Farshad Zandi

  • Thesis Title: Proportional reactive power sharing for inverter-based microgrids in islanded mode
  • Grade: Master of Science
  • Final: Sept. 2016
  • Supervisor: Dr. Bahador Fani
  • Abstract

    The conventional droop methods are normally employed to share the active and reactive powers among the distributed generation units. These methods cannot guarantee the ideal reactive power sharing due to difference of the line impedances and the network asymmetries. This research proposes a new control strategy for improving the reactive power sharing accuracy using a nonlinear voltage-reactive power characteristic. The proposed characteristic reduces the reactive power generation of the micro-sources which produce more reactive power by adjusting their operating points, thereby it prevents the micro-sources from overloading and decreases the reactive power sharing error. Nevertheless, due to inherent connection between the terminal voltage of micro-sources and their generated reactive powers, the proposed strategy may result in voltage drop at terminals of the sources. Therefore, a voltage restoration mechanism has been also presented to preserve the voltage within its acceptable range. This mechanism adaptively increases the micro-source reference voltage relative to the active power generated by the source which improves the reactive power sharing accuracy under heavy load conditions as well as compensating the voltage drop. Hence, the proposed strategy has two main objectives: improvement of reactive power sharing and improvement of voltage regulation.