Planning Of AC/DC Hybrid Distribution Network With Distributed Energy Resources

The distribution network faces users directly and bears the main load of the power grid,whether the configuration of which is proper would be directly concerned with power supply quality and affect the residential power utilization and social benefits.With the development of economy,the requirements for both quantity and quality of social power utilization are constantly rising,and the upgrade and expansion of network frame are also urgently needed.Recently,the penetration rate of distributed generation(DG)in distribution network is increasing and exerts an influence on distribution network,whose proper planning would be of great significance for optimal planning and operation of distribution network.In addition,with the rising of the density of DC load,the research of AC/DC distribution network is gradually increasing.Under the above background,in this paper,the work with respect to the planning of distribution network with DG is as follows.Firstly,for the uncertainties of DG output and load,a multi-scenario method based on the classification of timing characteristics and hybrid clustering is proposed.Through the analysis of factors affecting DG output and load,the timing characteristics of all uncertain units are classified into multiple typical timing situations.In each situation,the hybrid clustering algorithm based on a large number of historical data is carried out to achieve several scenarios with a certain probability,and then four statistical indicators including expectation,standard deviation,skewness and kurtosis are used to verify the similarity degree between the obtained scenario set and the original data set.The proposed approach can transform the uncertain factors into scenario set,laying the foundation for the planning of distribution network considering uncertainties.Secondly,for the interaction of DG and network frame in coordinated planning,a nested improved bi-level method based on the heuristic intelligent algorithm is proposed,and a multi-objective bi-level coordinated planning model for DG and network frame in AC distribution network based on the multi-scenario timing characteristics is built.The optimization decision for the configuration of network frame and DG is carried out in upper level and lower level,respectively,and the objective functions are built,respectively,from the perspective of system overall optimization and maximization of DG benefits.Through the nested solving of upper and lower level,the model can ensure the optimal combination of DG and distribution network frame for every feasible solution in the population of intelligent algorithm,therefore,the interaction can be addressed.Through the case study,the superiority of muti-scenario method and nested bi-level method can be validated.Finally,a planning approach considering transfroming part of the AC lines into DC lines and building DC network is proposed,and a planning model for AC/DC hybrid distribution network with DG based on the multi-scenario timing characteristics is built.In the planning model,the DG configuration,the lines to be transformed into DC form,the access location and the decision of DC or AC form of newly built lines are considered as optimizing variables,and the investment of DG,network and converters of DG and load,active power loss and voltage stability are considered in the objective functions.The case study indicates that the proposed approach can effectively transform the AC distribution network into AC/DC network,providing a better reference for the development of AC/DC hybrid distribution network.