In this paper the power systems control using the sliding mode control applied to interconnected systems is presented. For it the power system is modeled as a multi-machine interconnected system with disturbances. For control design it is considered as known a limited number of variables that must be measured. The approach design, the tests of robustness and stability are presented, and the results of simulations in a power system of three machines simulated in Matlab/Simulink and Neplan are shown