Distributed Control of DC Microgrids With Improved ZIP Load Adaptability

This article presents a distributed consensus-based controller for dc microgrids to achieve proportional current sharing and weighted average voltage regulation in the presence of ZIP [constant impedance (Z), constant current (I), and constant power (P)] loads. The proposed algorithm allows the regulation of the global weighted average voltage in a distributed manner. The precondition on initial bus voltages is relaxed. Furthermore, this study investigates the negative conductance introduced by constant power loads. Based on the properties of Laplacian matrices, the positive definiteness requirement on the conductance matrix is relaxed. A sufficient stability condition on ZIP loads is obtained with improved adaptability. By using the Lyapunov method, large-signal stability is analyzed rigorously for a wide range of loading conditions. The current sharing and voltage regulation errors are proved to converge to zero exponentially. Finally, simulations based on a switch-level dc microgrid model illustrate the advantages of the designed control algorithm.