Muneeb Ahmed. Int. Journal of Engineering Research and Applications www.ijera.com ISSN: 2248-9622, Vol. 6, Issue 5, (Part - 6) May 2016, pp.14-19 www.ijera.com 14 | Page Topology and Control of Current-Fed Quasi Z-Source Inverter Muneeb Ahmed, Xupeng Fang College of Electrical Engineering and Automation Shandong University of Science and Technology, China ABSTRACT Quasi Z-source inverter is improvement to traditional Z-source inverter. Current-fed quasi Z-source inverter (CF-QZSI) is an enhancement to Z-source inverter (ZSIs), it owns lower component rating, decreased source stress, decreased component compute and prosaic control synthesis. With its distinct structure, the CF-QZSI can operate the traditional zero states to buck the output voltage, which improves the inverter dependability greatly, and provides a tantalizing single stage dc-ac conversion that is able to buck and boost the voltage. For dedications with a variable input voltage, this inverter is a very competitive topology. The paper presents a comprehensive study on the new features of CF-QZSI which include the advantageous buck-boost function, improved reliability and reduced passive component rating, its characteristics is verified by the simulation results . Keywords- Current-source inverter, Voltage source inverter, Current-fed quasi Z-source inverter, buck-boost. I. INTRODUCTION The voltage source inverter and current source inverter provide an attractive single-stage dc-ac conversion that is able to buck or boost voltage, increase efficiency and reduce cost. However, traditional inverters have drawbacks, i.e. behave in a boost or buck operation only, and thus the obtainable output voltage range is limited, either lower or higher than the input voltage. The main switching device of VSI and CSI are not interchangeable, and the capacitor passes through high voltage. Z-source inverter can overcome the inherent drawbacks of the traditional inverters. The quasi Z-source inverter (qZSI) is the improvement to traditional Z-source inverter, voltage-fed qZSI have more attention than the current-fed qZSI. The main drawback of current-fed Z-source inverter is that the inductor passes through high current. The traditional current-fed quasi Z-source inverter uses dc current source as the input. The dc current source can be created by using uncontrollable diode rectifier, battery and fuel-cell series an inductor. Six switches are used in the traditional three-phase inverter. Semiconductor devices are used as the switches.SCR or power transistor with a series diode can be used to provide unidirectional current flow and bidirectional blocking. Newly developed switches the reverse blocking IGBT (RB-IGBT) also promotes the research on CSI [9], [10]. If we compare to current source inverter (CSI), the standard voltage source inverter have 8 switching states, including 6 active states and two zero states. When the upper three or lower three switches are gated on, shorting the load terminals. Current source inverter have 9 nine valid states, 6 active and three zero state. The three zero states produce zero ac line currents. In this case, the dc-link current free wheels through either the switches pole. The remaining states produce non-zero ac output line currents. This paper mainly focuses on the new feature of current-fed quasi Z-source inverter, especially the switching technique. II. CURRENT-FED QZSI CIRCUIT ANALYSIS To improve the traditional ZSIs, four new quasi-Z-source inverters, have been developed which feature several improvements when compared to the traditional ZSIs. They are voltage-fed qZSI with continuous and discontinuous input current, current-fed qZSI with continuous and discontinuous input current. The current fed qZSI in a manner consistent with the current-fed ZSI, are bidirectional with the diode, D. The qZSI shown in Fig. 1, features reduced current in inductor L 2 and L 3 , as well as reduced passive component count. Again, due to the input inductor, L 1 , the qZSI in Fig. 1 do not require input capacitance. All four qZSI topologies also feature a common dc rail between the source and the inverter bridge, unlike the traditional ZSI circuits. Furthermore, these qZSI circuits have no disadvantages when compared to the traditional ZSI topologies. These qZSI topologies therefore can be used in any application in which the ZSI would traditionally be used. L1 L2 C1 C2 L3 D C3 C4 C5 DC current Source LR RL Quasi Z-source network Three-phase Inverter Three-phase Load IGBT1 IGBT3 IGBT5 IGBT4 IGBT6 IGBT2 D1 D3 D5 D4 D6 D2 in I 1 L I 2 L I pn I pn V . Fig 1 current-fed qZSI with continuous input current RESEARCH ARTICLE OPEN ACCESS