Three-Phase-to-Three-Phase AC/AC DC-Link Five-Leg Converters Based on Three- and Two-Level Legs

The five-leg back-to-back converter shares a leg between the grid and load sides. In the conventional five-leg converter, all legs are of same type, i.e., either two- or three-level legs. This paper presents topologies of five-leg converters based on the combination of two- and three-level legs. The proposed configurations permit one to obtain intermediary characteristics between the five-leg converter with all three-level legs and that with all two-level legs. The choice of the number of two- and three-level legs and how combine them are shown in order to obtain some characteristics of the grid- and load-side converter voltages. The modeling of the system and the pulsewidth-modulation strategy based on carrier-based and space-vector approaches is presented. Analysis of the total harmonic distortion and power switches losses are also addressed to characterize the configurations. Experimental and simulated results show the system feasibility.