Design of Modified Droop Controller for Frequency Support in Microgrid Using Fleet of Electric Vehicles

Abstract

Droop control has been extensively used by academia and industry for managing frequency fluctuations at microgrid (MG). This controller generates series of reference signals to different distributed energy sources (DES) such as diesel generator, PV, and wind system based on their respective maximum capacities. However, the combination of inertial and noninertial DES leads to frequency fluctuations at MG. Therefore, this paper proposes a novel frequency support strategy by controlling the operation of DES and controllable loads, i.e., electric vehicles (EVs). Moreover, fleet of EVs batteries maximum capacity depends upon constraints, such as state of charge (SoC), random arrival, and departure patterns. Hence, to accomodate EVs' batteries with droop controller, it has been enhanced with communication links and feedback mechanism and referred as modified droop controller (MDC). This MDC would be now able to dispatch reference signals to both DES and EVs. However, for meeting reference signal given to fleet of EVs, an aggregator (AG) is proposed. AG can alter the charging and discharging rates of EVs' thereby satisfying EVs' needs in terms of battery's SoC. Extensive simulations have been done using the proposed scheme on data available from Santa Rita Jails' MG.