Torque Ripple Modeling and Mitigation for PMSM by Harmonic Current Injection Based on General Airgap Field Modulation Theory

In this paper, the modeling and mitigation method of torque ripple are investigated for permanent-magnet synchronous motor (PMSM). A new torque ripple model is proposed for three-phase PMSM based on general airgap field modulation theory. The mapping relationship between the torque order and the current order has been revealed. The qualitative and quantitative relationship between the stator harmonic current and torque ripple is established directly without other intermediate variables. The phase and amplitude of the torque component are found to be proportional to the phase and amplitude of the injected harmonic current. Therefore, only a few constant coefficients are required by finite element analysis (FEA) simulation. With the proposed torque model, directional mitigation of torque ripple can be realized by harmonic current injection method with low computational burden by FEA. Repetitive control is employed for harmonic current injection. FEA simulation and experimental results at different operating conditions verify the validity of the proposed torque model and ripple mitigation method.