Impacts of Electric Vehicle Charging on Electric Power Distribution Systems

Robert Bass, Portland State University


This proposed research will use Electric Avenue as a platform for investigating the impacts electric vehicles (EVs) may have on electric power distribution systems. During the week of October 22-29, students from OTREC, under the direction of John MacArthur, performed a week-long survey of usage at Electric Avenue. The students monitored EV use along the Avenue and performed driver surveys. Concurrently, PGE installed a temporary power quality (PQ) meter on the main feeder into Electric Avenue to monitor the power consumed during that week. In addition, each of the eight charging stations at Electric Avenue is continuously metered (though this monitoring is done in 15 minute intervals with 1.2 kW resolution, a sampling rate and resolution that are too wide to discern meaningful value regarding power quality). My research group is in the process of time-aligning the survey data, the station metering data and the PQ meter data. We will then begin to assess the impacts individual charge controllers may have on distribution systems, as well as how aggregation of charge controllers affects overall PQ. The early stages of this work are currently being performed by an undergraduate electrical engineering student, Nicole Zimmerman, through funding from the PSU MCECS Undergraduate Research and Mentoring Program (URMP). The objective of this research is to expand the electric utility industry’s understanding of the impacts Electric Vehicles may have on power distribution networks. Harmonic currents have the potential to shorten the lifetime of power systems devices, particularly distribution transformers and instrument transformers (CTs and VTs) due to insulation failure and core saturation. Utilities plan their asset management by anticipating the nature of loads connected to the system and selecting assets designed to handle those loads. EV charging stations are non-linear loads; these loads have a harmonic content. IEEE standard 519-1992 dictates the total harmonic distortion (THD, a metric of PQ) a load may present. However, the THD of a charger changes during the charging cycle. Further, the THD on a utility feeder is compounded when multiple EVs are connected to the same service. We would like to investigate both of these phenomena. This proposal seeks funding to gather additional PQ data and to investigate a wider array of EV vehicle chargers. The October 22-29 PQ data set was gathered by measuring PQ at the service entrance, the point at which all eight of the charger circuits meet. Consequently, it is difficult to ascertain the affects individual stations have on PQ, as all eight EV charging stations use the same service. Therefore, we plan to rent a PQ meter for two months, and apply the meter to individual branch circuits, thereby allowing us to investigate the PQ of single charge controllers. We also plan to collect additional data at the service in order to better understand how THD compounds as more vehicles connect to the same service.

Project Details

Project Type:
Project Status:
End Date:
September 30,2013
UTC Grant Cycle:
OTREC Small Starts
UTC Funding: