Tripping Sequence Approach to Reduce Fault Current to be Interrupted in LVDC Microgrids

With the increasing use of solar energy, DC Microgrid with lower capacities are formed with connection to the traditional main grid. If a short circuit fault occurs in DC microgrids, the contribution of multiple sources including main grid and DC sources might lead to very high fault levels that are difficult to break. While technologies for manufacturing the DC circuit breaker with higher breaking capacity are on-going, another approach by changing tripping sequences in DC protection systems, which could reduce fault currents to be interrupted by a single circuit breaker, was studied in this paper. With the aid of MATLAB/Simulink and OPAL-RT 5700 real time simulation, effectiveness of the proposed approach was evaluated on a Simulink stimulation model of 500 V, 1 MWgrid-connected DC Microgrid. The result obtained indicated that the fault current level interrupted by the DC circuit breakers was reduced by up to 63%.