Stability and Reserve Constraints in Optimal Dispatch Models

Abstract

The United Nations Framework Convention on Climate Change (UNFCCC) is strongly committed to accelerating the transition of the power sector towards a high penetration of Variable Renewable Energy (VRE) sources, with the goal of reducing global dependence on fossil fuels for power generation. However, this transition poses a significant challenge, as the increasing VRE share in power systems gradually decreases their rotational inertia. This reduction in rotational inertia negatively impacts the stability and safety of power systems, creating new operational challenges. To address this, transmission system operators (TSO) have defined strategies to compensate for unexpected imbalances between load and generation by contracting primary and secondary reserves. Nevertheless, a method that compensates for the inertial response excursion after a disturbance adapted to these tools has not yet been fully identified. This work proposes a deterministic estimation of inertia constraint in UC/OD models. The Rate of change of Frequency (RoCoF) is estimated from an Optimal Dispatch model by considering the worst-case contingency in the test case. Then the lower inertia limit required to operate the system with stability is estimated. The estimation of the inertia limit is done offline the optimization and added as a new constraint in the UC/OD model. Finally, different scenarios of VRE penetration are defined to evaluate the impact of this new constraint with a sensitivity analysis. Results show that the proposed method can be complementary applied to UC/OD models to reduce the risk of unintended load shedding, which might lead to cascading failures and blackouts.ARES-CDD and ARES PRDBOL2022 programmes7. Affordable and clean energy13. Climate actio