Research On Directional Protection Technology Of Active Distribution Network

With the continuous reduction of fossil energy reserves in the world,human beings are increasingly relying on new energy to replace fossil energy,especially the research on clean energy and renewable energy,which also promotes the development of new energy power generation,that is,the generation of distributed power.Distributed Generation supply(DG)has many advantages,such as relieving the pressure of power supply,improving the voltage quality and voltage level on the user side.However,the distribution network has limited capacity for distributed generation.in order to improve the efficiency of new energy generation,it is urgent to improve and perfect the distribution network.A large number of grid-connected operation of distributed generation supply increases the permeability,while relay protection is also greatly affected,the complexity of operation may lead to protection misoperation and other problems.therefore,we should put forward corresponding solutions to this problem,the main content of this paper is to analyze the problem and give solutions.Due to the continuous grid connection of distributed generation,the unidirectional power flow of distribution network becomes multi-directional power flow,which causes a lot of influence and problems to the protection of distribution network.this paper analyzes and compares the methods and conclusions that have been put forward to deal with this problem,introduces all kinds of protection measures and principles of active distribution network as a whole,analyzes the current distribution system with distributed generation supply in China,and looks forward to the development prospect of active distribution network.On this basis,we analyze some problems of protection when the distributed generation is connected to the grid.Including the isolation strategy of distributed power supply and the control mode of distributed power supply when fault occurs,the influence of fault location and fault type on protection is analyzed,and the calculation and analysis are carried out from a mathematical point of view.Finally,considering the traditional distribution network protection need voltage information,but the distribution network itself can not provide a large number of voltage information,this paper proposes a new method to judge the fault direction,compared with the previous method,this method only need current information can find out the fault line,fault line protection at both ends of the action at the same time,so as to cut off the fault line.The sensitivity of the criterion is improved by introducing a normalization angle.under the condition of ensuring the accuracy of the criterion,the criterion has good sensitivity.the voltage transformer installation quantity is greatly reduced by using this protection method.In this paper,an active distribution network model is established in the simulation module of MATLAB software,which is simulated under different fault types and fault conditions.The simulation results show that the protection method and criterion are applicable to all kinds of fault types and fault conditions.