Integrated Multi-Input Bi-Directional DC-DC Converter for Hybrid Energy Storage Systems

Multi-input bidirectional DC-DC converter is quite vital for a single system to interface multiple sources and allow energy exchange between sources and loads. In this paper, a general multi-input DC-DC converter topology and its control strategy are proposed for hybrid energy storage system. This converter can connect any number of power sources and make any ports controllable bidirectionally. To interface $N$ power sources, only $N+1$ controllable power switches are needed, which makes converter more compact with largely reduced power devices and driving circuits. Without loss of generality, a case with two sources $(N=2)$ is utilized as a typical study case for experimental verification. Experimental results show this converter can interface two individual power sources simultaneously and ensure flexible power flow control with all ports bi-directionally. $N=2$ converter structure can be developed as an integrated converter module, which is able to combine with traditional bidirectional buck/boost DC-DC converter (BBDC) to construct series-connected or parallel connected integrated converters for multi-source applications.