Design and Analysis of a Single-Phase Multilevel AC–AC Converter With Inherent Commutation

In this article, the design and analysis of a single-phase multilevel AC–AC converter with inherent commutation are proposed. This converter features a common ground configuration and ensures continuous input and output currents. It can be easily scaled to accommodate various voltage levels. Inherent commutation is achieved by integrating positive and negative switching cells, incorporating an AC link, and semiconductor devices. Accordingly, commutation issues are resolved without requiring an RC snubber circuit or a dedicated safe commutation strategy, simplifying the overall switching pattern and control complexity compared to conventional counterparts. Furthermore, the number of high-frequency switches is reduced. In the three-level implementation, only two unidirectional switches operate at high frequency, while one switch is modulated at the line frequency. Additionally, the total voltage and current stresses imposed on the switches are reduced. By eliminating the body diode of high-frequency switches from the power transfer path, the proposed topology mitigates the reverse recovery issue of the body diode, thereby facilitating the use of high-frequency MOSFETs. The comparisons of the number of components, switching device power (SDP), and efficiency confirm that the proposed converter exhibits low losses, making it an economical, compact, and lightweight solution. To validate its performance, a practical three-level prototype is fabricated, with the experimental results presented and discussed in detail.