AC/DC Distribution Network Planning Considering Active Response Of Electric Vehicles

Supported by national strategy,Electric Vehicle industry is ushering in a new era of vigorous development with the reduction of cost and improvement of power batteries’ safety and durability.A well-distributed and scientifically-operated charging system providing smart,efficient,economical and low-carbon charging service for owners is the guarantee for the sustainable growth of Electric Vehicles.The power system is the main source of energy for Electric Vehicles.As devices couple the transportation network with the power grid,and massive distributed energy storages on the user side,the large-scale Electric Vehicles will bring significant opportunities and challenges to the power system which is transforming to a clean,flexible,diversified and Interactive one.With the support of China’s new energy vehicle subsidy policy,new energy vehicles have experienced rapid growth in recent years.And electric vehicles are the main development direction of new energy vehicles.Large-scale development of electric vehicles needs to supply energy through the distribution network.The access of the electric vehicles’ disorderly charging load will further increase the peak-valley load difference of the distribution network,the distribution network planning capacity and planning cost.If the active response of electric vehicles can be achieved and the electric vehicles can be charged in order,then they can avoid load peaks of the distribution network and reduce the distribution network planning capacity.In addition,considering that electric vehicles are typical DC loads,if DC subnets can be introduced into the distribution network,and the future power grid shape will be developed in the direction of AC/DC hybrid distribution networks.Since the construction costs of DC feeders are relatively low,AC/DC distribution networks can be effectively reduce distribution network planning costs.Research on distribution network planning that takes the active response of electric vehicles into account.The main works of the study are as follows:(1)The paper studies the charging behavior characteristics of electric vehicles.On this basis,the mathematical model of electric vehicles disordered charging is researched.Considering disordered charging will increase the peak-valley difference of the load,an active response model of electric vehicles is proposed,including peak-flat-valley charging transfer and cross-regional charging transfer with mobile energy.It can realize the active response of electric vehicles from the time and space dimension.(2)From the perspective of distribution network planning,the load characteristics of electric vehicles are studied.Electric vehicles can be used as both DC loads and AC loads.On this basis,the difference between the traditional distribution network planning and the distribution network planning considering the access of electric vehicles is analyzed.And the planning process and methods of the distribution network are researched to lay a theoretical foundation for the following planning to use appropriate algorithms.(3)An AC distribution network planning model that takes account of electric vehicles’ active response is established.The objective function is minimize the construction,operation and maintenance cost of distribution network and charging station.The restrictions include distribution network power flow constraints,node voltage upper and lower limits,feeder capacity,distribution network logic and electric vehicle charging requirements.Then reducing the capacity of charging stations and substations through peak-flat-valley charging transfers;reducing the capacity of charging stations through cross-regional charging transfer with mobile energy.So the cost of distribution network planning is reduced.(4)The structure of the AC/DC hybrid distribution network is analyzed.Considering that a large number of DC loads will be connected to the distribution network in the future,the AC/DC hybrid distribution network has the advantages of both AC and DC distribution networks.An AC/DC hybrid distribution network planning model considering the active response of electric vehicles is established.On the basis of the AC distribution network planning model,the construction costs of DC feeders and converters are included in the objective function,and the planning model is solved by genetic algorithm.