Characteristics of Electric Vehicle Charging Sessions and its Benefits in Managing Peak Demands of a Commercial Parking Garage

In this study, we use 28,262 charging sessions data collected from over 40 plug-in electric vehicle (PEV) charging stations during a period from March 2013 to September 2016. Following metrics are calculated for each charging session: (1) arrival and departure times; (2) plug-in and charging duration; (3) number of charging sessions; and (4) charging load flexibility. We develop two options in the discretized charging control algorithm: Option A changes only the charging start time and optimally shifts the entire period when the vehicle is actively charging within the connected charging session, and Option B splits the active charging period into 15-min segments and optimally spreads them over the connected charging session. Overall, the monthly bills savings are 21.3% and 23.5% in the summer season, 11.4% and 13.7% in the winter season, and 17.9% and 20.2% over the year for the control option 1-A and 1-B, respectively. Additionally, we develop a control algorithm in which all current charging sessions are re-optimized each time a new vehicle arrives and initiates a charging session. Greater cost savings can be achieved, e.g. 25.1% reduction for the summer season.