The possibilities of mathematic simulation using for examination of RES connecting system behaviour

Photovoltaic and wind systems belong to the most perspective renewable sources of electrical energy that can contribute to limitation of unfriendly influence of power sources on the environment and also can increase renewable sources part used for satisfaction of customers demand on electric energy. But their usage is limited by fulfilling certain conditions that are connected with efficient and reliable operation of electrical power network. The matter is to find out the maximum possible power output of these sources that could be incorporated into distribution power system (DPS). It is necessary to find how they can respect the changes of the output caused by instability of the natural conditions and their influence on the operation and control of DPS and the measures that are to be adopted at their connection. Last but not least it is also the economic aspect of an increased concentration of renewable energy sources (RES) in DPS.