Enhancing Low-Carrier-Ratio Induction Motors with Pulse Pattern Control for Peak-to-peak Torque Ripple Optimization

Aiming at mitigating the torque ripple in high-power traction systems operating under low-carrier-ratio conditions, a peak-to-peak torque ripple minimization pulsewidth modulation (PTRMPWM) strategy is proposed for the induction motors. The relationship between voltage vector sequences and flux linkage is first established in the proposed method. Then, a novel criterion is developed for the evaluation of torque harmonics and the reconstruction of electromechanical torque. Moreover, the functional relationship between induction motors’ peak‑to‑peak torque ripple and switching angles are derived, and a constraint equation is formulated. Additionally, a computational method is developed to determine the solution set of switching angles, which is independent of motor parameters and load conditions. Also, a simple and robust modulation mode transition strategy is introduced, ensuring stable operation of the proposed modulation modes. Finally, the effectiveness of the proposed modulation strategy is validated through simulations and experiments on a scaled-down experimental platform, where it is compared with existing optimal PWM methods. The experimental results demonstrate a significant reduction in torque ripple, achieving up to a 27.17% decrease compared to conventional approaches.