A Three-Winding Coupled-Inductor-Based Dual-Switch High Step-Up DC–DC Converter for Photovoltaic Systems

Abstract

This article proposes a new high step-up dc–dc converter for photovoltaic applications. A dual-switch structure with a three-winding coupled inductor (3WCI), whose secondary and tertiary windings are integrated with switched-capacitor cells, is adopted to achieve a high-voltage gain with a small duty cycle, thus avoiding an extremely high duty cycle. The input current is continuous, and the voltage gain could be adjusted by two parameters: the switches’ duty cycle and 3WCI's turns-ratio, thus increasing the design flexibility of the proposed converter. In addition, low-voltage-rated <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s with small <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state resistances are selected, and their losses are reduced due to the low-voltage stress and small duty cycle of the switches. Moreover, the current-falling rates of most diodes are controlled by the 3WCI's leakage inductances. The operating modes, detailed analyses, and design considerations for the proposed converter are presented. Additionally, comparisons with other high step-up converters are provided. A 200-W laboratory prototype with an output voltage of 400 V is fabricated and tested using various input voltages to validate the theoretical analyses.