Research Of Direct Torque Control System Based On DSP

In the field of AC machines control, a strategy called variable frequency control is mostly used. After vector transformation control is presented, the AC machines control technology can theoretically solve the problem on the static and dynamic performance relative to the DC technology. As a high performance and new machines control strategy developed in 1980's, direct torque control solves the problems that computation in vector transformation control is complex, the control characters are easily affected by the changes in machines parameters, real results of the experiments can't achieve the level of the theoretical analysis. So now direct torque control has become an emphasis in the field of AC machines control. Some simulation and experiment researches about this strategy are presented in the paper.Firstly, according to the mathematical model of asynchronous machines and the principle of direct torque control, the theoretical and experimental analysis about hexagon and round track of flux is proposed in the paper. In the researches about hexagon track, SMITH triggers are used, so is flux self-control. As to round track, the method of voltage vector selection is taken. We can select the proper voltage vector by the position and magnitude of stator flux as well as the magnitude of torque. In sum, both of these two algorithms are realized through selecting proper voltage vector. In addition, the performance criterion are respectively described, and the torque ripple under low-speed is analyzed and compared in this paper.Not only the theoretical and simulating analysis is carried out, but also experimental research. Because direct torque control requires very high performance of Real-time, the popular microcomputer core DSP is used as controller in the design of hardware. Its high speed of running is suitable for the experiment. In the main circuit, there is a highly integrated power element: IPM as inverter, which includes seven IGBT, has high switch frequency and fault diagnosis function. IPM greatly decreases the bulk of system. The experimental results show that this control strategy proposed can acquire better control effect.