This paper proposes a decentralized currentsharing control strategy to endow fast transient response to paralleled DC-DC converters systems, such as DC microgrids or distributed power systems. The proposed controller consist of two main control loops: an external voltage droop control for current-sharing proposes and an internal current loop. The external droop control loop is designed as a voltage loop with embedded virtual impedance, which avoids the use of a slow voltage loop and a separate extra virtual impedance loop that may limit the system bandwidth. The internal current loop, thanks to the external control loop simplification, plays a major role in the system bandwidth, so that an adaptive PI controller is proposed for this matter. In the paper, two different droop control methods have been modeling, designed, simulated, and tested: the conventional virtual-impedance-loop based V-I droop and the proposed embedded-virtual-impedance based I-V droop. In order to compare the dynamic response performances between two droop controllers, their state-space models have been developed and analyzed in this paper. The results show that the dynamic response of the I-V droop control is faster than that of the conventional V-I droop control. Furthermore, by analyzing the effects from I-V droop control parameters, the errors can be reduced faster by enlarging the proportional terms, but with no fluctuations, and then completely eliminated by restoring back to small proportional values. Meanwhile, there exists a trade-off phenomenon between the fast dynamic response and good  steady-state performance, thus an adaptive PI controller is proposed to both improve dynamic response and guarantee good steady-state performance simultaneously. Experimental results are shown to verify the accuracy of the models and the effectiveness of the proposed control framework.

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This paper presents a research project focus on the development of future intelligent direct-current (DC) microgrids which is being deployed for highly efficient integration of distributed generation and modern electronic loads. The project is based on the collaboration between research institutes in China and Denmark, aiming to explore the different aspects of DC microgrids: design, modelling, control, coordination, communications and management. In addition, a future Living Laboratory will also be integrated into the Intelligent DC Microgrids Laboratory, which will serve as demonstration facility for low voltage direct-current (LVDC) distribution systems. Research is carried out in both Intelligent DC Microgrid Laboratories, focused on industry in China and residential applications in Denmark.