Robust Control of Islanded Microgrid Frequency Using Fractional-Order PID
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RESEARCH PAPER
Robust Control of Islanded Microgrid Frequency Using Fractional-Order PID Shabnam Khosravi1
•
Mohammad Taghi Hamidi Beheshti1 • Hassan Rastegar2
Received: 13 March 2019 / Accepted: 14 December 2019 Ó Shiraz University 2020
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. Keywords Frequency control Microgrid Robust control Fractional-order controller List of D G(s) Gp(s) H PBESS PDEG PPV Pt PWTG R TBESS Tg TPV Tt
Symbols Load damping coefficient Nominal open-loop microgrid system Set of uncertain G(s) Inertia constant BESS output power DEG output power PV output power Total generated power WTG output power Speed droop characteristic BESS time constant Governor time constant PV time constant Turbine time constant
& Shabnam Khosravi [email protected] Mohammad Taghi Hamidi Beheshti [email protected] Hassan Rastegar [email protected] 1
Department of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran
2
Department of Electrical Engineering, Amirkabir University of Technology, Tehran, Iran
TWTG D Df DPL
WTG time constant Uncertainty block Frequency change Load power change
Abbreviations BESS Battery energy storage system CMPC Centralized model predictive control DEG Diesel generator DG Distributed generation FC Fossil fuel FESS Flywheel energy storage system FOPID Fractional-order proportional–integral–derivative GM Gain margin LFC Load frequency control LMI Linear matrix inequalities MG Microgrid MT Microturbine PHEV Plug-in hybrid vehicle PID Proportional–integral–derivative PM Phase margin PV Photovoltaic RES Renewable energy source WTG Wind turbine generator
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Iranian Journal of Science and Technology, Transactions of Electrical Engineering
1 Introduction In recent years, due to a quick decrease in fossil fuels and an increasing demand for high-quality and reliable electrical power, new generating sources in electrical power systems have emerged. Centralized power generation units are giving way to smaller and more distributed
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