Short-term renewable energy uncertainties and inertia consideration in power system generation expansion planning

In modern power systems, renewable energy (RE) sources are increasingly integrated to reduce reliance on fossil-fuel-based generation. However, the uncertainties and lack of rotational inertia associated with renewable energy generators (REGs) pose challenges to grid stability. This paper proposes a novel mixed-integer linear programming (MILP) model that optimizes energy costs while enhancing system inertia in the presence of RE uncertainties. The model incorporates both REG uncertainties and inertia requirements into the planning process. To validate its effectiveness, RE uncertainty data from Mangaung Municipality, Free State Province, South Africa, is used for analysis, and the model is tested on the IEEE 6-bus test system. Simulation results demonstrate that the proposed approach improves system inertia from 5.875 s to 6.304 s while reducing energy costs from $1752.88/MWh to $1614.50/MWh in Case 3, where both RE uncertainties and system inertia are considered. These results show a clear advantage over Case 1 (cost minimization only) and Case 2 (inertia maximization only), highlighting the model’s ability to balance economic and stability objectives in renewable-integrated power grids.