A constant current sine wave inverter using harmonic injection modulation with T-LCL immittance conversion topology

This paper presents a pure sine wave inverter (SWI) for photovoltaic (PV) applications. In contrast to the sinusoidal pulse width modulation (SPWM), which is commonly used for switching the SWI and has several drawbacks such as low fundamental output voltage, this paper presents an advanced modulation technique called harmonic injection modulation (HIM) to build a pure sine wave inverter. The proposed switching technique results in an output of low harmonic distortion while maintaining the desired level of output voltage. A T-LCL immittance conversion circuit has also been implemented in contrast to the conventional LC filter for reducing the total harmonic distortion (THD). It is observed that the T-LCL immittance conversion circuit offers much improved performance while providing a nearly constant output current. The simulation results of the proposed SWI have also been compared with SPWM inverter and a few other inverters built in different modulation techniques.