This paper deals with a study of the control strategy of a hybrid power plant based on integration of a solar thermal with Brayton cycle. The integration of solar energy with a conventional power-generation system such as the Gas Turbine (GT) is a very promising technique to produce electricity and heat using renewable energy and at the same time ensure predictability of generation for the grid. In the power-generation system here described, solar energy is used to preheat the air leaving the compressor and directed to the combustion chamber of the GT where, before being fed into the turbine, receives additional energy, in a conventional manner, with the gaseous fuel (i.e. natural gas). This allows on one hand to operate the plant even during periods of absence of solar radiation (at the night) and on the other it allows to compensate with the gaseous fuel unanticipated events on the solar radiation caused by the movement of clouds, thus guaranteeing to the grid power generation predictable and programmable. In this paper is described the design criteria of a solar-hybrid system based on a gas turbine of 50 MW, the design of the control system strategy and the built of the mathematical model in the platform LegoPC / Matlab / Simulink. With the simulator of the power-plant were carried out various transient that allowed exploring some of the characteristics and operating limits of this power-generation system solution.