The fluctuation and unpredictability of renewable energy generation pose challenges to the safety, stability, and economic operation of power systems. Energy storage can effectively smooth the fluctuations of renewable energy generation and track the power generation output plan, eliminating the impact of prediction errors. This chapter mainly analyzes the impact of renewable energy generation fluctuations on the operation of power systems, and the main control methods of energy storage to smooth wind power fluctuations, with wind power as the main focus.