A hybrid multilevel inverter using single source neutral-point clamped front end and cascaded H-bridge with flying capacitor based structures

摘要

A novel three-phase multilevel inverter using a single dc source is proposed in this paper, which uses flying capacitors for generating different voltage levels. Pole voltage levels can be of five levels or higher than that. The structural similarity of the front end of the proposed inverter with that of the three-level neutral-point clamped inverter and the presence of redundant switching states helps in the voltage balancing of flying capacitors as well as dc bus capacitors. This inverter topology has advantages over traditional multilevel topologies in terms of the number of devices, fault-tolerant operation and performance under variable modulation index and load conditions. Simulation results are presented to illustrate the performance of a five-level proposed inverter fed induction motor drive. However, this topology can be extended further for higher levels by cascading multiple H-bridge circuits.