New Multilevel-Flying Capacitor Inverters with Coupled-Inductors

In the paper a new five level (5L) inverter based on unidirectional Flying-Capacitor switching cells is presented. It is named 5L-Flying-Capacitor with Coupled-Inductor (5L-FC-CI) and consists in parallel connection of two unidirectional (P and N) three level (3L) Flying Capacitor switching cells with a coupled-inductor. The PWM output voltage is vastly improVed and the switch control dead times is eliminated, particularly when compared with the 3L inverter obtained with bidirectional Flying Capacitor cells. The phase shifted carrier (PSC) modulation is used to control the new 5L topology. Thus, the proposed structure ensures an apparent switching frequency in each winding of coupled inductors twice of switching frequency. The analysis of the new inverter is verified by numerical simulations both for single and for three phase topologies and their features are generalized for N odd voltage levels (NL).