A Review on Self-Balanced Switched-Capacitor Multilevel Converter

The multilevel converter technology presents a promising solution across a spectrum of power applications, ranging from low to high power. This technology offers several advantages, including a relatively low total harmonic distortion (THD) and the generation of high-quality output waveforms. Multilevel inverter (MLI) topologies have garnered significant attention due to their distinct benefits, such as reduced voltage stress on switches, smaller filter requirements, and enhanced electromagnetic compatibility (EMC). Recent developments have focused on MLI configurations with reduced device counts (RDC), which promise improved reliability and performance over traditional MLIs. MLIs have found extensive applications in various industries, including electric vehicles, ship propulsion, rolling mills, the paper industry, and metal forming processes. Despite their utility, conventional MLI topologies like cascaded H-bridge (CHB), neutral point-clamped (NPC), flying capacitor (FC) inverters, T-type inverters, and modular multilevel converters (MMC) face inherent limitations. These limitations include the lack of inherent voltage boosting capabilities and challenges related to voltage balancing among capacitors, resulting in complex circuitry, control systems, and increased costs. To address these challenges, researchers and engineers are exploring novel MLI topologies with reduced component counts, aiming for optimal efficiency and cost-effectiveness. Switched capacitor (SC)-based MLIs have emerged as a promising alternative, offering inherent voltage boosting and capacitor voltage self-balancing capabilities, alongside high-resolution voltage waveforms. This work focuses on the development of innovative MLI topologies with minimal component counts, high voltage gain, cost-effectiveness, and reduced voltage stress on power switches. Specifically, five-level SCMLI topologies are proposed for medium-and high-power applications, featuring bipolar voltage generation without a backend HB, and capacitor voltage self-balancing through a series/parallel approach. PWM control techniques are employed to regulate power switches effectively in the proposed single-phase five-level topology.