Optimal Planning of Energy Storage in Wind Integrated Systems considering Frequency Stability

Renewable energy resources have become key elements of the modern electric power grid due to their environmental benefits, low costs of generation, and government regulations. Yet, their lack of rotational kinetic energy makes the grid vulnerable to frequency instability, which can impede day-to-day operations of the grid. This challenge can be mitigated with the help of energy storage systems (ESS), which are capable of providing virtual inertia. This paper proposes a novel planning strategy for optimally sizing ESS to alleviate frequency stability issues of a wind integrated system while minimizing the operational costs of the system. This work develops a stochastic optimization framework that minimizes the daily operating cost of the system while satisfying a frequency stability constraint. The frequency stability constraint ensures that the ESS provides the virtual inertia required to maintain frequency stability under a disturbance. Uncertainties in wind power forecast are incorporated in the optimization framework with the help of a scenario tree model. The proposed approach is demonstrated on the reduced Western System Coordinating Council 9 -bus test system.