Torque ripple reduction of permanent magnet synchronous motor

Torque Ripple Reduction of Permanent Magnet Synchronous Motor Permanent Magnet Synchronous Motors (PMSM) are one of the most preferred electric motors because of their high power density, high efficiency and high torque/inertia ratio. Besides, PMSM's are small in size and require less maintenance. Because of these outstanding features, they have been widely used in various applications. In PMSM's Field Oriented Control (FOC), Direct Torque Control (DTC) and v/f control methods can be applied. In this study, the FOC method which provides a lower torque ripple compared to other control methods is preferred. The main disadvantage of PMSM's is torque ripples. These ripples can be caused from the structure of motor, and may be due to measurement and control systems. The torque ripples emerged in PMSM's are generally periodic. Therefore one of the most effective methods for the suppression of the torque ripples is the injection of optimal current harmonics. However, the injected harmonics should also be appropriate with respect to varying motor operating conditions. This requirement can be satisfied using an online and adaptive control mechanism. In this study, Adaptive Decision Fusion (ADF) based methods are developed to inject current harmonics in appropriate amplitude and phase. In these methods, decision values are linearly combined with weights which are updated online according to an active fusion method based on performing orthogonal projections onto convex sets describing these values. In harmonic injection, gradient of the speed error is used. By using the value of this error, speed and torque ripples have been tried to be reduced with three different methods by compensating the values of three different magnitudes in the motor. In the first method the q-axis current, in the second method q-axis voltage and in the last method, the reference value of the q-axis current has been compensated by injecting the appropriate harmonics. When determining the appropriate harmonic orders, in addition to the 1st, 2nd, and 6th harmonics mentioned in the literature, initially by running the motor in different operating conditions, the dominant harmonics that are effective in ripples have been specified. Experimental results show that, the speed and torque ripples are effectively decreased by all the three methods at different speeds and loads. Since at lower speeds and on load operating conditions more ripples occur, the validity of the method significantly arises. Keywords: Permanent Magnet Synchronous Motor, field oriented control, torque ripple, Adaptive decision fusion