Relevant research is carried out on selection of the smoothing reactance for HVDC projects.The concept of current slope factor is introduced to measure the effect of inhibiting fault current rising by smoothing reactor.And the relationship of DC current versus current slope factor during the course of fault is derived.Next
an integrated expression is deduced for selecting the reactance of the smoothing reactor by analyzing the main restrictions on the smoothing reactance.Finally
the proposed principle for parameter selection is verified in Ge-Nan HVDC project.