Quasi-Impedance-Source-Network-Based Nonisolated High-Step-Up DC-DC Converter

Abstract

The high-step-up dc-dc converter is a key for numerous renewable-energy-based applications such as photovoltaic and fuel cells. Due to the low-voltage output of these renewable sources, a high-step-up stage is required, which bridges the gap of renewable to utility state. In this article, a noncoupled high-step-up Z-source dc-dc converter, utilizing a quasi-Z-source (QZS) network, is presented. The proposed topology is a combination of QZS structure and switched-capacitor cells, which maintains continuous input current and low-voltage stress across capacitors. In addition to these merits, the converter can achieve a high-step-up voltage at a low duty cycle, which results in lower conduction losses on semiconductor devices. The working principle, steady-state waveforms, related expressions, and comparative study are included in this article. The proposed converter can be extended for the use of a single-stage step-up Z-source inverter and also for hybrid output applications. Finally, experimental results are presented to verify the feasibility of the converter in both open and closed loops. © 1972-2012 IEEE.