Modified Droop and Master-Slave Control for Load Sharing in Multiple Standalone AC Microgrids

This paper proposes a combined droop and master-slave control strategy for concurrent operation and control of standalone AC Microgrids operated in a distribution network. The combined droop and master-slave method developed for accurate load sharing among Voltage Source Inverters (VSI) improves voltage and frequency regulation in AC microgrid. The master VSI of microgrid is controlled through modified hierarchical droop controller which compensates voltage drop across feeder impedance and maintains load voltage at nominal value. The slave VSI is operated as a current source in microgrid and controlled in current control mode of VSI. In proposed control scheme, the local load demand in microgrid is compensated fully through slave VSI. This improves voltage and frequency regulation of microgrid as local load variations do not affect microgrid voltage and frequency. The dynamic performance of proposed control strategy for AC microgrid under varying load conditions is verified through real time simulator.