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## Optimal design methods of wind-solar hybrid power systems at the stage of investment feasibility study

The article is devoted to development of optimal design mathematical models for power systems using renewable energy sources (RES) on the stage of pre-investment feasibility study. Economic and social practicability of the carbon-free energy sector development in Russia is confirmed by calculated data of renewable energy sources potentials such as fuel, heat and power, resource saving and environmental (in tons of CO and CO2-equivalents) potentials. In order to increase the attractiveness of investing in renewable energy sector the optimal investment designing problem is defined and MILP economic and mathematical model is developed for ecological and economic optimization of decentralized wind-solar hybrid power supply investment projects. The macro structure of the model is considered. The basic mathematical relationships that form the region of feasibility are presented. Designed models can be used to justify the investment in distributed power systems.