Distributed Secondary Optimal Control With Fast Voltage Recovery and Minimum Generation Cost for Islanded DC Microgrids

Abstract

The conventional consistency-based distributed control methods of microgrids focus on the final state of microgrids and ignore the convergence performance. It is hard for such distributed control schemes to achieve optimal control of microgrids. This paper proposes a distributed secondary optimal control method for islanded DC microgrids to recover voltage and minimize generation cost through one-way point to point communication among the neighbor distributed generations (DGs). A kind of novel observer only using the neighbour DG’s information is designed to overcome the unavailability of all information. Applying linear quadratic optimal control theory, the distributed controllers are designed based on the novel observer and are derived by solving a Riccati equation to improve the convergence speed. The distributed controller can effectively achieve the objectives of voltage recovery and generation cost minimization, and the corresponding cost function is asymptotically optimal. The observer gains are effectively selected to ensure the stability of the observer. The feasibility of the proposed control method is demonstrated by simulation under various sources of uncertainty. The comparison results indicates that the proposed controller can achieve voltage recovery and minimize generation cost with a fast convergence speed.