Efficiency optimization of direct torque controlled induction motor drives for electric vehicles

Aim at the demands for high efficiency and fast dynamic response of electric vehicle drives, an efficiency optimization control strategy of the direct torque controlled induction motors is proposed. Firstly, the mathematical model of induction motors is established in stator-field-oriented reference frame considering core losses. Secondly, the function relationship between the power losses and the developed torque, rotor speed and stator flux is analyzed, and the computational formula of the stator flux amplitude which makes the power losses minimization is derived at different operating conditions. Consequently, the efficiency optimization of the driving system is achieved. The experimental results show that the proposed control strategy not only preserves fast torque dynamic response, but also improves operating efficiency of the driving system and lengthens the travel distance of electric vehicles.