Analytical Prediction and Minimization of Deadtime-Related Harmonics in Permanent Magnet Synchronous Motor

Abstract

The current, torque, and speed harmonics caused by deadtime effect in voltage source inverter (VSI)-fed permanent magnet synchronous motor (PMSM) usually lead to undesired torque ripple and extra electrical loss, etc. In this article, a mathematical model is proposed to predict the deadtime-related harmonics in VSI-fed field-oriented control PMSM, and a deadtime-related harmonic minimization method is proposed based on proportional-integral (PI) controllers tuning and under the premise of keeping the same control strategy. The expressions of current, torque, and speed harmonics caused by deadtime effects are obtained based on the complex amplitude expression of the voltage error harmonic and the derivation of the closed-loop transfer function from the deadtime-related voltage error to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d–q</i> axis current. Based on the derived expressions, optimization objective functions are built to search the optimal PI parameters for minimizing deadtime-related harmonics and reducing the torque ripple. The optimization constraint functions can be adjusted for transient performance requirements, so the transient performance can keep good even if the deadtime-related harmonics are minimized with the optimal PI parameters. Both simulation analysis and experimental data verify the correctness of the analytical prediction and the validity of the deadtime-related harmonic minimization method.