Study on the optimization of charge-discharge cycle of electric vehicle batteries in the context of Singapore

Continuing environmental concerns are moving electric vehicles into high gear of development. Plug-in type electric and hybrid vehicles are expected in the market anytime. The EV battery- charging load can potentially increase the demand on the utility distribution systems considerably. It is desirable that the EV battery charging load be contained during system off-peak hours without affecting the peak demand, thus utilizing the low cost electricity for charging EV. However, a sizable EV load can introduce a new peak in the early off-peak period. Optimization of the EV charging during the low cost off peak period is formulated to minimize the cost of EV charging in the context of Singapore system. Further, a significant amount remnant EV battery capacity may be available in the early evening hours. They may be utilized to compliment the distribution system if economically viable. The optimization of EV battery charging and discharging is formulated. The case studies presented show that significant saving is possible even at reasonable low levels of EV penetrations.