Power System Transient Support System Based on Synchronous Machine With Electromagnetically Coupled High-Inertia Flywheel

The increasing penetration of renewable energy, combined with the retirement of traditional thermal power plants, has caused significant transient issues in modern power systems. While conventional synchronous condensers (SCs) are widely deployed to address these transient challenges, their inertial support capability is fundamentally limited by the passive response characteristic and the relatively low inertia constant. To provide high-quality and robust transient support for the power grid, this paper proposes a novel Synchronous Machine with Electromagnetically Coupled High-Inertia Flywheel (SM-ECF) system. Specifically, the electromagnetic coupler (EC) allows for flexible differential speed operation of the flywheel and enables the rapid delivery of short-term active power. This configuration not only enables effective utilization of the flywheel's kinetic energy but also fully leverages the inherent advantages of the synchronous machine (SM). Subsequently, the detailed configuration, operating principles, and systematic control strategies of the proposed system are described. Furthermore, an active inertia support strategy is proposed, enabling the SM-ECF to provide highly flexible and effective inertial support. Finally, experimental validations confirm the effectiveness of the proposed system, demonstrating significant improvements in both the frequency nadir and the Rate of Change of Frequency (RoCoF).