Torque Ripple Reduction for Permanent Magnet Synchronous Motors with Asymmetrical Back Electromotive Forces by Maintaining Instantaneous Input Active Power

Due to manufacturing imperfections and assembly tolerances, operating temperature variations, faulty conditions, and other factors, the back electromotive forces become unavoidably asymmetrical, leading to significant torque ripples. In order to deal with this issue, this paper proposes a method to reduce the torque ripple in permanent magnet synchronous motors with asymmetrical back electromotive forces supplied by current source inverters. This method is achieved by maintaining a constant instantaneous input active power through the injection of appropriate negative-sequence currents. The proposed method is easy to implement and does not require measurement of the motor parameters, such as the asymmetrical back electromotive forces. Simulation results have confirmed the effectiveness of the proposed torque ripple reduction method.