Secure Operation of Distribution Systems with EVs Providing FFR

Sammanfattning

The increasing integration of Electric Vehicles (EVs) and Distributed Energy Resources (DERs) is significantly transforming the operation of power systems. One major consequence of high DER and renewable energy penetration is the reduction of system inertia, making power grids more sensitive to frequency deviations. Fast Frequency Reserve (FFR) is an effective frequency control action that slows down frequency drops by acting as synthetic inertia. EVs, due to their rapid response capabilities and bidirectional chargers, are promising providers of FFR; EVs can quickly stop charging and begin injecting active power into the grid. However, this introduces new challenges for Distribution System Operators (DSOs). If unmanaged, the sudden injection of active power from EVs during FFR events can lead to local overvoltages in the distribution network, posing risks to voltage-sensitive equipment and grid security. This thesis explores Reactive Power Compensation (RPC) as a potential voltage control solution to mitigate such impacts. A Security-Constrained Optimal Power Flow (SCOPF) model is developed to optimize RPC from EVs, ensuring secure operation during FFR events. The model is tested in a high-stress case study using the CIGRÉ European LV benchmark network, evaluating two RPC strategies with different optimization objectives. The results show that both strategies maintain voltage within operational limits across various scenarios, including high-load, high-injection, and disturbances such as sudden PV shading. While full voltage deviation mitigation was not possible due to network constraints and reactive power limitations, RPC significantly improved voltage profiles and helped ensure secure operation. These findings demonstrate the technical feasibility of combining EV-based FFR with local voltage support in the form of RPC, contributing to more flexible and resilient distribution systems.