Study On Reliability Analysis And Optimization Measures Of DC Distribution Network

With the rapid development of power electronics technology,DC distribution network has become an important direction for the construction of distribution network in the future.Compared with AC distribution network,DC distribution network has larger capacity and less space in the power supply corridor,provides better power quality,and has better acceptance characteristics for DC power supplies and loads such as distributed photovoltaic,electric vehicle charging stations and large data centers.Therefore,DC distribution network is one of the development trend of urban power grid in the future.Evaluating the reliability of DC distribution network is of great significance to the actual construction of DC distribution network in the future.In this paper,the reliability analysis of DC distribution network is carried out and the optimization measures are put forward.Firstly,the reliability modeling and prediction of the new power electronic equipment used in DC distribution network are carried out in this paper,and the reliability parameters are obtained.The internal redundancy configuration analysis of power electronic equipment is carried out with MMC station as a typical equipment,and the overall reliability index of key equipment under different redundant components,different redundancy and different redundant operation modes is calculated.According to the calculation results of redundant configuration,the optimal configuration scheme of equipment is put forward.Secondly,based on the reliability parameters of the equipment,the reliability evaluation of the DC distribution network with different structures is carried out by analytic method.The difference of reliability index between DC distribution network and AC distribution network is compared,and the difference of reliability index of DC distribution network with different structure is analyzed.The effects of redundancy of critical equipment and breaking converter on system reliability are also calculated.The optimal configuration scheme of current DC distribution network is obtained from the reliability calculation results.And then,the sequential simulation model of source-storage-load is established,and the reliability of DC distribution network with distributed generation is calculated by sequential Monte Carlo simulation.The evaluation results can be divided into three parts: comparing the system reliability before and after distributed power supply access,analyzing the system reliability of distributed generation of different access locations and different access capacity,and calculating the system reliability of different source-storage configuration schemes.According to the evaluation results,distributed generation configuration schemes suitable for DC distribution network are proposed.Finally,based on the reliability parameters of the equipment,the main structure of the system and the source-load operation scene,the optimal configuration model of DC distribution network switch based on reliability is established.The improved adaptive genetic algorithm with elite retention strategy is used to solve the model.The optimal configuration model of switch and the validity of solving algorithm are verified by an example system.