Abstract: To address the issues of high single-phase-to-ground fault current, intense transient processes, and slow operation of traditional mechanical switches in distribution networks, a novel ground fault suppression method based on thyristor high-speed closing and neutral-point voltage regulation is proposed. Firstly, a single-phase ground fault suppression model is established, unifying the calculation methods for three-phase unbalance and single-phase ground faults, thereby revealing the coupling relationship among neutral-point voltage, ground fault current, and line-to-ground parameters. Furthermore, the neutral-point voltage is taken as the control variable, the current flowing into the neutral point as the state variable, and the inherent line-to-ground parameters as disturbance variables. Introducing the concept of fault suppression degree based on neutral-point voltage regulation, a ground current suppression strategy centered on real-time neutral-point voltage control is constructed. Finally, considering the slow operation of traditional mechanical switches, a thyristor high-speed interrupter circuit is introduced to achieve rapid blocking of the neutral-point voltage and millisecond-level adjustment of the current path. Validation on an experimental platform shows that this method can effectively reduce the peak fault current in the initial fault stage, shorten the transient recovery time, and significantly enhance the system's ground fault suppression capability and operational stability.

Key words: neutral-point voltage regulation, thyristor, single-phase grounding, fault suppression