近年來再生能源以及電動車等新興市場的需求越來越龐大，這些裝置通常需要中、高功率的變流器來實現。傳統的二階變流器由於電晶體耐壓的限制，使得功率的發展受限。而多階變流器則使得電晶體的規格可以有較大的彈性，且其輸出電壓較接近正弦波，因此逐漸受到中、高功率市場的青睞。然而，多階變流器具有中性點電壓不穩定的問題，使其輸出品質受到影響。
本論文旨在改善中性點電壓震盪問題，以外加的雙向補償電路，抑制中性點電壓的震盪。本文首先針對變流器的基本架構進行介紹，接著分析中性點電壓震盪的成因及改善方法，並透過模擬以及實作驗證此方法的可行性。最後本文透過量測輸出總諧波失真及電晶體切換損等方式 ，與二階變流器比較其電氣性能。

Recently, the emerging markets of the renewable energy and electric vehicles require numerous medium and high-power devices. Power inverters play a significant role among those applications. However, the two-level inverter must use the power switches with higher voltage rating for the increase of capacity requirement. It would inevitably induce extra switching loss and total harmonic distortion. Alternatively, the multi-level inverter can overcome the aforementioned obstacles and achieve better output performance. However, the multi-level inverter has the intrinsic voltage fluctuation problem on the neutral-point, which affects the quality of the output waveform. This research is devoted to reduce the voltage fluctuation on the neutral point. The analysis of neutral point fluctuation and the pros and cons of the well-known mitigation methods are illustrated, followed by the introduction of the proposed bi-directional compensation circuit. The proposed solution was validated by simulation and experimental results. In addition, the performance comparison to the two-level inverter was conducted by assessing the total harmonic distortion and the switching loss.

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