Research On EV’s Load Characteristics And Impacts On Planning Of Distribution Networks

As a means of transportation with clean energy and less emissions,electric vehicles(EV)have been vigorously promoted by the country and the region,and the speed of development is accelerating and the scale is expanding.As a new type of load,a large number of electric vehicles access to the distribution network will test the safe and stable operation of the system.Therefore,it is necessary to analyze and calculate the characteristics of the charging load,and plan the construction of charging facilities and power distribution facilities in advance in order to adapt to the increase in demand for charging load.This paper will focus on the modeling of charging load,the analysis of load characteristics of orderly charging and the impact of electric vehicles on distribution network planning.The specific research work is as follows:(1)Modeling of EV’s charging load is established.Based on the trip chain theory,the temporal and spatial variables of EV’s travel are studied and the corresponding probability distribution model is established.Then Monte Carlo Simulation Method is used to extract each temporal-spatial variable and form a complete trip chain for each EV in one day.According to the charging frequency of EV and the investigation result of the charging location,the charging behavior of the EV’s owner is analyzed and two charging scenarios are set,and the charging load demand in different functional areas can be calculated by combining two charging scenarios.Finally,the influence of temperature on the charging load is considered,and the charging load profiles in different seasons are calculated.The established charging load model provides a basis for subsequent orderly charging studies and analysis of the impact on the distribution networks.(2)The impacts of EV’s disordered charging on distribution networks are analyzed.From the perspective of regional power grid,medium voltage feeder and low voltage distribution network,the effects of disordered charging on load curve characteristics,voltage deviation and distribution transformer’s load ratio are analyzed.It is found that the impact of disordered charging on the distribution network is mainly on the mediumlow voltage side.(3)The load characteristics of EV under orderly charging are analyzed.The orderly charging strategies are divided into price-based orderly charging and incentivebased orderly charging,and the charging load characteristics under Time-Of-Use electricity price and optimal control are simulated respectively.The difference of charging load demand under different response levels is analyzed.(4)The impact of EV’s access on planning process of distribution network was studied.At the medium voltage level,a two-layer optimal configuration model of the charging pile is proposed.By optimizing the number of charging piles in different functional areas and the position of the charging piles,the system load’s peak-valley difference and voltage offset are reduced.At the low-voltage level,a capacity planning method for distribution transformers considering electric vehicles is proposed to improve the acceptance of EV by low-voltage distribution networks.The research results have reference significance for the future distribution network planning to adapt to the large-scale access of EV.