Seven-switch five-level active neutral-point clamped converter and optimal modulation strategy

The five-level active-neutral-point-clamped (ANPC) converters are newly hybrid topologies which have the advantages of traditional neutral-point-clamped (NPC) and flying-capacitor (FC) multilevel converters. A novel seven-switch five-level ANPC (7S-5L-ANPC) inverter topology is proposed, which reduces the number of active semiconductor switches over traditional 5L-ANPC inverter topologies. It is capable of operating under any power factor conditions. The special modulation strategy for 7S-5L-ANPC is proposed and simulation shows only reactive current is flowing through the seventh switch. Thus, low current rating switch can be selected for the seventh switch. The proposed 7S-5L-ANPC inverter is very suitable for unity and high power factor applications such as photovoltaic (PV) application. A 1KW single-phase inverter prototype is built to verify the validity and flexibility of the proposed topology and modulation.