A resilient power grid system is important to ensure the delivery of power to consumers while minimizing the cost of new technologies. Due to the increase of electricity consumption and CO2 emission, renewable energies and energy storage system are a compelling alternative. We started to identify decisions that need to be made, and parameters associated to model a power grid system expansion plan. Then, we investigated a utility company demand for the next 15 years. Also, we identified their current resources, and used that as a starting point. Then, we formulated an optimization model for a power grid expansion with different types of renewable energies, such as solar and wind, to meet the demand and minimize the cost of installation; as well as, a battery storage system (Lithium-ion) that is considered to come up with an optimal solution of a resilient power grid. Moreover, uncertainties of renewables are considered in the model, and robust optimization formulation is used to model them. Existing coal facilities are considered as a part of the model as well, and this part is designed on the optimization model in a way that would help decrease the use of such facilities and still manage them to meet demand. Numerical experiments are performed on several scenarios, and compared to what the utility company has forecasted in terms of cost, and renewable energies integration.A resilient power grid system is important to ensure the delivery of power to consumers while minimizing the cost of new technologies. Due to the increase of electricity consumption and CO2 emission, renewable energies and energy storage system are a compelling alternative. We started to identify decisions that need to be made, and parameters associated to model a power grid system expansion plan. Then, we investigated a utility company demand for the next 15 years. Also, we identified their current resources, and used that as a starting point. Then, we formulated an optimization model for a power grid expansion with different types of renewable energies, such as solar and wind, to meet the demand and minimize the cost of installation; as well as, a battery storage system (Lithium-ion) that is considered to come up with an optimal solution of a resilient power grid. Moreover, uncertainties of renewables are considered in the model, and robust optimization formulation is used to model them. Existing coal facilities are considered as a part of the model as well, and this part is designed on the optimization model in a way that would help decrease the use of such facilities and still manage them to meet demand. Numerical experiments are performed on several scenarios, and compared to what the utility company has forecasted in terms of cost, and renewable energies integration.