Reliability-Enhanced Hybrid Grounding System Based on Active Neutral-Point Voltage Regulator and Low-Resistance

-In urban distribution networks, due to its strong reliability and simple operation, the low-resistance grounding system has gradually replaced the resonance grounding system represented by Petersen coil. However, when a high-resistance ground fault occurs, it is difficult for the low-resistance grounding system to identify the smaller fault characteristics, and the zero-sequence protection device cannot ensure the system reliability. In this letter, a hybrid grounding system (HGS) combining the active neutral-point voltage regulator (NVR) and low-resistance is proposed. By injecting compensation voltage into the neutral point, the fault phase voltage can be reduced below the threshold that can generate a fault arc. Additionally, the proposed coordinated control strategy can effectively switch between the two operation modes (active NVR and low-resistance) according to the actual fault types. Simulation and experimental results verify the rationality and effectiveness of the proposed concept and analysis.