Duo-active-neutral-point-clamped multilevel converter: An exploration of the fundamental topology and experimental verification

For medium-voltage (MV) industrial applications such as the HVDC and adjustable-speed ac-motor drives, the multilevel voltage-source converters are deemed the predominant topologies. One of the promising derived-topologies from the neutral-point-clamped (NPC) configuration is the active NPC (ANPC) structure with an improved balanced lossdistribution performance. This paper introduces duo-ANPC (D-ANPC) converter topology, which is controlled with a new modulation technique. The suggested control method regulates the flying capacitor (FC) voltages naturally at their reference values and preserves the indispensable attribute of the natural balance in the FC-based ANPC inverters. The D-ANPC converter's phase leg is formed by equipping the classic ANPC converter with additional two low-frequency (LF) MV power switches, adding up to six in contrast to four LF power switches in the ANPC. The proposed D-ANPC converter has considerable advantages over the classic multilevel inverters that makes it a competitive topology for MV applications. The substantial reduction in the number of the high-frequency (HF) MV insulated-gate bipolar transistors (IGBTs) by 50% in comparison with the classic ANPC converter as well as a drastic abatement in the total voltage rating and the stored energy of the FCs are the main significant advantages offered by the D-ANPC multilevel converter over the flying-capacitor-based inverters. This study explores the fundamental circuitry of the proposed D-ANPC multilevel topology and provides an exhaustive comparison with classic FC-based inverters. The experimental results are presented to validate the proposed D-ANPC topology and its modulation.