Robust voltage controller design for an isolated Microgrid using Kharitonov's theorem and D-stability concept

This paper proposes a new robust voltage control strategy for an isolated Microgrid (MG). The MG consists of several Distributed Generation (DG) units and local loads, which should be capable to operate in both connected and disconnected modes. To achieve this goal and suitable performance in both modes, robust control may provide many advantages. The proposed control structure proceeds to design a robust voltage controller based on Kharitonov's theorem for an isolated MG system. It utilizes an internal oscillator to frequency control and a proportional-integral (PI) controller to maintain voltage stability that is tuned by Kharitonov's theorem. For fine-tuning of the PI controller, D-stability concept as a complementary method is used. The PI voltage controller endeavors to minimize errors between direct and quadrature voltage components and their reference values. Performance of the robust voltage control method and isolated MG system are evaluated by several simulations in the presence of uncertainty in the system parameters. (C) 2012 Elsevier Ltd. All rights reserved.