A Proposed Approach to Fault Current Calculation for Microgrid Considering the Uncertainties of Fault and Distribution Generations Locations

Abstract

Fault current calculations inside a grid-connected and isolated AC microgrid is one of the major challenges due to the fault current contributions of inverter-based distributed generators units, which are different in location and inverter control during the fault. Therefore, this paper is aimed at calculating fault current for grid-connected and isolated microgrids using two methods; virtual impedance and the proposed method. The proposed method is used to calculate the short circuit current contribution of DG is controlled to analyze the equivalent model of inverter-based DG. The inverter control limits its current to 2p.u of the inverter rating. The proposed algorithm is tested on a standard IEEE 33-bus distribution network with 5 DGs using MATLAB code programs. The results show that the impact of q DG on the fault current is significant especially when faults occur at busses near to the DG location. The fault current value, calculated using the proposed method, is less than its value calculating by the virtual impedance method by more than 30% for grid-connected microgrid and by approximately 50% for the isolated microgrid.