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

Document Type : Original Article

Authors

Department of Electrical Engineering, Nour Branch of Islamic Azad University, Nour, Iran

Abstract

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 studies 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 are compared to the conventional droop and other distributed methods in case studies of load changes and plugging in/out of DG units. The results prove that the proposed method appropriately shares active and reactive powers among DG units. It also efficiently restores the frequency and voltages of DG units to their nominal values. Moreover, a mathematical stability analysis is obtained that proves the stability of the proposed DFT-based secondary controller.

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