Centralized-Decentralized Secondary Controller for Standalone PV-Battery Unit Type Microgrid

The encouraging use of renewable sources like solar photovoltaic (PV) for decreasing the dependency on fossil fuel based energy generation has led to realization of microgrids (MGs) on the existing distribution network. The intermittency of PV sources is taken care by storage device like battery. Handling intermittent power generation, proper power sharing among multiple parallel connected PVB systems, accommodating the time-varying load scenarios, shedding of noncritical loads under energy deficient conditions, etc., are some essential control requirements of such a MG system. In this work, a centralized-decentralized secondary controller (CDSC) is proposed for coordinating the operation of an individual PVB units in the MG system. The proposed centralized secondary controller (CSC) evaluates the different settings based on the received information from the local controller (LC). Further, the decentralized secondary controller (DSC) decides the references for the LC based on the information received from the CSC and LC measurements. The developed CDSC considers the actual power extracted from the PV array as well as the charging/discharging current limit constraints of the battery controller that increase the battery life. The proposed control architecture has been extensively tested for different operating scenario on a European distribution network using the PSCAD/EMTDC platform.