Rapid and Accurate Calculation of PWM-Induced Harmonic Currents in IPMSMs Considering Hysteresis and Eddy Current Reaction Effects

This article presents a method based on the small-signal time-harmonic finite element analysis (THFEA) to rapidly and accurately calculate pulsewidth modulation (PWM) induced harmonic currents in interior permanent magnet synchronous machines. Based on the small-signal THFEA, the functional relationships between harmonic voltages and harmonic currents are established, making it possible to rapidly calculate PWM-induced harmonic current spectra with PWM voltage spectra, which lays a solid foundation for achieving the fast and accurate calculation of PWM-induced ac copper losses. More importantly, in order to improve the accuracy of the small-signal model at high frequency, two-dimensional equivalent permanent magnet (PM) conductivity is used to accurately consider the PM eddy current reaction effect at different axial lengths, and a simple method is proposed to modify the differential reluctivity tensor obtained from the single B - H curve for considering the hysteresis and eddy current reaction effects in electrical steel sheets. The proposed method is compared with traditional time-stepping finite element method to demonstrate its merits in calculation speed and accuracy. The comparison of measured and calculated high-frequency impedances and current spectra also approves the accuracy of the proposed method.