Unipolar and Bipolar PWM Inverter

Inverter is basically an interface between DC source like photovoltaic cell and AC networks. There are many inverter topologies but output current distortion and efficiency are the two main parameters for the selection of inverters. Two such topologies are described herein. In this paper, the SPWM (Sinusoidal Pulse Width Modulation) technique of unipolar and bipolar inverters is presented and the models are simulated in MATLAB – Simulink. The H-Bridge inverter topologies (both unipolar and bipolar) are made up of power electronic switches and are fed with constant amplitude pulses with varying duty cycle for each period. The SPWM pulses are generated by comparison of two wavesa carrier wave, which is triangular in this case and a modulating reference wave whose frequency is the desired frequency, which is sinusoidal in this case. This pulse width modulation inverter is characterized by simple circuitry and rugged control scheme that is SPWM technique to obtain inverter output voltage control and to reduce its harmonic content.