A step-up/down inverter implemented with the boost-interleaved buck-boost dc-dc converter

A typical photovoltaic (PV) grid-connection power system is consisted of multi-stage converters to perform multiple functions simultaneously. In order to simplify system configuration, reduce cost, and improve conversion efficiency, this paper aims to develop a step-up/down inverter by adopting a boost-interleaved buck-boost (BoIBB) dc-dc converter and connecting with an H-bridge unfolding circuit with line-commutated operation. The proposed circuit can work functionally as either step-down or step-up inverter so that it is suitable for the applications with wide voltage-variation. Due to operating with buck or boost principle, partial energy can be directly delivered to output to improve efficiency. Besides, since only one power switch operates with high-frequency at one time, switching losses can be significantly reduced. Furthermore, high input current is shared by two inductors during step-up mode, leading to the reduction of conduction losses. Finally, a laboratory prototype with 110 Vrms / 60 Hz output voltage is then implemented accordingly to verify the validity and feasibility of the proposed inverter.