AC-DC-AC converter with shared legs based on cascaded six-leg and three-leg cells

This article proposes a three-phase AC-DC-AC converter with shared legs composed of a three-phase six-leg cell cascaded with one three-leg cell per phase. It is suitable for operation as uninterruptible power supply (UPS) and unified power quality conditioner (UPQC). A space-vector pulse-width modulation (SVPWM) strategy is considered to optimize the converter output voltages while minimizing the number of switch commutations and a DC-link voltage balancing algorithm is presented by employing a hysteresis control and choosing among the redundant states of the converter. Converter model, control strategy and experimental results are also presented. The proposed converter developed lower semiconductor losses than four considered conventional topologies, showing a considerable reduction in the switching losses, because its switches operated with reduced average frequency and current, and reduced reverse blocking voltage.