Comparison and performance analysis of unipolar and bipolar digitally-controlled single-phase inverters

Inverter is substantially an interface between DC source like photovoltaic cell and AC networks. There are many doable inverter topologies and switching schemes, and each one will have its own relative benefits and downsides. Efficiency and output current distortion are two necessary factors governing the selection of inverter system. In this paper, two inverter switching strategies are explored. These are the unipolar and bipolar current controlled inverter employing both the SPWM (Sinusoidal Pulse Width Modulation) and the THPWM (Third Harmonic Pulse Width Modulation) techniques. The models of these techniques are simulated using MATLAB-Simulink software. Simulation results are compared with results of an experimental prototype to confirm validity of results. The results are taken for both static and dynamic loads with different modulation index. Both simulated and experimental results are in a good agreement. The results showed that the unipolar switched inverter offers low current distortion over bipolar switched inverter.