Modeling, Simulation and Comparison of Common Control Techniques of AC Induction Motor Drive

Abstract

Abstract AC induction motor drives are now finding increasing acceptance in various industrial applications because of the performance they can provide. Applications of AC drives vary from running simple conveyor belts and blowers to implementing a sophisticated variable speed variable frequency drives (VFD), in which torque and speed are wellregulated. Based on the type of application, choice of an appropriate control technique is made. This paper presents a comparative study on most popular control strategies of Induction Motor Drives; constant V/Hz open/ closed loop control, field-oriented control (FOC), and Direct Torque Control (DTC). The comparison is based on various criteria including basic control characteristics, torque performance, speed performance and transient response with respect to the load torque and speed variations. Simulations of the above control techniques have been performed using MATLAB/SIMULINK™ software. The Adjustable Speed Drives are generally used in industry. In most drives AC motors are applied. The standard in those drives are Induction Motors (IM). Induction motors are widely used in application such as pumps, fans, elevators, electrical vehicles, heating, ventilation and air-conditioning (HVAC), robotics, wind generation systems, etc. Previously, DC machines were preferred for variable speed drives. However, DC motors have disadvantages of higher cost, higher rotor inertia and maintenance problem with commutators and brushes. In addition they cannot operate in dirty and explosive environments. The AC motors do not have the disadvantages of DC machines. Therefore, DC motors are progressively replaced by AC drives. The accountable for those results are the development of modern semiconductor devices, especially power insulated gate bipolar transistors (IGBT). The most economical IM speed control methods are realized by using frequency converters. Many different strategies of frequency converters are proposed and investigated in this paper. However, a converter consisting of a diode rectifier, a dc-link and a pulse width modulated (PWM) voltage inverter is the most applied used in industry. The high-performance frequency controlled PWM inverter – fed IM drive should be characterized by: Fast flux and torque response.Constant switching frequency.Low flux and torque ripple.Robustness for parameter variation. The abovesaid features depend on the applied control strategy. The main goal of the chosen control method is to provide the best possible parameters of the drive. Additionally, a very important requirement regarding control method is the simplicity (simple algorithm, simple tuning and operation with small controller dimension leads to low price of final product). A general classification of the variable frequency IM control methods is presented in Fig. 1