Optimal charge control strategies of EVs for enhancement of battery life and lowering the charging cost
Cable Based and Wireless Charging Systems for Electric Vehicles: Technology and control, management and grid integration
Given the significant advantages of electric vehicles (EVs), such as their high efficiency and their environmental benefits, EVs are considered as a promising alternative to conventional passenger vehicles. The incentive policies for purchasing EVs in many countries, the increasing cost reduction of the EV batteries, and the increased EV driving distance suggest a more widespread utilization of EVs in the near future. However, there are still some concerns against the increased connections of EVs to the distribution power systems, such as the potential increase of the electric load demand and the additional power quality issues that can be produced by the converters of the charging devices. Without any coordination, there is a potential of having an unexpected peak demand if the user can charge the EV without considering the power system conditions that can cause grid congestion or reduce the grid efficiency. An effective charge/discharge control strategy can be devised to mitigate the unexpected peak demand due to EV charging, while at the same time the EV batteries can also be used to support the power grid based on vehicle-to- grid concept. Further, it is necessary to consider the lifespan of the EV batteries, because the EV batteries are an expensive and a key part of both battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs). The additional and repetitive charging/discharging cycles required for the V2G services can affect the expected lifetime of the EV batteries. In order to account for the lifetime of the EV batteries, the degradation cost of the batteries needs to be considered for designing their energy management (EM) systems. An optimal control strategy for the enhancement of battery life and the reduction of the operational cost, for the case when the EVs are connected in power networks is therefore needed. In this chapter, discussions on the lifespan of the lithium-ion (Li-ion) batteries are initially provided and different methods that can be used for the battery thermal management system (BTMS) of EVs for the enhancement of battery life are introduced. In addition, various reported strategies for the optimal integration of EVs in the power systems are reviewed. Subsequently, an optimal EV charging control (EVCC) strategy is proposed for the EM of the EVs in a parking lot to lower the operational cost for the EVs, while considering the lifespan of the EV batteries. The operation of EVs in a parking lot to provide the V2G services is then investigated through different scenarios. The simulation results show that the proposed EVCC can minimize the charging cost of the EVs and provide effective V2G services, and when the degradation cost of the EVs is considered, a further cost reduction can be achieved.
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