This paper proposes a decentralized linear quadratic regulator (LQR) for secondary control layer of islanded microgrids. This approach regulates the system frequency while guaranteeing accurate active power sharing among all the sources. Unlike the existing works, a systematic approach is introduced to design a communication-less secondary controller based on an appropriate quadratic cost function via the optimal LQR technique. Its decentralized characteristics, simplicity in implementation, optimality, and straightforwardness of the design procedure are the major features of the presented approach. Design procedure is depended only to the cut-off frequency of the droop layer low-pass filter and renders an optimal performance. Simulation results validate the efficiency of the proposed approach.
