Z Source Multilevel Inverters
There are two hotly researched Z source/quasi Z source (ZS/qZS) multilevel inverters: the ZS/qZS neutral point clamped (NPC) inverter and ZS/qZS cascaded multilevel inverter (CMI) The ZS/qZS concept, integrating with those traditional multilevel inverters, inherits the merits of both topologies with improved inverter reliability due to short circuit immunity. This chapter presents the configurations, operating principles, and modulation schemes of the two ZS/qZS multilevel inverters. Three level NPC inverters, having many inherent advantages, are commonly used as the preferred topology for medium voltage ac drives. The CMI is a promising candidate for the next generation of PV power converters because it has features such as separate PV sources, transformerless, low harmonics, small filters, and low switching frequency. The system level modeling and control of a qZS CMI based three phase grid tie PV power system were addressed, and simulation results were demonstrated, providing a competitive candidate for high power medium voltage power systems.