為使人類文明得以永續發展，且不會有能源匱乏的問題發生，有效地利用再生能源成為近來最受矚目的議題。若欲將再生能源應用於大功率負載，如中/高壓市電併聯系統，通常使用三相直交流轉換器。且受限於現有功率開關元件的額定電壓，反流器大多使用多階轉換器。此外，傳統再生能源系統中的轉換器為二級式直交流轉換器，若能將其整合為單級式反流器，則可提升電源轉換效率。有鑒於此，本論文之主要目的在於研發一新型單級式單相多階反流器，以適用於再生能源之應用特性。且新型轉換器模組化後，僅需並聯三組即可衍生為三相多階反流器架構。
本論文之主要貢獻如下：首先，本文提出一具有電氣隔離特性之新型單級式單相五階反流器。新型轉換器係使用廣義零向量之概念，將傳統二級式反流器整合為單級式反流器，繼而提高轉換器之功率密度與電源轉換效率。新型轉換器與傳統五階反流器相比，傳統型具有八只功率開關，而本電路之反流器部分僅需使用六只功率開關，且其中兩只功率開關為低頻切換，有效降低開關之切換損失。第二點貢獻，針對本文提出之新型轉換器分析其操作模式及工作原理，並進一步推導出直流模型與交流小訊號模型，以作為閉迴路控制之依據。第三點貢獻則是根據本文理論分析之結果，實際製作一規格為20V直流輸入、110V有效值交流輸出及輸出功率額定200W的雛型系統，本轉換器之效率自輕載至滿載皆約為90.9%。最後，由實驗與模擬結果相互比較，可驗證此新型轉換器確實可達預期之效果。

For sustainable development, promotion of installing renewable energy systems has become one of the most popular issues recently. For handling larger power, a three-phase inverter is chosen for connecting to a medium/high voltage grid system. However, due to the limited voltage rating of power devices, a multilevel converter is usually adopted. Moreover, to increase the efficiency, a single-stage converter configuration is preferred than a two-stage converter. Therefore, the objective of this thesis is mainly focused on developing a novel single-stage single-phase multilevel inverter for renewable energy systems. Naturally, a three-phase system can be synthesized easily with three single-phase modules.
Basically, the contributions of this thesis can be summarized as follows. First, a novel single-phase single-stage five-level inverter topology with electrical isolation is proposed. Based on the generalized zero vector (GZV), it is seen that the conventional two-stage inverter can be integrated into a single-stage one to simplify the configuration and enhance the efficiency. Compared with the conventional inverter, only six active switches instead of eight switches are required. The proposed inverter can still keep the advantages of a conventional multilevel inverter. In addition, among them, two active switches are operated under very low switching frequency. Next, the corresponding mathematical model of the proposed converter is derived for convenient controller design of the converter. Finally, a 200W, 20V DC input and 110Vrms AC output prototype is constructed for verifying the effectiveness of the proposed five-level inverter. The maximum efficiency can be maintained to about 90.9% approximately with a rather flat profile form full load up to 20W.

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