The Research Of Collaborative Scheme For Automatic Reclosing Of Datun Distribution Network With Distributed Generation

With the wide application of new energy worldwide,China's power industry has begun to apply new energy technology to power system too.Distributed generation technology can transform new energy into electric energy.Its value to both environmental protection and economy,its advantages of safety,reliability and good peak load regulation performance can promote the full use of new energy in the field of power industry.Distributed generation has great influence on the distribution system.It may cause the damage to system components,or even cause a power cut over a large area.To prevent the occurrence of such hazards and to better control the negative influences,this paper has focused on those problems analysis and corresponding protection solutions.In the first part,the basic theory of distributed generation and grid connection technology is presented.And,main types of distributed generation technology,especially the mathematical model,operational principle,output power and current calculation of photovoltaic power generation technology are introduced in detail.Meanwhile,to ensure that photovoltaic power generation can maintain the maximum power,emphasis is placed on the power rating control strategy and voltage-current double closed-loop control strategy under the case of distributed generation.In the following part,taking the grid-connected photovoltaic power system as an example,the changes of distribution network under the case of photovoltaic power generation,especially the protection strategy of this network after grid-connection are detailed analyzed in this paper.Apart from the improved three-section current protection method,autoreclosing is considered as the main protection device.The accelerated protection before and after three-phase autoreclosing,and the current value setting of different positions where failure occurs under distributed generation are also studied.Since transient fault occurs a lot in electrical lines,and autoreclosing is more and more widely used,the possible problems after grid connetion such as abnormal reclosing,unsynchronized reclosing and arc burning,etc.are also introduced in this paper.In the last part,the protection of distribution network after grid connection of distributed generation is studied and verified.Firstly,the reclosing impulse current can be decreased by synchrocheck reclosing.This conclusion is based on the analysis of protection for reclosing and the analysis of control method for access capacity of distributed generation.Secondly,the cooperation and coordination problems between devices in protection system of distribution network,such as reclosing and fuse,voltage-time control sectionalizer,current control sectionalizer and other disorder problems of reclosing are studied.Based on those protection and coordination problems mentioned above,and taking the coordination between reclosing and fuse as as example,the parameter improvement process of protection and coordination is presented and verified.