INTELLIGENT AC DRIVE

Abstract

Vector control of industrial induction motor drives have gained the widest acceptance in high performance applications. Through this control method the highly coupled, nonlinear, multivariable induction motor is reduced to linear independent flux and torque control similar to that of a separately excited DC motor control. Field oriented control (FOC) means, in general, decoupled flux linkage and torque yielding fast torque response of AC motor to emulate DC machine behavior. This thesis treats the indirect field oriented control (IFOC) for the rotor flux because it provides pure decoupling between flux and torque.

The current controller plays very important role in current regulated pulse width modulation (CRPWM) inverter. The controller should be able to force the drive current to follow the reference current, generated from the IFOC algorithm, as quickly as possible and guarantee the decoupling control. A novel space vector modulation (SVM) based hysteresis current controller (HCC) is utilized. This technique utilizes all the advantages of the HCC and SVM techniques. The proposed configuration reduces significantly the number ofswitchings of the solid state switches and at the same time gives the same space vector as those obtained from the SVM technique. The current controller confines space vectors from a region detector and applies a proper space vector selected according to inner HCC for better current wave form.