Improving Power Quality and Power Sharing in Unbalanced Multi-Microgrids Using Energy Storage System

The integration of single-phase distributed generations (DG) and unbalanced loads to three-phase DGs brings challenges to the operating system of the microgrids (MGs). These challenges include unbalanced voltage and unequal power flow at the point of common coupling (PCC) of the MGs. The aim of this paper is to develop an Energy Storage System (ESS) with multi-function control for islanded multi-microgrids (MMG) consisting of single and three PV-DGs to enhance its power quality and power sharing of the MMGs. The proposed multifunction control consists of a reactive power compensation (RPC), a PCC power balance regulator (PBR) and a reactive power sharing algorithm (RPSA). The RPC and the PBR improve the three-phase PCC voltage and power unbalance of the MMG and the RPSA regulates the reactive power sharing among the MMGs. The proposed strategy is experimentally validated on the Opal-RT OP5600 real-time simulator. The voltage unbalance factor (VUF) at the PCC is reduced from 4.3 percent to 0.03 percent, while the three phase and the single phase reactive powers are shared proportionally between different rated DGs.