The Research On Coordinated Charging Of Electrical Vehicles

With the increasing tension of oil resources and continuous development of powerbattery, electric vehicle (EV) has become a major concern of new energy vehicles fromcounty to county. Various technical breakthroughs have brought great improvements inboth performance and economy of EVs, which contributes to the popularization of EVs.However, the large-scale application of EVs, especially the disordered charging mayproduce adverse effect on power grid. Therefore, the study on optimization controltechnology of EV charging has become an urgent need.This paper introduces the general process of analyzing the impact of EVs ondistribution grid based on the stochastic model of EVs. The radial network of IEEE30-node test feeder is adopted to evaluate the impact of EVs on distribution grid bycomputing the power losses and the maximum voltage deviation. The allowablemaximum penetration of electric vehicle is also investigated in the premise of withoutgrid enforcement. On this basis, three methods of coordinated charging are proposed inthis paper.The first method is the optimized charging base on optimal power losses, which isproposed to minimize the power losses. The optimal charging profile of the EVs iscomputed in the case of random placement of EVs.The second method is the optimized charging based on optimal charging cost,which aims to minimize the cost of EV charging. With consideration of the chargingcharacteristic of power battery and other constraints, the optimal charging model forEV charging load in response to time-of-use (TOU) is formulated. Then, a heuristicmethod is designed to obtain the optimum charging power profile.The third method is the optimized charge-discharge strategy of EVs based on theminimum variance of wind power. The optimal charge-discharge control modelconsidering the fluctuation of wind power is proposed on the assumption that EVsperform vehicle to grid (V2G) power transactions. The Monte-Carlo method is used tosimulate the stochastic wind speed based on Weibull probability density function.Finally, the optimization model is solved by Genetic Algorithm (GA), and the resultsprove the availability of the proposed model and approach.In conclusion, this paper focuses on the impact of EVs on distribution grid and thecorresponding control measures, several coordinated charging methods have beenproposed. The work of this paper could provide some guide for further research of EVs-friendly access to power grid.