A Novel Diagnosis Algorithm of Open Phase Fault in Grid-Connected Transformer for Energy Storage System

Recently, the installation of renewable energy sources (RES) including ESS (energy storage system) is being rapidly increased according to the Korean government policy of low-carbon and green growth. However, when large scale ESS are installed and operated in distribution system, open phase faults may be occurred at points of common coupling. Specifically, when the open phase faults are occurred, the ESS should be stopped by islanding protection function of PCS (power conversion system), but it is reported that there are many undetected cases for open phase fault. And also, the phenomenon of open phase circuit may cause the problem of reverse power flow in grid-connected transformer. Therefore, this paper proposes a diagnosis algorithm of open phase fault in grid-connected transformer for ESS and performs a modeling of open phase faults using PSCAD/EMTDC S/W, in order to analyze the characteristics of open phase circuit at PCS side in ESS. From the simulation results based on the proposed diagnosis algorithm and modeling, it is confirmed that the proposed method is a useful and practical tool for the fault diagnosis concept of open phase circuit depending on the wiring connection type and iron core structures in grid-connected transformer.