With rapid growth of renewable energy sources (RESs) in modern power systems, the microgrids (µGs) have become more susceptible to the disturbances (e.g. large frequency/voltage fluctuations) than the conventional power systems due to decreasing their inertia constant. This low system inertia issue could affect the µGs stability and resiliency in the situation of uncertainties, thus threaten their dynamic security. Hence, preserving µG dynamic security is one of the important challenges, which is addressed in this study. Therefore, this study proposes a novel concept of frequency control incorporating a virtual inertia control-based optimal proportional–integral controller to emulate virtual inertia into the µG control loop, thus stabilising µG frequency during high penetration of RESs. Moreover, the proposed virtual inertia control system is coordinated with digital over/under frequency protection for enhancement of the frequency stability and preservation of the µG dynamic security because of the high integration level of the RESs. The simulation results of the studied µG are carried out using MATLAB/Simulink^® software to validate the effectiveness of the proposed coordination scheme. Results approved that the proposed coordination scheme can effectively regulate the µG frequency and guarantee robust performance to preserve the dynamic security of µG with high penetration of RESs for different contingencies.