Orderly Charging Strategy Of Electric Vehicles Based On Complex Network Theory

With the rapid development of the electric vehicles and the construction of charging piles,the disordered charging of a large number of electric vehicles is bound to have a negative impact on the distribution network.After large-scale electric vehicles are connected to the power grid,the quantitative assessment of the impact on the power grid and the research on the charging control strategy aiming at reducing the negative impact have increasingly become a hot issue.How to effectively avoid the negative impact of large-scale charging on the grid while meeting the charging needs of electric vehicle users is still an urgent problem to be solved.In recent years,complex network theory has been applied to the study of power network,and many positive conclusions have been obtained.In this paper,considering the shortcomings of the existing research on the orderly charging strategy of electric vehicles,the improved complex network theory is used to study the distribution network connected by electric vehicles.It not only retains the rationality of complex network theory in the analysis of power network,but also improves the existing methods from the aspects of modeling method,analysis angle and topological characteristics.This theory can reflect the integrity and interaction of electric vehicle and distribution network,and provide ideas and basis for the effective implementation of orderly charging strategy of electric vehicles.This dissertation is organized as follows:(1)Based on the space-time distribution characteristics of electric vehicles load,combined with the related theoretical methods of complex network about modeling and analysis,the collaborative evolution model is established.Transform the electric vehicles charging process into the evolution process of the topology.Define the topological and electrical statistics of the distribution network.From the perspective of network structure determining network function,this paper reveals the relationship between charging habits of users,distribution network topology and power flow level.(2)An orderly charging strategy for electric vehicles space is proposed.Considering the performance of power grid and the needs of users comprehensively,the best charging station is selected for electric vehicles.The effectiveness of this optimization strategy is verified from the aspects of network topology and network electrical characteristics.Finally,the simulation results of IEEE14 node system show that: Compared with the disordered charging,the optimization strategy proposed in this paper can balance power flow distribution,reduce the active network loss,and is conducive to the safe,stable and economic operation of the distribution network.(3)Based on the division of the traditional time-of-use electricity price period,according to the fluctuation of the grid load,the time-of-use electricity price period for electric vehicles is determined.Considering the constraints of user's charging demand and transformer's rated capacity,the minimum total charging cost and the minimum load variance are taken as the optimization objective function.A multi-objective optimal control method is proposed,which can reduce the peak valley difference and improve the customer satisfaction by dynamically responding to the charging time-of-use price.