Study On The High Penetration Of Distributed Generation Effect On Distribution Network

As energy crisis and ecological environment problems is more and more serious,thedisadvantages of electricity generation by using conventional method of centralized powerand long distance transmission mode is increasingly prominent,distributed generation asthe important supplement of the traditional power mode is power by new energy,With itsadvantages of energy conservation and environmental protection, high efficiency, flexibleoperation mode is more and more attention.the influence of the distribution network afterdistributed generation(DG) interconnection is studied in this paper.First of all,several common types of distributed generation is proposed in this paper,its basic structure,principle of power generation,power control mode andadvantages,existing problems are detailed introduced, the way of DG interconnection issimple introduced. According to output characteristics of DG, power control mode and gridmethod,the node type of different types of DG access point flow calculation is determined,when power flow calculation by newton-raphson method,PI node transformationcalculation and its algorithm process,PV node reactive violation process and its algorithmprocess,PQ (V)node process and its algorithm process are mainly studied.Second, the application and disadvantages of traditional two types of distributionnetwork voltage stability index under DG distribution network are derivational andanalyzed,the error is large when the first kind of voltage stability index process PV nodevoltage stability, and the linearity is worse in heavy load, which makes judgmentdifficult.The ability is poor when the second kind of voltage stability index process PVnode, and characteristic curve of intersection point could not exist in heavy load, whichmakes judgment of voltage stability difficult.A new method based on thevenin equivalentjudgment containing DG distribution network voltage stability is proposed in this paper,thenew index spatially-integrated SVS is defined, and the correctness and effectiveness areverified by example simulation. Combined with the index, the influence of distributionnetwork voltage stability under different types of DG location and capacity are quantitativestudied,the simulation results show that the asynchronous type DG interconnection is lowervoltage stability,access point should try to avoid the weak nodes of systemvoltage,synchronous type DG interconnection can improve voltage stability, when theaccess point right, it is more advantageous to improve the whole system voltage stability. The first kind of voltage stability index and spatially-integrated SVS index werecompared through example simulation,the results show that spatially-integrated SVSindicators can maintain better degree under the condition of heavy load,and can better dealwith PV node voltage stability problem.Finally,the influence of DG accessing location and capacity for the relay protectionand reclosing is studied,the results show that the influence of DG interconnection locationand capacity for current protection and reclosing is bigger,and the distance protection isless.When DG access to distribution network,it improve the downstream sensitivity ofcurrent protection and increase the scope of protection,but the larger DG capacity cause thelower protection mis-operation, which make the upstream sensitivity of current protectiondecline,even refuse to action;because of the position of the fault point relative to DG andthe different way of reclosing and relay protection,the problems of reclosing failure or notin the same period of reclosing may appear.