The Impact Of Distributed Generation On Distribution System Protection And Countermeasures

As the problems of the energy and environmental issues have become increasinglyprominent, the drawbacks of the power grid pattern with the features of large units, largepower grids and high voltage in China becomes increasingly obvious. The DistributedGeneration (DG) based on renewable energy technology developed rapidly in recent years.The operation of the distribution system is affected in many aspects for distributedgeneration is often connected to the distribution system. So distribution system protectionis considered to be one of the biggest technical obstacles for the development of distributedsystem. With the interconnection of distributed generation of the distribution system thetraditional current protection in the structure of the radiation distribution network can notmeet the requirements of protection which will result to protection tripping, blinding,reducing sensitivity and other issues. Therefore, it’s necessary to study the impact on theprotection caused by the connection of distribution network and the distributed power andto find a suitable protection schemes.This article firstly details the technology of interface in the distributed power grid andcontrol strategy of inverter-based distributed power.In the next,the fault characteristics areanalyzed, and structures the model of the PQ control inverter interfaced distributedgenerators with MATLAB/Simulink simulation, and make the simulation analysis on thethree-phase short-circuit fault characteristics, which laid the foundation for study of theeffect on the protection caused by the access of the DG to the distribution network.In order to study the effect on the protection caused by the access of the distributedgeneration to the distribution network, the fault current is analyzed when the PQ controlinverter interfaced DG are put into the simple distribution network. Then it explores thepossible impacts on the protection distribution network protection when the DG are putinto the distribution network from the respects of the access locations, the DG capacity andthe types of DG.The study draws the conclusion that the impact which is caused when theDG are put into the distribution network is greater than the impact which is caused whenthe conventional rotary type DG are put in. The impacts on the protection distributionnetwork protection when the DG are put into the distribution network are studiedaccording to the distribution grid reclosing and the protection configuration situationmainly in the aspects of asynchronous re-closing and non-pressure test, and the simulationmodels based on PSCAD/EMTDC about asynchronous coincidence gate and reclosing of the protection system non-pressure test are built to verify the impact on the distributednetwork.According to the structural characteristics of the distribution network containing DGand the future direction of development of electrical protection, a wide area differentialprotection scheme which is adapted to distribution network containing the DG is proposedon the basis of the IED communication protection. In the scheme the mutations in theamount of current values are used to determine the fault direction and the fact that theactual grid structure is divided into two parts including of back-up protected areas and theassociated domain of IED information exchanges is discussed.The fault location isdetermined according to the action value in the direction and the comprehensive fault valueof the direction, and on basis of this, the basic process of protection of the distributionnetwork with DG is put forward. Finally, the MATLAB/Simulink simulation is used toverify the correctness of the protection criterion, and effectiveness on of the scheme thedistribution network with DG.Finally, a comprehensive summary of the essay is drawn, and the further researchdirections are pointed out.