A 3-Phase Switched-Capacitor Single-Source MLI With Self-Voltage Balancing and Boosting Ability

This article introduces a new structure of switched-capacitor (SC)-based three-phase single-source multilevel inverter (MLI), which is designed to generate nine different output voltage (line-to-line) levels. A low-voltage grid-feeding photovoltaic system is the perfect use case for the inverter. The switching pattern is modeled in such a way that during voltage generation, the main dc source gets isolated, and voltage is supplied based on the SC units. As a result, the voltage of SC units is balanced automatically, and the SC units also provide boosted output voltage up to four times higher than the single-input dc source. Comparing this to other series-connected SC-based inverter topologies, such as flying capacitor and neutral-point-clamped inverters, no additional control complexity is mandatory. The system can be made modular to produce a higher level voltage output as well. The MLI topology, along with the whole system, is simulated in MATLAB/Simulink and PLECS simulation environment. A laboratory-scaled prototype was also built to justify the theoretical claim more boldly.