Third harmonic distortion and Phase shift analysis of Improved Transformless Voltage Source Inverter For Photovoltaic Grid-Connected System with Common-Mode Leakage Current Elimination

This paper analysis the phase shift between output volatge and current in the grid connectd tranformerless inverter due to existece of the filter inductanc. For the elimination of the common-mode leakage current in thetransformerless photovoltaic grid-connected system, an improved single-phase inverter is desined by adding two addional switches and filter inductance due to which phase shift occurs at the grid. For eliminating common mode leackege current in the transformerless inverter by two strategy one is unipolar sinusoidal pulse width modulation (SPWM) control strategy and another Bipolar sinusoidal pulse width modulation (SPWM) control strategy.By applying both this method with diffent inductance value we analysis the optimize value so that we willgenerate a sine wave with fewer harmonics,low phase between grid voltage and grid current,less cost and a simpler design