Design Of Speed Sensorless Vector Control System For Induction Motor Used In Electric Vehicle

AC asynchronous motor because of simple structure,low cost,durable,high reliability is very suitable for electric vehicle drive motor.Based on AC asynchronous motor vector control system,increased speed sensorless control control theory and method,can further improve the reliability of the motor drive system,improve the system fault tolerance,make the system easy to maintain,save the cost,which makes the electric vehicle AC asynchronous motor speed sensorless vector control theory and method become the hotspot research on driving system of electric vehicle.The triangle winding is adopted in the low voltage AC asynchronous motor.In this thesis,this kind of motor is taken as the research object.Disscused the special control methods on it.The main results are as follows:Built speed sensorless vector control system model for electric vehicle AC asynchronous motor,the model is mainly composed of voltage acquisition,current acquisition,coordinate transformation,motor speed and flux estimation,current PI regulator,PWM modulation module.Written the program,simulated and experimented for each module.Used the method of pole zero cancellation of system to calculate the current PI regulator parameter.Analyzed the system performance when motor parameter changes and pole zero cannot be completely cancellation.Space vector pulse width modulation technology in the situation of motor winding star connection is diferent from which in the situation of motor winding delta connection.In this thesis analyzed the diference of these two kinds of situations,especially for the situation of motor winding delta connection,designed the specific sector judgment and vector synthesis method in engineering application.In the aspect of the speed and flux estimation of AC asynchronous motor,used a kind of motor speed and flux estimation algorithm named FAST estimator designed by TI company.The algorithm has the advantages of high accuracy and high precision.It can be used to estimate the motor speed and rotor flux angle in the case of the input motor voltage and current.According to the relevant weak flux control theory,the reference value of the motor current excitation component is calculated to realize the weak flux control in the high speed situation for the characteristics of the wide range of motor speed regulation of electric vehicle.Designed The load model according with the actual situation of electric vehicle to simulate the whole performance of the system.Finally,the speed sensorless vector control system is tested on the experiment platform.According to the motor dynamic acceleration process and high-speed steady state region were tested,compared the measured value and estimated value of motor speed,analyzes the causes of error.The overall performance of the system meet the design requirements of electric vehicle.