A review on grid-forming flywheel energy storage: Enabling active support in high-penetration wind grids

The transition to high-penetration wind power introduces critical frequency stability and low-inertia challenges to modern power grids. Flywheel Energy Storage Systems (FESS), characterized by millisecond-level dynamic response and inherent electromechanical isomorphism, offer a physically backed approach to mitigating these vulnerabilities. This paper presents a comprehensive review of FESS applications in wind power generation, exploring the connection between component-level physical constraints and system-level active grid support. We first analyze the evolutionary trajectories and multi-physics limitations of core technologies, including composite rotors, magnetic bearings, and vacuum thermal management. Building upon this hardware foundation, the review systematically evaluates the paradigm shift toward Grid-Forming (GFM) control, highlighting how adaptive Virtual Synchronous Generator (VSG) strategies and distributed consensus protocols aim to balance transient grid support with mechanical fatigue limits. Furthermore, we synthesize recent advancements in multi-objective capacity optimization and time-frequency decoupling for flywheel-battery Hybrid Energy Storage Systems (HESS). The active defense capabilities of FESS during extreme grid events, notably black start and Low Voltage Ride-Through (LVRT), are also critically examined. Finally, the paper outlines future trajectories toward physics-informed intelligent control and Modular Multilevel Converter (MMC) offshore integration, providing valuable insights for leveraging FESS as a stabilization asset in renewable-dominated power systems.