Smooth and Robust Current Control of PMSMs With Decoupling-Type Extended State Observers

This article is focused on the current harmonic suppression of a permanent magnet machine with the enhanced extended state observers (ESOs). For traditional ESO, there are three defects: coupling issue between fundamental current regulation (FCR) and disturbance attenuation (DA), limited periodic disturbance attenuation (PDA) property, and coupling issue between aperiodic disturbance attenuation (APDA) and PDA. Three kinds of enhanced ESOs are then proposed. That is decoupling-type ESO (DESO), resonance-type DESO (RDESO), and notch-type DESO (NDESO). For DESO, the structure of traditional ESO is redesigned. Decoupling between FCR and DA is, thus, achieved but the other two defects still exist. For RDESO, an additional link is inserted into DESO. Foregoing decoupling property and enhanced PDA are thus achieved simultaneously. Whereas, decoupling between APDA and PDA still cannot be reached. For NDESO, the added link in RDESO is redesigned. Foregoing three defects are thus all solved. Experiments on a test rig have verified the effectiveness of proposed methods.