An Enhanced Drop Control Method for DC Microgrids with Accurate Current Sharing and DC Bus Voltage Restoration

Abstract

Aiming at the problems of traditional droop control in bus voltage stability and load current accurate sharing, an improved droop control strategy for autonomous DC microgrid with voltage self-recovery characteristic is proposed. The strategy obtains the line impedance information through the active identification method and introduces it into the droop coefficient in the form of negative compensation to suppress the adverse effect of line impedance inconsistency on current sharing. Besides, with the virtual bus voltage information, the translation compensation principle is utilized to realize the stable operation of bus voltage at the rated value. The proposed control method can not only simultaneously realize accurate load current sharing and the stability of bus voltage in the steady and dynamic process, but also can realize the decoupling control between them. Moreover, it has no need for interconnection communication, thus satisfying plug and play, greatly improving the reliability and scalability of the system. Finally, simulation results based on RT-lab platform verify the correctness of the theoretical analysis and the effectiveness of the control strategy.