A comprehensive evaluation framework for sizing renewable power plants in a hybrid power system considering UHV transmission and thermal ultra supercritical unit operating performance

Thermal power has been encouraged to collaborate with large-scale variable renewable energy (VRE) in hybrid power systems (HPSs). To optimize the VRE capacity and explore the deep peak-shaving performance of ultra supercritical units, we propose a comprehensive evaluation framework that optimizes the VRE size integrated with thermal power. First, we proposed a scenario-based uncertainty modeling method considering wind and PV power correlations. Second, a short-term daily optimization model was designed, along with a two-stage adaptive complementary strategy. Finally, a lifecycle techno-economic evaluation framework was established to determine the cost-effective VRE size. The framework was applied to a case study in Qinghai Province, China. The results show that (1) The optimal VRE capacity configuration is 2.5 times that of thermal power, including 3333 MW of wind power and 1667 MW of PV power, yielding a net present value of 4.43 billion CNY. (2) Converting traditional units to ultra-supercritical units can effectively improve the efficiency of coordinated operation and lead to more than 15% decrease in unit generation costs. (3) Relaxing power transmission constraints can effectively improve the operating performance of thermal units, and the unit generation cost accordingly decreases by 22.5%.