A two-stage coordinated capacity expansion planning model considering optimal portfolios of flexibility resources

Renewable energy sources, such as wind and solar photovoltaic, have been widely deployed in power systems due to the decarbonization transition target and technological advances. The large-share integration of renewable generation contributes to the construction of a low-carbon power system and imposes significant flexibility requirements for the power system. The reliability and security in power system operation and RES generation accommodation are deeply involved with the configuration mixes and the portfolio of flexible resources. Therefore, this paper proposes a coordinated capacity expansion planning model with a variety of flexibility technologies, including thermal power flexibility retrofitting, energy storage systems, demand-side responses, as well as concentrating solar power plants. A scenario-based approach is adopted to capture uncertainties from electric load and renewable generation. The proposed planning model is constructed as a two-stage stochastic planning framework, where the first stage optimizes investment strategies of flexible technologies while the second stage determines the optimal power dispatch for all generation assets under different operation conditions. The hourly operation simulation model is also embedded in the proposed planning model with detailed operation constraints. The effectivity of the proposed coordinated planning model is verified by a modified reliability and operation test system. Numerical results show that different combinations of flexibility technologies have distinct impacts on the power system’s economic and environmental performances, which implies the significance of finding an optimal portfolio of flexibility resources in the power system with large-scale renewable energy sources