Research On Reconfiguration Method Of AC/DC Hybrid Distribution Network

Compared with AC distribution network,DC distribution network has the advantages of low line loss,high reliability of power supply and strong ability of distributed energy absorption.Therefore,the development trend of distribution network is to build AC-DC hybrid system based on traditional AC distribution network.However,the introduction of DC distribution network will bring many challenges to the traditional distribution network.How to realize the optimal operation of AC-DC hybrid system by means of distribution network reconfiguration has become an urgent problem to be solved.This paper analyses the basic concepts of graph theory and the common points of distribution network,and introduces the basic topological structure of distribution network.Based on graph theory and basic theory of distribution network reconfiguration,a distribution network with 16 nodes of IEEE is divided into loops,which simplifies the network structure.The standard form of cuckoo algorithm is introduced,and the search performance of Levy flight is analyzed.By comparing CS algorithm with PSO,DE,SA and ACO,the advantages and disadvantages of various algorithms are given.Based on the requirement of distribution network reconfiguration,a method of network data storage is presented.Branches are numbered and state variables of branch switches are added to facilitate network reconfiguration.The concrete form of decimal coding based on loop partition is proposed,and the method of distinguishing infeasible solutions is given.Considering the poor convergence performance of standard cuckoo algorithm in the later stage,a greedy strategy is introduced to enhance the local search ability of the algorithm.The performance of the algorithm is improved by the ratio of global search and local search in the execution process of the adaptive step size scaling factor and the adaptive discovery probability control algorithm.Taking the optimal system loss as the objective function,the simulation of IEEE33 bus distribution system and PG&E69 bus system is carried out.The results show that the improved cuckoo algorithm has good search efficiency and precision.Because there will be many power electronic devices in the DC distribution network,which is different from the AC distribution network,the topology structure of the DC distribution network is briefly introduced at first.Considering the power flow calculation,the node processing method of DC distribution network and Newton Raphson algorithm for solving DC power flow are given.The AC/DC hybrid model for simulation test is constructed,and the steady state model and control mode of VSC converter are explained.Considering the active power loss and different control modes of VSC,the AC/DC hybrid system is simulated and verified.The results show that the improved cuckoo algorithm proposed in this paper can effectively solve the network reconfiguration problem of AC distribution network in the system.