Resiliency Impacts of Plug-in Electric Vehicles in a Smart Grid
Research Team: Ghazal Razeghi (lead), Jennifer Lee, and Scott Samuelsen
UC Campus(es): UC Irvine
Problem Statement: While plug-in electric vehicles (PEVs) may tax the electrical grid under normal operations, PEVs can provide benefits during grid outages since they are essentially mobile energy storage resources. This concept. referred to as Mobility Services+, uses PEVs as a resiliency resource during grid outages to increase the reliability and resiliency of the grid by (1) serving critical loads through vehicle-to-home (V2H) or vehicle-to-grid (V2G) electricity transmission by discharging the batteries on the PEVs, and (2) assisting in restoring the grid after an outage by providing the necessary power and energy to restart a utility asset such as a transformer. During normal operations, however, the high electricity demand of PEVs can negatively impact the distribution network by stressing system components such as transformers. This can result in accelerated aging, increased chance of failure, and ultimately reduced reliability and resiliency of the electric grid.
Project Description: This project assessed the impact of PEVs on the resiliency of the electricity distribution system by: (1) assessing the use of PEVs as a resiliency resource during grid outages (Mobility Services+), (2) assessing and simulating the impact of PEVs on the distribution infrastructure during normal operations, and (3) determining the local environmental impact of clustering PEVs. A previously developed model of a smart grid consisting of two distribution circuits and a distribution substation was modified to enable the use of PEVs in vehicle-to-home (V2H) and vehicle-to-grid (V2G) configurations. Scenarios were simulated in which PEVs were used to serve critical loads in a home or community shelters, and a model was developed to assess the feasibility of using PEVs in grid restoration, which determined the inrush current of the substation transformer to determine the required power and energy for startup. The use of clustered PEVs and scattered PEVs in grid restoration was also considered. During normal operations, the stress on system components from high PEV demand resulted in accelerated aging and possible failure, thereby negatively impacting distribution infrastructure during normal grid operations. Smart charging is required to retain an acceptable level of resiliency. In contrast, during grid outages, this study demonstrated that PEVs can be used as an environmentally friendly resiliency resource to both serve critical loads and facilitate grid restoration with the qualification that implementation requires system upgrades including smart switches, upgraded inverters, energy management systems, and communication links.