Implementation of Three Phase AC Chopper using dSPACE

Abstract

Speed of induction motors can be controlled in various different ways out of which field oriented control and V/f control are widely used. Inverters provide variable frequency as well as output voltage and are widely used in ac drives, UPS, SMPS, etc. The topology of three phase AC chopper which has been proposed here provides control of both voltage as well as frequency. It consists of an uncontrolled rectifier, a buck-boost dc to dc converter and an inverter. Here the frequency control is provided by the buck-boost converter which performs buck/boost operation so as to convert its input frequency into the reference frequency provided to it in the closed loop, while the voltage control is provided by operating the inverter as AC chopper. Simula- tion for single phase is carried out initially in MATLAB/simulink. Its open loop and closed loop operation for reference frequencies below 50Hz are observed by simulation. Finally, such three units are used to form three phase topology, the simulation is car- ried out with each unit provided the supply voltage as Vmsin(wt), Vmsin(wt-120) and Vmsin(wt-240) respectively. This three phase topology provides variable voltage and variable frequency control of induction motors. The dSPACE 1104 R & D controller board is studied thoroughly so as to use it for hardware implementation.