Research On Relay Protection Of Multi-GG Distribution Network

In recent years,with the depletion of fossil fuels and the ecological environment deterioration,distributed generation have rapidly developed for its clean and efficient features.But the distributed generation accessing to the distribution network affected the exact action of the protection device,so that that has reduced the compatibility between the protections,and has a serious impact on distribution network as well.Therefore,it is of great practical significance to develop a reasonable solution to the problem of the distributed generation's influence on the protection system.This dissertation mainly carried out the following four aspects of the research work:(1)Firstly,the classification and operation mode of distributed generation are introduced.For the inver-interfaced distributed generation,the working principle,control strategy,sine wave pulse width modulation(SPWM)technology of the inver-interfaced distributed generation are analyzed,and design the model of the inver-interfaced distributed generation within the PQ control.Then,the rationality of the model has been verified from simulation software PSCAD / EMTDC.(2)The influence of the distributed generation's access position and the injection capacity on the current three-stage current protection is analyzed theoretically.The overturned example's results show that when the fault point is different from the DG's location,the injection capacity of DG has impacted relationship to the fault current.The 10 kV distribution network model was built on the PSCAD / EMTDC software platform,and the influence of the location of the fault location on the system protection device was simulated.(3)Based on the above theoretical analysis and simulation experiments,this dissertation proposes an adaptive protection algorithm for distribution network based on impedance changes at both ends of the line.The protection algorithm is not affected by the distributed generation's capacity and access location.The feasibility of the proposed algorithm is verified by simulation analysis on the PSCAD / EMTDC.(4)Based on the development trend of power grid intelligence,this thesis designs a multiagent intelligent protection system based on impedance measurement algorithm at both ends.Through the task planning of each agent,the information interaction between each agent is used to cooperate with each other to solve the problem.A variety of fault problems in distributed generation network are solved,and the intelligent protection of the distribution network system are achieved.