Design and test of a 300Wh composites flywheel energy storage prototype with active magnetic bearings

A flywheel energy storage prototype was designed and built to get high energy density and low bearing loss. The aluminium alloy hub formed by thin plate and shell connected the bearing shaft and the rim which was composed by glass fibre and carbon fibre reinforced composite. Finite element analysis on stress field of the composite flywheel indicated that the flywheel could run at the rated speed of 700 r/s (rotation per second) safely. The flywheel was supported by 5-degrees of freedom active magnetic bearings (AMBs). The flexible modes of the rimhub-shaft system were analyzed by using finite element (FE) based software. The complex non-synchronous vibration was observed, analyzed and suppressed during testing of the flywheel system. The control method of adding phase compensator to the velocity channel in the cross feedback controller was presented to make the supporting AMBs work better while the flywheel passed through its first flexible mode. The field balancing at high speeds enabled the flywheel to reach the speed of 475 r/s with small amplitude of synchronous response.