8/2/2019 Vector Control of Induction Motor Abstract

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PSPE 7 VECTOR CONTROL OF INDUCTION MOTOR

ABSTRACTInduction motor, particularly squirrel-cage type induction motors, have a

number of advantages when compared with dc motors. Some of these areruggedness, lower maintenance requirements, better reliability, lower cost, weight,volume and inertia, higher efficiency and the ability to operate in dirty and explosiveenvironments. The major drawback of dc motors is the presence of commutators andbrushes, which require frequent maintenance .Also, the DC motors are not suitablefor explosive and dirty environments. Because of their advantages, induction motorsare widely used than all the motors put together.

Vector control of an AC induction motor is analogous to the control of aseparately excited DC motor. In a DC motor the field flux produced by the field currentis perpendicular to the armature flux produced by the armature current. These fields

are decoupled and stationary with respect to each other. Therefore when thearmature current is controlled to control torque the field flux remains unaffectedenabling a fast transient response. Vector control seeks to recreate these orthogonalcomponents in the AC machine in order to control the torque producing currentseparately from the magnetic flux producing current so as to achieve theresponsiveness of a DC machine.

A 3 phase machine can be represented by an equivalent 2 phase machineusing direct (d) and quadrature (q) axes for both stator and rotor. The current in theseaxes are controlled to control the induction motor and hence called Vector Control ofInduction Motor. These two decoupled components can be independently controlled

by passing though separate PI controllers. The outputs of the PI controllers aretransformed back to the three-dimensional stationary reference plane using theinverse of the Clarke-Park transformation. There exists three possibilities for suchselection and hence, three different vector controls. They are: Stator flux orientedcontrol, Rotor flux oriented control, and magnetizing flux oriented control. This thesisstrives to develop a Simulink model of closed loop speed control of 3 phase inductionmotor on a three-phase inverter using indirect vector control of induction motor usingmatlab.As power converters are built from linear and nonlinear electric elements suchas power semiconductor switches, electrical machines, and control systemscontaining linear and nonlinear elements. Effective modeling and simulation of suchsystems require a software tool that can handle all these functions in an integrated

environment. So, MATLAB/SIMULINK software tool is used to simulate and for thestudy of this system.