Evaluation of Automatic Generation Control Modes Using ANATEM Software

System interconnection is a fundamental practice for the optimum use of resources, increasing system realiability and also reducing operating reserves. It is a common practice to interconnect systems, especially in countries with continental dimensions, such as Brazil. In these systems, there is a need not only to control the frequency, but also the power interchange among control areas that compose it, requiring a secondary level in the load-frequency control denominated Automatic Generation Control (AGC). It has three operating modes, defined according to the Area Control Error (ACE): Tie-Line-Bias (TLB), Flat-Frequency (FF) and Flat-Tie-Line (FTL). This article evaluates these types of control against to the occurrence of a sudden load step in the system. The control modes operate according to their functions, and those systems that operate with TLB mode combinations contemplate the frequency control of this mode, which has the characteristic of sharing this control with the adjacent control areas. Therefore, when appropriately modeled, the controls operate according to their functions, and the strategy adopted must be such that no tendency to instability is introduced into the system.