基于改进过压限制器和ACDTS的混联半波长系统故障保护策略OA北大核心CSTPCD

The transient characteristic of AC/DC hybrid half-wavelength transmission system is quite different from conventional hybrid system.When an asymmetric fault occurs along the half-wavelength line of the hybrid system,the DC system will be impacted by power frequency overvoltage and overcurrent along the line.This paper analyzes the propagation process of faults along the half-wavelength line of the hybrid system in detail,and studies the mech-anism of fault propagation coupling.In view of the overvoltage problem on DC side,it is proposed to install an im-proved overvoltage limiter on the DC bus side,add an auxiliary voltage limiting channel to suppress the DC side ov-ervoltage in stages,and reduce the current value of a single channel,which improves the voltage limit level of sys-tem protection.On the other hand,for the overcurrent problem on DC side,it is proposed to connect bidirectional thyristors in parallel at the interface of the converter station to realize the equivalent three-phase short circuit of the AC system,and isolate the fault overcurrent fed by the AC side bus to ensure the safety of converter station equip-ment and lines.Simulations are used to verify the feasibility of the two protection strategies.