Information-Exchange-Reduced Distributed FixedTime Secondary Control for DC Microgrid with Enhanced Stability

DC microgrids are a feasible grid system to host multiple distributed generators (DGs). In terms of the control and coordination of hosted DGs, the enhanced stability and fast dynamics of DC microgrids are required. To achieve these objectives, this paper proposes a comprehensive strategy that meticulously accounts for the impacts of transmission line impedances and constant power loads (CPLs). The strategy is architected with a dual-layer control approach: a stability enhancement controller is embedded within the primary control layer, while a novel distributed fixed-time controller is deployed in the secondary control layer, ensuring a robust and fast system performance. Specifically, for the primary control layer, the maximum tolerable CPL is firstly calculated using the reduced-order model and the impedance ratio criterion, contributing to more accurate and less conservative results. Additionally, a stability enhancement controller is designed to reshape the system's equivalent output impedance, improving both steady-state and transient stability of the DC microgrid and enabling the accommodation of larger CPLs. For the secondary control layer, a novel fixed-time secondary control scheme is put forward to achieve a concurrent DC bus voltage regulation and current sharing among DGs within a fixed time. Importantly, this method requires the transmission of only one variable to neighboring DGs, significantly decreasing communication traffic compared to the existing latest methods. The stability of the proposed scheme is theoretically proved through Lyapunov-based analysis. Case study results are presented to demonstrate the efficacy of the proposed strategy.