A multistage H‐infinity–based controller for adjusting voltage and frequency and improving power quality in islanded microgrids

摘要

This paper proposes a novel methodology for controlling voltage and frequency of islanded microgrids and meanwhile improving the system power quality. The proposed methodology is based on applying a multi-stage H-Infinity (H infinity) controller with different control loops to restore the nominal values of voltage and frequency after any load variation. These control loops include power control, current control, and voltage control loops. The H infinity is also applied with an LCL filter to enhance the system power quality. The proposed controller is applied to a test system under three different loading conditions and the obtained results are compared with that obtained by applying the model predictive control (MPC) method. The results are compared with that obtained by applying a proposed traditional control method in the same test system. A comparison between the droop controller and the proposed controller, MPC is performed based on fitness value, controller response time, and maximum frequency deviation. In addition, the system stability is analysed using root locus, system step response, singular value decomposition, and bode diagram. The results prove the effectiveness and the efficiency of the proposed method in restoring voltage and frequency and improving the system power quality.