Study On Drive System Of Electric Vehicles Based On The Vector Control

Nowadays,energy saving and environmental protection is the central topic of the automotive industry.In this case,the promotion and development of electric vehicles as the representative of the new energy vehicles beomes one of the important ways to solve these problems.Compared with other motors,permanent magnet synchronous motor has obvious advantages in terms of performances such as efficiency,power density,etc.With the development and cost reduction of permanent magnet materials,the price of permanent magnet motor is declining.The paper took the PMSM as the control object and made a deep analysis about the drive system of the vector control on electric vehicles.At first,this paper introduced the structural features of the surface permanent magnet synchronous motors and the interior permanent magnet synchronous motors.And it elaborated in detail coordinate transformations,mathematical modeling of PMSM and control technology of the SVPWM.Based on this,two kinds of common vector control strategies such as id=0 and MTPA control below the base speed for PMSM were analyzed in theory together with PI regulator.Secondly,using the Matlab2012b/simulink simulation platform,it achieved PMSM vector control systems based on the control of id=0 and the formula method of MTPA.Through comparative analysis of simulation,it indicated that the drive system based on the formula method of MTPA control had the advantages of large starting torque,good stability of speed and torque,high power utilization of DC side,small copper consumption of system.The reason why the paper adopted an approximation calculation method-curve fitting was that the expressions between electromagnetic torque and the stator current component were too complex for the realization of formula method as well as electric cars need the real-time digital control system.Using the toolbox of curving fitting,the paper introduces curve fitting to improve the MTPA formula method.It compared errors between the torque with stator current components and polynomials about one,three,five-times.It demonstrates ultimately that the approximation degree of five-times curve fitting polynomial was more ideal.And it meanwhile verified the correctness of the MTPA vector control of PMSM base on five –times curve fitting in Matlab2012b/simulink simulation environment.By comparison with the control of formula method of MTPA control,the results showed that drive system based on MTPA control of the five–times curve fitting had the advantages of good performance of dynamic and stability,easy hardware implementation.Finally,the mainstream control chip TMS320F2812 was applied as the control core the to design the main circuits,control circuits,software,test platform and test of PWM.