Research Of Direct Torque Control For Permanent Magnet Synchronous Motor Based On DSP

With small size, light weight, simple structure, rapid dynamic response and high power factor, the permanent magnet synchronous motor (PMSM) is widely used in the modern AC drive system. In the development of permanent magnetic materials, power electronics, motor manufacturing and the level of control algorithms have achieved remarkable progress, PMSM as the executive component of AC drive system, which shows a huge value for its research and development. Along with this trend, the research on the control theory of PMSM has been made lots of achievements. Direct torque control (DTC) has become one of the most common method in the field of high dynamic performance AC variable frequency speed control system, which has been applied in the direct torque control of three-phase induction motors. But problems like the torque ripple and bad performance at low speed limited the application of direct torque control in the PMSM AC speed control system.This paper focuses on the research of PMSM-DTC system, the basic principle and implementation scheme of control system are analyzed and designed. First of all, the structural characteristics and classification of PMSM are briefly introduced, and mathematical models of PMSM are set up in different coordinate system in this paper, and the principle and characteristic of PMSM-DTC system is also analyzed. On the basis of typical PMSM-DTC system, the causes of the torque ripple of PMSM-DTC system are analyzed. The effect of zero vector in the direct torque control between induction motor and PMSM are compared and analyzed. Moreover, the control effects of the zero vector on the stator flux and the electromagnetic torque in the PMSM-DTC system are analyzed and demonstrated in the paper. On the basis of the conclusion, this paper presents a novel PMSM-DTC system based on duty ratio modulation (DRM).On the basis of theoretical analysis and simulation model of system, the feasibility and effectiveness of the simulation model of the system are verified and analyzed. And the simulation results of PMSM-DTC system, which is based on duty ratio modulatiuon (DRM), showes that it can effectively reduce the flux and torque ripple and improve the performance of the control system. From the perspective of a digital implementation of the system, the hardware design is introduced in this paper besides. The hardware of PMSM-DTC system is designed based on DSP and introduced in this paper particularly. In addition, the main software architecture of PMSM-DTC system based on DSP is designed and introduced, and the program design flow chart of the PMSM-DTC system is analyzed. The verification is accomplished based on the hardware platform and software platform, the experiment shows that the system is consistent with the theoretical analysis and simulation test results.