Optimal, Nonlinear, and Distributed Designs of Droop Controls for DC Microgrids

In this paper, the problem of optimal voltage and power regulation is formulated for distributed generators (DGs) in DC microgrids. It is shown that the resulting control is optimal but would require the full information of the microgrid. Relaxation of information requirement reduces the optimal control into several controls including the conventional droop control. The general setting of a DC microgrid equipped with local sensing/communication network calls for the design and implementation of a cooperative droop control that uses the available local information and coordinates voltage control in a distributed manner. The proposed cooperative droop control is shown to include other controls as special cases, its performance is superior to the conventional droop control, and it is robust with respect to uncertain changes in both distribution network and sensing/communication network. These features make the proposed control an effective scheme for operating a DC microgrid with intermittent and distributed generation.