Short-term operation scheduling in renewable-powered microgrids: a duality-based approach

Abstract—This paper considers the operation scheduling prob-lem in renewable-powered microgrids, which is used to determine the least-cost unit commitment (UC) and the associated dispatch, while meeting load, environmental, and system operating require-ments. The intermittency nature of the renewable energy sources, as well as microgrid’s capacity to operate either in parallel with, or autonomously of, the traditional power grid, pose new challenges to this classic optimization task. A probability-based concept, proba-bility of self-sufficiency (PSS), is introduced to indicate the proba-bility that the microgrid is capable of meeting local demand in a self-sufficient manner. Furthermore, to the best of our knowledge, we make the first attempt in approaching the mixed-integer UC problem from a convex optimization perspective, which leads to an analytical closed-form characterization of the optimal commitment and dispatch solutions. The simulation results show that 1) the proposed method achieves an efficient performance that incurs no loss of optimality with lower complexity than existing algorithms; 2) an energy storage system (ESS)with suitable capacity contributes to the self-sufficiency target of a microgrid, and the stored energy varies less remarkably as the microgrid tends to operate more independently; 3) the proposed method provides guidelines in decid-ing the ESS size to achieve a desired PSS. IndexTerms—Distributed generators, duality, economicdispatch, microgrid, renewable energy resources, unit commitment (UC)