An analytical model for an electric vehicle (EV) powertrain has been developed in this paper to study the vehicular dynamics, based on a Nissan Leaf EV. The electrical components of the powertrain include a battery pack, a battery management system (BMS), a DC/DC converter, a DC/AC inverter, a permanent magnet synchronous motor (PMSM), and a control system while the mechanical system consists of power transmissions, axial shaft and vehicle wheels. The driving performance of the EV is studied through the realworld driving tests and simulation tests in Matlab/Simulink. In the analytical model, the vehicular dynamics is evaluated against changes in the vehicle velocity and acceleration, state of charge (SOC) of the battery, and the motor output power. Finally, a number of EVs are introduced in the system to optimize the power dispatch. The greenhouse gas emissions of EVs are analyzed under various driving and charging conditions, and compared with conventional internal combustion engine (ICE) vehicles. For a given driving cycle, Nissan Leaf can reduce CO2 emissions by 70%, depending on its duty cycle and the way electricity is supplied.
With the increasing penetration of new and renewable energy, incorporating variable adjustable power elements on the demand side is of particular interest. The utilization of batteries as flexible loads is a hot research topic. Lithium-ion batteries are key components in electric vehicles (EVs) in terms of capital cost, mass and size. They are retired after around 5 years of service, but still retain up to 80% of their nominal capacity. Disposal of waste batteries will become a significant issue for the automotive industry in the years to come. This work proposes the use of the second life of these batteries as flexible loads to participate in the economic power dispatch. The characteristics of second life batteries (SLBs) are varied and diverse, requiring a new optimization strategy for power dispatch at the system level. In this work, SLBs are characterized and their operating curves are obtained analytically for developing an economic power dispatch model involving wind farms and second life batteries. In addition, a dispatch strategy is developed to reduce the dispatch complex brought by the disperse spatial and time distribution of EVs and decrease the system operating cost by introducing incentive and penalty costs in regulating the EV performance. In theory, SLBs are utilized to reduce the peak-valley difference of power loads and to stabilize the power system. Test results based on a ten-unit power system have verified the effectiveness of the proposed dispatch model and the economic benefit of utilizing SLBs as flexible loads in power systems. This work may provide a viable solution to the disposal of waste batteries from EVs and to the stable operation of fluctuating power systems incorporating stochastic renewable energy.
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