Family Of High Step-Up Multi-Input Converters With Continuous Battery Current Based On Three Port Boost Topology and Switched Capacitors

In this paper, a family of non-isolated high step-up multi-input DC-DC converters with continuous battery current and low voltage stress on semiconductor elements is proposed for a battery-photovoltaic power system. The proposed converter combines the three-port boost and buck topologies to transfer power from/to the energy storage units (ESUs) with the continuous current extending the battery life-time as a common ESU. Furthermore, switched capacitor technique along with the main boost switch is utilized for operating modes that deliver power from ESUs and the energy generator units (EGUs) to the output along with higher voltage gain and continuous input current. Hence, the battery power conversion in all operating modes is performed in continuous battery current and consequently, battery life-time extension is achieved. Unlike many three-port boost converters, the simultaneous power transfer in single input double output state is provided which eliminates the required time multiplexing in similar topologies and thus, higher current stress and conduction loss are avoided. Moreover, the number of series semiconductor components in the battery charging path from EGU is reduced and higher efficiency is achieved. Finally, a modification in the proposed converter is performed to increase the converter power range. In the modified converter, the output diode is substituted with an inductor which reduces the current ripple and suits the converter for higher power applications. The converter step-up and step-down operating modes are discussed in detail and a 100 W prototype is implemented to verify the theoretical analysis.