A Single-Phase Seven-Level Nested Switched-Capacitor Converter With Enhancing Lifetime and Reducing Size of Flying Capacitors

This article introduces a seven-level nested switched-capacitor (7L-NSC) inverter topology designed to reduce the flying capacitors and extend their operational lifetime. The proposed 7L-NSC topology utilizes two symmetrical flying capacitors, each rated at one-third of the dc source voltage. The redundant switching states along with a capacitor voltage balancing method based on an overall priority index provide proper operation of the proposed topology in all operating points. By incorporating redundant switching states and a capacitor voltage balancing method based on an overall priority index, the topology ensures stable operation across various operating points. Comprehensive comparisons with existing seven-level structures highlight the advantages of the 7L-NSC in terms of the number of components and their voltage ratings, as well as the required capacitor volumes and their voltage ripples. A comprehensive lifetime analysis of flying capacitors, comparing the proposed topology with prior designs, is performed. Through detailed mathematical modeling and evaluation of capacitor voltage ripples under varying load conditions and modulation indexes, it is demonstrated that the proposed 7L-NSC significantly enhances the operational lifetimes of capacitors as a result of symmetrical voltage distribution and reducing stress. A laboratory-prototyped 7L-NSC topology is implemented along with the simulation to verify the feasibility of the proposed inverter under different operating conditions.