Numeral Calculation Modeling For Probability Distribution Of Electric Vehicle Charging Load And The Distribution Network Operating Characteristics Index Evaluation

With the large-scale popularization of electric vehicles in the future,the rapid growth of electric vehicle charging load has brought huge challenges to the operation and planning of the distribution network.How to model the charging load of electric vehicles and assess the operation characteristics of the distribution network within the electric vehicle charging load is of great significance to the optimization analysis of the future distribution network.Traditional electric vehicle charging load probability modeling usually adopts Monte Carlo simulation method,which has problems such as many coupling parameters and time-consuming calculation.When analyzing the impact of electric vehicle charging load on the operating characteristics of the distribution network,traditional probabilistic evaluation indicators are usually calculated by statistical multi-scenario models,which are greatly affected by the selection of scenarios and difficult to reflect the original probability characteristics of the analysis object accurately.The differences in the operating status of statistical data are ignored in the tranditional way,resulting in part of the problem data being overwhelmed by normal data,so the evaluation indicators may not effectively reflect the operating problems of the system.In response to the problems above,this thesis has carried out certain research on the analytical modeling of charging load probability of electric vehicles and the evaluation of the operation characteristics of the distribution network.The specific innovation work is summarized as follows:(1)A numerical calculation modeling method for probability distribution of electric vehicle charging load which based on the combined state of charge(CSOC)is proposed.Multiple trips of the same vehicle are disassembled into independent single trips,and OD(Origin Destination)analysis is carried out on the travel characteristics of the single trip to reduce the parameter coupling error.The CSOC dynamic probability model considering the dynamic travel probability characteristics of vehicles in the traffic system is established to determine the initial and the final CSOC probability density function for a single trip.By using the law of large numbers,the space-time probability distribution function of electric vehicle charging load is established.A case of 12-node road network is used to calculate the spatial-temporal probability distribution of the charging load.Compared with the traditional Monte Carlo simulation method,the proposed method does not have the problem of coupling error,and greatly improves the calculation efficiency under the premise of ensuring the calculation accuracy.(2)A probabilistic index evaluation method based on the calculation results of probabilistic trends is proposed.The voltage qualification index,the voltage deviation index and the line heavy load index is selected to evaluate the operating characteristics of the 10 k V line and the distribution network.The feature weighting method is used to improve the reflection ability of evaluation index and the entropy method is used to determine the weight to avoid the influence of human factors.The operating characteristics of an actual power grid under various different parameters such as the numbers of electric vehicles,the charging modes,the capacity of distributed generation,and the reconstruction of network are evaluated.The analysis results show that the proposed evaluation indicators can effectively reflect the differences in indicators of different external influencing factors,and verify the effectiveness of the proposed evaluation indicators.