Distributed Data-Driven Secondary Regulation for the Conflict Between Voltage Recovery and Accurate Current Sharing in DC Microgrids

Abstract

The problem of voltage restoration and current balancing has been a hot topic in the study of DC microgrids (MGs), and how to engineer a secondary controller to solve the conflict between these two is the concern of this paper. With the above consideration, an optimal distributed data-driven secondary control strategy is proposed in this paper, which relies entirely on the input and output (current measurements) data of DC MGs. The proposed framework completes the design of a secondary control strategy for DC MGs based on a data model for the first time, which incorporates the physical coupling relationship between voltage and current into the controller design and is independent of the global circuit parameters and topology information. As a result of the proposed cost function with future current prediction, the designed secondary control strategy not only retains the advantages of consensus control, such as facilitating the plug-and-play of generation units, but also enables DC MGs to achieve better output current quality at steady state, fast dynamic response and improves robustness to external disturbances. Unlike the existing schemes based on average voltage observer, this paper resorts to a combination of limiting the voltage reference value generated by the secondary controller and a current cooperative strategy based on the learned data model to achieve an easy-to-use trade-off between the two objectives of voltage regulation and current sharing in DC MGs. From the design and implementation point of view, the solution proposed in this paper is going to be simpler. Then, an analytical model of a closed-loop DC MG system under the proposed control scheme is developed, and the analysis of stability and consensus of weighted output current is given accordingly. Finally, the proposed control strategy is tested on a hardware DC MG system with solar panels and an MPPT controller to verify its feasibility.