Power systems nowadays are becoming more complex, also with constantly growing electricity consumption. A new phenomenon of renewable energy sources connection into power system is also influencing the power system complexity. This paper deals with the possibilities of usage of software tools for power system studies in more complex way. The modeling of supplementary services in 39-bus of New England system is presented at the beginning of this paper. Also, the mutual interaction of renewable energy sources – offshore wind farm and UPFC was the subject of research. Advantages and disadvantages of such combination are presented in this paper.