This paper addresses ac microgrid stability under high penetration of converter-interfaced loads (CILs). According to the Nyquist admittance ratio criterion, destabilizing interaction dynamics are yielded among the interfacing voltage-source inverter (VSI) of the ac microgrid and CILs. Active stabilization techniques are proposed to maintain the overall system stability from the VSI side using admittance-based small signal analysis. Sensitivity and robustness analyses are presented to assess the dynamic coupling among active damping and voltage tracking controllers of the interfacing VSI. A complete Matlab/Simulink model of an ac microgrid with multiple CILs is used to demonstrate the effectiveness of the proposed active compensation techniques.