Optimal day-ahead active and reactive power management for microgrids with high penetration of renewables

Abstract

In recent years, efforts have been made to increase the proportion of electricity demand met by Renewable Energy Sources (RESs). Distributed Energy Resources (DERs) play a crucial role in this frame, particularly in Microgrids (MGs) where DERs and clusters of loads are interconnected. This paper presents an Energy Management System (EMS) developed for a low-voltage MG installed in Italy, connecting Photovoltaic (PV) units, a Wind Turbine (WT), a Battery Energy Storage System (BESS), a Combined Heat and Power (CHP) unit and loads: the EMS aims to optimize the day-ahead scheduling of the MG, considering both economic and power quality criteria. The mathematical model incorporates the capability curves of the inverters connected to DERs and allows for curtailment of PV and WT units, with curtailment costs assessed using the Levelized Cost of Electricity (LCOE). Penalties for the absorption of reactive power from the external network are considered and evaluated in accordance with the current regulatory framework. Optimal Power Flow (OPF) equations are integrated into the EMS model, too. A preliminary analysis, carried out on a simplified MG, evaluates the impact of linearizing the DERs capability curves and OPF equations on the EMS’s outcomes. Finally, a sensitivity analysis evaluates the impact of different operational constraints and of different objective function formulations on the operation of the MG, discussing key energy and economic results.