Current-fed quasi-Z-source inverter with voltage buck-boost and regeneration capability

The conventional current-source inverter has two major problems: unidirectional power flow and voltage boost operation, which makes it impossible to be used in many applications such as hybrid electric vehicles (HEVs) and general purpose variable speed motor drives. The Z-source inverters (ZSIs) can solve both problems. The quasi-Z-source inverters (qZSIs) were recently proposed as an important improvement to the traditional Z-source inverters. Besides the advantages inherited from the ZSIs, the qZSIs also have several of their own merits. The current-fed qZSI/ZSI is bidirectional with an additional diode, unlike the voltage-fed qZSI/ZSI that needs a switch to achieve bidirectional power flow. This paper presents a comprehensive study on the new features of the current-fed qZSI, including the advantageous buck-boost function, improved reliability, reduced passive component ratings, and unique regeneration capability. A modified SVPWM method is proposed and the available operating regions (motoring and regeneration operation) are analyzed in this paper. Since the current-fed qZSI has the same operation with the current-fed ZSI, many results of this paper are also applicable to the current-fed ZSI. A reverse blocking IGBT (RB-IGBT) based current-fed qZSI prototype was developed in the laboratory. Experimental results are shown to verify the theoretical analysis.