An hierarchical control of AC microgrid composed of distributed power resources based on voltage source converter

Due to the effect of line impedance and unequal load distribution, reactive power supplied by distributed power resources (DR) based on voltage source converter could not be shared according to their droop gains and the power quality will also be affected in AC microgrid. In this paper, a novel hierarchical control of ac micro-grid according to different time scales is proposed to improve power sharing and power quality. In short time scale, larger droop gains is adopted to improve power sharing. In larger time scale, the no load frequency and voltage set points of droop characteristics are adjusted, improving the voltage and frequency quality. The proposed hierarchical control can both limit the reactive power sharing errors and improve the power quality, which can be applied in complex microgrid configurations. Finally, the performance of the proposed control strategy is verified by digital time-domain simulation in PSCAD/EMTDC software.