本文提出一三相多脈波、多階變流器架構，利用多組三階式三相全橋變流 器串級輸出以得到低諧波電壓。本研究所發展的系統只需一組直流電壓源，利用後級的多組隔離變壓器串聯組合以疊成所要的低諧波輸出電壓波形。雖然傳 統上利用變壓器移相連接到多組轉換器的應用已包括12 脈波到48 脈波等之應用，但這些組合架構通常都應用於交流到直流轉換器上，配合三相二級體整流以獲得低諧波之輸入電流。本研究則是將其反向應用到直流到交流轉換器上，其原理也是利用電壓合成的階梯波形，通過改變變壓器匝數比與曲折連接，達到低諧波輸出電壓的目的。本研究以實作一1 kVA 的12脈波–三階變流器為例，利用相移變壓器與轉換器移相控制組合來產生近似正弦波的階梯波形，以說明所提方法確實可行。

This paper proposes a three-phase multi-pulse multi-level inverter using multiple sets of three-phase three-level full-bridge structure, whose output are cascaded through a series combination of isolation transformers to obtain low harmonic three-phase output voltages. The developed system is built with only one set of DC voltage source. The use of multiple sets of phase-shifted transformers to get low harmonic currents has been presented in many applications, included 12-pulse to 48-pulse, etc., but these are usually a combination for AC-DC converter whose secondary outputs are followed by three-phase diode rectifiers. This study applied a similar idea to the DCAC inverter, through the synthetic step voltage waveforms to reach the threephase output voltages with low harmonics. Finally, a prototype of 12-pulse inverter structure with 1 kVA rating was set to verify the proposed idea.