| Direct Torque Control(DTC)is a quick-respond high-performance control scheme used for the three-phase asynchronous motor. DTC is based on the direct control of the stator magnetic link and electromagnetic torque.After reading a lot of papers written in English and Chinese, this paper have clearly understood the present condition of my subject, this paper introduce the definition of the space vector and stator magnetic link, bring out the concept of voltage vector; after introduce the relationship of the magnetic link vector and voltage vector, explain how the trajectory of the magnetic link becomes a similar circle; after introduced the principle of close loop control of the magnetic link and electromagnetic torque, explain the algorithm of the similar circle trajectory; at last using the DTC diagram, explain the function of each unit of the system. The paper brings up the scheme to estimate the transient voltage unused the voltage sensor.The next, this paper makes the mathematic model and do some simulation using the MATLAB/SIMULINK tool, based on the principle of the DTC system. The mathematic model include: the motor model, the control model and the invertors model. The result of the simulation proves that the trajectory of the magnetic link is almost circular, the rotor speed follows the given speed. The result proves this system has very high motion state and static state performance.Finally, this paper completes the hardware design and the programming and debugging of the open loop start and the closed loop motion used the DSP core, do the experiment of open loop start. The result of the simulation and experiment prove this system is correct, this scheme is practicable. |
