An optimization approach for designing multilevel converters

Optimization techniques have become powerful tools in the design of power electronics converters. In this paper an optimization technique is proposed to design a multilevel converter. Unlike the majority of previous converter optimization, this technique considers multiple characteristics to be optimized. Efficiency, inductance, loss distribution and component cost are optimized through a weighted objective function. The technique selects between the NPC and the ANPC topologies as each presents key advantages at specific conditions. A model to calculate the switching and conduction losses and the loss distribution for each topology was derived. The semiconductor technology is not restrained to a single type. Instead IGBTs, MOSFETs, and diodes are considered along with the switching frequency. The optimization is carried out for both inverter and rectifier operation, both with three loading conditions. As expected, some key characteristics of the topology and semiconductor become pronounced as conditions vary, resulting significantly different optimal designs.