Study On Direct Torque Control Method Of Asynchronous Motor Based On Speedless Sensors

Direct Torque Control(DTC)is a new method for AC motor speed regulating since Vector Control.It is based on stator static axis,which has a simple mathematic model and realizes some high level performances, such as robustness to undulation of input voltage,low sensitivity to parameters change.In this paper,a test equipment based on DTC technique is developed, and the new method of DTC based on speed sensor less for AC motor is present.The content is as follows.1)Building a simulation model based on DTC for AC motorA good DTC simulation model is built based on MATLAB6.5/Simulink and S-Function programming.It provides a very good simulation platform for kinds of DTC strategies' researching.A three-lays inverter is act as power supply,and a whole simulation plat for AC motor control system based on DTC technique is built to versified the simulation model.2)Designing a new speed-adaptive flux observerA new speed-adaptive flux observer which based on model reference adaptive control system theory is designed.The observation of stator flux is combined with estimate of speed were proceeding,and the observed stator flux could be applied to direct torque control system.Expound two keystone parts in design is emphasized,which are stationing the pole of flux observer and selecting plus matrix.Station the pole of flux is resolved by using MATLAB to finally find aim gain matrix,the reference observer is based on motor state space equation,which used stator current and stator flux as state variable,motor itself as reference model,the designed observer as modulation model,speed observer as modulation parameter.Because the state equation's state variables are stator current and stator flux,the stator flux can be observer direct.After defining Lyapunov's stability theory the speed self-adaptive scheme is confined. And then the speed sensor less direct torque control simulation system was designed.3)Building a speed sensor less DTC simulation model Based on the element and S-function in MATLAB/SIMULINK,the simulation former of speed sensor less direct torque control system was set up.The emulate experiment results indicate that this system is perfect, such as the speed estimate is quick and nicety,The arithmetic is simple, all this is easy to implement on line.And also the system has preferably observe precision of stator flux even in the low gear,so the control character of motor can be improved.The torque dynamic respond is quick, so the limitations of error accumulate and zero point excursion which is on simple integrator can be conquer.At last,it discusses a scheme,which is the speed sensor less direct torque control system of asynchronous motor is digitized realization based on the controller's core is TMS320F2812.