A Negative Stiffness Injection Method for PMSM in the Five-DoF Magnetic Levitation System to Suppress the Vibration

Magnetic bearings (MBs) are widely applied in high-speed permanent magnet synchronous motors (PMSMs), which can reduce the friction loss and mechanical vibration. However, variation of air-gap length between stator and rotor during levitation can generate the unbalanced magnetic pull (UMP), which increases the vibration of levitation system. Therefore, a negative stiffness injection method for PMSM in the levitation system is proposed in this paper, which weakens the vibration acceleration of shell by injecting negative d-axis current. Simulation results show that all orders vibration accelerations are suppressed after adopting the proposed method. Besides, the vibration acceleration can be reduced with the increase of negative stiffness.