This paper investigates a novel control strategy of supercapacitors to improve the dynamic stability of the interconnected PV-based AC microgrid clusters in standalone operation. An emerging definition of supercapacitors is proposed to emulate the dynamic inertia response. This definition establishes the dynamic connections between the state-of-charge (SOC), the frequency of the standalone AC microgrid clusters and the power of supercapacitors. Then this paper presents a theoretical analysis of dynamic stability on two-area PV microgrid clusters. According to the type of AC microgrid, the dynamic inertia constant is also analyzed. Based on the dynamic stability analysis of two-area PV microgrid clusters and the dynamic inertia constant analysis of supercapacitors, the adjustable virtual inertia control method of supercapacitors is proposed to extract the stored energy for the dynamic inertia response. The aim of the proposed control scheme is to solve the low inertia and weak damping of the standalone interconnected PV microgrid clusters. The effectiveness of the proposed control scheme is validated by Matlab/Simulink platform.