In　general,　wind　power　output　of　clustering　wind　farms　must　be　massively　transmitted.　The　wind　power　in　each　wind　farm　is　correlated,　intermittent,　fluctuant,　and　cannot　be　accommodated　all　the　time,　causing　the　intractable　decision　of　economical　transmission　capacity　of　a　project　transmitting　wind　power　to　a　power　grid.　Furthermore,　the　drastic　fluctuation　of　clustered　wind　power　results　in　enormous　challenges　regarding　the　safety　of　a　power　system.　For　these　reasons,　the　concept　of　a　wind-hydrogen　power　system　for　clustered　wind　farms　is　proposed.　Next,　a　multiobjective　model　for　optimizing　the　capacities,　including　the　transmission　project,　hydrogen-producing　system,　and　fuel　cells,　is　constructed　based　on　the　joint　distributed　character　of　wind　speed,　which　consists　of　maximizing　social　benefit　and　the　qualified　rate　of　smoothing　clustering　wind　power　fluctuations.　Finally,　a　case　is　analyzed　in　detail,　accounting　for　the　wind　volatility,　wind　curtailment　probability,　and　the　costs　of　both　hydrogen　production　and　the　fuel　cells.　©　2018　John　Wiley　&　Sons,　Ltd.