Single-DC-Source Three-Phase Modified Packed U-Cell Inverter With Reduced Components and Active Capacitor Voltage Balancing

This article introduces a modified Packed U-Cell (PUC) inverter to establish a three-phase configuration using a single dc source to overcome the drawbacks of the multi-individual dc sources in the conventional three-phase PUC topology. The three-phase modified PUC is designed by the cascading connection of a flying capacitor and Hybrid Packed U-Cell (HPUC) in each phase, where the whole circuit design is fed by a single-dc-source voltage. The single-dc-source three-phase modified PUC inverter is also expandable by expanding the HPUC structure. The floating capacitors are actively balanced by integrating the abundant redundant switching states into the designed pulsewidth modulation technique through a voltage balancing algorithm. The performance of the three-phase nine-level modified PUC inverter and its floating capacitor voltage balancing is evaluated through theoretical and experimental analyses under all stand-alone and grid-connected operation conditions. The comparative study demonstrates that the three-phase modified PUC has fewer active and passive devices compared to other counterpart three-phase multilevel topologies.