TẠP CHÍ PHÁT TRIỂN KH&CN, TẬP 9, SỐ12 -2006 Fast and robust torque control in a very wide range of speed is very needed by various industrial AC drive applications. Therefore, since 1986 [1], direct torque control (DTC) has been introduced to satisfy this desire. In order to achieve more economical control, conventional speed sensor has been replacing by sensorless speed estimation. The sensorless schemes are used to improve reliability and decrease maintenance requirements. | TẠP CHÍ PHÁT TRIỂN KH CN TẬP 9 SÓ12 -2006 SENSORLESS SPEED ESTIMATION OF INDUCTION MOTOR IN A DIRECT TORQUE CONTROL SYSTEM Pham Dinh Truc 1 Hoang Dang Khoa 2 1 University of Technology VNU-HCM 2 Ho Chi Minh City University of Industry Manuscript Received on January 26th 2006 Manuscript Revised December 04th 2006 ABSTRACT Fast and robust torque control in a very wide range of speed is very needed by various industrial AC drive applications. Therefore since 1986 1 direct torque control DTC has been introduced to satisfy this desire. In order to achieve more economical control conventional speed sensor has been replacing by sensorless speed estimation. The sensorless schemes are used to improve reliability and decrease maintenance requirements. In this paper concerned sensorless techniques of induction machine controlled by DTC algorithm are openloop estimators and MRAS schemes 2 3 . To demonstrate clearly the advantages and disadvantages between two kinds of sensorless techniques obtained simulation results are compared. By enhancing speed estimation the pure integrator is replaced by a low-pass filter to avoid DC drift and saturation problems 2 . Keywords Sensorless DTC Direct Torque Control IM Induction Motor . 1. INTRODUCTION Nowadays comparing with the field oriented control FOC direct torque control DTC is known as a simpler and easier scheme to perform 2 4 5 . With DTC technique the instantaneous values of flux and torque are estimated from the stator voltages and currents in order to comparing with the command values. Residual results are used to determine the optimum inverter switch states through a look-up table to supply for induction motor. As a result torque can be controlled directly. The stator voltage being used for the estimation is obtained from DC link voltage the switching states of the inverter The inverter is assumed to be supplied from an ideal AC-DC converter which takes AC voltage from the AC grid and provides the inverter a constant DC input
