Current-fed quadratic full-bridge buck converter for PV systems interfacing: Dynamic characterization

Interfacing a single photovoltaic (PV) module into either a single-phase or a three-phase inverter requires an interfacing converter with wide conversion range 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 discusses the dynamic characteristics of the current-fed quadratic full-bridge buck converter (CFQFB) in photovoltaic application. 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. In addition, the paper will discuss the effects emerging from a non-ideal source, paying particular attention to the properties of the PV module. The analytical claims are verified with extensive measurement results from a corresponding 190-W prototype.