Aiming　atproblem　of　absence　of　effective　coordinationbetween　AC　side　overvoltage　protection　and　DC　controlstrategy　andtaking　DC　system　single　pole　blocking　leadingabrupt　power　reduction　as　example,　this　paper　analyzes　filter　action　strategy　and　change　rate　of　active　and　reactive　power　respectively　after　single　pole　blocking　failure.　Then　a　new　principle　of　an　adaptive　AC　overvoltage　protection　is　put　forward.　With　single　pole　blocking　in　DC　system,　considering　equipment　insulation　level,　the　proposed　scheme　can　adaptively　adjust　overvoltage　protection　time　settings　without　changing　original　protection　characteristics.　It　can　slid　over　filter　clearing　time　and　prevent　load　loss　caused　byAC　overvoltage　protectionaction.　When　overvoltage　is　caused　by　AC　grid　disturbance,　it　can　operate　correctly　according　to　original　logic　andensure　equipmentsafety.　Simulation　results　show　that　this　new　scheme　canstrengthen　protective　relay　coordination　between　AC　and　DC　systems,　and　thus　of　great　importance　in　improving　hybrid　system　stability.　©　2016,　Power　System　Technology　Press.　All　right　reserved.