Research On Fault Location And Recovery Technology Of Distribution Network With Distributed Generation

With the depletion of traditional energy sources,distributed generation technologies have developed rapidly.Distributed generation mainly uses renewable clean energy sources such as wind power,photovoltaics,and geothermal energy,which can provide useful supplements for distribution networks.However,with the massive access of DG,the topology of traditional distribution networks have changed,the distribution of power flows,and fault currents are also affected.Fault location and fault recovery of traditional distribution network self-healing technologies method no longer applies.Therefore,it is necessary to study the fault location and self-healing technologies of the active distribution network under the new situation.This paper introduces the concept of active distribution network,analyzes the research status of active distribution network,fault location and fault recovery of active distribution network with DG.Then,the self-healing technology of the network has been studied,the model and algorithm for fault location and fault recovery have been analyzed to achieve timely and accurate fault location after faults in the active distribution network,and to restore as much power as possible in the power-off areas.The main work of the dissertation includes the following four aspects:(1)Considering the incomplete information of distribution network and the more complex structure and fault information of distribution network caused by distributed photovoltaic access,in order to ensure the accuracy and real-time performance of fault location,and to meet the requirements of economic,reliability,and risk of distribution network at the same time.Considering configuring FTU measurement devices at some key nodes,which can be used as a boundary node to divide the distribution network for the distributed fault location.Establishing the optimization layout multi-layer model of FTU in the active distribution network.The reliability index is used as the target to screen the FTU preset layout nodes in the upper model,and the FTU layout nodes can be used as boundary nodes of perform preliminary regional division.While the economy and risk indicators are used as targets in the lower layer to optimize the FTU layout partition through a genetic algorithm.Finally,the effectiveness of the proposed algorithm is verified in a 33-node system.(2)Based on the FTU optimized configuration results of the distribution network,the fault location of the active distribution network is studied.Firstly,the fault characteristics of the active distribution network are analyzed.Then,considering the disadvantage of ‘easy precocity' of the PSO algorithm,the tabu list and aspiration criterion of the tabu search is used to optimize the global search capability and convergence speed of Particle Swarm Optimization(PSO).Then a fault location mathematical model of active distribution network is established,analyze the application of TSPSO algorithm based on region division in active distribution network.Finally,the effectiveness of the algorithm is proved through the improved 33 node distribution network system.(3)Considering the randomness of DG power and fluctuation of distribution network load,the island distribution scheme of active distribution network is studied.Firstly,a state probability model for distributed photovoltaic power generation that considers factors such as lighting,environment,and climate is established,which is used to forecast DG output with different hours.Analyzing the fluctuation characteristics of load,establishing load multi-state model in different time periods,and comprehensive load important levels and time scales form the time-series priority recovery set.Then,the depth-first and breadth-first algorithm is used to divide the planning islands of distribution network based on different failure periods,to form the plan island set.Finally,the improved 33-node power distribution system simulation is used to verify the validity of the matching islanding scheme.(4)Considering the planned island and the response characteristics of interruptible load,a network reconstruction scheme of active distribution network is established based on delaminating and districting.Firstly,establish a mathematical model for recovery of active distribution network faults with the best recovery value and the best number of switch operations,Then,the fault recovery is divided into two phases.The first phase is a regional islanding scheme in which the fluctuating load and random DG are matched to optimize the recovery value,to guarante priority power supply for important loads in the system.While the second phase utilize interruptable load to optimize the number of switching actions,to achieve the goal of global coordination for fault recovery,and improving the switch lifetime.Through the above two phases,fault recovery of the active distribution network is completed.Finally,the effectiveness of the scheme is verified by the improved 33-node system and the 69-node system.