Stability analysis of a magnetically-levitated large flywheel using flexible rotor modeling

Stability analysis of the flywheel energy storage system supported by active magnetic bearings is studied in this paper. The system is designed to store 5 kWh at maximum speed of 18,000 rpm and the gyroscopic coupling is strong that the dynamics of system changes with respect to the running speed. To analyze the stability of the system accurately, we derived mathematical models for the system components including the rotor, active magnetic bearings, amplifiers and sensors. The rotor model is based either on rigid-body dynamics or flexible rotor model using finite-element approach. We checked the stability of the system using the derived models and found that the model based rigid-body dynamics can be misleading, and an accurate rotor model using flexible rotor dynamics must be used in order to predict the stability properly.