In this dissertation, a detailed dynamic performance study on excitation systems for synchronous generators in plants of Embedded Generation is presented. It's been conceived a plant and this interconnected to a distribution grid with embedded or distributed generation characteristics. IEEE 421.5 Std. mathematical models are used here: IEEE DC1A, AC1A, ST1A and ST2A compound-and diverse stability studies are carried through with intention of following these systems performance front to some factors as: critical power, critical fault-clearing time, short-circuit levels at distribution net and transmission net interconnection, grid X/R relation. Finally terminal voltage profile during load disturbances is taken in consideration for parallel with grid and island mode. Up-to-date cost data are presented and added to the technical performance in order to indicate the better configuration for plants with this characteristic of decentralized generation.