This paper presents an approach to modeling of wind power plants in electric power system long-term planning tasks. There are shown the results of analysis of real wind power plant production curves from two small European power systems, performed in order to identify annual energy production and distribution of different groups of capacity values. Further, the paper reveals a method for modeling of imaginary production curves, based on obtained results. The paper also shows the way of generating simplified production curves that meet the requirements of long-term planning tasks, including modeling of several wind power plant parallel operation.