Key Technology Research Of Voltage And Torque Control For Induction Motor Used In Electric Vehicle

With the rapid development of global industrialization, energy and environmental problems have become increasingly. As a clean, efficient, intelligent and sustainable green transportation, electric vehicles have been rapidly developed. Due to its significant merits such as simple structure, low manufacture and maintenance cost and wide speed range, induction motor has been widely applied in electric vehicle, especially in large vehicles.Key technology of induction motor field weakening and torque control strategy, which is applied in electric vehicle have been researched in this paper. First, within the base-speed, dynamic and static performances under basic induction motor vector control system have been analyzed in detail. On this basis, combined with the mathematical model of the induction motor and the voltage limit and current limit during the operation, optimal current moving trajectory in high-speed field weakening region which is above basic-speed has been discussed. Induction motor field weakening control algorithm based on direct slip frequency adjustment has been proposed, which could improve the dynamic response performance in field weakening region especially in overloading weakening zone and better meet the accelerating demand for electric vehicles. On the basis of the principle, Paper compare it with traditional field weakening strategy, field weakening strategy based on voltage loop and field weakening strategy based on the improved algorithm of voltage loop and so on. Second, aiming at inaccurate rotor field orientation, which is caused by variation of rotor time constant in high-speed field, two correction rotor field oriented control strategies have been introduced, by which control system robustness of motor parameters has been improved. As the actual application requirements for torque command is issued by foot throttle of electric vehicles, this paper proposes a real-time stator flux observation method based on a minimum order rotor flux observer, through the stator flux and the stator current multiplication cross obtained the electrical torque, designed a high precision electric vehicle induction motor torque closed-loop control system. The effectiveness and practicality of magnetic field orientation optimization as well as torque closed-loop control system have been verified by simulation. Finally, set up an experimental platform of electric vehicle with induction motor, then through experimental to verify the key technology of the induction motor vector control, high-speed field weakening control, torque closed-loop control. The experimental results verify the analysis and design of this article...