A Novel Nonisolated Four-Port Converter for Flexible DC Microgrid Operation

In this paper, a new nonisolated four-port dc-dc converter is proposed for dc microgrid applications. The proposed converter offers a main feature of controlling the dc link voltage regardless of resources availability. By using four IGBT switches and only one diode, three different sources can be interfaced to a boosted dc link load. Different operation modes of the proposed architecture are discussed, testified, and validated experimentally. The buck-boost capability of the proposed topology allows an enhanced flexibility to integrate various sources with distinct voltage-current (V-I) characteristics while sharing load power among all ports. In this context, steady state analysis is performed to determine the voltage gains between all ports. The control strategy is developed for the proposed topology to manage power flow between sources and load achieving basic operations for renewable resources such as MPPT for PV. A theoretical based study is performed on the proposed converter including steady-state analysis, state-space averaging followed by small signal modeling and frequency response-based controller design. The converter different operating conditions are validated experimentally.