Frequency stability in microgrids under islanded operation mode is one of the most important control problems in new power system design. Due to increasing number of microgrids (MGs) in power systems, and variable inherent of renewable energy sources, this issue gets more attention recently. In industrial environments, PI controllers due to low-cost, reliability and simplicity in design are more popular; but in new power systems these controllers may not provide desirable performance. For sake of this challenge, in this paper after a brief review on the frequency control in MGs, a new intelligent secondary control method using a supervisory fuzzy logic controller is proposed with two main goals: holding of structure simplicity that is desirable in industrial environment and implementable capability without opening the existing conventional PI control loops. In this method which is applied on an AC MG, if system dynamics change, the PI controller parameters do not need to be retuning, and the supervisory fuzzy logic controller minimizes the MG frequency deviation.
