| Suffering from the increasingly severe energy crisis and environmental pressure,governments of various countries are paying more and more attention to the development of the electric vehicle industry.Compared with traditional fuel vehicles,electric vehicles have incomparable advantages in energy consumption.In recent years,with the breakthrough of electric vehicle battery technology,the continuous development of smart grids,and the policy support of governments of various countries for the electric vehicle industry,the market share of electric vehicles has increased rapidly.However,because the charging characteristics of electric vehicles are highly uncertain in time and space,the charging and discharging of large-scale electric vehicles connected to the grid under uncontrolled conditions will bring huge challenges and threats to the grid.In this context,the research on the optimal operation strategy of the distribution network for electric vehicle access is of great significance to the development of the electric vehicle industry and the optimization of the distribution network.The main research contents are summarized as follows:Firstly,the load forecasting problem of electric vehicles is studied.Considering the travel habits of electric vehicle users and the charging characteristics of batteries,based on the uncertainty of the initial charging time and charging duration of electric vehicles,the charging demand load of electric vehicles is deduced based on probability modeling method,and the daily load curve of electric vehicles is predicted.It provides data support for the orderly charging of electric vehicles and the planning and operation of distribution network.Secondly,on the premise of meeting the charging demand of electric vehicles,an optimal power flow model based on the safe operation of the distribution network is established.The constraints considered in the model include node voltage,line power flow,distribution transformer capacity and charging energy balance.The objective function is to minimize the generation cost of power grid and optimize the charging power of electric vehicles.The simulation results show that the primal-dual interior point method(PDIPM)with predictive correction process has good convergence performance,and the proposed optimal scheduling strategy for electric vehicles can effectively reduce the active operating cost of the system,and improve the stability and safety of system operation.Finally,the problem of orderly charging of electric vehicles guided by the time-of-use(TOU)price strategy is studied.Based on the price demand elasticity coefficient matrix and the division of peak,flat and valley time periods,we will observe the guiding effect of this guidance method on the orderly charging of electric vehicles.On the basis of minimizing the peak load and peak-valley difference of electric vehicles,the objective function adds two new indicators that affect the operation of the distribution network: minimizing voltage fluctuations and minimizing active power loss.Using adaptive particle swarm algorithm to solve,optimize the charging power of electric vehicles and give the optimal electricity price.The simulation results prove that through reasonable time division and scientific time-of-use price setting,the voltage quality of the distribution network nodes can be improved,the active power loss of the distribution system can be reduced,the income of electric vehicle users can be increased,and the goal of multiple wins can be achieved. |
