Study Of Asynchronous Motor Speedsensorless Direct Torque Control System

One method of AC induction motor called Direct Torque Control(DTC) was raised after Vector Control(VC).Following Vector Control technique,the quick development of DTC makes itself a new high performance AC driving technique paralleling to the Vector Control.Direct Torque Control System (DTCS) has some distinctive features,such as simple control algorithm,quick torque responses few motor parameters etc.In this dissertation,the realization of speed observer and the design of stator flux observer are studied profoundly based on the productions of task team.In DTC system,the exact flux value is very important.At present,there are three flux models what used in DTC system:u-i model,i-n model,u-n model.After discussing these models,for the drawbacks,the paper gives a full order flux observer,which to avoid these questions,and the stator flux can be observed much better.There are three typical way to realize speedsensorless system,direct account based on motor equation,kalman filter and MRAS.In this dissertation,based on the MRAS flux observer and on the basis of the stability theorem of Lyapunov,it designed a simple speed estimator.A new speed- sensorless DTC system is composed.A simulation system of model reference adaptive adopted speedsensorless DTC system is developed by using MATLAB/SIMULINK software package.The simulation results show that,compared with the system using i-n flux model,this system using full order flux server has better reliable stator and dynamic stator when it running in the course that the system starts and runs loading with and without load,high speed and low speed etc.In speedsensorless DTC system,Calculate speed is inosculating to motor's actual speed under all of the running states of motor. It also have good effects even when staor resistace or rotor resistance has changed.So we can draw a conclusion as:using the method can improved the precision of the observed speed, strengthen the robustness of system,and widen the range of drive system.In this dissertation,it tried to make the model reference adaptive adopted speedsensorless DTC system come true in a equipment.Discret equations of blocks are deduced and are carried out in programmer.A complete set of control algorithmintroduce PU(per-unit),and enhance accuracy of operation.Used a new way to realize the speed regulator carried out the integrals by discretization operation.The paper designs and carries out model referece adaptive adopted speedsensorless DTC system using 2.2KW asynchronous machine and TMS320F240 development device.