Research On Fault Phase Selection And Fault Positioning In Microgrid

Micro-grid is an effective method access to distribution network for distributed generation(DG),which has been developed rapidly in recent years.However,with the wide application of micro-grid technology,higher requirements for its safety,stability and reliability have been put forward.Micro-grid fault analysis and positioning technology are proposed to improve the safety of micro-grid power supply.This paper firstly investigated the common fault diagnosis method of power grid,compared the main difference between large power grid and micro-grid,and analyzed the limitations of applying fault diagnosis model of large power grid to micro-grid,on this basis,fault phase selection and fault location problems were studied.The main contents are as follows:1)The common faults in the micro-grid system were summarized,and the development status of the fault diagnosis of the micro-grid was discussed.The basic principle of fault phase selection was analyzed,and the advantages and disadvantages of various phase selection methods were compared.2)Based on the control strategy of the inverter,the fault current characteristics of the inverter interfaced generation(IIG)were analyzed and the network of each order component was established when the tie line is short-circuited in the grid-connected system with IIG.Due to the weak feeding of IIG output current,the fault current was limited by the maximum current of the inverter.The original phase selection method was no longer suitable for fault phase selection with IIG.Therefore,a new fault phase selection method for weak feeding system was presented.The method used the relative phase relationship between negative sequence voltage and zero sequence voltage,and the phase difference between positive sequence voltage sudden change and negative sequence voltage to identify the fault phase under weak feeding condition.The reliability of the method was proved by simulation.3)This paper has built the micro-grid experiment platform based on EtherCAT for fault diagnosis.The fault diagnosis method was used to analyze the fault current characteristics based on the fault recording wave data and to mark the time of the fault current.