Hierarchical Control of Bridge-of-Bridge Multilevel Power Converters

Multilevel converters are among the members of the family of power-converter topologies for realizing higher power levels and better waveform quality. In addition to the established topologies of neutral-point-clamped three-level and cascaded H-bridge converters, novel topologies that offer attractive features, such as ease of modularity and functionality, continue to be introduced. Among these, the bridge-of-bridge multilevel converters have the potential for realizing multimegawatt systems with ease. This paper is aimed at presenting a systematic approach to developing their dynamic and steady-state models, leading to a hierarchical-control approach that is intuitive to realize and versatile in application. This paper presents the dynamic and steady-state models and computer simulations that demonstrate the approach in dc-1 phi/ac and 3 phi/ac-3 phi/ac power-conversion applications. An experimental validation of the models using a dc-1 phi/ac asymmetrical-half-bridge converter is presented.