Frequency Control in EV Clusters: Experimental Validation and Time Response Analysis of Centralized and Distributed Architectures

The increased penetration of Renewable Energy Sources and of Electric Vehicles (EVs) in the electrical grid poses challenges to the stability and performance of the electrical system. To mitigate these problems, ancillary services can be provided by clusters of EVs during the charging process. The delay in the provision of frequency services from a cluster of EVs is analyzed, considering both a centralized and a distributed control architecture. The distributed architecture was tested on a cluster of EVs in the DTU Risø facilities. The communication delays in the system have been quantified. Both the centralized and distributed architectures have been modeled on Simulink® using the estimated delays, and the average delay following the grid frequency has been determined. After comparing the results, the distributed architecture was found to slightly be faster in following the reference than the centralized architecture, even though different aspects of the control system have been identified to be responsible for an increased delay, including saturation in the power setpoint for each EV, and presence of instability in the control system.