本論文首先介紹常見LLC-SRC(LLC-Series Resonant Converter)架構以及交錯式LLC-SRC架構，以了解這兩種電路在實際應用上符合的需求以及低壓大電流應用下的缺點。再針對上述需求和缺點提供三相Y-Δ接諧振轉換器以解決問題，並提供三種分析法分析此電路，最後實際實現此電路樣機。其中三種分析包含，電路動作分析以了解電路組成架構以及操作時序；時域分析探討電路動作行為、等效電路圖以及動作方程式；並在頻域分析利用第一諧波近似法(First Harmonic Approximation, FHA)求出穩態下輸出對輸入的轉移函式，以描繪出轉換器增益曲線；最後用狀態平面分析法(state-plane analysis)進一步研究諧振槽在每個區間下的動作行為，並描繪出狀態平面圖，搭配最佳軌跡控制法(Optimal Trajectory Control, OTC)可改善轉換器在暫態下的電壓和電流突波等問題。本論文利用PSIM模擬來驗證此架構的優點以及電路分析的準確性，最後實現一台規格為輸入380 V、輸出48 V最大瓦數5千瓦之三相Y-Δ接諧振轉換器，搭配同步整流技術，最高效率可達96.7 %。

First of all, this dissertation introduces the conventional LLC-SRC (LLC-Series Resonant Converter) and interleaved LLC-SRC topology to understand the practical application requirements and the disadvantages when the application is under low output voltage and high output current. Then in response to above problems, this dissertation provides a three-phase Y-Δ connected resonant converter to solve it, and use three kinds of method to analyze this topology. At the end, the prototype topology is completed. The three methods contain the analysis of the circuit operation for knowing the circuit composition and operation sequence; Using time domain analysis for understanding the detail operation, equivalent circuit model and circuit equation; Then use the FHA (First Harmonic Approximation) to approximate the steady state transfer function and depict the three-phase Y-Δ connected resonant converter gain curve; Finally, the state plane analysis is uses for learning more about the state of resonant tank and uses with OTC (optimal trajectory control) to improve the load transient dynamic response. In order to verify the advantage and accuracy of circuit analysis about three-phase Y-Δ connected resonant converter, this dissertation presents PSIM simulation and experimental result. The specification of simulation and experiment is 48 V/5 kW. The peak efficiency can reach 96.7 % with synchronous rectification.

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