Under the context of a high proportion of renewable energy generation and widespread application of power electronic devices, the frequency stability of power systems is facing severe challenges. To address frequency instability issues of isolated synchronous grids that lack the support of large interconnected AC networks, this paper investigates technical strategies adopted by international isolated synchronous grids under high renewable energy penetration, and proposes technical reference pathways for developing a new-type power system tailored to the conditions of the China Southern Power Grid. First, the technical progress of the grids of Ireland, Texas, and Australia in addressing frequency stability challenges under high renewable penetration is reviewed. Then, frequency stability measures are summarized, including accurate assessment and optimization of critical inertia, the establishment of online inertia monitoring systems, and new methods for managing frequency regulation resources. The effectiveness of these measures in improving frequency stability in each isolated synchronous grid is also analyzed. Finally, a quantitative analysis is conducted based on the actual situation of the China Southern Power Grid, providing technical references and insights for the development of new-type power systems.