Three-Phase Boost Multilevel Inverter Based on Coupled-Structure Switched-Capacitor and V²SVM

Abstract

Recently, a new type of three-phase boost inverters was developed by using switched-capacitor (SC) units to feed the traditional three-phase inverting bridge. With the cooperation of the coupled structure and a specific modulation strategy, this type of inverters has many attractive features. In this article, an SC-based multilevel inverter (MLI) with this coupled structure is developed by using a triple-mode SC unit with varied terminal voltage to feed the three-phase bridge. Compared with the existing topologies, the proposed SCMLI has advantages of higher boost factor and more output levels. In addition, with the improved virtual vector space vector modulation strategy, the capacitor voltage ripple is optimized by selecting the vector’s redundancy states, and the switching stress dv/dt of the end-side inverting bridge is reduced to two third of its blocking voltage. The topology, working principle, capacitors’ voltage ripples, and power losses as well as comparative study are analyzed in detail. Finally, its feasibility and performance are experimentally evaluated by a downscale prototype with a rated power of 1200 W and the measured efficiency is above 97.6%.