Dynamic control strategies for islanded DC microgrids integrating renewable energy, fuel cells, and battery-EV storage

This paper presents a novel droop control strategy for an islanded DC microgrid that integrates renewable energy resources, including photovoltaic (PV) panels, a wind turbine, and fuel cells as generation sources, along with a battery storage system (BSS) and a current-loop-controlled electric vehicle (EV) as flexible storage units. The EV contributes flexibility by charging during low-demand periods and discharging during peak or overload conditions. Unlike conventional proportional–integral (PI) control, which offers accurate voltage regulation but limited dynamic performance, and classical droop methods, which suffer from a trade-off between current sharing accuracy and voltage deviation, the proposed strategy uses adaptive droop coefficients to achieve a balance between bus voltage stability and equitable power sharing without requiring large droop gains. The main contributions are as follows: (i) formulation of an improved droop framework that mitigates the classical trade-off between voltage deviation and sharing accuracy; (ii) coordinated integration of RES, BSS, and EV into a unified control system, enabling dynamic charging and discharging of the EV in response to load fluctuations; and (iii) comparative evaluation with conventional PI control to highlight the practical advantages of the proposed method. Two case studies are investigated: (a) renewable variability and load disturbances, including irradiance fluctuations, wind speed changes, sudden load variations, and load shedding, and (b) different load levels ranging from underload to overload conditions. Simulation studies, carried out in MATLAB/Simulink with a Nissan Leaf battery EV model, confirm that the proposed droop control strategy maintains DC bus voltage stability, reduces current stress in overload conditions, and achieves balanced power distribution more effectively than the conventional PI approach. The results demonstrate that the strategy enhances reliability, dynamic performance, and operational sustainability, establishing it as a robust and scalable solution for future islanded DC microgrids.