| As a necessary option to achieve the strategic goal of "double carbon",the "electrification" of automobiles plays an irreplaceable role in solving serious problems such as environmental pollution and fossil energy shortage.The trend of rapid development of electric vehicles has become the consensus of the whole society.In the early development of electric vehicles,the charging load is small,and the impact on the power grid is not obvious.With the increase of car ownership and the increasing penetration rate of electric vehicles,the charging load has a serious impact on the safe and economic operation of the power grid.Therefore,it is necessary to analyze the temporal and spatial distribution characteristics of the charging load,evaluate the impact of the charging load on the power grids at different levels,and consider the layout of charging piles and the selection of power grid equipment in the distribution network planning stage,so that the power grid can adapt to the rapid growth of the charging load and meet the charging needs of the majority of car owners.The main research work of this paper is as follows:(1)Establish the electric vehicle charging load prediction model.First,analyze the categories of electric vehicles and related supporting facilities,and study the performance of different types of power batteries.Secondly,summarize the driving and charging laws of all kinds of electric vehicles,and establish a charging load calculation model based on Monte Carlo sampling simulation algorithm in combination with the electric vehicle ownership,battery capacity,charging power and other parameters,to predict the space-time distribution of charging load based on the time-sharing price mechanism,so as to provide an accurate data basis for the subsequent research on the impact of charging load on the distribution network.(2)Analyze the impact of charging load on the power grid.The impact of charging load on the power grid is analyzed from three levels: urban power grid,10 k V feeder distribution network and distribution network transformer.At the level of urban power grid,the change of peak valley difference and peak value of daily load curve is mainly analyzed.At the level of10 k V feeder distribution network,the changes of node voltage offset and network loss are mainly analyzed.At the transformer level of the distribution network,it mainly analyzes the change of transformer load rate and load rate.It is concluded that the charging load has a profound impact on the operation of power grids at all levels,among which the equipment operation in residential areas has the deepest impact.(3)Distribution network planning considering charging load.First,on the distribution network planning process,analyze the difference between charging load and not.Aiming at the problem of large node voltage deviation of 10 k V feeder distribution network after charging load is connected,a two-layer optimal configuration model of charging piles is proposed.By optimizing the number of charging piles in different functional areas on the upper layer and the access position of charging piles in different nodes on the lower layer,the distribution of charging load in the distribution network is changed,and the peak valley difference of system load and node voltage deviation are reduced.At the level of distribution network transformer,an optimization model is proposed to meet the grid operation reliability and security constraints,with the goal of minimizing the cost in the whole life cycle of the transformer,optimize the selection and sizing of transformers,meet the growth of charging load in the planning period,maintain the capacity load ratio in a reasonable range,and improve the economy of grid operation.The research results have reference significance for the future distribution network planning to adapt to the large-scale access of electric vehicle charging load. |
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