This paper presents an advanced control method for islanded microgrids. The proposed control method is based on H-infinity (H∞) controller. The method is applied to regulate the system frequency and voltage to allowable range against the disturbances caused by load variations and meanwhile improve the system power quality in islanded MG. To prove how efficient is the proposed method, it is compared with two other controllers including a base V-f controller and a conventional droop controller. The V-f control method consists of two control loops to control the voltage source inverter (VSI). The conventional control method applies a droop control with the V-f control method to improve its performance. The proposed control method is based on H∞ to modify the operation of the conventional control method. The three controllers are applied to a test system simulated in Matlab/Simulink environment for two case studies. The first one is a MG supplying linear loads (i.e. no harmonics effect), whereas the other one is a MG supplying nonlinear loads. The results prove that the proposed control method is more efficient than the other two methods in adjusting the system voltage and frequency of the islanded MG against the disturbances caused by load variations. It also can improve the system power quality by reducing the THD of current and voltage waveforms.
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