Electric Vehicle Ac System Speed Control Design

Driving system of electric vehicles is the heart, also it is one of the key technologies for electric vehicle.And it directly determines the performance of electric vehicle. The control strategy of the driving control system include two kinds, the vector control and direct torque control . The two control methods have better ditynamic and static characteristics. Vector control in accordance with the rotating magnetic field equivalence principle t decompose the stator current vector into the rotor magnetic field direction two DC component and controlled respectively through coordinate transformation , so as to realize asynchronous motor flux and torque decoupling controlling, in order to achieve DC motor controlling effect. It makes the AC variable frequency technology to step forward. After several decades of practice, many scholars have made a lot of work.Through continuous research and improvement, eventually it can compare to DC speed controlling system. It not only satisfies operation needs of the large electric cars for high speed in the field of torque and large range of constant power output, but also solves the problem of large volume of the prior motor.The core of the traditional digital control system is single chip microcomputer or microcomputer .But a motor control system consisting of DSP has higher precision and speed, large storage capacity, the logic control function and various interrupt processing ability, the rich digital input and output port, communication, special motor control PWM output port. Various control hardware is integrated in the same chip. It can not only realize the motor control system with high performance, low power consumption, low cost, wide application range, especially the important trend of development for industrial production in motor control. It has important significance in scientific research, technology development and productivity.This paper introduces the design of asynchronous motor vector control system for an electric vehicle based on DSP. The system is based on TI's TMS320LF2407A DSP chip. It based on vector control, and it is designed based on the voltage space vector SVPWM technology. The system hardware design is the design of the main circuit and control circuit design. The main circuit uses the typical AC-DC-AC voltage type inverter structure, comprised of a rectification circuit, filter circuit and the inverter circuit ; the control circuit is composed of two parts, namely TMS320LF2407A DSP core circuit and external expansion circuit based on the core circuit. The software design uses the modular designing, including the main program modules and the interrupt service subroutine module. The Asynchronous motor vector control system has the characters of good stability, high reliability, small overshoot, anti-interference ability is strong, flexible and easy to control etc..