Method for actively suppressing ferromagnetic resonance of distribution network by resistive current

In the neutral-point ungrounded distribution network, the non-linear characteristics of the magnetizing inductance of the electromagnetic voltage transformer (PT) are easy to saturate under certain conditions, resulting in ferromagnetic resonance overvoltage, which seriously affects the safe operation of the system. Aiming at the 10 kV neutral point ungrounded system, this paper proposes a method for the neutral point of the distribution network to inject the harmonic elimination resistive current to suppress the ferromagnetic resonance, and the selection of the optimal value of the resonance elimination injection current is explained. Inject a harmonic elimination current into the neutral point of the system to quickly consume grid resonance energy and eliminate ferromagnetic resonance. Through simulation verification, it is found that the proposed method only needs to inject the harmonic elimination current into the neutral point of the system for a short time to make the distribution network out of resonance, and the zero-sequence voltage returns to zero. The time required for the grid to resume normal operation is the shortest.