A Realization Of Induction Motor Speed Sensorless Direct Torque Control System Based On DSP

Direct Torque Control (DTC) scheme has been widely studied and used during recent years due to its novel strategy, simple control structure and excellent performance.In DTC system, the concept of space vector is introduced to analyse and control the AC motor, the electromagnetic torque and flux are calculated and controlled in the stationary reference frame, and the optimal PWM gating signals are generated to control the inverter according to output of the Bang-Bang regulator. It does not need the complex vector transformation and the simplification of the AC motor any more. Instead, it has simple control structure, direct control method and clear physics concept of signal processing, all of which make the control method simple and easy. DTC system is high-performance adjustable speed system with fast torque response.In DTC system, speed observation is necessary, but the installation of speed sensor cause costing, easy infected by environment and reducing reliability problem. So the speed estimator becomes hotspot in DTC system study. At present, the studying speed observation has direct calculation and model reference adaptive system (MRAS) speed estimator two methods. This paper first realizes the traditional DTC in a 2.2KW AC speed variety test-bed. It specially improves on hysteresis compare, the way of sending out pulse and switch that makes a foundation for the lasting the DTC performance optimized.Second, this paper analyses the theory of model reference adaptive system speed estimator based on rotor flux and developed a simulation system. Finally, it is validated by middle, high speed range experiment in that test-bed. From the last result, the steady precision has relation to speed. The higher speed is, the higher precision is.Besides, due to the method of model reference adaptive system speed estimator based on reactive power isn't infected by stator resistance. This paper also analyses and validated it. From the present result, it has a low speed precision compared to speed estimator based on rotor flux. From the literature looked up by author, it doesn't have experiment result.