A new five-level voltage-source-inverter using unidirectional switching cells and a coupled-inductor

Abstract

Recently, a new five-level (5L) inverter has been developed. It is named 5L-USC1 and was based on the use of four 2L unidirectional switching cells (USC) and a coupled-inductor (CI) for each phase. This topology was derived from three-level Neutral-Point-Clamped (3L-NPC) inverter. In the paper a new 5L inverter based on basic USC is presented. It is named 5L-USC3 and is based on the use of six 2L unidirectional switching cells and a coupled-inductor for each phase. The proposed topology is derived from 3L-Active-NPC inverter by separation the bidirectional switching cells into two USC groups. The new 5L topology has more degrees of freedom in comparison with the recent 5L-USC1 inverter. As a result, the apparent switching frequency of the output voltage is four times the switching frequency of power devices and so, the current ripple is reduced by half. The apparent switching frequency in each inductor winding is twice the switching frequency of the power devices and thus, the magnetically coupled-inductor windings are considerably reduced.