A control strategy for optimizing the power flows supplied by two different storage units

The DC distribution networks can easily benefit from integration of electrical storage systems, such as batteries and supercapacitors, to manage the network operations. A proper combination of these two storage units can lead to a storage system able to satisfy power requests lasting from seconds to hours. However, the use of more than one storage unit gives rise to the problem of deciding how to split the power between the two technologies. In the paper, authors propose a control strategy to divide the power demand between the two storage units ensuring, at the same time: i) a peak shaving action for the interface converter opportunely slowed; ii) the lifetime increase of storage units by means of a proper control adapted to the dynamic performances of each storage device; iii) the keeping of the state of charge of each unit around a desired value. In the paper, the effectiveness of the proposed strategy is shown by means of numerical simulations. In particular, very good results are obtained also when the power demand is completely random.