A new multiple converter topology for battery/ultracapacitor hybrid energy system

In conventional hybrid energy storage systems (HESSs), parallel bi-directional boost converters are used as interface between each storage system and the dc link. One of the disadvantages of the configuration is that during the energy transfer between two energy storage systems two converters are active which in turn lowers the overall efficiency. In this paper, a new multiple converter topology for HESSs is proposed. In the proposed topology one of the boost converters is replaced with a bi-directional buck-boost converter and by adding one additional semiconductor switch the topology can be reconfigured to bypass one of the converters during the energy exchange interval. This improves the overall efficiency. Furthermore, the buck-boost converter allows extending the range of the output voltage. The principle of operation and different operating modes of the proposed topology are explained in detail and verified in simulation.