Direct Torque Control Without Speed-Sensor

This paper introduces the outline of AC motor drive control and the theories of modern AC motor drive technologies, such as VVVF, DTC and FOC. This paper analyses both the disadvantages of a speed control system with speed sensors and the advantages of a speed control system without speed sensors. This paper also presents the current situation of the speed-sensorless technology, especially the applications of this technology in FOC systems. This paper presents a new method to estimate the angle of the stator flux( 9 ). After studying a lot of documents,we present a speed-estimating method for direct torque control system. This method is based on the theory of DTC, but it takes advantage of the convenient of both the theory of DTC and the theory of FOC. We need only to sample the stator's current to estimate the speed of the rotor, at the same time the integration of the voltage is avoided. So the calculation of the method is very simple , and the thought of the method is very clear. This paper demonstrates the method theoretically on one hand, and has a digital simulation of it on the other hand. The results of theoretical analysis and digital simulation are all show that the speed-calculating method is reasonable. Based on all this theoretical analysis and digital simulation, a experimental control system was designed and fabricated. It has been tentatively testified that the experiment system is rational on the hardware combination and software program through many experiments on a 5.5KW AC motor.