Hybrid three-phase four-wire inverters based on modular multilevel cascade converter

This paper presents two hybrid four-leg inverters that can be be employed in unbalanced three-phase systems. The proposed topologies are based on a modular multilevel cascade converter (MMCC) with double-star chopper cells (DSCC) associated to a conventional two-level (2L) leg. A comparative analysis in terms of the harmonic distortion and semiconductor power losses between the proposed configurations and others four-leg inverters is presented. Additionally, a voltage balancing algorithm of the floating DC capacitors of the DSCC leg is presented to ensure the energy balance. At last, to investigate the proposed system and control strategy, simulation and experimental results are presented.