Voltage quality enhancement in islanded microgrids with multi‐voltage quality requirements at different buses

Abstract

Keeping voltage quality in isolated microgrids while feeding non-linear and/or unbalanced loads is one of the major challenges in the control of these networks. This study proposes a new hierarchical control for enhancing voltage quality in sensitive load bus (SLB) of isolated microgrids considering non-SLBs (NSLBs (DG buses and local buses)) with voltage quality limitations. At the primary level of this hierarchical control, a droop controller is responsible for controlling voltage and frequency of microgrids. The duty of the secondary control level is that in the case of the reduction of voltage quality indices at SLB, it enhances them to their determined levels by sending proper control signals to the primary level to determine each DGs compensation effort. It is worth noting that improving the voltage quality indices at SLB can lead to a drop in NSLBs voltage quality indices. Although NSLBs do not have the strict voltage quality limitation of SLB, but keeping the voltage quality of these buses in their allowed limitation is necessary. The third level of the proposed hierarchical control is designed to guarantee the voltage quality indices limitation at NSLBs. Simulation results are given to demonstrate the effectiveness of the proposed control scheme.