Research On Distribution Network Reconfiguration With Distributed Generation Based On Improved Harmony Search Algorithm

With the problem of global energy crisis and environment becomes more and more serious,distributed generation has been greatly developed because of its advantages of clean and environmental protection,and it has been favored by many scholars both at home and abroad.However,the large scale of DG is connected to the grid makes its penetration rate gradually increased in the distribution network,which will bring a certain influence to the distribution network,such as the power flow distribution,the active power network loss and the voltage distribution,and so on.Distribution network reconfiguration changes topology by changing section switch and loop switches in the network,which can effectively reduce the active loss and improve the power quality.Therefore,how to use distribution network reconfiguration to solve the influence of DG accessed to distribution network has important theoretical and practical significance.This thesis focuses on the distribution network reconfiguration with the goal of improving the acceptable capacity of DG.The main research contents are summarized as follows:(1)Aiming at there will be a large number of infeasible and invalid solutions in the process of distribution network reconfiguration,an effective topological simplification method and a modified method of infeasible solutions are adopted,which can effectively improve the efficiency of distribution network reconfiguration.Using the related knowledge of graph theory to reasonably express the topological structure of distribution network,and the topology of the distribution network can be reasonably simplified by using the degree of nodes,equivalent branch and multiple edge,so that it can avoid the problem of combination explosion in the solution space.The topological structure coding rules based on basic ring matrix and the generation principle of control solution vector are adopted,so that it can reduce the probability of generating solution vector that does not satisfy the constraint condition.(2)Aiming at the deficiency of traditional harmony search algorithm in parameter setting,an improved harmony search algorithm based on adaptive adjustment of parameters is proposed.Firstly,the optimization mechanism of traditional harmony search algorithm is introduced in detail,and the influence of parameter setting on the optimization performance of the algorithm is analyzed.Then,according to the optimization mechanism of the algorithm,the adaptive adjustment mechanism of parameters is introduced.At the same time,in order to further avoid the algorithm falling into local optimum,a local optimal judgment mechanism is added,which makes the improved harmony search algorithm have better optimization performance.(3)Aiming at the acceptable capacity of DG is not included in the traditional distribution network reconfiguration optimization model,which the location and capacity of the DG is assumed to be given,and the influence of the acceptable capacity of DG on the system is not considered.A bi-level optimization model is established for the distribution network reconfiguration containing DG.The upper level of the optimized model selects the voltage stability index and the grid-loss change amount caused by DG accessed as the optimized aim to determine the acceptable capacity of DG,and the lower level of the optimization model then views it as the initial conditions,and selects the maximized network loss reduction rate and the load balance degree variation as the optimized aim to determine the reconstructed network topology.In addition,an improved harmony search algorithm is applied to resolve the bi-level model through continuous iterations of the upper-level and lower-level till the expected aim can be achieved,and the optimal DG configuration and network topology structure are obtained,which further improves the acceptable capacity of DG.