Adaptive Aperiodic and Periodic Disturbances Observer Based on Enhanced LESO for Speed Fluctuation Suppression of PMSM

Extended state observer (ESO) has been widely used in torque disturbances compensation due to its outstanding performance. However, achieving accurate compensation for periodic torque disturbances using conventional methods is difficult, which results in significant speed fluctuations and a consequent reduction in the performance of the control system. To resolve the problem, an adaptive aperiodic and periodic disturbances observer based on enhance linear ESO (LESO) is proposed in this paper. The periodic and aperiodic disturbances are accurately estimated by one LESO and another cascading LESO, respectively. And then, the estimated disturbances are used for inner control loop feedforward to suppress speed fluctuation. In addition, a frequency locked loop (FLL) is employed to enable the feedback error gain of the constructed enhanced LESO to adaptively track the frequency of periodic disturbances. Further, the stability of the enhanced LESO and FLL are thoroughly discussed and rigorously proven. Finally, the feasibility and effectiveness of the proposed scheme have been verified on a 5.5 kW PMSM.