Direct Single-Loop μ-Synthesis Voltage Control for Suppression of Multiple Resonances in Microgrids with Power-Factor Correction Capacitors

This paper presents a robust single-loop direct voltage control strategy featuring effective suppression of uncertain resonant modes generated due power-factor correction (PFC) capacitors and residential capacitive loads in distributed generation (DG) microgrids. The proposed controller adopts an improved uncertainty modeling approach, which facilities the realization of a robust controller based on structured singular values (mu) analysis. The resultant controller is used as a direct voltage controller where no additional damping technique, either passive or active, is required. This feature reduces the sensor requirements in the DG interface controller and enhances the bandwidth characteristics of the closed-loop voltage-controlled converter. Mathematical and comparative analyses are provided to show the advantages of proposed mu-synthesis controller over the conventional H-infinity controller in maintaining robust stability as well as robust performance of the microgrid in presence of parameter uncertainties and uncertain resonant peaks caused by connection of PFC capacitors. Systematic design approach for the proposed controller is presented. Time-domain simulation studies and comparative experimental results are presented to show the effectiveness and robustness of the proposed controller in microgrid applications.