Novel Compensation Methods Using Energy Storage System (ESS) in Islanded Unbalanced Single-/Three-Phase Multimicrogrids

The integration of single-phase microgrids (MG) and unbalanced loads to three-phase MGs results in power quality issues at the point of common coupling (PCC). These issues include unbalanced voltage, unequal power flow, and inaccurate reactive power sharing. In this article, an energy storage system (ESS) has been proposed with novel control methods to help mitigate unbalance issues in these islanded multimicrogrids (MMGs). It presents two novel control methods: modified reverse droop control and multifunction control to compensate the reactive power of the MMG and generate the needed active and reactive power references of the ESS. The developed control methods mitigate PCC voltage and power unbalance of the MMG and also achieve the load power sharing proportionally among different rated photovoltaics (PV) inverters. In addition, the system stability with the proposed control is also presented under different scenarios. The proposed multifunction controller operation is validated using Opal-RT real-time simulator and experimentally using control hardware-in-the-loop. The results demonstrate that the PCC unbalanced voltage and power are reduced significantly by 97.8%, and the proper reactive power sharing is achieved among the different PV inverters in the proposed system.