Switched-capacitor-based modular t-type inverter with reduced switch count

Abstract

Switched-capacitor (SC) based inverter topologies are very attractive for renewable energy applications to step-up low dc voltage to higher ac voltage in single-stage without the need of front-end dc-dc converters, thus improving overall system efficiency, reliability and power density. This paper presents a new modular multilevel inverter based on switched-capacitor technique. Herein, series-parallel conversion technique is utilized to effectively self-balance the switched-capacitor voltages. Compared to other latest SC-based MLIs topology, the proposed structure features several advantages such as: low number of conducting semiconductor devices in load current paths and SC Charging paths. In addition, each capacitor is charged for at least half of the fundamental period that reduces voltage ripple and improves the inverter efficiency. Consequently, the presented inverter is suitable for high levels generation to achieve the rated ac voltage directly from a low voltage dc source. The merits and feasibility of the proposed inverter are verified through simulation for seven levels with sinusoidal PWM at different modulation indices and load conditions.