Analysis and Design of the Quasi-Z-Source Inverter for Wide Range of Operation

Impedance source inverters are experiencing a solid evolution since the first release of the traditional Z-source inverter (ZSI) in 2003, and among the abundant structures, quasi-ZSI (qZSI) is commonly studied for many applications due to its simple structure and having a continuous input current. Despite such attractive performance of the qZSI in various applications, it suffers from an inferior performance during partial-load operation, resulting in a limited range of operation. Hence, this paper introduces a conceptual study of the qZSI partial-load operation, demonstrating two important aspects in order to maintain the highest possible performance within the desired operating range. Firstly, a design aspect concerning the proper sizing of the impedance network inductance using linear and non-linear chokes is introduced. Secondly, a control aspect is proposed based on utilizing higher effective switching frequency through switching among different modulation schemes. Finally, a 3 kVA qZSI prototype is utilized in order to experimentally validate the reported analysis and discussions.