Quasi-Z-Source Inverter Topologies with Reduced Device Rating: a Review

Abstract

Quasi-Z-Source Inverter (QZSI) has introduced a new wave of interest in engineering industry and research. Reduction in device rating has been the main objective in introducing QZSI topologies. The introduced topologies in QZSI have proven to be feasible in a wide range for high power with medium voltage applications. This paper mainly focuses on QZSI topologies with continuous input current conduction and also power conditioning in the renewable energy system. Based on a detailed comparison of these topologies suitable QZSI can be arrived for a given application. Keyword:Continuous input current Quasi Z-Source inverter Reduced device rating Copyright © 2017 Institute of Advanced Engineering and Science.All rights reserved. Corresponding Author:Premalatha L., School of Electrical Engineering, VIT University, Chennai -600 027, India. Email: premalatha.l@vit.ac.in INTRODUCTIONQuasi-Z-Source Inverter (QZSI) is derived from the original Z-Source Inverter (ZSI) where it can be utilized to all power converters i.e., DC-AC, DC-DC, AC-DC, AC-AC. ZSI can operate in boost inverter or buck inverter but not as buck-boost inverter [1]- [3].By introducing QZSI some of the disadvantages in traditional ZSI can be overcome. The QZSI has the wide range of applicability in the renewable energy system, where it gives a single stage power conversion with buck-boost characteristics and improve the reliability of the inverter [4]- [8]. In shoot through states, both power switches in a leg are turned on at the same time and it is used to step up the voltage and the output voltage in QZSI can be boost to designed value. Research based on these QZSI has concentrated on modelling and control, photovoltaic and other electrical applications. The QZSI can buck and boost the input voltage in single stage with two control variables; shoot through and modulation index. New topologies of QZSI which has been derived from original ZSI can be proposed for PV applications, because of continuous input current and reduced capacitor rating. QZSI has a prescribed application to combine with renewable energy system for a wide voltage range to distribute for power grid [9]- [12].Moreover, the voltage stress on capacitors and current stress on inductors and diodes in QZSI are lower than traditional ZSI for same input and output voltage. QZSI avoids inrush current at starting, where destroy of the devices can be avoided and also these topologies are more viable for solar cell and fuel cell applications it may acquire high voltage gain to match the source voltage difference [13], where for the same input and output voltages, it can use lower duty cycle and higher modulation index, which results in less switching stresses, better output power and lower input current ripple. The advantage of including inductors in the QZSI network will limit the current ripple through the devices during boost conversion mode.