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This paper investigates the issue of accurate reactive, harmonic and imbalance power sharing in a microgrid. Harmonic and imbalance droop controllers are developed to proportionally share the harmonic power and the imbalance power among distributed generation (DG) units and improve the voltage quality at the point of common coupling (PCC). Further, a distributed consensus protocol is developed to adaptively regulate the virtual impedance at fundamental frequency and selected harmonic frequencies. Additionally, a dynamic consensus based method is adopted to restore the voltage to their average voltage. With the proposed methods, the microgrid system reliability and flexibility can be enhanced and the knowledge of the line impedance is not required. And the reactive, harmonic and imbalance power can be proportionally shared among the DG units. Moreover, the quality of the voltage at PCC can be greatly improved. Simulation and experimental results are presented to demonstrate the proposed method.Index Terms-microgrid, adaptive virtual impedance, reactive power sharing, harmonic power sharing, imbalance power sharing, distributed control, consensus protocol. NOMENCLATURE ω DGReference angular frequency of the DG unit ω *The nominal angular frequency of the DG unit E DG The reference voltage magnitude of the DG unit E * The nominal voltage magnitude of the DG unit m n Droop coefficients P Q Measured active and reactive power after low-pass filtering X DGf,i The reactance of DG equivalent positive sequence impedances Q Rated,i The rated reactive powers of DG units E DGh,i Reference harmonic voltage magnitudes of the DG units E DGI,i Reference imbalance voltage magnitudes of the DG units Q Har,i Harmonic power of the i th DG unit Q Imb,i Imbalance power of the i th DG unit n h,i Coefficient of the harmonic droop controller m I,i Coefficient of the imbalance droop controller

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