Control for Passing Through Critical Speeds of an Energy Storage Flywheel System by Bias Current Control

In this paper, we address a new method of switching the critical speed by control the bias current of magnetic bearing. The bias is changeable in the sense that is a function of the rotational speed, and varies on-line in a manner that the critical speed of the rotor is controlled far away from the rotational speed of the rotor. The total stiffness of system is switched with the additional stiffness, the critical speed is switched also. In order to demonstrate the validity of the proposed method, the method is applied to a 10MWh class energy storage flywheel system to realize the control of passing through critical speed in the range of control. A simulation study illustrates the performance of the proposed bias current control method is validity for control of passing through the critical of magnetic bearing systems.