Font Size: a A A

Research On Fault Location And Power Supply Recovery Strategy Of Distribution Network With DG

Posted on:2021-01-21Degree:MasterType:Thesis
Country:ChinaCandidate:S Y QiaoFull Text:PDF
GTID:2392330620978889Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
Fault location and fault self-healing are the basic contents of intelligent distribution network.With the large-scale grid connection of various DG's with friendly environment and flexible generation,it increases the difficulty and complexity of the implementation of distribution network self-healing characteristics.In this paper,the photovoltaic and wind power with strong volatility as the representative DG,the fault location method and power restoration strategy of the distribution network after the DG access are studied.(1)Firstly,the influence of DG access on voltage distribution,relay protection and fault location is analyzed theoretically.The analysis results show that the access of DG can improve the distribution network voltage distribution,so the reasonable configuration of DG is very important for island division and power supply restoration strategy;The access of DG may reduce the selectivity,sensitivity and even loss of the original relay protection scheme,resulting in misoperation or misoperation of the protection.The accuracy of the fault location method based on the relay protection action as the fault criterion will be reduced,and this fault location method can only locate the short-circuit fault,with poor versatility;The access of DG makes the traditional single source radial distribution network become active distribution network,and the fault current flows in two directions,which makes the traditional fault location method applied in radial distribution network difficult to adapt to the flexible switching of DG.(2)Secondly,the traditional fault location method based on the feeder terminal unit(FTU)is not universal and can not adapt to the flexible switching of DG.The steady-state and transient characteristics of single-phase to ground fault in small current grounded system are analyzed.The fault criteria based on the amplitude of steady-state zero sequence current and the fault criteria based on the phase difference of zero sequence voltage and current for the system grounded through arc suppression coil are given.This paper analyzes the influence of DG grid connection on the zero sequence current distribution of single-phase ground fault in distribution network,and builds a 10 k V distribution network model with photovoltaic and wind power in RTDS/ rscad.Through the simulation of the power output fluctuation of photovoltaic cells and wind turbines,the correctness of the model is verified,and the single-phase ground fault in the case of DG off grid and grid connection is simulated,theoretically analyzed and simulated The results show that the connection of DG hardly changesthe distribution of zero sequence current,so the above fault criteria are still applicable to the single-phase ground fault location of distribution network with DG.For the influence of DG grid connection on relay protection,the adjustment scheme of setting value is given to adapt to the traditional radial distribution network fault location strategy.For large capacity DG grid connection,the fault criterion based on fault current directionality is given.Combined with the above fault criteria,the corresponding FTU state coding mode is given,which provides the data source for the later fault location method research.(3)Then,aiming at the fault location problem,based on the above FTU state coding,the switch function and the corresponding evaluation function which can adapt to DG switching are established,and the fault location problem is transformed into the function optimization problem.In view of the inherent defects of heuristic optimization algorithm,which is easy to fall into local convergence and lack of self checking ability,a fault location method based on matrix recurrence is proposed.Matrix recurrence method solves the evaluation function by orthogonal matrix derivation.The comparison of the two derived optimal solutions is taken as the judgment condition of whether the iteration is completed or not,avoiding the skip of traditional heuristic algorithm The problem of multiple iterations with local convergence.Through MATLAB programming test,it is proved that the proposed method can locate the fault section accurately and quickly,which lays a foundation for fault isolation and development of power transformation means.(4)Finally,in order to formulate the power supply recovery strategy,considering the load priority and the island operation ability and grid connection operation ability of DG in the case of distribution network fault,a reconstruction model of distribution network fault recovery with DG is established,and the objective function of minimum power loss load,minimum network loss and minimum switching times is given.The objective function is solved by MOPSO algorithm,and the switching operation is obtained Programme.Taking ieee33 node distribution system as an example,the simulation test in MATLAB software proves the effectiveness of the power supply recovery strategy adopted in this paper.The reconstructed distribution network relies on the advantages of DG island operation,which can not only restore power supply to the maximum extent,but also effectively reduce network loss and improve the rationality of distribution network voltage and power flow distribution.There are 56 figures,20 tables and 72 references in this paper.
Keywords/Search Tags:distributed generation, fault location, matrix recurrence method, recovery and reconstruction, MOPSO algorithm
PDF Full Text Request
Related items