Research On Performance Improvement Of Direct Torque Control Of Two-phase Conduction Brushless DC Motor

Brushless DC Motor(BLDCM)has the advantages of high efficiency,simple structure and large power density so that it has been widely used in a variety of fields.It is of great economic and social significance to research and analyze the drive system of brushless DC motor with high performance.The electromagnetic torque is considered as a kind of controlled variable to achieve direct control of the motor torque through Direct Torque Control(DTC)technology,which is much simpler and better at highlighting the dynamic and static performance.Since proposed,it has been the hot spot in the field of high-performance motor control.Centered on direct torque control technology of brushless DC motor,this paper is aimed to improve the control performance of brushless DC motor on the basis of two-phase conduction BLDCM and lay a foundation for the further development and application of brushless DC motor.Firstly,the structure and working principle of BLDCM was introduced in detail in this paper,and the mathematical model of star connection was established.In addition,the implementation method of the pure torque loop DTC system for BLDCM was also introduced,while the corresponding Matlab/Simulink simulation model was established.Secondly,proceeding from improvement of the motor control method to enhance the control performance,it was pointed out that the freewheeling diode would be conducted with the changed size of the off-phase back EMF through the research on space voltage vector,especially zero voltage vector(ZVV),when the traditional six-sector control method was used in the function of ZVV with pure top tube or down tube,resulting in off-phase follow current and the increase of torque ripple.To solve this problem,a zero-vector control method for twelve sectors of DTC was proposed with the theoretical basis of twelve-sector zoning to rebuild a corresponding voltage vector option list.The simulation and experimental results showed that the twelve-sector control method was able to eliminate the phenomenon of traditional six-sector off-phase follow current effectively,reducing the motor torque ripple and improving the system performance significantly.Thirdly,based on simplifying control system hardware,especially sensors,to improve control performance,the resolution ratio position sensor DTC system of BLDCM was built on methods of acquiring rotor position with low-resolution signal and controlling twelve sectors.In addition,it was proved that this system could improve the performance of brushless DC motor significantly through simulation and experiments.Finally,the hardware platform of brushless DC motor was designed on the basis of DSP TMS320F28335,and the relevant experiments were verified on the experimental platform.