Three-phase five-level active-neutral-point-clamped converters for medium voltage applications

In this paper various five-level active-neutral-point-clamped converters (ANPCCs) are proposed. These, as for the conventional ANPCC structure, are constructed with a combination of neutral-point-clamped and floating capacitor converter technologies. Depending on the new circuit arrangement, better total semiconductor conduction losses and/or the requirement of lesser active switch part count are achievable when compared to a conventional ANPCC. Additionally, a modulation scheme providing well regulated, balanced and low voltage ripples across the dc-bus capacitors for the studied ANPCCs is presented. The voltage balancing across the phase capacitors is performed by selecting the multilevel converter redundant switching states, which results in different current direction across this device. The technique is implemented in a carrier-based PWM modulation scheme.