Torque Ripple Minimization of PMSM Drive with Speed Ripple Feedback Considering Non-linearities of PMSM

In this paper, a torque ripple minimization method using the speed ripple feedback is proposed. Generally, parameters of permanent magnet synchronous motor contain harmonics due to slotting and cross-coupling effects. Such nonlinearities cause torque and speed ripple, leading to noise and vibration during the operation of the machine. Therefore, this paper proposes the harmonic speed controller to mitigate torque ripple. First, the proposed controller estimates the harmonic speed of the machine. Next, in order to regulate the harmonic speed to zero, the proposed controller generates the harmonic torque reference. Since the proposed algorithm continuously uses the measured speed, it is able to generate accurate harmonic torque reference even when the known machine parameters contain errors. Furthermore, the proposed controller is composed of the two PI controllers for each harmonic speed so that both the magnitude and phase of the harmonic torque reference are controlled. As a result, considering both inertia and friction in the drive system, an accurate harmonic torque reference is generated. The experimental results demonstrate the validation and the effectiveness of the proposed method in variable speed operation.