Modeling and Simulation of Autonomous DC Microgrid with Variable Droop Controller

The emergence of highly efficient and cost-effective power converters, coupled with the growing diversity of DC loads, has elevated the importance of DC microgrids to a level comparable with AC microgrids in the modern power industry. DC microgrids are free from synchronization and reactive power dynamics, making them more reliable and cost-effective. In autonomous mode, achieving effective voltage regulation and satisfactory power sharing is critical to ensuring the overall stability of the microgrid. As the common DC bus of the microgrid connects distributed generators (DGs), storage devices, and loads through power electronic converters (PECs), the controllers of these PECs must regulate the bus voltage effectively, track reference signals to meet power demands, and enable satisfactory load sharing. In this work, a real time decentralized droop controller is implemented for an islanded DC microgrid to enhance the voltage regulation at the DC bus and current sharing efficacy between the sources subject to load transients. A novel control strategy is presented in which the conventional droop control is modified considering the load dynamics. The performance of the proposed control strategy is compared with the conventional voltage droop control strategy. The fluctuations in the DC bus voltage, which is the major cause of voltage instability of the DC microgrid is effectively reduced by the proposed strategy. The proposed strategy is validated by comparing it with the conventional fixed droop control method on the MATLAB Simulink platform. The variable droop control strategy outperforms the fixed droop method by addressing sudden voltage fluctuations in the DC bus, which occur due to the inherent load current dependency of the fixed droop approach. This technique achieves enhanced voltage regulation, which is crucial for microgrid stability.