Definition of Static and Dynamic Load Models for Grid Studies of Electric Vehicles Connected to Fast Charging Stations

TL;DR

This paper introduces novel static and dynamic load models for electric vehicles at fast charging stations, improving accuracy over traditional constant PQ load assumptions in power system analyses.

Contribution

It develops and validates computationally efficient static and dynamic load models that account for EV charging complexities, enhancing grid impact assessments.

Findings

Proposed models outperform constant PQ loads in accuracy.

Simulation shows improved impact assessment on IEEE14 system.

Standard models may underestimate or misrepresent EV effects.

Abstract

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.