Review on secondary and tertiary control structures for Microgrid

Abstract

Abstract— With the large scale integration of Distributed Energy Resources (DERs) into the existing power system, there has been a significant impact on the operation of distribution networks; the major impacts being power quality problem along with congestion and voltage regulation issues. This demands coordinated control approaches which allow Distributed Generation (DG) units to actively participate in voltage and frequency regulation. To realize the same, hierarchical control structures constituting the primary, secondary and tertiary control structures are implemented. These controllers are classified as the centralized or the decentralized type. Thus by employing droop controls or impedance based controls desirable outcomes such as power sharing, non linear load sharing and harmonic reduction is possible thanks to coordinated operation of secondary and tertiary control layers with primary or local layer. This paper aims at establishing a basic understanding of these control layers as applied to AC and DC microgrids along with detailed explanation of modified structures from the conventional control structures in a typical microgrid.