Unipolar PWM based four leg voltage source inverter fed unsymmetrical two phase induction motor drive with closed loop V/F control

This paper deals with the unipolar modulation based pulse width modulation(PWM) method for two phase four leg voltage source inverter and it's realization for an asymmetrical two phase induction motor. The effectiveness of such an inverter is verified by comparing with the other inverters used for the unsymmetrical two phase induction motor based on the total harmonic distortion in the unbalanced output voltage of the inverter. Since the output of the inverter is the input supply voltage of the machine, performance of the motor will be affected with the inverter topology. Carrier-based unbalanced PWM strategy is used because of its fixed switching frequency, low ripple current and well defined harmonic spectrum characteristics. The proposed modulation strategy will ensure the independent control of magnitude and keeps the phase difference between the unbalanced output voltages in quadrature. Closed loop V/F control is used for the speed control of the motor. The performance of these inverter topologies and the induction motor has been studied and confirmed by the simulation using MATLAB /SEVIULINK.