Z-Source-Based High Step-Up DC–DC Converters for Photovoltaic Applications

Abstract

This article proposes three high step-up Z-source (ZS)-based dc–dc converters by integrating the conventional ZS network with switched-capacitor (SC) cells. The proposed converters offer a simple structure with a smooth input current, a high-voltage gain, and low voltage stress on the semiconductor devices. In addition, the proposed converters, unlike some existing ZS-based topologies in the literature, do not impose any limitation on the duty cycle of the power switch. These characteristics make the proposed converters excellent candidates to interface a low-voltage solar photovoltaic (PV) panel with a high-voltage dc bus in PV applications. Among the proposed three converters, the operating principles and steady-state analysis of the one with more components are presented in detail. However, the steady-state voltage and current relationships are also tabulated for two other proposed converters. In addition, design considerations are presented. The performance of the proposed converters is compared against similar existing high step-up dc–dc converters with regards to the component count, normalized voltage stress on the power switch and diodes, and voltage gain. Finally, the theoretical analyses and calculations are validated through experimental results using a 400-W/400-V laboratory prototype.