Design of an Intelligent Energy Management System for Standalone PV/Battery DC Microgrids

Standalone PV/Battery Storage systems require a proper energy management strategy to control and coordinate the energy transfer between the different DC microgrid assets. This paper proposes an intelligent energy management system (EMS) for isolated DC microgrids that achieves the following objectives: a) maintaining a stable DC link voltage under different operating conditions by shifting the PV system operating mode from maximum power point tracking (MPPT) to voltage regulation (VR) at light loading and excess PV system output conditions; b) implementing a new load shedding and restoration strategy in isolated microgrids based on the battery state of charge and solar irradiance conditions to maximize the energy supply period to critical loads. The designed intelligent EMS also takes into account the protection of microgrid assets through limiting the battery charging/discharging current within its physical manufacturer limits by implementing a dual loop PI control algorithm. The new EMS is tested in MATLAB/Simulink and a satisfactory performance with smooth mode transitions from PV MPPT/VR and load shedding/restoration has been achieved. The critical load supply period through a fully-charged battery and under zero PV system output condition is doubled for the simulated scenario using the proposed shedding strategy compared to the no-load-shedding case.