Research On Protection Of Distribution Network Containing Distributed Generation And Design Of Microcomputer Protection Device

With the energy situation and environmental problem getting more serious,Distributed Generation(DG),represented by renewable energy like solar and wind,is getting more and more attention and development.As a large number of DG connected to the distribution network,the traditional structure has been changed.So the traditional protection strategy can not work correctly.On the other hand,with the construction of the intelligent distribution network and the development of microcomputer protection,wide area protection strategy based on multipoint information becomes possible.With this background,this paper studies the influence on distributed network protection after DG connected.Besides,this paper gives a detailed analysis and design of microcomputer protection device.Firstly,grid-connected inverter model of inverter interfaced DG base on constant power control strategy is established and the failure analysis has been done.Base on it,the simplified model can be got for protection analysis.Then,the influence on traditional three-step current protection with DG connected to the distribution network is studied.And based on typical distribution network model,simulation analysis is executed with different capacity and position of DG.In addition,the influence of DG on reclosing is analyzed,pointing that the reclosing may appear misoperation or non-synchronization closing.Based on the microcomputer protection device,the wide area protection strategy is studied.By collecting multipoints information,the wide area protection can realize fault location and removed through comprehensive analysis and judgment.Grid-connected inverters are usually used when DG connected to the distributed network.It may cause a large number of high order harmonics,and lead to high demand of the quickness of protection.So,the sliding window discrete fourier algorithm is studied,which is suitable for microcomputer protection.In view of the SDFT stability problems,the unstable reasons are studied and a new method is proposed to solve this problem.At last,this paper introduces the system architecture and working principle of microcomputer protection device in detail,and the specific hardware and software design method is given.