The new generation of Electrical Generator Sets (EGS) is based on the variable speed generation concept. The diesel engine changes the speed according to the load of the set. The optimum speed is hereby calculated according to the load of the EGS with as the optimality criterion the minimum fuel consumption. The analysis of the dynamic behavior of such new EGS concept shows some new problems with power and voltage drops at sudden increase of the load. The dynamical properties of EGS concept with variable speed technology could be improved by using an Energy Buffer. Solutions of concept EGS with the energy buffer and their advantage or disadvantage are discussed in this paper.