Improving quality of supply in small-scale low-voltage active networks by providing islanded operation capability

This study presents a novel approach for ensuring the power quality and reliability of supply required for low-voltage networks with distributed energy sources. For this purpose, a control strategy which enables active network uninterrupted transfer to islanded mode and continues its operation when the quality of supply from the utility grid is insufficient is proposed. Islanded operation is initiated based on an immunity curve, which defines the tolerance of the considered system for different voltage disturbances. The proposed strategy is based on expanding the functionality of the energy storage system and the application of a central controller. Moreover, it does not interfere with the method for control of energy sources. An original mechanism was developed and implemented to reserve power and energy in the ESS, enabling the switch to islanded mode at any time. A simulation model of the considered network was developed using the PSCAD/EMTDC platform to verify the proposed strategy. Simulation results illustrating the functioning of the state of charge storage control mechanism and demonstrating the flexible operation of the network in grid-connected and islanded modes are provided. The results clearly confirm the effectiveness of the proposed control strategy for improving the quality and reliability of power supply.