Understanding and Managing the Impacts of Electric Vehicles on Electric Power Distribution Systems.

摘要

In the United States, transportation accounts for 31% of all U.S. greenhouse gas emissions and 180% of all domestic crude oil production1. Electrification of the transportation sector is one potential path to simultaneously reduce greenhouse gas emissions and dependence on foreign oil. However, transportation electrification is not without challenges. In order for electrified transportation to result in substantial greenhouse gas emissions reductions, the fuel sources for electricity need to come from low-carbon resources, such as wind and solar power plants. And, the aging U.S. electricity infrastructure will need to be modernized in order to incorporate large amounts of electrified transportation without substantially degrading electricity reliability. While there are a number of useful studies on the greenhouse gas impacts of transportation electrification, only recently have researchers begun to understand the impacts of electricity on electric power infrastructure. Thus, the primary goals of this research project were to understand these impacts in detail and to develop new methods for reducing the impact of transportation electrification on the electricity transmission and distribution infrastructure. In particular, this report focuses on understanding and mitigating the impact of transportation electrification on the medium and low voltage distribution infrastructure, through which electricity is transported from the bulk power grid, through neighborhoods, to individual homes and businesses. Distribution systems in residential neighborhoods with particularly high plug-in electric vehicle adoption rates may see substantial load increases in the relatively near future, making this problem particularly timely. In prior work2, researchers identified these distribution system impacts to be notably ill understood. This project focused specifically on the impacts of electric vehicles on two key components of power distribution systems: residential service transformers, and underground cables. Service transformers are one of the most important components of the power grid. Every home and business connects to the power grid through these relatively small transformers. Because of cost considerations they do not include any telemetry systems that can inform utilities of their health, making it difficult for utilities to know when these components are overloaded. Most residential service transformers are rated to serve between 10 and 50 kVA of load, and typically serve 5-15 homes or small businesses. Yet a single plug-in electric vehicle (PEV) with a fast charging system (240 V Level 2 charging) will consume about 7 kVA. Three electric vehicles will nearly use the entire capacity of a 25-kVA transformer. Because of this potential for overloads, this project studied the impact of PEVs on service transformers in detail.