Study On Optimal Reconfiguration Of Distribution Network

In recent years,the much higher quality of the power is required by customers.The electric power industry encounters many challenges.Many attentions have been focused on the power quality and power supply efficiency.The line loss rate and failure rate in distribution network is high in our country.Intelligent distribution network has been paid more and more attention along with the further progress of smart grid construction.Distribution network reconfiguration is one of the primary functions of Distribution Management System(DMS).It has important significance to improve operating economy and reliability of the power supply.This paper analyzes the distribution network reconfiguration from different aspects.Power flow calculation is the base of distribution network reconfiguration.The basic equations of power flow calculation are solved by the Newton-Raphan method.A balanced distribution network—IEEE 33 nodes test system and an unbalanced distribution network—IEEE 34 nodes test system are studied respectively.The calculation results to power flow of IEEE 33 nodes test system connected with distributed generation(DG)show that the active power loss is reduced and the quality of voltage is improved effectively due to DG.Because switch state can be represented in binary form,this paper studies the discrete binary particle swarm optimization(BPSO).According to the simulation results of three-feeder system,IEEE 33 nodes test system and American PG&E 69 nodes system,this paper compares the opened switches group,the active power loss,the active power loss reduction percentage and minimum voltage before/after reconfiguration.The results indicate that when BPSO is used in static distribution network reconfiguration,the active power loss is reduced significantly and the voltage level of the system is improved effectively.Simulation results of static distribution network reconfiguration to IEEE 33 nodes test system including DGs show that the active power loss of the system is further reduced through reconfiguration.A concept of two-stage real-time reconfiguration in dynamic distribution network reconfiguration is proposed.The method and the model of two-stage real-time reconfiguration of distribution network,in which the time-variance of load and DG output,the static voltage characteristic of load and the three-phase imbalance of distribution network are emphatically considered,are put forward.The network loss and network loss rate under the original topological structure and three kinds of reconfiguration modes of distribution network are compared.Simulation results of modified three-feeder system and IEEE 34-bus system show that using the proposed two-stage RTR method not only the distribution network loss can be effectively reduced,but also both security and reliability of distribution network can be enhanced.A new dynamic distribution network reconfiguration method based on dynamic programming is proposed.The problem of determining the optimal time interval when the reconfiguration times is given and how to determine optimal reconfiguration times are studied respectively.Simulation results of IEEE 33 nodes test system show that optimal reconfiguration times,the time interval in each time of reconfiguration and minimum active power loss can be calculated through dynamic programming.This paper studies the multi objective distribution network reconfiguration problem that considers how to minimum network active power loss,switching and reliability costs.Time-varying models of feeder section load,failure rate and customer interruption cost are made.Customer load profiles,seasonal varying data of feeder section failure rates,repairing time and customer interruption costs are considered when making annual distribution network reconfiguration program.Simulation results of three-feeder system indicate that not considering time-varying effects and using only simplified fixed load and reliability parameters could underestimate the total loss to the utility and its customers as a whole.The total annual operating cost can be effectively reduced by using the annual distribution network reconfiguration program in this paper.