A Study On Protection For Distribution Systerm Of Photovoltaic Microgrid

For the past few years,since energy and environmental problem became prominent,th e drawbacks of the traditional pattern of centralized power had emerged.DG as a suppleme nt to large power grid,developing fast because of its high energy efficiency,it has better e nvironmental compatibility and other advantages.With the development of micro-grid distr ibuted generation emerged,Photovoltaic micro-grid is an important form of distributed pow er grid.The access of DG has changed the topology of distribution network caused tradition al relay protection system of micro-grid can't satisfy the requirement and influenced autom atic reclosing at the same time.With the development of smart grid,micro grid has broad pr ospects,therefore the researching of distribution network protection program which is suita ble for micro-grid is essential.This paper analysis fault response of the inverter interfaced distributed generators(IIDG),here determines the PQ-controled DG as the equivalent source model,provide theoretical foundation and basis for the subsequent simulation.DG changes the characteristics of single power supply,radiant,one-way tide,which leading to current protection device appear the phenomenon such as refusing action and error action,bring down the selectivity and sensitivity of protection.On this basis,analysis the influence of current protection and reclosing,built the simulation model in PSCAD/EMTDC,and verify the relevant conclusions.Finally,a protection scheme based on wide-area protection is used in this paper.The sc heme divided into two key steps: the first step is to use the intelligent electronic device(IE D)to collect current information,locking fault area through the comparison of fault current amplitude;The second step is aimed at the fault branch,using the information of IED to acc urate positioning fault zones and removal it.In this scheme,the description matrix of feeder network has good visibility and small footprint,convenient calculation and analysis.This s cheme needs small information to fault location,and has mature theory,high reliability and strong adaptability.This paper carries out the simulation with PSCAD/EMTDC on this prote ction scheme to verify the correctness and feasibility of this scheme.