Three-Port Bidirectional DC–DC Converter for Application in Renewable Energy Systems

This paper proposes a new three-port bidirectional DC–DC converter designed for integration into photovoltaic systems with battery energy storage. The proposed topology features three ports: two for power supply (one powered by batteries and the other by photovoltaic panels) and a third for the load. Due to its bidirectional characteristics, this converter facilitates power flow both from the batteries and/or photovoltaic panels to the load, as well as from the photovoltaic panels to the batteries. The converter operates in open loop, and this paper presents qualitative and quantitative analyses of the converter operating in continuous conduction mode (CCM) for two power flow scenarios. Additionally, an illustrative design is detailed for a nominal power of 1.5 kW, a switching frequency of 30 kHz, a battery voltage of 48 V, a photovoltaic panel voltage of 142 V, and a load bus voltage of 250 V. The theoretical analysis is validated through experimental results. Some of the main highlights include operating the inductor at twice the switching frequency, significantly reducing both the inductor's size and the input current ripple. Furthermore, the optimal battery current ripple occurs at a duty cycle close to 50%, where it is practically zero. The converter efficiency was analyzed in all power flow scenarios at various operating points, reaching up to 97.33%. Furthermore, a supplementary video showcasing its functionality is included with this manuscript.