Harmonic disturbance suppression for magnetic bearing system based on synchronous rotating frame transformation

Harmonic disturbance is an obstacle to stable operation of magnetic bearing systems. In this paper, a novel method to suppress harmonic disturbance is proposed based on synchronous rotating frame (SRF) transformation. Among all harmonic disturbances, the impact of the third harmonic disturbance is relatively large. Thus, this paper is mainly focused on the third harmonic disturbance suppression. The harmonic disturbance is extracted by the method based on the SRF transformation and first-order low-pass filter. The method of complex-coefficient is employed to derive the transfer function. The Nyquist criterion and root locus approach are used to analyze the stability of the system. Considering both stability and dynamic performance, an analytical formula of optimal parameter is designed. Simulation results and experimental results show that the method proposed can suppress harmonic disturbance effectively. Compared with the conventional methods of harmonic disturbance suppression, the proposed method has better dynamic performance. This method has only one parameter and an optimal state of the system can be achieved using the optimal parameter which can be adjusted conveniently.