Optimal Planning Of Urban Charging Facilities Considering The Load Fluctuation And Voltage Offset

The popularity of Electric Vehicle(EV)is one of the important means to deal with the worsening environment and promote energy conservation and emission reduction.At present,countries around the world are vigorously promoting the development of EV.The construction and development of charging facilities is an important link in the popularization of EV.According to the degree of concentration,urban charging facilities can be divided into distributed charging piles and centralized charging stations.Distributed charging piles generally refer to scattered and non-clustered charging facilities with both fast and slow charging modes.Charging piles are mainly AC,which mainly meet EV users’ slow and regular charging needs.Centralized charging stations generally have three or more charging piles.According to the main types of charging piles in the stations,they can be divided into fast charging stations and slow charging stations.There are many types of EV in cities.The charging demand type and the temporal and spatial distribution of charging demand are different.To build a complete EV charging service network,decentralized charging pile planning should be carried out at parking points in various functional areas of the city and centralized fast charging station planning should be carried out in the urban road network.In order to meet the slow and regular charging requirements of EV in urban functional areas and reduce the negative impact of charging facilities in the distribution network,a distributed charging pile planning method based on minimum load fluctuation and voltage offset was proposed to plan the charging piles needed to be built at parking stations in urban functional areas.The total daily charging demand can be obtained from the randomness of daily traveling distance of EV.According to the different queuing modes of EV users at the parking points in each functional area,two queuing theory models of loss system and waiting system were established to obtain the total number of charging piles in each functional area.A charging pile number distribution model was established with the minimal mean of network loss,the minimal mean of load fluctuation rate and the minimal sum of voltage offset of the distribution network to determine the number of charging piles needed to be built at the stopping points of each functional area.The rationality and effectiveness of the proposed distributed charging pile optimization planning method are verified by an example analysis.In order to meet the rapid charging demand of EV in urban road network,two different optimization planning methods of urban fast charging stations were proposed.In the first method,an optimal planning model is built with the minimal sum of investment cost,operation and maintenance cost and user cost of the fast charging station.The genetic algorithm and Voronoi Diagram range division method are used to solve the proposed optimization model.In the second method,the location,capacity of fsat charging stations and optimal path planning of each charging demand point are carried out with the optimization goal of minimizing the mean time of charging paths at each charging demand point.Floyd shortest path algorithm combined with genetic algorithm is used to solve the problem.In addition,in order to reduce the impact of EV charging load in the distribution network,the load fluctuation and voltage offset of the distribution network were considered in the planning of fsat charging stations.Finally,the two optimal planning methods for fsat charging stations are simulated respectively,and the results verify the rationality and effectiveness of the proposed optimal planning methods for charging stations.