Study on Disturbance Observer Designs for Digital Current Control of IPMSM

Disturbance observers are widely used in the field of machine current control to improve parameter robustness. However, when the machines run at high speed and low carrier ratio, whether the traditional disturbance observer designs are still effective is still unknown, which is an interesting topic to explore. In this paper, different disturbance observer designs are studied, which shows that common extended state observer (ESO) and luenberger disturbance observer (LDO) suffer serious performance losses at low carrier ratios. To address this problem, an LDO with extra state feedback (LDO_ESF) design is proposed. The effectiveness is verified by experiments.