A generalized switched-capacitor-based modular T-type inverter topology with reduced switch count.

Abstract

Switched-capacitor (SC)-based multilevel inverters (MLIs) have gained great attention in renewable energy applications owing to their self-balancing of capacitor voltage and ac voltage boosting. Using SCMLI, single-stage dc–ac power conversion is made possible without needing a front-end dc–dc boost converter that improves overall system efficiency, reliability, and power density. However, in most existing SCMLIs, the discharging duration of the rear-end SCs is much longer than its charging duration, especially when a high number of SC units are adopted. While a high number of level generation is expected to produce a better resolution ac voltage, a significant increase in capacitor's voltage ripple, in contrast, distorts the ac voltage despite using large capacitors. Recently, the switched-capacitor modular t-type inverter (SC-MTI) topology resolved the problem by extending the charging period of all SCs to at least half of the fundamental switching period. However, the high switch count of SC-MTI introduces a trade-off in terms of efficiency and cost. In this paper, a new SCMLI topology that retains the good traits of SC-MTI with switch count reduction is proposed. The merits and feasibility of the proposed SCMLI are verified through simulation and further validated through experimental results for seven-level considering various operating conditions.