Fault Diagnosis Scheme for Ring-Type DC Microgrid Using Bus-side Capacitor and Positive Line Current

DC microgrids are becoming increasingly popular due to their compatibility with new renewable energy sources. However, the low inertia of DC microgrids makes them susceptible to faults, which limits their development. The paper proposes a fault diagnosis scheme based on bus-side capacitor current and its Pearson correlation coefficient with positive line current, which can achieve fault detection and fault classification. By utilizing only positive pole information, different fault diagnosis strategies under different fault resistances are proposed. The bus-side capacitor current is adopted to ensure rapid fault diagnosis for low-resistance faults. The Pearson correlation coefficient between the bus-side capacitor current and positive line current is used for high-resistance faults diagnosis. Both the requirements of low-resistance fault diagnosis speed and high-resistance fault accuracy can be satisfied. Meanwhile, the proposed scheme can reduce the number of sensors, which helps to reduce the construction costs of DC microgrids. The feasibility of the proposed scheme has been verified in MATLAB/ Simulink. The faults can be detected and classified within 1.2 ms with high fault resistance up to 10.