Hierarchical Fuzzy Logic Controller for Islanded DC Microgrids with HESS

Battery energy storage systems (BESSs) are integral portions of islanded microgrids. The efficiency and life span of such batteries highly depend on the charging/discharging profile of the battery. In this paper, we propose a hierarchical control algorithm to control the operation of a hybrid system. The system under consideration is an islanded DC-microgrid composed of Li-ion batteries (LIB), supercapacitors (SC), and PV arrays. The control algorithm consists of two layers: a) a supervisory layer overseeing the states of all controllable devices and is based on fuzzy logic control, and b) a local control layer for each device based on PI control. The goal of the algorithm is to achieve a stable DC-bus voltage despite the rapid changes in states from the variability of the load and PV. In addition, it determines the power flow of each component of the microgrid considering the high response of the SC to save the battery from over-discharging.