DC-DC Converter Assisted Fault Current Control in DC Microgrid

Due to absence of natural zero crossing and fast rise in dc current during fault, the fault current clearing in dc microgrid has been a challenge. The fault current is high in pole to pole fault. It is even higher in the presence of multiple dc generators as all the generators feed the maximum possible current in the network during the fault. This results in very high currents in the lines. In order to clear the fault in such a case, the dc breaker needs to break high fault current. However, the dc breaker operation at high fault current level is difficult and unsafe. Therefore, in this paper, a control scheme is proposed for dc-dc converter which reduces the fault current level at which the dc breaker operation is effective and safe. It uses an additional current control loop which is activated during the fault event. This modified control scheme ensures that the current fed by the converter into the network during the fault is low and thus resulting in low line currents in the network. The proposed control scheme is validated using a detailed simulation.