In　an　autonomous　ac　microgrid　system,　a　peer-to-peer　decentralized　solution　would　be　a　preferred　choice　for　the　coordinative　control　of　distributed　generation　units.　However,　due　to　the　dispersed　sources　and　loads,　and　mismatched　line　impedances,　it　is　hard　to　achieve　satisfactory　power　sharing　performance　and　power　quality　without　communication　links.　Therefore,　a　comprehensive　decentralized　solution　based　on　dual-frequency-droop　is　proposed　in　this　article.　With　only　local　information,　appropriate　virtual　impedances　could　be　obtained　to　compensate　the　mismatched　complex　line　impedances　in　the　required　frequency　range,　and　hence　active,　reactive,　unbalanced,　and　harmonic　powers　could　be　shared　accurately　among　parallel　inverters　under　various　load　conditions.　Then,　the　frequency　deviation　caused　by　the　droop　control　is　effectively　attenuated　without　affecting　power　sharing　through　a　dynamic　droop-slope　regulator.　Moreover,　the　causes　of　steady-state　ripples　on　virtual　impedance　waveforms　are　carefully　analyzed,　and　the　design　criterions　to　eliminate　these　ripples　are　provided.　Finally,　case　studies　are　provided　in　simulations　and　experiments　to　validate　the　effectiveness　of　this　method.