A Minimum Power Loss Approach for Selecting the Turns Ratio of a Tapped Inductor and Mode of Operation of a 5-switch Bidirectional DC-DC Converter

One of the most important aspects for the reliable operation of a DC Microgrid is the DC-bus voltage regulation within the system. For this, Supercapacitors (SCs) are widely used as auxiliary devices since they can provide sudden bursts of power and demand/supply currents with high gradients. Since commercial SCs usually present low voltage levels and, with the increasing trend of raising the DC-bus voltage, their connection in such systems requires power electronics interfaces capable of providing a wide range of voltage conversion. In this scenario, Tapped Inductors (TIs) provide a means for achieving low/high voltage gains in non-isolated DC-DC converters with neither too small nor too large duty cycles (D) by adjusting their turns ratio (n:1) to a desired value at a given operating point. However, a proper methodology for the actual choice of this value and the impacts of this on important aspects of the system, such as the converter efficiency, are still lacking in the literature. This way, this paper concerns a 5-switch DC-DC converter, based on a TI and that presents voltage gains that vary with D with Buck, Boost and Buck-Boost characteristics, where the main objective is to present an approach to determine the mode of operation and the turns ratio of the TI for reducing the losses on the power switches.