Method for suppressing ferromagnetic resonance in distribution networks based on flexible grounding technology

When a single line-to-ground (SLG) fault occurs in a distribution network, ferromagnetic resonance is easily triggered by magnetic saturation of the potential transformer (PT) after the fault disappears. To solve this problem, a method is proposed for ferromagnetic resonance suppression (FRS) in distribution networks based on flexible grounding technology. A controllable voltage is injected at the neutral point of the distribution network through a flexible grounding device (FGD) to suppress the neutral point voltage (NPV) of the system to zero, quickly restoring the system to the normal operating state, preventing magnetic saturation of the PT core, destroying the conditions for ferromagnetic resonance in the system, and realising FRS. The proposed method provides a release channel for the charge accumulated in the line-to-ground capacitance, consuming the electromagnetic energy stored in the circuit. Various resonant conditions are simulated in a PSIM 9.1 environment to verify the FRS process and effect of the proposed method. The simulation results show that the proposed method can quickly achieve FRS with a good detuning effect, simple control and a high response speed.