A Fast Fault Diagnosis Scheme for Ring Bus DC Microgrids With Fewer Sensors

This paper proposes a fast fault diagnosis scheme to realize fault detection and classification with fewer sensors for ring bus DC microgrids. After the analysis on mechanisms of line faults in the microgrids, the measurements of the local converter, including the voltage of the DC-link capacitor and the output current, are used to detect pole-to-pole (PP) faults and pole-to-ground (PG) faults, employing the sum of multi-step difference. Based on the deviation between the estimate and the actual output voltages, a simple and effective fault classification method is proposed in this research. The detection results of two neighboring units are exchanged to locate the fault line with low bandwidth distributed communication. Apart from PP faults, PG faults in both poles can be detected and distinguished, sharing the voltage and current sensors with the controllers of the converters, and the construct cost of the system can be reduced. The performance of the proposed scheme in different cases has been tested in MATLAB/Simulink, including high impedance faults, close-in faults and signal with noises. Further, the effectiveness of the scheme is validated under Hardware-in-loop (HIL) platform.