Dynamic Properties of Current-Fed Quadratic Full-Bridge Buck Converter for Distributed Photovoltaic MPP-Tracking Systems

Interfacing a single photovoltaic (PV) module into either a single-phase or a three-phase inverter requires an interfacing converter with wide conversion ratio and sufficient dynamic headroom. In terms of avoiding issues with common-mode currents between the PV module and the inverter, a converter with galvanic isolation is preferred. This is especially important with the emerging thin-film modules that have larger cell-to-frame parasitic capacitances compared to traditional modules. This paper presents the dynamic properties and analysis of the current-fed quadratic full-bridge buck converter. The foundation for the proposed topology is based on the concept of true current-fed converters that differ fundamentally from the conventional voltage-fed converters. The relevant analytical steady-state equations and the dynamic model are presented with the operational details of the proposed converter. The analytical claims are verified with extensive measurements from a corresponding 190-W prototype. According to the measurements, the prototype performed well in PV application and reached an efficiency of 92% at the maximum power point of the PV module.