Abstract:Firstly,the event that UHV reactive power control action leads to DC power runback is introduced. And then,the causes for DC power runback led by manual removal of HP3 filter are analyzed,and the problems existing in control function software of the absolute minimum filter are pointed out. Finally,on the basis of the existing reactive power control function, the hidden dangers in full power operation situation are analyzed,and the feasible solutions are proposed,which can provide a reference for other converter stations in China.