Today's electrical appliances are more and more built with and controlled by power electronics and processors, and their number is growing. This development can bring both advantages and disadvantages for the power quality of the electricity supply system. An advantage, for example is the growing number of home appliances that are equipped with a power factor corrector front-end. This type of appliance behaves as a resistive load and has a very good power factor. A disadvantage is the constant power load (CPL) character that shows up when the appliance is stabilized against grid voltage fluctuations by a power electronic front-end. This paper investigates the oscillatory grid voltage effect of certain amounts of CPLs in a small isolated grid system and the impact on the quality of the voltage. Results of computer simulations show that an oscillatory grid voltage due to an interaction of a CPL with the voltage control system of a generator is possible and can be reduced by changing the parameters of the voltage control system.