基于波形匹配电流源注入的网源直连系统接地故障有源消弧技术

Active Arc Suppression Technology Based on Waveform-matching Current Source Injection for Ground Fault of Generator-grid Directly Connected System

海洋核动力平台中压系统采用网源直连拓扑结构,系统接地故障频发且常产生电弧。该文首先分析现有消弧方法的作用机理和消弧效果不佳的主要原因。从保障定子铁芯及系统安全出发,提出一种在发电机中性点注入波形匹配电流源的有源消弧技术方案。该方案通过主动降低故障相基波和3次谐波对地电压,将故障点电压抑制在电弧重燃电压以下,保证接地故障电弧可靠熄灭并避免重燃。最后,提出一种基于故障风险的接地故障辨识判据,能够与现有接地保护有效配合,在保证系统安全的前提下可靠辨识接地故障类型。PSCAD/EMTDC仿真结果证实了所提方法的有效性。

The medium voltage system of the floating nuclear power plant adopts the topology of generator and grid directly connected mode.Ground faults frequently happen and produce arc.This paper first analyzes the mechanism of the existing arc suppression methods and the main reasons for their poor effect.In order to ensure the safety of the stator iron core and the system insulation,an active arc extinguishing technology scheme is proposed,which is to inject waveform-matching current source into the generator neutral point.It can suppress the fault point voltage below the arc reignition voltage by actively reducing the fundamental and third harmonic voltages of the fault phase,so as to ensure reliable arc extinguishing and avoid reignition.Finally,a fault risk-based ground fault type discrimination criterion is proposed,which can effectively cooperate with the existing ground fault protection and reliably identify the fault type on the premise of ensuring the system safety.Effectiveness of the proposed method is verified by the simulation results of PSCAD/EMTDC software.