Research On Active Thermal Control Of Induction Motor In Electric Vehicle

Electric vehicles not only have the advantages of low noise and high energy efficiency,but also ease the environmental pollution and shortage of resources caused by driving traditional fuel-powered vehicles.It is one of the most promising new energy vehicles at present.Induction motors for electric vehicles have become one of the commonly used drive motors in the field of electric vehicles,especially in the field of low-speed electric vehicles because of their advantages of reliable operation,simple structure and convenient manufacture.Unlike traditional industrial motors,induction motors for electric vehicles require large starting torques and excellent instantaneous output capability.For example,in the case of climbing or crossing obstacles,motors are required to rapidly increase output in a short period of time to obtain excellent driving experience.However,high torque operation will make the motor temperature rise rapidly,bringing a potential safety hazard for its reliable operation.To prevent damage to the motor due to excessive motor temperature,temperature protection is usually provided.However,the existing temperature protection measures are usually passive protection,such as setting a static torque current limit or setting a conservative temperature protection value for the temperature.When the motor is over-temperature,over-temperature protection is enabled to decelerate the torque output to prevent motor thennal overload.In fact,there is a large thermal inertia of the induction motor for electric vehicles,that is,the change of the motor temperature always lags the change of the current,which provides the conditions for the active control of the temperature of the induction motor.As a closed-loop control technology,active thermal control technology can dynamically adjust the key parameters according to the temperature feedback of the power device.Compared with the above-mentioned passive temperature control method,active thermal control technology is more flexible in control method and has higher temperature control accuracy,which can avoid the latent damage stress of the temperature-sensitive module effectively and enable the entire system to operate"safely" continuously for maximum allowable temperature and temperature cycles.At present,the active thermal control is mainly used in power devices,aerospace and other fields,less research in the field of electric vehicle induction motor control.Based on the idea of active thermal control of power devices,this paper proposes a method of active thermal control of induction motor for electric vehicles by introducing temperature closed loop into vector control system.In this paper,the induction motor was taken as the research object,and its mathematical model and coordinate transformation were deduced in detail.Based on this,the simulation model of the induction motor vector control system based on Matlab/Simulink was established and the simulation results showed that the system had a good control performance.Then,the temperature rise model of induction motor is established based on the principle of loss analysis and thermal balance.The temperature information of motor and the space vector control were combined to propose the active thermal control method of induction motor.And the active thermal control of induction motor based on Matlab/Simulink model,ompleted the simulation study.The simulation results before and after the addition of active thermal control were analyzed and compared to verify the effectiveness of the proposed active thermal control method.Then,this paper had analyzed and designed the main modules of power supply circuit,drive circuit,detection circuit and communication circuit of induction motor control system in terms of hardware and software.Among them,for the design of communication protocol,this paper independently designed the application layer protocol based on MODBUS protocol,and completed the formulation of message type,format definition and communication protocol.Finally,this paper taked the squirrel-cage induction motor of model HHY3-72-H12-YJ as the research object and established the experimental platform of the drive system of the electric vehicle.The induction motors were respectively operated in the control system before and after adding the active heat control.The experimental results showed that the proposed active thermal control method of induction motor mentioned in this paper can significantly improve the short-time output capability of induction motor under the premise of ensuring the safe operation of the motor,and has important engineering practical value.