Study Of Electric Vehicle Induction Motor DTC Based On The Torque And Flux Variable Structure Control System

As rapid increase of traditional cars has caused a series of problems, such asenergy, environment and pollution, etc, electric vehicle with no pollution, no noise,energy conservation and environmental protection will undoubtedly become the futuredevelopment direction of cars. Motor drive control technology as one of the keytechnologies of electric vehicles plays a vital role for drive performance of electricvehicle.So it has important practical significance in research and development of themotor drive control technology. In the field of electric vehicle drive control, inductionmotor with advantages of small size, light weight, low cost and maintenance-free hasbeen widely used. And its control technology is tend to be of high-performance andintelligent.For the stator flux and torque are calculated and controlled in the statorcoordinate, Direct Torque Control（DTC） of induction motor which eliminates thecomplex coordinate transformation is the new technology of frequency conversionspeed control after the vector control technology. The DTC technology has simplestructure, good static and dynamic performance. It is easy to implement. But double-flux and torque hysteresis controllers are used in the conventional DTC system.Thereare some problems such as large ripples of the torque and the flux and current,variable switching frequency, so the applications in electric vehicle subject to certainrestriction.In this dissertation, fundamental reasons of the torque and flux ripple of theconventional DTC are expounded based on detailed analysis of the structure andprinciple of the induction motor conventional DTC system. Contrary to torque andflux ripple at low speed of the conventional DTC, the torque and flux control based onSliding Mode Control of induction motor DTC system combined with space vectorpulse width modulation theory is proposed in order to improve torque and flux ripple.The variable structure sliding mode controller, designed according to exponentialreaching law, can improve the dynamic performance in normal operation rangeeffectively and reduce the system’s dithering in the sliding mode operation range, viagiving appropriate parameter value.In this dissertation, on the platforms of Matlab/Simulink, the torque and theflux control based on the variable structure sliding mode control of induction motorDTC system is simulated. The simulation results demonstrate the torque and flux ripple has effectively improved and the system has getten a good dynamic response.Finally, based on TMS320F28335the hardware and software for electric vehicleinduction motor direct torque control system are designed. The experimental resultsproperly show lower torque and flux ripple. All that have proved the identificationmethod is effective.