Feasibility Study on the Future Impact of Electric Vehicle Fleets on the Power System Inertia Floor

Abstract

The use of electric vehicle fleets such as clean school buses and readily available charged batteries in charging stations is proposed to participate in the frequency regulation of the grid when the support is needed, especially during a huge disturbance on the grid. As the nation moves into more cleaner generating resources which are added to the grid through inverter-based resources, the inertia of the power system is decreased. The goal is to reduce the floor of synchronous inertia necessary to maintain stable operation. To prove the concept, the synthetic Texas 7k bus case system with varying inertia values are used. The base case is assumed to have 100% inertia with 386GWs inertia capability. The dynamic model of this case is modified to vary the inertia to certain percentages of the base case inertia for comparison. The simulation results shows that the rate of change of frequency (RoCoF) and the frequency nadir at some inertia level reduces to a value below the Under-frequency load shedding (UFLS) threshold frequency when there is an N-2 generator contingency of 2558 MW generation loss on the system. However, with the implementation of the electric vehicle fleets through the Vehicle-to-grid application, the RoCoF and frequency nadir improves to a value higher than the UFLS threshold frequency under the same contingency of 2558 MW generation loss.