Optimal Power Sharing and Voltage Restoration in DC Microgrids Based on Adaptive Droop Control

The stable operation of islanded DC microgrids is conditioned by two essential objectives. One is to maintain the bus voltage at its nominal value, and this can ensure system stability. The other is to achieve cost-effective power allocation among distributed generation units, which guarantees economic efficiency. These two objectives are often conflicting. Adding droop control to the voltage and current dual closed-loop control can achieve primary current sharing. However, it inevitably introduces steady-state voltage deviations on the DC bus and results in inflexible or not optimal power sharing. To resolve these inherent limitations, this paper proposes a innovative distributed secondary control strategy. The method is designed to meet both requirements within a unified framework. In the primary control layer, it uses adaptive droop gains to optimize power distribution in real time based on changing load requirements which enables distributed generation units to achieve cost optimization and maintain supply–demand equilibrium. The secondary control layer implements distributed compensation through local bus voltage measurement and restricted secondary information sharing between controllers for each unit to create corrective secondary control signals which it sends to its primary controller. The system design removes voltage deviation while bringing bus voltage back to its standard value without creating the problems found in centralized control systems. The proposed system depends only on local sensor data and neighbor-to-neighbor data exchange to achieve scalability and improved system robustness and decreased communication requirements. The MATLAB/Simulink simulation results show that the strategy provides precise voltage control and exact power distribution and maintains economic stability during loading changes and disturbances. The results confirm that the proposed method provides a practical and efficient solution for future islanded DC microgrids with high penetration of distributed energy resources.