Reliable Fault Isolation Algorithm for DC Micro-Grids Using Local Measurements

In a ring configuration microgrid, due to the inherent characteristics of distributed energy sources, the bidirectional power flow dominates the unidirectional flow which will not empower the conventional current-based protection techniques. Moreover, traditional methods fail to identify exact faulty line during high resistance faults. The aim of the work is to propose an effective protection algorithm that emphasizes the enhancement of dependability of the relay even during fault condition with high magnitude resistance. To start with, the current difference index has been evaluated to detect the disturbance or fault in the system. In continuation, the resistance has been computed by utilizing voltage and current sampled data immediately after inception of the fault. Further, the sign of ∆R is employed to differentiate the internal and external faults correctly. The proposed algorithm has been simulated under many abnormal cases like different fault resistances at multiple fault locations and different load switching conditions in MATLAB/Simulink software. The comparative assessment of this proposed method has been done with existing protection methods justifying that proposed method is reliable and enhances relay dependability and security.