A New Method for Hybrid Energy Storage Capacity Determination in Isolated Micro Grid

In recent years, hybrid energy storage (HES) to increase lifetime and reliability extremely are used in renewable systems and microgrids. In this paper, a new method for determining battery and supercapacitor capacity in an isolated microgrid is presented. Difference between Generation and load power using discrete fourier transform is transferred to the frequency domain and by determining the cut-off frequency, the optimized cost function is obtained; so that high frequencies are provided by supercapacitor and low frequencies by the battery. In the presented method, determining the capacity of the storages is done in such a way that in addition to the good response to loads, the lifetime of storages is maximized. The use of the proposed method due to the hybridization of storages improve the dynamic performance of the system by reducing the number of battery charging and discharging, decreases storage cost. Due to necessity and importance of storages in the isolated microgrid, the considered microgrid is isolated from the main grid that is consisted of different distributed generations. The proposed algorithm is tested on an isolated microgrid and the results confirm method effectiveness.