Robust decentralized voltage control of an islanded microgrid under unbalanced and nonlinear load conditions

This paper presents a new decentralized control strategy for the islanded operation of a microgrid under unknown load conditions. In the islanded mode of operation, the microgrid should provide the load with a set of regulated balanced three-phase voltages. The load which is parametrically and topologically uncertain can also be unbalanced and/or nonlinear. Thus, the use of conventional control strategies results in the poor performance and even instability of the microgrid system. The proposed method assumes that the load current is a measurable disturbance signal. The robust optimal control approaches are used to design a controller to overcome the disturbances resulting from the unknown loads dynamics. The optimization problem is converted to a convex problem and is solved using the linear matrix inequalities (LMIs). The performance of the designed controller is verified using time-domain simulations carried out in PSCAD/EMTDC software.