由於單相交直流轉換器以及直交流轉換器的輸入端與輸出端為交流電，因此其瞬時功率皆帶有二倍線頻的諧波成份，即頻率為交流電源頻率的兩倍，於此稱為二次諧波。而傳統文獻上為了改善此二次諧波的影響，必須增加額外的電路與主動式開關以引導二次諧波成份，因此成本也隨著提高，且控制較為複雜。而業界上則是使用過於龐大的濾波元件以降低二次諧波成份，不僅無法有效的設計元件值，也降低功率密度，額外增加成本。有鑒於這個困境，本論文的主要目的在於尋找不須額外增加任何元件，且能夠有效消除二次諧波成份的控制策略。
而本論文主要貢獻點如下：第一點貢獻為提出一新型單級功因校正器，其不僅能夠擁有高功率因數與高轉換效率，僅需三個主動式開關，且皆為共地，因此製作驅動電路時不須額外隔離，且提供了更多的控制自由度。第二點貢獻為提出一個近似的二倍線頻諧波等效電路，其在目前文獻上，尚未被提出。第三點貢獻為利用本論文所導演之二倍線頻諧波關係式與等效電路，進行分析並提出一消除輸出電壓二次諧波成份之控制策略與電路元件設計流程，如此可大幅減少實體電路中濾波元件之體積。最後依據本文理論與分析之結果，設計與研製一規格為輸入電壓110 V均方根值，與輸出電壓48 V直流值，以及額定功率為200 W之雛型系統，並經由電路模擬軟體與實驗結果相互驗證所提新型轉換器的可行性，從輕載至滿載皆可有效消除輸出電壓二次頻諧波成份達97%，功率因數維持於0.98以上，且轉換效率維持90.7%以上。

It is a well known fact that, the instantaneous power of a single phase rectifier or inverter, always contains a double line frequency component. As a result, it is necessary to either add additional components to reduce the harmonic or increase the filter capacitor. In view of this dilemma, the motivation of this thesis is mainly focused to search for an effective double line frequency harmonic reduction control technique without adding additional components. Basically, the major contributions of this thesis can be summarized as follows. First, a novel single stage power factor corrector (PFC) topology is proposed. The new PFC contains only three active switches with a common terminal. This can not only simplify the gate driver but also provide more control flexibility. Then, an approximate double line frequency harmonic equivalent circuit is proposed for practical applications. To the author’s best knowledge, that double line frequency harmonic equivalent circuit has never been proposed in the world. Third, based on this model, a harmonic reduction technique is proposed to reduce the double line frequency harmonic without adding any component. Finally, a prototype PFC with 110V AC input, 48 V DC output and 200 W rating is constructed for verifying the effectiveness of the proposed control. Experimental results show that more than 97% of the output double line frequency harmonic can be reduced adding any extra component while the PF is kept above 0.98 and the efficiency remains above 90.7% from 40 W to 200 W loading. Keyword: Power factor corrector, double line frequency harmonic, Bridgeless

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