Model-free predictive current control (MFPCC) that only needs the input and output data of the system can eliminate the influence of the motor parameters mismatch. In the conventional finite control set MFPCC (FCS-MFPCC), the delay and distortion that exist in the current variations update can affect the future current prediction and the current tracking performance. This article studies an improved current variations updating mechanism to improve the update frequency. Based on the ultralocal model, the current variations corresponding to the different voltage vectors can be updated at every control period. Then, the stator currents can be predicted with the accurate current variations, and the optimal voltage vector can be selected by minimizing the cost function without using motor parameters. Besides, a sliding mode observer is designed to observe the ultralocal model's parameters fast. Furthermore, the two voltage vectors and the optimal duration are introduced to improve the current tracking performance. Meanwhile, in order to guarantee the accuracy of the future current prediction, the current compensation strategy is studied to revise the current estimation. Finally, the effectiveness of the proposed FCS-MFPCC strategy is verified through the simulation and experimental results.

Traditional active disturbance rejection control (ADRC) is not adequately capable to deal with current disturbances including periodic harmonics of permanent magnet synchronous motor (PMSM). Thus, an improved ADRC with a cascade extended state observer (CESO) based on quasi-generalized integrator (QGI) is proposed to attenuate the periodic and aperiodic disturbances in the current loop. In the proposed strategy, a CESO with two cascaded levels is designed to enhance the estimation accuracy of aperiodic disturbances and decrease the steady-state observation error of periodic harmonics. The QGI is embedded into the second cascade level of CESO to improve its estimation accuracy harmonic disturbances. With the periodic harmonics accurately estimated, the subsequent improved ADRC based on feedback control law can effectively enhance the rejection of such disturbances. The theoretical analysis is comprehensively conducted to investigate the disturbances estimation performance, stability, disturbances rejection capability and robustness, while the parameter tuning strategy is studied based on the control bandwidth. Finally, the effectiveness and superiority of the proposed scheme are verified on a PMSM bench through the experiments.

A control strategy that combines a novel reduced-order vector resonant controller and a generalized active disturbance rejection control (ROVR-GADRC) is proposed in this article to suppress the current disturbances containing periodic harmonics of a permanent-magnet synchronous motor (PMSM). First, the ROVR controller is designed, which integrates the advantages of both the complex coefficient filter and the vector resonant controller. Compared with the existing resonant control methods, the proposed ROVR can separate and extract the positive and negative sequence harmonics, and avoid the phase delay and peak point simultaneously. Second, a generalized extended state observer is introduced to enhance the suppression of low-frequency disturbance. Then, the composite control strategy is developed. Besides, the stability, disturbance rejection performance, parameters configuration, robustness, and tracking performance of the proposed ROVR-GADRC are comprehensively analyzed. The proposed current controller simultaneously performs harmonics suppression of specific phase sequence and other unknown disturbances attenuation. Finally, the feasibility and effectiveness of the proposed method is verified on a PMSM platform through the experimental results.

It is well-known that there is a trade-off between robustness to disturbances and measurement noise sensitivity in the active disturbance rejection control (ADRC) framework based on extended state observer (ESO). To this end, this article proposes a novel variable structure ADRC (VSADRC) for permanent magnet synchronous motor (PMSM) speed control to enhance the disturbance rejection and the noise suppression simultaneously. In this technology, a variable structure ESO (VSESO) with two-stage interconnected observer is proposed to avoid directly employing noise-contaminated signal, in which the extended disturbance differential is appended to achieve higher-level disturbance estimation. By doing this, at low frequencies, the magnitude curve slope is 40 dB/dec for the VSESO and 20 dB/dec for ESO, while at high frequencies, it is –40 dB/dec for the VSESO and –20 dB/dec for ESO. Furthermore, the stability and output characteristics of the proposed strategy are comprehensively investigated. It is revealed that the superiority of the studied scheme in disturbance rejection and noise suppression. Finally, the experimental results verify the feasibility and effectiveness of the proposed VSADRC.

Periodic torque ripples caused by current harmonics seriously affect the control accuracy of the Permanent magnet synchronous motors (PMSMs). A conventional approach to reducing current harmonics is the use of a proportional-integral resonant controller in the current loop. Nonetheless, harmonics can still cause steady-state errors. Furthermore, the PI-based control structure is sensitive to parameter mismatches and uncertain disturbances, which will decrease the tracking performance of the current loop. To overcome the drawbacks of the traditional control method, a hybrid robust resonant control strategy was developed in this study. First, a vector resonant controller was enhanced by introducing fractional-order calculus (denoted as the fractional-order vector resonant (FOVR) controller in this article) so that it can suppress harmonic components more effectively. Then, a robust internal mode controller (Robust-IMC) was designed to improve the robustness and dynamic response and further reduce the current harmonics. Finally, by combining the FOVR controller and Robust-IMC, a control method-FOVR-Robust-IMC was designed as the robust control law to ensure satisfactory robustness and harmonics suppression performance. Meanwhile, the stability and robust stability of the developed control strategy were also analyzed. The results demonstrated that the proposed FOVR-Robust-IMC effectively reduced the harmonic components and improved the robustness to parameter mismatch.