Optimal Energy Management of Battery Supercapacitor Aided Solar PV Powered Agricultural Feed Mill Using Pontryagin's Minimum Principle

The commercialization of renewable energy sources is often obstructed due to the cost of energy storages such as batteries, which are unavoidable due to intermittent nature of these energy sources. Average power density and low cycle life of batteries lead to frequent replacement and put additional economic burden toward the replacement cost at its end-of-life. The battery supercapacitor-hybrid energy storage system (BS-HESS) with efficient energy management system (EMS) has shown the potential to improve the battery life in various applications. Here, we exploit the Pontryagin's minimum principle (PMP) for optimal power-split between battery and supercapacitor in HESS for a stand-alone photovoltaic assisted agricultural feed mill such that the battery life is improved. Also, we employ a new technique called hybrid maximum power point tracking, by introducing an extra term in the performance index, to take care of the effects of partial shading and provide fast response to sudden change in solar irradiance. We verify the effectiveness of the proposed PMP-based EMS via simulation and comparison with conventional methods. Simulation results show that the HESS along with PMP-based EMS can improve the battery cycle life compared to rule-based EMS and battery-only storage. Finally, we implement the proposed PMP-based EMS in hardware prototype to prove its practicality. The results obtained are satisfactory.