This paper proposes a consensus-based secondary frequency control scheme for islanded microgrids. The scheme only deals with droop equation and secondary control variables, and coincides with the hierarchical control concept. In this way, the effects of primary control level are integrated into the active power variation as a disturbance signal. Finite-gain L2-stability of the system, from the disturbances to the system states, is then investigated. Minimum requirements for convergence of the system to the desired operating point are also extracted theoretically. The scheme is then augmented with an online Kron reduction strategy, which prevents the spanning trees in the communication network from cutting, and provides the distributed generation units with smooth plug-and-play functionality, when they get disconnected physically. The effectiveness of the proposed scheme for different case studies is validated in MATLAB/Simscape ElectricalTM software environment.
