High-Capacity, Low-Power Axial AMB for Flywheel Energy Storage Systems: Design, Analysis, and Validation

Flywheel Energy Storage System (FESS) has the characteristics of fast charging and discharging, suitable for integration with renewable energy to stabilize the grid. The capacity of a Flywheel Energy Storage System (FESS) is directly proportional to its rotor mass. Consequently, the higher the load its axial bearing can support, the greater the flywheel energy storage capacity it can achieve. When solely relying on electromagnets as suspension actuators, Active Magnetic Bearings (AMBs) face a significant limitation in their application to FESS due to substantial energy losses. This study presents a novel axial AMB that leverages permanent magnet forces to counterbalance rotor weight. Through a combination of theoretical analysis, simulation, and experimental validation, the axial AMB's structure is proven to exhibit excellent linear characteristics. Our experiments showed that the axial AMB operates effectively with a Linear Quadratic Regulator (LQR) controller. Notably, the control current decreases linearly as the supported axial weight increases. Importantly, when the output axial force equals the flywheel's weight, the system achieves a notably low current consumption. As a crucial component bearing the flywheel's load, the axial AMB's linear relationship between axial output and control current is vital for controller robustness. This study proposes an axial AMB exhibiting linearity and low power loss, aiming to make a pivotal contribution to the development of magnetic suspension flywheel systems.