Improved droop control for effective load sharing and voltage regulation in DC microgrids

DC microgrids are becoming more prevalent at a household level due to renewable technologies integration such as photovoltaic and wind power; the electric power could be cheaper and more efficient. DC systems have also been more advantageous over AC systems due to their low conversion losses. However, the DC link voltage appears to be variable during operation due to different random effects. This paper focuses on DC voltage droop control to regulate the output voltage of converters and defines a power management scheme to improve the quality and stability of the whole system by keeping the bus voltage within acceptable limits. Therefore, the droop parameters are optimized to suppress the current circulation and voltage drop between converters. The maximum power must be tracked from renewable resources during different operating modes of the system. The ESS and the engine generator cover the power shortage after all available renewable energy is consumed. Keeping the state of charge of the ESS within allowed bands is a key role of control system. Load shedding or power generation curtailment should automatically take place if the maximum tolerable voltage variation is exceeded. PSiM based simulation results are presented to evaluate the performance of the proposed control measures.