Current total harmonic distortion calculation of interior permanent magnet synchronous traction motors for HEV/BEV applications

Abstract

Hybrid electric vehicles and battery electric vehicles use three-phase power inverter(s) to drive electric traction motor(s) using pulse width modulation (PWM) methods. Various types of PWM schemes provide the same fundamental component of the output voltage but different harmonic components. This results in different harmonic flux linkage and harmonic current, causing different machine copper loss and core losses. An accurate model of the current total harmonic distortion (THD) for various PWM schemes can provide an insight into which PWM method can minimize the electric machine copper loss and core losses, hence, increasing the overall fuel economy of the vehicle system. Most of HEV/BEV products use interior permanent magnet (IPM) synchronous machines for traction. Literature review shows that existing methods of calculating the current THD are only valid for an inductance load or a surface permanent magnet synchronous machine with equal d- and q-axis inductances. Error occurs if the method is applied to an interior permanent magnet synchronous machine with unequal d- and q-axis inductances. This paper investigates a method that can accurately calculate the current THD for IPM machines. The accuracy of the proposed method is verified by computer simulations.