Rotation-Frequency Oscillations Suppression Strategy For Ac Drive System With Large Inertia Rotating Load

Mechanical faults in AC drive systems lead generally to periodic load torque ripple which reflects as speed vibration and leads to harmonic components in motor stator current. The deterioration of speed and stator current, called rotation-frequency oscillations in this study, may degrade motor control accuracy and even cause for instability. In this study, a strategy using active control of stator current is proposed to suppress the rotation-frequency oscillations in AC drive systems. First, the magnetomotive force and permeance approach is used to study the influence of the mechanical faults on the stator current of permanent magnet synchronous motor (PMSM). Second, in the proposed strategy, an improved current regulator cascading a proportional-integral regulator with a quasi-proportional resonance (QPR) regulator is designed, and the mechanism of rotation-frequency oscillations suppression strategy is analysed. In addition, digital realisation method and parameters design process for QPR regulator are introduced. Experimental evaluation of the proposed strategy is implemented on a PMSM traction system under mechanical faults, load disturbance and so on. Test results show that with the proposed strategy, speed vibration and current harmonic components caused by mechanical faults are suppressed significantly.