Reliability-Based Metrics to Quantify the Maximum Permissible Load Demand of Electric Vehicles

The continuous increase of electric vehicles (EVs) is expected to introduce several challenges to power systems among which is the deteriorating reliability of power supply. This paper proposes two adequacy metrics to quantify the maximum permissible EV loads for a power system without deteriorating its reliability and the required improvements to power systems to accommodate high penetrations of EVs, which are defined as follows: 1) extra effective available energy for EVs’ charging (EEAE-EVs) and 2) extra effective required generation to accommodate EVs (EERG-EVs). The EEAE-EVs provides a measure for the maximum amount of EV loads that a power system can accommodate without adding new generation while maintaining its reliability. The EERG-EVs provides a measure to the minimum amount of new generation that is needed to restore the reliability level of a power system if the load of EVs exceeds the maximum permissible load of the system. These metrics provide a decision aid to power system planners and operators on when and how to perform generation expansion. The importance of the proposed metrics is demonstrated on the IEEE Reliability Test System (IEEE RTS) with real EV charging data. The sequential Monte Carlo simulation method is used in evaluating the well known power system reliability indices, the EEAE-EVs, and the EERG-EVs. The results show that a power system can accommodate EV loads without deteriorating its reliability as long as EV loads do not exceed the EEAE-EVs of the system. For the IEEE RTS, the EERG-EVs shows that the amount of the required generation to maintain system reliability is about half of the added EV loads from 330–660 MW.