For a proper operation, this integrated system requires a stable operating condition by means of an adequate control. The power system is a dynamic one. It is constantly being subjected to disturbances cause. For a system with interconnected elements to be able to supply the power load demand, when the transients cause the disturbance, a new acceptable operating steady state condition must be reached. That is why, the power system must be a stable one. It is important that these disturbances do not drive the system to an operating unstable condition.