Resonant Switched-Capacitor Multilevel Inverter

For almost a decade, switched-capacitor multilevel inverters (SCMLIs) have been a prominent research topic in power electronics due to their attractive features, including inductor-less voltage boosting capability, ease of control and implementation, as well as self-voltage balancing of capacitors. However, a major shortcoming of SCMLIs is the imperative parallel charging process of the capacitors from a DC source or another internal SC-based unit, which causes unwanted inrush currents, EMI generation, and excessive current stress posing a critical challenge for high power applications. Consequently, the deployment of SCMLIs in future photovoltaic and motor drive applications remains uncertain. To address these critical issues, this article introduces a novel class of SCMLIs featuring an integrated resonant (Res)-based charging operation with a soft-switching and soft-charging procedure. For the first time, this innovative concept is applied to an active boost neutral point-clamped (ABNPC)-based five-level (5L) converter, enabling full DC-link utilization at the AC output through a resonant network without any inrush or current stress issues. The 5L-ABNPC-based variant of the proposed Res-SCMLI, which can be modulated through both phase-shifted or level-shifted standard PWM strategies, consists of four bidirectional and four normal FETs, two DC-link capacitors, and one floating self-balanced capacitor. Extensive analysis, a comparative study, and validation through simulation and experimental results from a 3 kW SiC-based single-phase laboratory-built prototype for both open-loop and grid-connected conditions confirm the effectiveness of this approach.