this paper, a decentralized robust controller for the Load Frequency Control (LFC) of a power system in the deregulated environment is proposed. A generalized model for the LFC scheme is developed based on the possible contracts in the new environment. The connections between each control area with the rest of the system and the effects of the load following contracts are consider-ed as a set of new input disturbances in the control area dynamical model to achieve decentralization. The idea of the mixed H2/H∞ control technique is used to solve of the LFC problem. The motivation for using this control strategy is both to achieve the desired level of robust performance against uncer-tainties and to minimize the effects of area load disturbances under contract variations. This newly developed design strategy combines advantage of the H2 and H∞ control synthesizes and gives a powerful multiobjectives design addressed by the Linear Matrix Inequalities (LMI) techniques. The proposed method is tested on a three-area power system with the possible contracted scenarios under large load demands. The results are shown to main-tain robust performance in the presence of specified uncertainties and system nonlinearities for a wide range of area load demands and disturbances in comparison with the PI controller.