Research on Optimal Capacity Allocation of Hybrid Energy Storage System Consisting of Li-Ion Battery and Redox Flow Battery for Smoothing Wind Power Fluctuations

The growth in wind turbine capacity and grid integration is increasingly disrupting grid stability. This article proposes a hybrid energy storage system (HESS) using lithium-ion batteries (LIB) and vanadium redox flow batteries (VRFB) to effectively smooth wind power output through capacity optimization. First, a coordinated operation framework is developed based on the characteristics of both energy storage types. Empirical modal decomposition is used to separate the raw wind power into a direct grid-connected component and a fluctuation component that the HESS needs to manage. A two-layer energy optimization management strategy is then designed to optimize short-term responses to wind power fluctuations and long-term coordination of the storage system's charging state. Next, a capacity allocation model for the HESS is established to minimize comprehensive costs while considering charging/discharging power and charge state constraints. Finally, data from a 200 MW wind power plant are analyzed to verify the model's effectiveness. The results show that the HESS, combining LIB and VRFB, enhances system efficiency and economic performance while meeting wind power fluctuation smoothing needs. This provides valuable theoretical and practical guidance for the storage capacity configuration of new energy systems.