Overloading of distribution transformers in smart grid due to uncoordinated charging of plug-In electric vehicles

Random uncoordinated charging of multiple plug-In electric vehicles (PEVs) in residential distribution systems could become a reality in the very near future. The potential for stresses and network congestion is significant since PEV charging represents a sizeable and possibly random operation in distribution systems. Coordinated and smart charging regimes are currently being investigated as possible long-term solutions. However, it could take several years before smart grid infrastructure is ready to support smart coordinated charging. Therefore, until smart charging becomes available, it must be determined how present-day distribution systems will cope with uncoordinated random PEV charging activities. In particular, the burden on local distribution circuits such as transformers and cables, which are the critical links in distribution systems, must be investigated under PEV loads. This paper carries out an analysis into the impacts of random uncoordinated PEV charging on the performance of distribution transformers. Such operation may lead to an overall reduction in the reliability and economy of future smart grids. Simulation results are presented which demonstrate various random uncoordinated PEV charger activities for a modified IEEE 23 kV distribution system connected to several low voltage residential networks populated with PEVs. The performance of various distribution transformers within the simulated smart grid is examined.