Research On Fault Location Method In Distribution System With Inverter Interfaced Distributed Generator

With the conventional energy sources exhausted gradually and environment pollution growing severely,inverter interfaced distributed generators(IIDG)using renewable energy,such as solar energy and wind energy,are connected to the existing distribution networks on a large scale.The original distribution network structure,a radial one with a single source,is changed completely as a result of the connection of IIDG.So are the power flow and fault characteristics of the distribution network.It brings new challenges to precision of fault location.Therefore,it is significant to study the fault location method for distribution network with IIDG which can promote the reliability of the distribution network and its capability with IIDG.The main contents of this thesis are as follows.In the first place,this thesis considers the fault characteristics of distribution system with inverter interfaced distributed generators.In this thesis,the IIDG is modeled as a voltagecontrolled current source and an equivalent distribution network model is established.In addition,this thesis analyses the influence of access capacity and access positon of IIDG on fault current in the distribution network.Determination of operating values of detecting devices in the distribution network will be difficult because of the change of fault characteristics.As a result,the conventional fault location methods based on accurate operating values cannot be employed directly.In the second place,this thesis researches the advanced impedance based fault location method.In consideration of the low coverage rate of voltage transformers on feeders in distribution networks and the difficulty of calculation of detecting device operating values,this thesis presents a fault location method based on impedance location which is economic and feasible.At first,a fault location equation is built utilizing the pure resistive character of transition resistance.Possible fault points are computed according to the equation,which are regarded as virtual nodes in the network.Furthermore,a new nodal impedance matrix is established including the virtual nodes.According to comparison of calculation value and measuring one of line voltage in the substation,the final fault point is determined.The fault location method overcomes the defects of conventional methods that false points may be generated.Simulation work verifies the effectiveness of the method.Finally,this thesis presents a fault location method for distribution network with IIDG in view of line centralized capacitance.The conventional fault location method is unable to reflect the fault output characteristics of IIDG.This thesis presents a fault location method for distribution network with IIDG based on advanced impedance location,considering the influence of line capacitance on fault location precision.The method is verified according to simulation.