Abstract: The stator flux oriented direct torque control technique is becoming widely used in high performance motion control of induction motors. However, the conventional stator-flux-oriented control schemes have the disadvantage of poor performance in the low-speed operating range, due to the stator resistance variables and uncertainties. A stator current based model reference adaptive system (MRAS), using Popov’s super-stability theory, is presented to estimate motor parameters, which constitutes a closed-loop system by the stator current feedback. The scheme considers not only stator resistance and speed, but also rotor resistance. Therefore, the convergence speed of estimating process is quickened, and the estimate precision is improved. On the basis of the scheme, a stator flux estimate technique based on stator resistance compensation is also presented, and the simulation system of the direct torque control project is established. The simulation results verify the validity of the proposed scheme.

Key words: Direct torque control Pseudoreduced-order flux observer Model reference adaptive system, Stator resistance