The implementation of a control model for a BESS (Battery Energy storage system) is presented, it is incorporated into an electrical power system with two areas of control that include conventional generation and non-conventional renewable power generation in the form of photovoltaic and wind generators, and this is done to study the effects a BESS has on generation control. The control models presented were simulated using Simulink® and from the results we can observe that the BESS helps to reduce the error in frequency of the power system; This improvement is determined by observing that the use of a BESS reduces the standard deviation and the integral square error of the variation in frequency of the control areas in the power system.