Five-Level Unity-Gain Active Neutral-Point-Clamped Inverters Designed Using Half-Bridges

Abstract

This paper proposes two novel 5-level active neutral-point-clamped (ANPC) inverters that double the voltage gain of the conventional topology from half to unity. Each phase of the proposed topologies is constituted by three half-bridges that control a flying capacitor to generate 5 symmetrical ac voltage levels. The natural voltage balancing of dc-link and flying capacitors in the proposed topologies implies that the sensors and voltage balancing controller commonly used in the conventional ANPC inverter are no longer necessary. In addition to switch count reduction, the most noteworthy merit of the proposed topology is its ease of implementation with commercial half-bridge modules, where the design of dedicated circuit is not needed. The operation of the proposed 5-level unity-gain ANPC (5L-UG-ANPC) inverters is analyzed and validated through simulation and experimental tests.