本文應用選擇諧波消除(selective harmonic elimination）技術計算一反流器系統之開關切換角度，此反流器系統配合曲折繞接式（zig-zag）變壓器於輸出端。不同於選擇諧波消除技術常用的四分之一波對稱之波形，本文之脈波寬度調變波形使用半波對稱波形。儘管使用半波對稱波形在計算上較繁雜，但可提供較多的解並有機會得到較好的解。由於選擇諧波消除技術可直接控制特定諧波，因此適用於對特定諧波有抑制能力的設備如曲折繞接式變壓器。本文提出的系統中，兩組變壓器的一次側電壓由兩組六開關之全橋反流器供應，且此兩組反流器之電壓波形有30度之相位差。此變壓器可將12n加減1次以外的諧波抑制在變壓器二次側，因此半波對稱的選擇諧波消除方法設計消除12n加減1次的諧波成份與控制基本波的大小。根據上述規範，本文建立一小型系統來驗證其可行性。
關鍵詞： 選擇諧波消除、 曲折繞接式變壓器

Abstract
This thesis applies the selective harmonic elimination (SHE) technique to determine the switching angles for an inverter system that is cooperated with special connected transformers called zig-zag connected transformers. Unlike quarter-wave symmetry, most employed in SHE strategy, half-wave symmetry is used in this thesis. Although half-wave symmetry needs more calculation burdens than quarter-wave symmetry, it provides wider solution space and better solutions. Attributed to directly controlling harmonics, SHE technique has the adaptability to associate with apparatus which are congenitally immune to specific harmonics, such as the zig-zag connection transformers. In this thesis, two sets primary windings of the transformers are supplied by two 6-switch full-bridge inverters with 30 electrical degrees phase shift. Prohibited by the transformers, harmonics with orders other than 12n add/subtract 1 (n is positive integral number) will not appear in the line-to-line voltage of the secondary side. Then, SHE technique with half-wave symmetry is employed to handle harmonics with orders equal to 12n add/subtract 1, and controls the amplitude of the fundamental. Based on specifications described above, a small-size prototype is built to verify the practical validity of the proposed system.
Keywords: Selective harmonic elimination, zig-zag connection.

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