Direct Torque Control Technique in Induction Motor Drives - a Review

The aim of this paper is to review the origin and developments of direct torque control (DTC), an advanced control technique of induction motor drives yielding superior performance. The direct torque control is one of the excellent control strategies available for torque control of induction machine. It is considered as an alternative to field oriented control (FOC) technique. The DTC is characterized by the absence of PI regulators, co-ordinate transformations, current regulators and pulse width modulated signal generators. DTC also allows a good torque control in steady state and transient operating conditions. In this paper, development of DTC is discussed. The DTC based on space vector modulation (SVM) and switching table has been reviewed. With successively improving reliability and performance of digital technologies, digital control techniques have predominated over analog techniques. Digital control techniques are carried out with microcontrollers, digital signal processors due to their software flexibility and low cost which are being reviewed. Intelligent control techniques like neural networks (NN) and fuzzy logic based DTC are reviewed. Field Programmable Gate Arrays (FPGAs) are a useful platform for the implementation of high bandwidth control systems and the role of FPGA on DTC based induction motor drive is also presented.