在分散式電源系統中，再生能源的間歇性和不穩定性可透過由基載和儲能裝置組成的備援系統來改善。燃料電池很適合作為基載系統，只要不斷提供燃料就可以無汙染地一直持續發電，然而燃料電池的電壓很低且響應速度慢，因此必須在燃料電池和直流匯流排(DC-Bus)間加上一個高升壓比轉換器進行升壓和功率調節。將近30倍的高升壓比對轉換器的設計是一項考驗，本文以效率提升的觀點研究四種高升壓比轉換器架構，在切換頻率為18 kHz和100 kHz下分別去比較。本研究主要是以電流饋入式全橋轉換器為比較基準，加入軟切和錯相去進一步提升效率並抑制電壓突波。本文詳述在相同規格下比較四種架構操作在兩種不同切換頻率的效率，模擬和實驗結果證實文中所提出方法在提升效率上的可行性。實驗結果顯示250 W之錯相主動箝位電流饋入式全橋轉換器與其它三種架構的100 kHz轉換器相比，在全負載範圍都有較高的效率，其效率最高可達94.86%。

The intermittency and instability of the renewable sources in the distributed power system can be addressed with the backup supply consisting of the base-load and storage system. The fuel cell is suitable to serve as the base-load system to output unlimited energy without pollution if the fuel is provided continuously. However, the fuel cell has slow response and low voltage. A high step-up DC-DC converter with the proper design is required to interface the fuel cell to the DC-Bus. The converter design of the high step-up ratio (30x) is challenging. In this work, studies on efficiency improvement of four high step-up DC-DC converter topologies with the operating frequency of 18 kHz and 100 kHz are investigated. Soft switching and interleaving approaches are applied to the current-fed full bridge converter to achieve efficiency improvement and voltage spike suppression. This thesis details efficiency comparison of the four topologies at high and low switching frequency. Simulation and experimental results validate efficacy of these two approaches. It shows that the 250 W 100 kHz interleaved active clamp current-fed full bridge converter with a voltage doubler has higher efficiency than the other three 100 kHz converters within the full load range. The maximum efficiency can reach 94.86%.

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