Extended-Optimal-Power-Flow-Based Hierarchical Control for Islanded AC Microgrids

This paper presents the application of a hierarchical control scheme for islanded ac microgrids with a primary droop control and a centralized extended optimal power flow control. The centralized control is responsible for computing and sending, in an online manner, the control references to the primary controls in order to achieve three operational goals, i.e., improvement of the global efficiency, voltage regulation through reactive power management, and compliance of the restrictions regarding the generation unit capacities. Two case studies are defined and online tested in a laboratory-scaled microgrid implemented in the Microgrid Laboratory, Aalborg University. The primary controllers are included in a real-time simulation platform (dSPACE 1006), while the extended optimal power flow is conducted in a central controller by using a smart meter and LabVIEW for data acquisition and MATLAB for its implementation, taking into account load and capacity profiles. The obtained results show the reliability of the proposed scheme in a real system and its advantages over the conventional droop control.

I. Introduction

Nowadays, the microgrid concept has an important role in enabling the integration of different distributed generation (DG) technologies, including renewable energy sources. The increasing integration of DG has meant a modernization of the current electric power system by providing more reliability and sustainability [1]–[3]. However, due to the distributed operation of the generation units, new technical challenges have emerged mainly related to the voltage quality along the feeders and the proper power sharing considering the capacity and characteristics of the DG units [4], [5].