Grid-forming　converters,　taking　droop-controlled　converters　and　virtual　synchronous　generators　(VSGs)　as　typical　examples,　have　shown　great　promise　as　the　interfaces　between　renewable　energy　sources　and　the　future　power-electronics-based　power　system.　However,　the　coupling　between　active　and　reactive　power　will　adversely　affect　the　dynamic　performance　and　stability　of　grid-forming　converters.　In　order　to　facilitate　quantitatively　analyzing　and　assessing　the　power　coupling　characteristics　of　various　types　of　grid-forming　strategies,　this　article　develops　a　unified　dynamic　power　coupling　model　based　on　a　first　amplification　coefficient　array　and　a　relative　gain　array　in　the　frequency　domain.　Then,　by　using　the　established　unified　model,　a　comprehensive　analysis　of　dynamic　power　coupling　properties　for　typical　VSG　control　and　droop　control　is　presented,　which　reveals　that　droop　control　is　helpful　in　weakening　power　coupling　while　VSG　control　is　prone　to　amplify　the　coupling.　Moreover,　the　influences　of　the　pivotal　control　parameters　in　droop　and　VSG　controllers　on　power　coupling　characteristics　are　discussed　in　detail,　which　can　provide　novel　supplementary　guidelines　for　parameter　design　of　droop　and　VSG　controllers.　Finally,　the　experimental　results　verify　the　correctness　of　theoretical　modeling　and　analysis.　©　1986-2012　IEEE.