Adaptive Sliding-Mode-Based Speed Control in Finite Control Set Model Predictive Torque Control for Induction Motors

The conventional model predictive torque control (MPTC) for induction motor drives evaluates the electromagnetic torque and stator flux linkage in the cost function. However, in the speed outer loop design, the torque reference in the cost function generally utilizes a classic proportional-integral (PI) controller, which is not only dependent on motor parameters but also sensitive to the change of the load torque. In this article, an adaptive sliding-mode-control-based MPTC (ASMC-MPTC) method is proposed to improve the robustness of the finite control set model predictive control (FCS-MPC). First, the influence of the mismatched parameters for FCS-MPTC is introduced and the shortcoming of the PI-based MPTC (PI-MPTC) is analyzed. Then, a sliding-mode-control-based MPTC (SMC-MPTC) is studied, in which the exponential reaching law is introduced to control the trajectories of the state variables. To further improve the control performance of SMC-MPTC, the exponential reaching law is optimized to adjust the switching gain adaptively, thus the ASMC-MPTC is proposed. The PI-MPTC, SMC-MPTC, and ASMC-MPTC are compared theoretically and experimentally, and the results show that the proposed ASMC-MPTC has the best disturbance rejection ability and robustness against motor parameters variation and load torque change.