engleski

Islanded microgrid optimal control system to enhance small-signal stability

Compared to interconnected power grids, islanded microgrids are more sensitive to active power disturbances due to lower specific rotational inertia and lack of spinning reserve. Because of these properties, islanded microgrid control and power quality assurance are challenging tasks. Even small power imbalances can lead to grid blackout, if not addressed in a proper and timely fashion. This paper presents a dynamic model based on elastically coupled rotational inertial masses, enabling a simple small-signal stability analysis. The modelled microgrid contains multiple renewable power resources (thermal, hydro, photovoltaics and wind turbines) supplemented with battery energy storage system. The model is linearized in the vicinity of several characteristic operating points and such linearized model is used to develop a linear quadratic regulator (LQR) to control distributed resources' power output. Dynamic properties of LQR microgrid control are investigated by means of root locus analysis and comprehensive computer simulations. Simulation results illustrate that incorporating appropriate LQR control laws in a peer-to-peer control system enables its use for small-signal stability enhancement without incorporating a traditional droop frequency controller, whereas the root-locus analysis illustrates how LQR input parameters affect closed-loop poles and, thus, the small-signal stability properties.

Microgrids ; electromechanical model ; islanding ; frequency control ; stability ; linear quadratic regulator (LQR)

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