Power Management Control Strategy in Photovoltaic and Energy Storage for Off-Grid Power Systems

The recent development of smart converters with integrated advanced control features in off-grid power systems enables an effective integration of renewable energy and storage elements. In particular, this paper presents a power management control strategy that is implemented in smart converters operating with photovoltaic (PV), battery energy storage (BES) and ac loads, and that is intended for off-grid applications. The power management control strategy that is implemented within a combined dc-and ac-centric power system architecture, which provides complementary advantages and viable solutions for residential and commercial PV-BES installations. The benefits of dc- and ac-centric architectures are combined to achieve BES management and flexibility in the placement of energy sources within the ac network. The power management control strategy presented in this work circumvents the BES overcharge and undercharge issues. The control methods are implemented in a grid-forming battery converter and a grid-feeding PV inverter capable of transmitting and receiving the communications for any chemistry-based BES multi-stage charge battery requirements. Communications are transmitted through the ac power line, without extra communication protocols for energy balancing. The proposed ac load shedding feature provides power rationalization in the event of insufficient energy supply from PV and battery ports. The power management control strategy is validated by the experimental results obtained using 6kVA power converters with traditional lead-acid and lithium-ion in a BES multi-stage charge profile.