本論文旨在研究多階層換流器在電容性與電感性負載時電路的特性。當多階層換流器的階層大於三階且負載為電容性或電感性時，在開關滯怠時間內有些多階換流器架構會無法由原預期的路徑續流，使其被迫流經輸入電源端而造成電壓階層的變換。本論文回顧許多既有架構，探討該問題是否存在這些架構中。回顧後將有電流路徑續流問題的架構依解決方法分類，而本論文著重在其中一個解決方法進行探討。最後實作一五階換流器，其規格為輸入電壓為400V,dc，輸出電壓220Vrms,ac 輸出視在功率3.75 kVA，來驗證此問題的存在，並根據所提出的解決方法來改善此現象，並對改善前與改善後的特性做比較。

This thesis mainly studies on the capacitive load and inductive load characteristic of multilevel inverter. When load is capacitive or inductive, some topologies are not able to provide the expected current path during switching dead time. Therefore, the current is forced to flow through the input source and results in voltage level change. This thesis reviews some existing topologies, checking whether there is current path problem or not. After review, these topologies with current path problem will be sorted by their solution to the problem. This thesis focuses on one of the solutions to study. Finally, a five-level multilevel inverter, whose input voltage is 400 V,dc, output voltage is 220Vrms,ac and output apparent power is 3.75 kVA, is implemented to verify that the problem exists. The solution presented is also implemented to improve the characteristic of the circuit when load is capacitive or inductive. A comparison of the characteristics before and after the solution is implemented and is presented to show the difference.

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