Composite energy storage system with flexible energy management capability for micro-grid applications

Grid connection of renewable power generators in large scale drastically affects the power quality in the grid because of high uncertainty of the renewable sources and their uncontrolled variation. Hence, renewable energy based micro-grids are a better way of utilizing renewable power. Usage of energy storage becomes mandatory, when such micro-grids are used to supply quality power to the loads. Ideally, the storage should have both high energy density and high power density features which is very difficult to find in a single storage. This paper proposes a Composite Energy Storage System (CESS) comprising of battery and ultracapacitor as high energy density storage and high power density storage respectively to meet the above mentioned requirements. The proposed power converter configuration and the energy management scheme can actively share the power flow among the different energy storages. Results are presented to show the feasibility of the proposed scheme.