Adaptive and Decentralized Control Strategy to Support Coordination of Multiple DC Microgrids Considering Transmission Line Impedance

Abstract

Multiple DC Microgrids (MGs) can be interconnected by interlinking converters (ICs) to support each other through coordinated control strategies. However, the nonnegligible transmission line resistance results in inaccuracies in decentralized coordination at steady state. To address this issue, an adaptive and decentralized control strategy is proposed to eliminate the impact of transmission line resistance and facilitate accurate power sharing among the DC MGs. The proposed strategy injects a perturbance to estimate the transmission line resistance based on the IC signals sampled before and after the perturbance, obviating the need for additional measuring devices on the transmission line. With the estimated results, the proposed strategy compensates for the transmission line resistance through virtual resistance, achieving accurate power sharing among the DC MGs under coordinated control. The compensation and coordination operations rely on the local signals from the IC, ensuring this power coordination in a decentralized manner. Furthermore, the estimation and compensation algorithm is decoupled at each IC port, allowing the easy extension of the proposed strategy. This paper discusses the application of the proposed strategy in three scenarios: two interconnected DC MGs, and several DC MGs interconnected via a multiport IC or multiple ICs. Using the example of two DC MGs with line impedance considered, the system stability is analyzed based on a small-signal model. Lastly, the feasibility of the proposed strategy in these scenarios is validated by the simulation and hardware-in-loop tests.