Electric Vehicle Motor Drive System Control Method Research

As the “heart” of pure electric vehicles,the motor drive system determines the key performance of electric vehicles such as the highest speed and output torque.In recent years,with the rise of the new energy electric vehicle industry,the motor drive system control method has become a research hotspot.This thesis starts from the actual needs,studies the high-performance control method and software design applied to the motor drive system of electric vehicles.Based on this,a torque-controlled motor drive controller prototype is developed.First,in order to simplify the controller design and improve the control efficiency,this thesis establishes the current decoupled controlling mathematical model of the permanent magnet synchronous motor based on the rotor rotation coordinate system,and proposes an overall control scheme for the motor drive system using vector control.Secondly,aiming at the shortcomings of the traditional classical vector control method applied directly to the motor drive system of electric vehicles,this thesis deeply investigates the high-performance current control method and high-efficiency PWM technology under the framework of the vector control system.In the aspect of high-efficiency current control method,the method of combining the maximum torque and current ratio control,the constant torque control and the minimum flux-to-torque ratio control method is used in the motor speed increasing process,and the current trajectory is automatically generated based on the magnitude of the voltage vector and the speed.This control method effectively solves the shortcomings of poor robustness,insufficient torque output capability,and narrow system speed range of conventional methods.While using the current feedback PI controller,feedforward and anti-saturation compensation processing is performed on the output of the PI controller.Experiments show that this method improves the system's rapid response and anti-interference.In the aspect of high-efficiency PWM technology,the system voltage is modulated by using space voltage vector pulse width modulation technology in order to improve the utilization of the system's DC voltage and reduce the output torque ripple.Finally,this thesis proposes a novel vector control system scheme that satisfies the demand of electric vehicle motor drive system.For the software programming of the above control scheme,unlike the general program design,the system software developed in this thesis uses a layered software architecture consisting of a framework layer,a hardware layer,and a functional module layer,which effectively reduces the coupling of software modules and facilitates subsequent software expansion.Among them,the interrupt program design uses two levels of nested interrupts to handle common system failures while completing the system's complex calculation tasks,which ensures the real-time and security of system control.Through the bench test,the performance characteristics of the motor drive controller prototype such as speed output,torque output,power output,and system efficiency developed by this project were tested.The test results show that it meets the basic performance requirements of electric vehicle motor drive system.