The work was done to analyze the problem of stability of synchronous machines and the way to reduce small perturbations, by improving dynamic features of electroenergetic system. A well known procedure of installation of an additional control signal was used, with a purpose to reduce the electromechanical oscillations by active influence. Stressing was put on the method of configuring and setting the stabilizator, using measuring results given by recording of the plant features of the excitation control system of the synchronous generator. The problem of setting and configuring the power system stabiliser is especially expressed in systems with electromachinery excitation, the one that was observed in this work. Using the data given by recording the excitation control system on synchronous machines in Hydro Power Plant Dubrovnik the estimation of stabilizator parametring was proposed and accepted. Somewhat more complicated configuration of the electromachinery excitation control system imposed the necessity of extending the methods of parametring suggested in the literature. Available measure results of the excitation control system characteristics were used to obtain a model which behaviour in quality and quantity only slightly distinguishes from real system. The model was given by degree enlarging while it contributed to decreasing the difference between measured and calculated amounts. With that model, the sensitivity of the matric system characteristic values was analyzed and the area of optimal adjustment of the stabilizator parameters was determined. Two essentially different configuration cases in Hydro Power Plant Dubrovnik where generators with the same characteristics work on two separated electric power systems, with very different equivalent reactancies required the problem of dynamic stability of the system to be analyzed, with the stressing on the influence of equivalent system reactances, Analyses of the external reactances influence was done in all chapters of this work, by making calculations for both plant cases mentioned. The work is concluded with the chapter about the method of setting the poles of the characteristic system equation, where the problem of improving dynamic characteristics is solved by setting the characteristics of the excitation control system without additional devices that generate the stabilizing signal.