| For the modern industry,the light structure is simple,reliable operation of the motor in the industrial automation,household appliances,electric vehicles,aerospace.medical equipment and other fields,has been unable to fully meet the demand,permanent magnet synchronous motor(PMSM)in the above with a bit On the basis of both easy to maintain,small size,light weight,high efficiency of these advantages,in today's society has been widely used.In the control scheme of PMSM,direct torque control(DTC)is known for its advantages such as simple structure,fast dynamic response and robustness.Because of its relatively simple structure,relatively low cost,so the traditional DTC system is still in the existing electric vehicle market occupies a large share,especially in the low-end models and some scenic spots,the factory electric tour buses,patrol cars on the application of second to none.In its practical sense,it is important to study the direct torque control of permanent magnet synchronous motors.This thesis focuses on the DTC of PMSM,and its main contents are:1.Based on the PMSM mathematical model under the stator synchronous rotating coordinate system,the principle of the basic DTC of the PIGM is analyzed The influence of the voltage vector on the torque angle is analyzed quantitatively.The reason why the basic DTC starting current is too large and the pulsation is analyzed.Finally,the steady and dynamic characteristics of the basic DTC are verified.2.In order to better study the control system of electric vehicles,the electric vehicle powertrain system is firstly researched and the performance and technology of various motor moving systems are optimized.It is also necessary to strengthen the analysis of the dynamic characteristics of electric vehicle operation.This paper analyzes the driving field close to the ideal vehicle,analyzes its force,and normally drives the constant torque output when the electric vehicle is running at the rated speed,and runs at constant power when the speed is above the rated speed.3.The performance of the traditional DTC system of permanent magnet synchronous motor has been analyzed.It is found that the traditional system has the problems of poor speed performance and large torque ripple.This is mainly because the control of the motor state of the object changes,the system mutation load and nonlinear strong Coupling caused by the motor at high speed may not be obvious,but the motor at low speed when the problem is more obvious.There are many methods to improve the DTC direct torque control system of permanent magnet synchronous motor.Due to the complexity of the improved DTC system,this paper can only focus on the theoretical and practical application of traditional DTC control system.4.The DTC experiment platform of permanent magnet synchronous motor based on TMS320F28335 is built and the traditional DTC scheme of PMSM is realized on this platform.The estimation scheme of stator flux linkage is improved.The experimental results show that by adjusting the duty cycle and improving the stator flux Method,which can significantly improve the torque and flux of the DTC and optimize the low speed performance of the DTC.At the same time,through MATLAB simulation to simulate the various conditions of electric vehicle driving,in a variety of different conditions,PMSM traditional DTC program is feasible and effective. |
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