Study on Torque Ripple Suppression in Low-Speed Permanent Magnet Synchronous Motors Using the Current Averaging Method and Harmonic Voltage Injection

Low-speed permanent magnet synchronous motors (LS-PMSM) have been widely adopted in fields such as mining and oil extraction due to their excellent stability and high efficiency. In practical applications, current harmonics cause a decline in motor control performance and, in severe cases, can damage the motor. This paper analyzes the mechanism of harmonic generation in LS-PMSM and derives a mathematical model for these harmonics. To address the 5th and 7th harmonics, which are particularly prominent, an improved harmonic voltage compensation module was added to the efficiency-optimized control system. The current averaging method was employed to extract harmonic currents in real time, and a fuzzy PI controller was used to perform closed-loop control of the harmonic currents, thereby obtaining accurate harmonic voltage compensation values. Finally, the control effectiveness of the harmonic voltage compensation was analyzed through simulation. The results indicate that this method can effectively suppress 5th and 7th harmonics and reduce torque ripple. Furthermore, the improved algorithm enhances the accuracy of harmonic current extraction and improves the dynamic performance of the controller.