後，方才判定濃度不足所造成。如此可避免誤判。迄今大多數研究都是針對定負載的情形下設計控制法則。在負載變動時，輸出電壓會隨之改變，且會呈現短暫而迅速的暫態響應。這是造成定負載下所設計的決策法則無法適用於變動負載的主要原因。本研究針對變動負載的情況下提出一套決策法則，考慮輸出電壓隨負載改變的暫態響應特徵，進而提出一套決策法則。我們發現若負載由低至高時，電壓會在短時間內產生過低的電位。若負載由高至低時，則電壓也會在短時間內產生過高的電位。我們針對這種現象提出一套決策法則。此法則可在變動負載的條件下正確地判斷濃度是否偏低，且在正確的時間點供應純甲醇以維持濃度在一合適的範圍內。最後，我們建構了DMFC測試系統，其中包含了燃料電池模組、燃料電池模組存放盒、電子負載機、循環幫浦、EMS控制板、混合溶液槽、高濃度甲醇溶液槽、純水溶液槽。

關鍵字

直接甲醇燃料電池 ； 濃度控制

並列摘要

In recent years, energy shortage becomes a serious problem. Many kinds of renewable energy are taken into consideration as alternatives. Among many new energy solutions, the hydrogen energy is perhaps the most ideal candidate. As a renewable, its by-product is the water and a little carbon dioxide. Among fuel cells, the direct methanol fuel cell (DMFC) is much emphasized for low power applications for example, 3C-products. The main issue of this thesis focuses on the power source management system and an effective method for maintaining methanol concentration, namely Voltage Double-Check Concentration Control (VDC3), will be proposed. VDC3 can decide the feeding timing of pure methanol to maintain the methanol concentration in a suitable range. The change of output voltage is affected by the loading current. An impermanent overshoot or undershoot phenomenon of output voltage is found when the load changes from low to high or high to low, respectively. The proposed decision maker VDC3 is developed according to these phenomena. Compared to the existed algorithm in the literature designed for constant load, this research proposes a sensor-less control algorithm for varied load. It considers the features of transient response caused by loading change. The proposed algorithm can judge whether the methanol concentration is insufficient and inject pure methanol at correct timing to maintain the methanol concentration in a suitable range.

並列關鍵字

Direct methanol fuel cell ； Concentration control

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