Novel Family of High-Gain Nonisolated Multiport Converters With Bipolar Symmetric Outputs for DC Microgrids

Bipolar dc grid systems are fast gaining attraction for renewable energy source integration, because of their merits of higher reliability, efficiency, and robustness as compared to the unipolar dc grids. However, the progress in multiport converters, resulting into lower cost and more compact design for bipolar microgrid systems, is fairly slow. Therefore, this article proposes a novel family of five nonisolated multiport dc-dc converter topologies with bipolar symmetric outputs. The performance and key operational features of the proposed converters under varying input voltages, duty cycles and loads are numerically verified and experimentally on an in-house test setup to prove the concept of the proposed converters. In the experimental validation, the operation of the converter under simultaneous and arbitrary individual power transfer from two input ports is tested. Furthermore, the easy integration of the proposed converters with a multilevel inverter to achieve high-quality ac voltages is demonstrated. As compared to the few existing counterparts, the proposed converters have a competitive edge in terms of higher number of input ports and voltage gains. Alongside the possibility of arbitrary independent power flow from the input ports, inherently symmetrical outputs require a simple balance control for asymmetrical members of the family.