Comparative Evaluation of Dual-Purpose Converters Suitable for Application in dc and ac Grids

This paper presents a comparative evaluation of several topological solutions to the universal power electronics interface for the dc or single-phase ac grids using the same terminals. The idea of a dual-purpose approach lies in the utilization of the same semiconductors in the dc-dc and in the dc-ac configuration, resulting in minimal redundancy. Particular focus is on the power density improvement and control. Out of the three solutions under investigation, the first is the buck-boost cell with unfolding circuit presented earlier. The second solution is a conventional voltage source inverter with an intermediate boost cell considered as one of obvious competitors. The third design is based on a phase-modular solution with buck-boost cells. The design example and experimental prototypes of the universal power electronics interface converter rated for 3.6 kVA power in the ac mode and more than 5 kW in the dc mode are presented. Our experimental results demonstrate the ability of operation in the ac or dc grids with main corresponding modes. Possible applications along with main benefits are addressed in the conclusions.