近年來的製造業以及再生能源等對於中、大功率的電力裝置有著龐大需求，電力變流器在其中扮演重要的角色。然而提昇功率等級之後，傳統二階變流器必須使用規格更高的功率開關，切換損失、電磁干擾等電氣問題變得更加嚴重，而多階變流器克服上述電氣限制，且擁有良好的輸出品質，逐漸受到廣泛應用。不過中性點箝位式以及T型多階變流器皆含有中性點電壓擾動的問題，從而影響變流器的輸出品質。
本論文旨在實現基於正弦脈衝寬度調變(SPWM)，以零序成分注入法抑制中性點電壓擾動的改善方法，並應用至三相三階T型變流器。本文將首先介紹變流器架構與調變技術，接著利用數學模型說明直流側電容電壓擾動的成因，以及軟硬體兩種層面的改善理念，最後透過模擬軟體與實作驗證改善方法的可行性且觀測實際效果。

Recently, the manufacturing industry and renewable energy require numerous medium and high-power devices, power inverters play a significant role among those applications. However, two-level inverters must use the power switches with higher voltage rating for the increase of capacity rating. It would induce extra switching loss and suffer from electromagnetic interference. Alternatively, multilevel inverters can overcome the aforementioned restrictions and achieve better output performance. Nevertheless, both neutral-point-clamped (NPC) and T-type multilevel inverters have the voltage fluctuation issue on their neutral-points, which could impact the output voltage quality. This research employs a method to mitigate voltage fluctuation on the neutral-point using zero-sequence component injection to the sinusoidal pulse-width modulation. Mathematical analysis of voltage fluctuation on the neutral-point has been illustrated, followed by the improvement using the software and hardware approaches. The effectiveness of the pro-posed method is validated through both simulation and experiment results.

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