A Distributed Finite Time Based Secondary Average Controller for Voltage/Frequency Regulation and Active/Reactive Power Sharing of AC Microgrids

Microgrid, as a new structure of power systems, has challenges that should be addressed; regulating the frequency and voltage and power sharing are among the most critical challenges of AC microgrids (MGs). This paper studied a novel two-level control strategy composed of a modified droop controller at the primary level and a distributed finite-time (DFT) average controller in the secondary layer to achieve more precise active and reactive power sharing along with frequency and voltage alignment by implementing this strategy in an islanded AC MG. Thus, a typical AC MG, including three distributed generation (DG) units, is simulated in MATLAB/SIMULINK software, and the proposed method is first formulated, modeled, and then simulated. For validation and better comparison, the results obtained by the proposed method were compared to the conventional droop and other distributed methods in case studies of load changes and plugging in/out of DG units. The results proved that the proposed method appropriately shared active and reactive powers among DG units. It also efficiently restored the frequency and voltages of DG units to their nominal values. Moreover, a mathematical stability analysis is obtained that proved the stability of the proposed DFT-based secondary controller.

Keywords:

AC microgrid , distributed secondary controller , finite time , frequency/voltage alignment , modified droop controller , power-sharing