Extendable switched-capacitor multilevel inverter with DC strings and self-balancing capacitors

A multilevel inverter (MLI) is a critical component used to convert lower voltage levels to higher power loads in the field of renewable energy. By integrating switched-capacitor (SC) units with DC-AC converters, it can offer advantages over conventional two-stage conversion systems, including improved efficiency, optimal component count, and smaller passive element sizes for both inductors and capacitors. This paper introduces a novel extendable SC-MLI with the flexibility in cascading numbers of DC inputs and SC units to generate higher voltage levels and boost gain, making it an ideal topology for practical applications such as static synchronous compensators (STATCOMs). A STATCOM needs to generate different AC voltage amplitudes with low total harmonic distortion (THD) of 5%, as set by IEEE Standard 519-1992, across various modulation indexes MI to compensate for reactive power and enhance power system efficiency in modern networks. Moreover, the proposed topology requires lower-cost components, further enhancing its suitability for practical use. Then, the proposed topology is compared with the other existing extendable SC-MLIs in terms of the number of components, voltage stress, boost gain, cost, and conversion efficiency. Finally, a lab scaled experiment is conducted to verify the proposed topology with the PLECS-based simulation and theoretical analysis. • A novel switched-capacitor multilevel inverter (SC-MLI) is proposed. • The proposed SC-MLI can achieve high voltage gain with a reduced complexity. • Self-balancing capacitors are used to enhance reliability and eliminate external control. • Extendable topology enables scalable levels using direct current (DC) strings for flexible applications. • High efficiency and voltage stability are validated through simulations and experiments.