  The growing deployment of electric mobility calls for power system analyses
to investigate to what extent the simultaneous charging of electric vehicles
leads to degraded network operation and to validate the efficiency of
countermeasures. To reduce complexity and CPU time, a common approach while
performing these analyses consists in replacing electric vehicles and their
charging stations with constant PQ loads. However, this approach is inaccurate,
as the power absorbed by these elements actually depends not only on voltage
but also on the state of charge, charging method, cathode chemistry of the
battery pack, and converter controls in the electric vehicle and charging
station. By considering all these aspects, this article develops a novel static
load model and a vector fitting-based dynamic load model for electric vehicles
connected to fast charging stations. These computationally efficient
representations can replace the standard constant PQ load model of electric
vehicles to assess more accurately their impact in static and dynamic grid
studies. Simulation results of the IEEE14 system modified by adding fleets of
electric vehicles prove the accuracy of the proposed models and highlight the
shortcomings of the standard electric vehicle representation as a constant PQ
load in some cases.
