Rotor Loss Analysis of PMSM in Flywheel Energy Storage System as Uninterruptable Power Supply

The limit of the maximum speed of flywheel rotation in a flywheel energy storage system (FESS) is broken with the improvement of modern science and technology [4]- [7]. The FESS in this paper is designed for short-time and high-power application. The loss of mechanical friction is reduced by the application of magnetic bearing and vacuum. The accuracy and stabilization of the system are much better than before owing to advanced power electronics. Permanent magnet synchronous machine (PMSM) is selected as a flywheel driving motor by its high-efficiency and good control feature. The FESS in this paper is used as uninterruptable power supply when the power source is needed to change. PMSM in FESS is running under no-load with a very high speed. The duration of maximum load is less than 1 min. The no-load loss of PMSM in FESS is significantly important to efficiency and reliability of the system. This paper focuses on rotor loss in the no-load running condition. The theoretical principle is provided for design of FESS with PMSM.