Energy storage units are very vital for damping the oscillations due to the sudden changes in power system. The integration of small capacity energy storage unit to the power system in each area can effectively restrain the system oscillations. Hence in this paper, the energy storage devices, SMES (Superconducting Magnetic Energy Storage) units and RFB (Redox Flow Batteries) have been integrated into the interconnected deregulated LFC (Load Frequency Control) power system model and their effectiveness in improving the system performance has been realized and compared. The proposed controller design is applied to an interconnected two-area two-unit thermal deregulated power system with one reheat and one non-reheat unit in each area. This paper also proposes a new design of intelligent controller for load frequency control of interconnected deregulated power systems with energy storage devices using Artificial Cooperative Search algorithm. To prove the scalability of the proposed framework, the design has also been implemented on a three-area interconnected deregulated power system model. The simulation results show the effective and efficient performance of RFB energy storage unit and the effectiveness of ACS (Artificial Cooperative Search) algorithm tuned controller in improving the system performance of interconnected deregulated power system. (C) 2016 Elsevier Ltd. All rights reserved.