Abstract

The per-phase leg of an improved active-neutral-point-clamped (I-ANPC) multilevel converter is realized by the cascaded connection of the standard ANPC topology and the concatenated H-bridge modules consisting of the flying-capacitors (FCs). This article proposes an innovative approach for the active control of the I-ANPC inverters. The introduced methodology is developed on the basis of the logic-equations set for the active voltage balancing of the FCs within the H-bridge modules, and controlling the generated output voltage. It derives logic-variables employing the direction of the output current, and the deviation of the FCs' voltages from their target operating levels in the H-bridge cells. These logic-variables are fed into a set of logic-equations derived for the control of the I-ANPC inverter. The regulation of the floating-capacitor voltages at their reference values along with synthesizing the required pulsewidth modulation voltage-level at the output having fast dynamics are the control objectives to achieve. The derived logic-equations and the proposed control method are explored and verified by the experimentally measured results obtained from the 5-kW prototype of a five-level converter.