Distributed Control of DC Microgrids for Optimal Coordination of Conventional and Renewable Generators

DC microgrids are increasing in popularity due to their simplicity and high energy efficiency, and becoming an appealing solution for the coordination of multiple conventional generators (CGs) and renewable generators (RGs). This article presents a distributed discrete-time control scheme to achieve the optimal coordination of CGs and RGs, where the generation cost of the CGs is minimized and the energy utilization of RGs is maximized. A certain degree of proportional load sharing among the RGs is also achieved to improve the stability margin and dynamic performance of dc microgrids. The designed control algorithm can maintain the bus voltages in their safe operating ranges. Besides, since the proposed control algorithm is developed in the discrete-time domain directly, it can avoid the possible instability impact of the digital implementation of control algorithms. Based on the Lyapunov analysis, the stability and convergence of the closed-loop system are analyzed rigorously. Finally, simulation results based on a detailed switch-level dc microgrid model illustrate the advantages of the proposed optimal control algorithm.