This paper analyzes system voltage oscillation and proposes a new systematic method for voltage stability control in the power system. Recently, renewable energy and distributed power generation have been introduced into power systems because of worldwide societal interest in environmental problems. However, renewable energies such as photovoltaic and wind power generation are unstable due to their dependence on natural sources. This has made power systems more complicated and potentially prone to large outages, particularly due to voltage instability phenomena. However, power system voltage stability has been handled as a static condition problem in many cases, and considered peak load situations where the load is expected to increase in the future. Yet when renewable energy penetration becomes significant, time evaluation of voltage stability becomes necessary. This paper analyzes dynamic voltage instability phenomena in power systems, and proposes a voltage stability control. Finally we carry out simulations for a single machine with one load model system to confirm the validity of the proposed method.