A Miniature Flywheel Energy Storage System Supported by Hybrid Magnetic Bearings with H-Inf. Controller

his paper discusses a prototype of miniature flywheel energy storage system. The system consists of a rotor with a flywheel disk and a pair of hybrid magnetic bearings (HMBs). The HMB is composed of both superconducting magnetic bearings (SMBs) and active magnetic bearings (AMBs). The rotor measures 270 mm in length and 24 mm in diameter with a flywheel disk (100 mm in diameter). The rotor mass with the flywheel is 1.2 kg, which is supported by the repulsive force between two permanent magnets (PMs). The rotor model is represented by secondorder functions. H-infinity control method and zero bias method are applied to the AMB. In this paper, the design and dynamics of the flywheel energy storage system are discussed. The H-infinity controller is successfully applied to the system. The experimental results show that by using the HMBs the displacement of the rotor is much smaller than that with SMBs, that the HMBs suppress both radial and axial displacements, and that the H infinity control is applicable to the storage system.