Study On Key Technologies Of Electric Vehicle Controllers Based On Induction Motors

The consumption of fossil fuels is increasing with the constant growth of the global car parc.The electric vehicle,as a kind of new energy vehicle without pollutant discharge and fossil fuel consumption,is popularized energetically all over the world.The induction motor is an AC motor which is simple in structure,lower in cost and easy to maintain,so it is widely applied to the drive motor of electric vehicles.Currently,electric vehicles happen to jitter phenomena caused by the torque ripple of induction motors when driving at a low speed,which has a strong impact on the driving experience.Besides,compared with traditional fuel vehicles,electric vehicles have a poorer endurance mileage,which is an important factor to influence the consumers' purchase decision of electric vehicles.Therefore,this present paper studied the above two problems.Firstly,this present paper built a mathematical modelling of induction motors and studied the impact of the change of the rotor time constant on the motor torque by deducting the transformation of coordinates in the vector control and the principles of field orientation;secondly,an on-line identification of the motor parameters was made for reducing the impact of these parameters.To improve the identification precision,this present paper suggested the model reference adaptive system(MRAS)which can identify the rotor time constant and stator resistance simultaneously on the basis of rotor flux observer;thirdly,this present paper analyzed the motor loss and deduced the optimal flux of induction motors by building a modelling of minimum iron loss for motors.After discussing the impact of the iron loss resistance on the loss modelling,this present paper improved the previous algorithm of energy-saving control,carried on the on-line identification for the iron loss resistance by a closed-loop state observer,and designed a loss minimization control algorithm based on the parameter identification by organically combining with the MRAS.Finally,this present paper set up a simulation and test platform of the induction motor control system for electric vehicles,carried out the simulation and test by imitating varied working conditions of electric vehicles and verified the feasibility of the suggested theories.The results indicated that the algorithms designed in this present paper,the identification precision of motor parameters and the reduced motor energy consumption can inhibit actively the jitter of vehicles and increase the endurance mileage.