Energy Management System for a Photovoltaic System With Battery Storage Participating in Grid Voltage Quality Improvement
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Coupling an energy storage to a photovoltaic (PV) system not only increases the self-consumption but also solves the over-voltage issues if the cycling of the storage is properly controlled. Whatever the application the storage is used for, the primary concern of the system owner is to maximize the profits. Therefore, this paper addresses an energy management system for a PV system coupled with battery energy storage, which maximizes the daily economic benefits while minimizing the power injection to the grid. A time dependent grid feedin limit that gives high priority to peak PV production hours is proposed to minimize over-voltage issues caused by reverse power flow. The daily operational cost that includes the energy cost and the battery degradation cost is considered as the objective function. The non-linear constrained optimization problem is solved using dynamic programming. The adjustable grid feed-in limit can successfully minimize the power flow into the grid by diverting as much energy as possible to the battery even though the battery degradation cost is higher. In addition, there is a potential for these systems to participate in load-levelling if peak-hour sell-back price for the energy from storage is higher than the off-peak utility electricity price.