Optimal load management of EV battery charging and optimization of harmonic impacts on distribution transformers

The growing concern about CO₂ emissions and dependency on gasoline contributes to the increasing application of electric vehicles (EVs). EV battery chargers are non-linear loads and large-scale scale application of EVs increases the grid harmonics significantly. The grid harmonics have negative impacts on the components of the power system including distribution transformers. In this paper the impacts of EV charging on the load loss, hot-spot temperature and life time of distribution transformers are studied. Moreover, the EV charging load is formulated as an optimization problem and Karush-Kuhn-Tucker optimality conditions are employed for obtaining an optimal EV charging schedule. The EV load management program presented in this paper, maintains the safety operation of distribution transformers by minimizing their life time reduction.