Scalable Control of Large-Scale DC Microgrids: A Novel Line-Independent and Mode-Related Scheme

This article proposes a novel scalable control strategy for large-scale direct current microgrids (LSDCmGs) consisting of multiple distributed generation units (DGUs). The objective is to facilitate real-time plug-and-play (PnP) functionality for DGUs, despite the presence of power transmission line coupling. In brief, the insertion or removal of DGUs does not require reconfiguration of adjacent controllers to maintain the stability of the entire LSDCmGs. To achieve this goal, a generalized free-weighting matrix technology is introduced. The strict assumptions previously made on Lyapunov matrices are ingeniously shifted to free-weighting matrices by this technology. As a result, scalable control is achieved and conservatism is reduced simultaneously. Moreover, the topological structure of LSDCmGs frequently undergoes changes due to external factors, equipment failures, and line issue. Markov chains are employed to accurately model these variations, providing a more realistic analysis of the microgrid's operational states. Additionally, by selecting a mode-related structured Lyapunov-Krasovskii function, sufficient criteria are derived to realize tracking of a given reference voltage in the LSDCmGs under PnP operation. Finally, the effectiveness of the proposed scalable strategy is validated through a case study involving the LSDCmGs with five DGUs.