Direct Torque Control For The Electric Vehicle Induction Motor Drives

With the development of power electronics, AC drives are replacing DC ones step by step. The representative technologies for ac motor control have VVVF, VSVF, VC and DTC.To obtain a quick response, the torque of the motor must be controlled effectively. But VVVF can only control the air-gap flux and cannot adjust the torque. Based on the steady state equations of the motor for the design of VSVF, VSVF can control the torque to a certain extent, but it cannot implement the real control in the dynamic process. Although vector control approach can dramatically improve the dynamic peculiarity in the theory, the vector control approach makes the complex reference frame change, rely on the parameters of the motor to a large extent. At the same time, the completely uncoupling in the dynamic process is not ensured and the effectiveness of the torque control is reduced. But DTC a kind of the more advantageous control technology that places stress on controlling torque of the motor directly, which overcomes the disadvantages of VC and brings the second natural fly-by of the speed regulation control theory of ac motor. The theory and technology of DTC have a lot of advantages, however, as a kind of the new birth theory and technology, the unperfected aspects and some ones are difficult of being solved. Owing to the reasons above, DTC has become one of research hot points. In this thesis the author made a study of asynchronous motor model, designed a hybrid simulation system of DTC and analyzed the characteristics of the DTC system and the existing problems. The power hardware system is based on TMS320LF2407 and intelligent power module (IPM), and the DSP software is programmed to realize the modulation. The experience and reference are provided in applying the TMS320LF2407 in DTC.