418 Journal of Power Electronics, Vol. 11, No. 4, July 2011 JPE 11-4-4 Parameter Identification of an Induction Motor Drive with Magnetic Saturation for Electric Vehicle Yu-Seok Jeong † and Jun-Young Lee * †* Dept. of Electrical Eng., Myongji University, Yongin, Korea Abstract This paper presents a simulation model and a parameter identification scheme of an induction motor drive for electric vehicle. The induction motor in automotive applications should operate in very high efficiency and achieve the maximum-torque-per-ampere (MTPA) feature even with saturated magnetic flux under very high torque. The indirect vector control which is typically adopted in traction drive system requires precise information of motor parameters, particularly rotor time constants. This work models an induction motor considering magnetic saturation and proposes an empirical identification method using the current controller in the synchronous reference frame. The proposed method is applied to a 22kW-rated induction motor for electric vehicle. Key Words: Electric vehicle, Induction motor, Magnetic saturation, Parameter identification, Simulation model I. I NTRODUCTION Electric Vehicle (EV) typically employs a permanent mag- net (PM) synchronous machine for propulsion owing to its high efficiency and wide operating range under size and weight restrictions. As car companies race to improve electric and hybrid vehicles, their reliance on metals like neodymium used in motors and lithium used in batteries found in electric and hybrid cars, is raising a host of new geopolitical issues over access to the minerals. It is believed to be near a breakthrough in developing electric motors for hybrid cars that eliminates the use of rare earth metals, whose prices have risen sharply in the past year as China restricted their supply [1]. Toyota is striving to develop a different type of electric motor to escape a simmering trade conflict involving China’s grip on a rare mineral, and an induction motor is revisited for high power, e.g. electric vehicle and fuel cell vehicle. While the space angle between the rotor flux vector and the stator d-axis of the stator in a PM synchronous motor can be directly measured, that of an induction motor is not a directly measureable quantity and thus it is more difficult to control. With the rotor-flux-oriented control there are two main implementations to obtain the space angle of the rotor flux vector [2]. In flux feedback control, so called direct vector control, it is calculated from the measured or estimated stator flux. In flux feedforward control, so called indirect vector control, it is obtained by adding the electrical rotor angle and the slip angle which strongly depends on the rotor time constant. The rotor time constant is equal to the ratio of the Manuscript received Feb. 5, 2011; revised May 19, 2011 Recommended for publication by Guest Associate Editor Byoung-Kuk Lee. † Corresponding Author: jeong@mju.ac.kr Tel: +81-31-330-6363, Fax: +82-31-321-0271, Myongji University * Dept. of Electrical Eng., Myongji University, Korea rotor inductance varying with magnetizing current to rotor resistance varying with temperature. Numerous researches have discussed identification algorithm of the rotor parameters by either on-line or off-line [3]–[7]. Despite its parameter sen- sitivity, the indirect vector control has gained more widespread for automotive applications where the maximum torque should be produced even at standstill. Efficiency of electric drives is a crucial index for automotive applications due to a limited power source, e.g. a battery/a fuel cell. The maximum-torque-per-ampere (MTPA) operation is preferred rather than the rated flux operation common for industrial drives [8]. The electric motors for vehicle are typically designed in very compact size allowing higher flux level than rated and often experience magnetic saturation. This work proposes an identification scheme of mo- tor parameters using the dq-axis equivalent circuit in the synchronous reference frame rather than the conventional single-phase equivalent circuit. The simulation model of an induction motor considering magnetic saturation using Matlab/Simulink R  is also developed to evaluate its control dynamics. The proposed method is applied to a 22kW-rated induction motor which is proper for compact-sized electric vehicle. II. MATHEMATICAL MODEL OF AN I NDUCTION MOTOR I NCLUDING MAGNETIC SATURATION The stator and rotor voltage equations of an induction motor in the synchronous reference frame neglecting iron losses can be expressed in the complex vector form as  v e dqs = R s  i e dqs + d dt  λ e dqs + jω e  λ e dqs 0 = R r  i e dqr + d dt  λ e dqr + j ( ω e - ω r )  λ e dqr (1)