A Single-Phase Hybrid Six-Leg AC-DC-AC Multilevel Converter

Abstract

This paper presents a single-phase hybrid six-leg AC-DC-AC multilevel converter. The configuration is composed of a three-leg neutral point clamped (NPC) converter connected in series with a three-leg two-level converter. The proposed converter provides a sinusoidal input current with unitary input power factor and it feeds the load with a stable AC voltage. The system model, operation principles and a control strategy are presented and discussed. Additionally, a space-vector PWM technique is developed to control the dc-link capacitors, produce optimal voltage waveforms and to reduce the switching losses. The space-vector strategy guarantees nine-level output voltage waveforms at both input and output converter sides. Experimental and simulation results are presented to validate the theoretical studies.