Optimal asymmetry for cascaded multilevel converter with cross-connected half-bridges

DC-AC conversion has been revolutionized by multi-level converters due to their high power quality, high modularity and high voltage operation with standard semiconductors. New multilevel topologies, voltage asymmetries and control techniques have been developed in the last decade to improve the performance of these power converters. This paper proposes a novel voltage asymmetry for a three-phase cascaded multilevel converter based on cross-connected half-bridge cells. The proposed asymmetry is compared with the state-of-the-art asymmetry in the same topology and with several asymmetries and topologies as the conventional Cascaded H-Bridge (CHB), the Asymmetric Cascaded H-Bridge (ACHB) and the Neutral Point Clamped (NPC). This paper presents a comparison and analysis of voltage levels generated, the number of IGBTs and isolated voltage supplies required. Simulation results are presented for a converter of 11 kV and 4 MVA. The proposed configuration increase the number of voltage levels in three-phase loads, reducing the Total Harmonic Distortion (THD) under 1%. On the other hand, the total blocking voltage was not reduced, but the number of isolated power sources required for the proposed topology is very low in comparison with other topologies.