Determining Time-of-Use Schedules for Electric Vehicle Loads: A Practical Perspective

Abstract

Analyses have shown that electric vehicle (EV) loads may considerably affect the secondary service voltage quality. One of the ways to mitigate voltage drop concerns is to use a time-of-use (TOU) pricing scheme. A TOU pricing scheme utilizes the off-peak generation for EV charging, thus deferring any immediate grid upgrade and improving the grid sustainability. This paper evaluates various aspects of EV charging under a TOU schedule, with off-peak rates starting at hours ranging from 8 P.M. to 3 A.M. The study is conducted using an actual residential distribution circuit. A best practical time to begin the off-peak rates is determined so that the effects of EV charging on the secondary service voltages are minimized while ensuring that EVs are fully charged by 7 A.M., thus maximizing both grid and customer benefits. The analysis suggests that the best time to begin off-peak rates is between 11 P.M. and 12 A.M. Furthermore, the analysis also suggests that setting up TOU off-peak rates at the latter half of the peak load demand, for example, at 8 P.M., is detrimental to the distribution circuit voltage quality. The result indicates that the existing utility TOU scheme may exacerbate voltage drop problems due to EV load charging. INDEX TERMS Distribution system, electricity market, electric vehicle (EV), time-of-use (TOU) pricing.

Electric Vehicle Charging on Residential Distribution Systems: Impacts and Mitigations

“…However, the proposed TOU structure in [35] does not take the convenience of EV owners into consideration. An optimal TOU schedule that benefits both utility companies and customers, while taking EV charging into consideration, is developed and presented in this paper [36]. The objective is to develop a practical approach for setting up a TOU schedule based on customer load demand, EV charging demand, and service transformer loading constraints.…”

“…Both grid and customer benefits can be simultaneously maximized in this way. The analysis suggests that the optimal time to begin off-peak rates is between 11 pm and 12 am [36].…”

“…A summary of our evaluation approach and results are discussed in this section. Please refer to [36] for the detailed approach and results.…”

“…The EV load profile is specified by the charging scenario under evaluation. Various charging scenarios considered in this section, and their evaluation parameters, are summarized in Table IX [36]. The charging scenarios specified in Table IX are simulated for both a 24-kWh (Nissan Leaf [65]) and a 16-kWh (Chevy Volt [66]) EV battery load.…”

A Regional Time-of-Use Electricity Price Based Optimal Charging Strategy for Electrical Vehicles

“…Peak-Valley TOU [17] (1) peak-valley difference TOU [19] (1) energy cost [20] (1) charging cost Real-Time [21] (1) the difference between load curve and ideal load curve (2) network Losses [22] (1) the total cost for charging all EVs within the day…”