Smart charging of electric vehicles to minimize the cost of charging and the rate of transformer aging in a residential distribution network

Authors: ARJUN VISAKH, M P SELVAN

Abstract: Electric vehicles (EVs) exhibit several benefits over combustion engine vehicles, making them an attractive mode of mobility for the future. However, supplying the electrical energy required to recharge their batteries could adversely affect the power system infrastructure. The most severe impact of EV integration is expected to be on the distribution transformers, which are among the costliest equipment in the distribution network. Sustained overloads on the transformer could lead to accelerated aging and early retirement. As the rate of EV deployment rises, so does the probability of transformer overloads and the subsequent loss of life. There is a need for smart charging schemes in which the distribution system operator can schedule the charging of EVs in an optimal manner that prevents overloads and extends the transformer's life. However, EV owners might hesitate to surrender the charging control of their vehicles for the utility's benefit alone. Charging-cost minimization has been identified as an effective motivation for EV users to participate in charge management schemes. This paper presents a smart charging scheme, which minimizes the cost of charging EVs by optimizing their charging powers with respect to a real-time pricing tariff. As the electricity price changes dynamically with the system demand, cost minimization is equivalent to network decongestion. A decongested network is less susceptible to overloads and equipment damage. Simulation results show that with smart charging, the charging cost incurred by EV owners as well as the rate of aging undergone by the transformer can be significantly reduced.

Keywords: Electric vehicles, smart charging, charging-cost minimization, transformer aging, hot-spot temperature

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