Robust Control of Islanded Microgrid Frequency Using Fractional-Order PID

Abstract

In this paper, a robust fractional-order PID (FOPID) controller is proposed to regulate islanded microgrid (MG) frequency. The considered MG is composed of a photovoltaic system, a wind turbine generation, a diesel generator, a battery energy storage system, the control unit, and loads. Some challenges in islanded MGs such as unpredictable variation in output power of renewable energy sources and model uncertainties, affect the system performance and lead to frequency deviations from the nominal value. For designing the proposed robust controller, the wind power and solar radiation are considered as disturbance inputs. Also, uncertainties are assumed in the inertia constant and the load damping coefficient parameters of the system. The FOPID parameters are determined by minimizing some constraints that guarantee robust stability and robust performance of the system. The performance of the proposed FOPID controller is compared with those of the classic PID and H∞ controllers. The effectiveness of the controller is illustrated through appropriate simulations.