Operation Loss Minimization Targeted Distributed Optimal Control of DC Microgrids

Abstract

DC microgrids are growing in popularity due to their advantages in terms of simplicity and energy efficiency while connecting dc sources and dc loads. In traditional hierarchical schemes, optimization and control are implemented at different time scales. The loose integration lowers its energy efficiency and makes it hard to achieve real-time optimization. Even a slight disturbance can result in deviations of bus voltages and output currents from their optimal operating points. Additionally, most real-time control schemes cannot guarantee the boundedness of individual bus voltages. Targeting these problems, a distributed optimal control algorithm is presented in this article for dc microgrids to minimize operation loss (converter loss and distribution loss) in real time and maintain all bus voltages within predefined ranges. First, the Karuch-Kuhn-Tucker condition of the original constrained optimization problem is converted to an equivalent optimality condition, which is suitable for control design. Then, a distributed control algorithm is designed to drive the system's operating condition toward the optimal one. Convergence to the optima is guaranteed through rigorous Lyapunov-based stability analyses. Finally, simulation studies with a detailed switch-level model demonstrate the merits of the proposed controller.