Secondary control in microgrids for dynamic power sharing and voltage/frequency adjustment

This paper discusses the operation of the central controller for a microgrid. The central controller is responsible to maintain the voltage and frequency of the microgrid within the acceptable ranges while the distributed energy resources supply the required power demand of the loads based on the droop control. The desired ratio among the output active power of the distributed energy resources is determined by the distribution network tertiary controller. To achieve a dynamic variation for the output active power ratios among the distributed energy resources, the central controller has to adjust the references of the rated active power and the droop control coefficients. As this may lead to unacceptable voltage and frequency in the microgr-id, the central controller has to adjust the references of the voltage and frequency consequently. The proposed central controller strategy for the microgrid is validated through PSCAD/EMTDC simulations.