Increasing penetration of wind energy resource raises concerns about system frequency regulation because wind turbines lack in control capability necessary to provide regulation in compensating generation-load imbalance. Inherent variability on every time scale, in fact contributes to a need for more sophisticated regulation; existing load-following spinning reserves may be too slow or limited in responding to the imbalance. One feasible solution for enhancing regulation capability is the use of Hybrid Energy Storage System (HESS) as proposed in this paper. In this research, the HESS is designed to be composed of a Li-ion battery and supercapacitor (SC), exploiting their respective high energy and power capabilities to fully handle long-term and short-term changes. This paper demonstrates the effectiveness of HESS for frequency regulation in meeting the grid code while smoothing the net variability (load-wind) for an isolated power system modeled using an electromagnetic transient program.