Harmonic Suppression for PMSM Applied to MSTMP Based on Virtual Even-Order Fractional Repetitive Controller

Current harmonics will produce losses, which make motor heated. The high temperature of the motor applied to turbo molecular pump (TMP) will degrade ultrahigh vacuum performance severely. Current harmonics should be suppressed effectively. The repetitive controller (RC) has been widely used in harmonic suppression. To address key challenges of conventional RC, this article proposes a novel virtual even-order fractional RC. First, the virtual fundamental frequency is introduced and the even-order RC is constructed. Second, the Lagrange interpolation is designed to fit the fractional part of the delay coefficient. Then, the low-pass filter (LPF) is replaced by a finite impulse response (FIR) filter and is removed out of RC internal model. The proposed method can improve the convergence speed of harmonic suppression. The tracking deviation in the high-frequency band is reduced and the harmonic suppression accuracy is improved. Finally, the effectiveness of the method is verified on the high-speed magnetically suspended TMP.

I. Introduction

Turbo molecular pump (TMP) is widely used in applications where vacuum environment is required, such as semiconductor manufacturing equipment, ultrahigh vacuum (UHV) and mass spectrometry. Compared with conventional TMP, the magnetically suspended TMP (MSTMP) takes the advantages of no contact, no frictional losses and elimination of the lubrication [1]. Thus, MSTMP is used to get the ultraclean vacuum environment [2]. The turbine, which is the load, is driven by a motor and rotates at a high speed. The permanent magnet synchronous motor (PMSM) has the advantages of compact structure, high power density and high operating efficiency [3], [4], which is the key drive unit in MSTMP.