本論文主要研究為應用於微電網系統之高功率雙向直流/直流轉換器，採用雙向升降壓式非隔離型電路架構作為電源電壓轉換及控制的功率級電路。此架構一般會將功率開關操作在硬切換，導致損耗提升，且會產生電磁干擾及高頻雜訊等問題。因此本論文提出一種控制策略，使功率開關具備零電壓切換特性。針對此架構提出的控制策略，其概念為控制功率開關交互切換，利用電感電流自然換向的特性；也就是提供導通路徑，使得電感電流在復歸為零時得以續流。此換向後的負向電流會迫使功率開關上寄生電容內所儲存的能量被釋放，達成零電壓切換特性，大幅地降低傳統硬切所造成的切換損失。特別是即使輕載時，也能輕易地以此方式，提升輕載時的轉換效率，達到全範圍負載高效率之目標。本論文詳細分析電路架構之動作原理，並依據設計準則實作一台2 kW具自然換向高功率雙向轉換器，其轉換效率於70%負載以上時均可達到96%以上。

This thesis proposes a high-power bidirectional DC/DC converter for micro-grid system applications. The power-stage circuit topology is a non-isolated buck-boost DC/DC converter. Conventionally, this topology is hard-switched, which results in significant switching losses, as well as induces electromagnetic interferences and high-frequency noises. Contrarily, a novel control strategy is proposed in this thesis, in which zero-voltage-switching (ZVS) of power switches can be realized with simple pulse-width-modulation. The term “natural commutation” here means that inductor current keeps flowing reversely through the switched-on path. This reversed current will accordingly release the energy stored in the parasitic capacitance of the power switches, which significantly reduces the switching loss. Specifically, even at light-load condition, the conversion efficiency can be improved easily by this control strategy and achieves high efficiency under wide-range load variations. The circuit topology and the operation principles are analyzed in detail in this thesis. According to the design rules, a 2 kW bi-directional converter is built to test its feasibility. The power efficiency is higher than 96 % .

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