Evaluation of Conduction and Switching Losses in Cascaded Multilevel Inverters

This paper evaluates the state of the art in switching and conductivity losses for ac drives fed from three-phase voltage source cascaded multilevel inverters. Cascaded multilevel inverters schemes having relevance for industrial application are described and their respective advantages and disadvantages are explained. Secondary effects such as the influence of current displacement factor, dependent conductivity loss and modulation index in cascaded multilevel inverters schemes and switching energy are discussed, and adequate compensation methods are presented. Obtained results manifest the performance of the switching and conductivity loss principles for a nine level cascaded inverters with sinusoidal pulse width modulation. This paper provides a guideline and quick reference for the practicing engineer to decide which methods should be considered for an application of a given cascaded multilevel inverters switching and conduction losses.