In modern power systems, electronic-based power sources such as wind generators or photovoltaic (PV) systems are increasing. That is, the power from traditional generators is reduced. Thus, system rotating inertia is reduced rapidly if renewable power generation increases. To mitigate the risk in a power system with low inertia, various effective methods have been proposed including the developments of synthetic inertia, energy storage systems, demand responses, and synchronous compensators. In this study, we applied synchronous condensers to power systems with a high penetration of renewable power generation. By introducing the principles and controls of a typical synchronous condenser, we summarize its operating experience and projects in various countries. A case study was carried out to simulate steady-state and transient responses in power systems with synchronous condensers. As a result, the advantages of installing synchronous condensers in a low-inertia power system are determined.