Power-flow-based energy management of hierarchically controlled islanded AC microgrids

Abstract

This paper presents a novel approach of employing hierarchical control to optimize the operation of islanded AC microgrids. The proposed method is an offline, centralized, power-flow-based energy management scheme which includes primary and secondary control dynamics in a modified power-flow formulation. The inner power-flow level maintains bus voltages and system frequency within the desired range and ensures power balance in the network. The outer optimization level ensures that the various components remain within their operational constraints, while optimizing a system-level objective. Two case studies are explored using a modified 14-bus medium voltage (MV) CIGRE benchmark microgrid to validate the proposed energy management algorithm. The first case includes minimization of conventional generator operating cost and renewable energy curtailment, both with linear and non-linear loads, and the second case includes minimization of conventional generator operating cost with load shedding. The results obtained from the case studies show the efficiency of the proposed energy management algorithm, and evidence its reliability for the optimal operation of islanded AC microgrids with multiple renewable energy sources.