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Coordinated charging of Plug-In Electric Vehicles (PEVs) in residential distribution systems is a new concept currently being explored in the wake of smart grids. Utilities are exploring these options as there are concerns about potential stresses and network congestions that may occur with random and uncoordinated multiple domestic PEV charging activities. Such operations may lead to degraded power quality, poor voltage profiles, overloads in transformer and cables, increased power losses and overall a reduction in the reliability and economy of smart grids. Future smart grids communication network will play an important role in PEV operation because the battery chargers can be remotely coordinated by the utility and harnessed for storing surplus grid energy and reused to support the grid during peak times.Based on a recently proposed PEV charging algorithm, this paper focuses on the impact of coordinated charging on distribution transformer loading and performance. Simulation results are presented to explore the ability of the PEV coordination algorithm in reducing the stress on distribution transformers at different PEV penetration levels. The performance of various distribution transformers within the simulated smart grid is examined for a modified IEEE 23 kV distribution system connected to several low voltage residential networks populated with PEVs.Index Terms-Battery charging, plug-in electric vehicles, transformers and smart grids.

The impact of different battery charging rates of Plug-in Electric Vehicles (PEVs) on the power quality of smart grid distribution systems is studied in this paper. PEV battery chargers are high power nonlinear devices that can generate significant amount of current harmonics. PEVs will be an integral component to the operation of smart grids and therefore their power quality impacts must be thoroughly analyzed. Based on decoupled harmonic load flow analysis, different PEV charging scenarios (e.g., time zone scheduling, charging rate and penetration level) are tested for a typical large distribution network topology. The impacts of PEV charge rate on voltage profile, fundamental and harmonic losses, transformer loading and total harmonic distortions are demonstrated.

This paper analyzes the potential impacts of Plug-in Electric Vehicles (PEVs) on the voltage profile, losses, power quality and daily load curve of low voltage residential network. PEVs are soon expected to grow in popularity as a low emission mode of transport compared to conventional petroleum based vehicles. Utilities are concerned about the potential detrimental impacts that multiple domestic PEV charging may have on network equipment (e.g., transformer and cable stresses). To address these issues, two charging regimes including uncoordinated (random) and coordinated (uniformly distribution) are considered. Based on harmonic analysis of a typical 19 bus low voltage (415V) residential network, different charging scenarios over a 24 hour period are compared considering voltage deviations, system losses, transformer overloading and harmonic distortions. Simulation results are used to highlight the advantages of the coordinated uniformly distributed charging of PEV in residential systems.

This paper investigates the stability domain of ferroresonance in asymmetric three-phase three-leg transformers considering magnetic couplings and hysteresis effects of the core. A newly developed and accurate time-domain transformer model capable of simulating dynamic and transient operating conditions is implemented in this study. The model is based on electromagnetic circuit theory and considers dynamic hysteresis effects (major and minor loops) as well as core topology, asymmetry, and magnetic flux cross-coupling interactions of the core legs. Unbalanced switching with series and shunt capacitances, which is known to increase the risk of ferroresonance, is studied with the developed model. The validity of the model under ferroresonant conditions is confirmed by comparisons with extensive experimental data. The main contribution is a new analysis of (a)symmetric three-phase transformer ferroresonance behavior with an accurate core model capable of predicting ferroresonance modes.Index Terms-Ferroresonance, hysteresis, nonlinear and threephase transformer model.

Plug-in Electric Vehicles (PEVs) will be an integral part of smart grids in the near future. This paper studies the impacts of different PEV battery charging profiles on the performance of smart grid distribution systems. PEVs are already growing in popularity as a low emission mode of transport versus conventional petroleum based vehicles. Utilities are becoming concerned about the potential stresses and overloads that may occur with multiple domestic PEV charging activity. Smart grids will play an important role in PEV operation because the battery chargers can be coordinated by the utility and harnessed for storing surplus grid energy and reused to support the grid during peak times. Therefore, an analysis is performed for a smart grid distribution system to demonstrate the impacts of different PEV charging scenarios. The paper compares charging rates (e.g., slow, medium and fast charging), PEV penetration levels as well as different charging periods over a 24 hour period considering existing system load profiles, and evaluates the overall performance of the distribution system. The impact on system load profile, total losses, transformer loading and voltage profile is examined.

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