Simulation Comparison Of DTC And SVPWM For PMSM

Permanent Magnet Synchronous Motor (PMSM) has characteristics of small volume, light, efficient, small inertia and reliability. It is widely used in servo , underwater propulsion. There were lots of papers about Direct Torque Control(DTC) and Space Vector Pulse Width Modulation (SVPWM) method to control the PMSM in the past, but there were few papers about the differences and advantages and disadvantages of the two technologies.Firstly, the paper discusses general outline of speed control methods and control strategies of PMSM. The paper introduces the main developing directions of PMSM. The purpose and the main content of the project are given in this dissertation, too. Then according to the mathematical models of PMSM, paper analyses DTC and SVPWM control strategies ,which are advanced methods. The DTC gets rid of circumrotating coordinate conversion and decreases dependence of system on motor parameter. According to current and voltage of stator, to calculate amplitude of torque and flux linkage. So to reach the aims of direct control torque and flux linkage. By detecting the current , voltage and rotor's angle. then through space coordinate conversion , we get expectation of stator flux linkage vector. Then we modulate the expectation of stator flux linkage vector to control torque and rotation speed of motor. Using MATLAB/SIMULINK mathematic tool ,we construct the two models.Digital simulation technique always is useful tool in analysis and calculation of ac adjustable speed drive system. We use MATLAB/SIMULINK mathematic tool to simulate the two control strategies and obtain the torque, current, flux linkage ,etc curve. By comparing two systems, We can get the result——DTC system has excellent torque dynamic control characteristic but it also results in large ripples of torque , current and flux linkage. SVPWM system's ripples of torque , current and flux linkage are smaller than DTC's, but the control system is more complex.