Scalable Voltage Control for DC Microgrids: Robustness to Network Structural Variations

Frequent plug-in/-out operations result in structural variations of DC microgrids (DCmGs), posing challenges to scalable control and often requiring costly redesigns to maintain stability. To address this issue, this paper proposes a scalable voltage control strategy for uncertain DCmGs, enabling plug-and-play functionality without controller redesign or system reconfiguration. A polytopic uncertain DCmG model is first formulated to simultaneously capture parameter uncertainties in distributed generation units (DGUs), power lines, and ZIP (i.e., impedance, current, and power) loads. A structured free-weight matrix technique is then developed to mitigate the adverse effects of line and load uncertainties on DGUs while yielding a more tractable linear matrix inequality formulation. The proposed scalable control method is implemented locally to ensure the dissipative voltage stability of each DGU, thereby preserving the dissipativity of the entire network. Numerical simulations validate the effectiveness of the proposed strategy in achieving faster convergence and reduced overshoot.