Although renewable energy sources become an important point in terms of increasing energy source diversity and decreasing the carbon emissions, power system stability suffers from increasing renewable energy and distributed generation penetration to the power system. Therefore, grid-scale energy storage systems are introduced to improve the power system stability. In this paper, large scale energy storage technologies that connected to the power system to improve the power system stability and power quality are reviewed and explained. Energy storage technologies for grid scale energy storage systems, application of energy storage systems, and control methods are discussed and summarized. In addition, some comparison results are given about energy storage technologies for grid-scale applications.