Research On Motor Controller Based On AC-link Technology

As an important part of the new energy field,electric vehicles are highly valued and supported by governments of various countries.At present,the motor drive system and battery charging system of electric vehicles are independent of each other,which not only wastes limited on-board space,but also causes idle resources.In order to effectively solve these problems,and at the same time respond to the energy conservation,emission reduction and green environmental protection new energy industry development policies advocated by the state,it is particularly important to study a new generation of highly integrated motor-driven charging integrated equipment.Based on high-frequency AC link technology,this paper studies the integrated topology of motor drive and charging.First,a comprehensive analysis of the current research status of vehicle chargers and motor drive technologies is introduced;four types of drive motors commonly used in electric vehicles and their control strategies are introduced.Based on the actual electric vehicle applications,permanent magnet synchronous motors are selected as the driving mode Control objects under.Secondly,the components of the integrated system topology are described,and the working mechanism in the charging mode and the driving mode is analyzed.In view of the common constant current charging method and constant voltage charging method,it is easy to cause lithium battery overcharge and undercharge.The constant voltage charging method is used as the charging control method of the integrated system;in view of the low control accuracy and large torque ripple of the direct torque control when the motor is running at low speed,the constant straight axis current control method in the field-oriented control is selected as the permanent Control method of magnetic synchronous motor.Finally,the simulation model of the integrated system was built through the Matlab /simulink software platform,and the charging mode and the driving mode were simulated and verified,respectively,and the simulation results in line with expectations were obtained.The simulation results show that when the integrated system is charging,the transition of each charging stage is smooth,which can achieve rapid charging of the lithium battery;when the integrated system drives the motor,the electromagnetic torque value stabilizes at 150 N.m and the motor speed rises linearly during the acceleration phase;When the motor speed rises to 3000 rpm and enters a stable speed stage,the electromagnetic torque value drops to 117.8 N.m,and the motor speed stops increasing and stabilizes at the set value.Whether it is an acceleration process or a steady speed process,the stator current waveform shows a good three-phase sinusoidal shape,and the speed is relatively stable after reaching a given value,which can achieve effective control of the motor speed,fully verifying the integrated system topology Feasibility of structure and control strategy.