本論文目的為研製一台輸入電壓800VDC，輸出電壓100VDC，最大輸出電流200A，最大輸出功率為20 kW的三相Y-Y LLC直流-直流轉換器。為了因應高功率的需求，本論文採用三相Y-Y LLC轉換器作為電路架構，相比於傳統諧振電路電路，三相Y-Y LLC電路仍然保有高效率、可高頻化的特性，且擁有更高輸出功率的能力。除此之外，輸出電容設計較大使輸出電容電流漣波較小，變壓器端一次、二次側皆使用Y接法，Y接法方式可以降低實際諧振槽元件數值不相同與其他元件誤差，所造成的不均流現象。
由於此規格下最大輸出電流高達200安培，所以本論文利用雙變壓器取代單變壓器，讓一次側變壓器串聯以降低變壓器跨壓，二次側並聯來分擔變壓器二次側電流，二次側使用全波整流二極體架構能使電流應力減半，讓功率元件有更多選擇的空間。
最後，本論文實現一台20 kW Y-Y接雙變壓器LLC電路，輸出電壓100VDC，控制上採用數位控制，使用IC為德州儀器的TMS320F28379做變頻控制，最高效率可達97%。

The purpose of this project is to develop a three-phase Y-Y LLC DC-DC converter with an input voltage of 800VDC, an output voltage of 100VDC, a maximum output current of 200A, and a maximum output power of 20kW. In order to meet the demand for high power, this paper uses a three-phase Y-Y LLC converter as the circuit architecture. Compared with the traditional resonant circuit, the three-phase Y-Y LLC circuit still retains the characteristics of high efficiency, high frequency, and higher output power capacity. In addition, the design of the output capacitor is larger so that the output capacitor current ripple is smaller, the primary and secondary sides of the transformer are Y-connected. The Y-connected method can reduce uneven current phenomenon caused by the difference of the actual resonant tank component value and the error of other components.
Since the maximum output current under this specification is as high as 200 amperes. Therefore, in the paper, dual transformers are used instead of single transformers, the primary side transformers are connected in series to reduce the voltage across the transformer, and the secondary side is current of the transformer, the full-wave rectifier diode structure on the secondary side can reduce the current stress by half, so that power components have more choices.
Finally, this project implements a 20 kW Y-Y dual-transformer LLC circuit with an output voltage of 100VDC, the control adopts digital control, using IC for Texas Instruments' TMS320F28379 for frequency conversion control, the highest efficiency can reach 97%.

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