Research On Distribution Network Line Protection Based On Fault Current Characteristics Of Distributed Wind Generation

The clean and renewable resource distributed access to the distribution network,making the original distribution network forms a double or even multi terminal distribution network.With the increase of wind power penetration,the traditional dispatching operation,planning and design,protection and control of distribution network will face great challenges.In particular,the distributed generation is controlled by the power electronic converter and presents its unique transient characteristics,having a great impact on the protection of the distribution network.So the traditional three-step current protection and the differential protection will be difficult to adapt.Aiming at the problem of how to configure the upstream and downstream protection of distributed wind generation access points,this paper studied systematically the line protection of distribution network distributed wind power,the main research work is made on the following aspects.This paper analyzes the fault current characteristics of different types distributed wind generation at first.Then the adaptability of distributed generation access to the distribution network on the current protection is analyzed,and the adaptability of distributed generation access to the distribution network on the differential protection is emphatically qualitative analyzed.And the above analysis is verified by simulation test.Then,this paper derived the fault short-circuit current expression of double fed induction generator based on the transient characteristics of doubly-fed induction generator.Among them,the relationship between the active output of double-fed induction generator and stator short-circuit current is mainly analyzed.An adaptive current instantaneous trip protection scheme based on different wind field output adjust value of protection operation is proposed for the protection configuration of the wind power access point downstream.A large number of simulation tests are carried out for distribution network with doubly fed wind turbines in the RT-LAB simulation software,and the effectiveness and applicability of the proposed protection scheme are verified.Finally,the fault current characteristic of permanent magnet synchronous generator is analyzed,which is different from that of the power system fault current.The line protection of distribution network with permanent magnet synchronous generator is proposed,by using the difference of the current ratio between the two ends of the fault line.Among them,the method can effectively avoid the influence of branch line and transition resistance on protection.The distribution network model with permanent magnet synchronous generator is built in PSCAD for simulation test.The accuracy and reliability of the proposed protection scheme is verified.