Modeling and analysis of five-port isolated bidirectional dc-dc converter for interfacing pv/fc/battery systems with bipolar dc microgrids

In this thesis, a novel five-port, three-input and dual-output, isolated bidirectional DC-DC converter (FPIBC) topology with an effective control system for power sharing and voltage balancing in bipolar DC microgrids (BPDCMGs) is presented. The proposed converter acts as the interface for the integration of a hybrid generation system comprised of the fuel cell (FC), the photovoltaic (PV) system, and the battery to BPDCMGs. The FPIBC consists of two full-bridge converters, a resonant tank, a high-frequency transformer (HFT), and a voltage balancer circuit. The symmetrical bipolar output voltages are ensured by a voltage balancer circuit composed of a fully controlled switch and four diodes, without any need for an additional converter. Less number of circuit elements are used in the proposed converter compared to the existing converters. A simulation model has been developed using the MATLAB/Simulink program to verify the effectiveness and usefulness of the aforementioned converter. Different case studies have been carried out under conditions of altered FC pressure, solar irradiation, battery charge/discharge status, load change and voltage imbalance to test the performance of the proposed converter. The performance of the system and the efficiency are verified with simulation results. The simulation results revealed that the system has an efficiency of at least 91.13% during case studies, the voltage imbalance was kept below 1%, and bidirectional power transmission function is performed successfully.