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Electric Vehicle Charging: Distribution Transformer Impacts, Smart Charging, and Transportation Modeling
- By Glenn McRae
In 2012, worldwide sales of Plug-in Electric Vehicles (PEVs) are expected to surpass 257,000 units, and North American sales are expected to exceed 66,200 units. Predictions estimate that U.S. PEV annual sales will reach 640,000 units by 2015. Additionally, 2012 marks the introduction of seven new PEV manufacturers, including BMW, Ford, Honda, Toyota, Volvo, Coda, and Fisker. This increased popularity in electric transportation enticed former Transportation Research Scholar and Master’s student in Electrical Engineering, Alex Hilshey, to contribute towards the Power industry’s preparations to support such a potentially large PEV fleet.
With rising adoption of these vehicles, electric utility providers are quickly becoming aware of the substantial electric load required to charge PEV batteries between travel tours; for example, a fully depleted Chevrolet Volt battery requires approximately 7.5 hours of charging at the standard charging rate (1.4 kWh/hr). Given mass adoption of PEVs, battery charging may create new load peaks during non-traditional times or may substantially increase the magnitude of pre-existing peaks by 1.4 kW per PEV at standard charging rates (AC Level 1) or by a whopping 7 kW per PEV at faster charging levels (AC Level 2). The additional load from PEV charging generates periods of time in which electric distribution infrastructure, specifically distribution transformers, may experience increased damage, which ultimately may result in costly replacements or upgrades.
Although distribution transformers, on an individual basis, are a relatively inexpensive component of the electric distribution grid, it should be noted that North America is currently serviced by over 40 million distribution transformers, making them the most used element of the electric distribution system. Therefore, understanding how PEV charging will impact distribution transformer aging is important to utilities who are making investment decisions towards PEV fleet support.
Given this interesting problem, Alex filled his time at UVM’s Transportation Research Center by producing models to estimate the impacts of PEVs on distribution transformers. The impact estimations require both predictions in PEV charging demand and simulations of transformer thermal aging. The Transportation Research Center provided Alex with an interdisciplinary environment where he used concepts in travel demand modeling combined thermal models of transformers from the mechanical engineering discipline to solve his electrical engineering problem catered towards informing the Power Systems field. In addition to impact estimation, Alex contributed to the research on PEV smart charging which is a component of the exciting new research field, collectively called “Smart Grid.”
For more information on Alex’s research e-mail him at firstname.lastname@example.org or see his publications:
Hilshey, Alexander, P. Hines, and J. Dowds, “Estimating the Effect of Electric Vehicle Smart Charging on Distribution Transformer Aging,” IEEE Transactions on Smart Grid, Accepted for Publication
Hilshey, Alexander, P. Rezaei, P. Hines, and J. Frolik, “Electric vehicle charging: Transformer impacts and smart, decentralized solutions,” IEEE PES General Meeting, Summer 2012, Accepted for Publication
Hilshey, Alexander, P. Hines, and J. Dowds, “Estimating the Acceleration of Transformer Aging Due to Electric Vehicle Charging,” IEEE PES General Meeting, Summer 2011