Asynchronous Motor Direct Torque Control System Parameter Identification

This paper focuses on the parameters estimation of direct torque control system of asynchronous motor. Firstly, it presents the components and working principle of direct torque control system of asynchronous motor briefly. It is taken into account that direct torque control system of asynchronous motor is based on accurate observe of stator flux. However asynchronous motor is influenced by working condition and its parameters change. Especially the stator resistance changes because of the temperature. That could result in the incensement of observing error of stator flux and electromagnetic torque. So the influence of parameters changing on observation accuracy of stator flux and electromagnetic torque is quantitatively analyzed by Matlab/Simulink and the influence on direct torque control system is also analyzed. Because stator flux u - i model characterizes small observing error in high speed and i - n model in low speed, combining tow models, a filter-based stator flux observer is presented, which improves the accuracy of stator flux observer.In order to restrain the blight of parameters changing on direct torque control system, recursive least square is used for on-line motor parameters estimation. Firstly, the principle of parameters estimation using recursive least square is expatiated. The method for invariable speed parameters estimation is deduced but it is limited to the situation that the speed changes little. By means of importing auxiliary variables, the method of large-scale variable speed parameters estimation is deduced. Combining this method with direct torque control system, a direct torque control system of asynchronous motor using variable speed parameters estimation is presented. Simulation experiments are carried on by Matlab/Simulink. The simulation result indicates that the parameter estimation algorithm is effective and the performance of direct torque control system of asynchronous motor is improved properly.