An Improved Pulse Width Modulation Technique for the Attenuation of Leakage Current in Five-Level Transformerless PV Cascaded Multilevel Inverter

This paper presents an improved pulse width modulation technique for the five-level transformerless grid connected/ stand-alone cascaded multi-level inverter (CMLI) for attenuating the magnitude of the leakage current. The improved PWM technique employs two modified reference waves for the production of five-level at the inverter output terminals. The improved PWM technique employs a single triangular wave for obtaining the five-levels at the inverter output terminals. The improved PWM technique reduced the total harmonic distortion (THD) in the grid current by shifting the harmonics to the even multiples of the carrier frequency. Due to the shifting of the harmonics to the higher order the size of the filter required at the output of the inverter terminals are reduced. The improved PWM technique attenuates the magnitude of leakage current flowing in the PV panels. The bulky elements like electromagnetic interface (EMI) and the common filter required for the five-level CMLI are reduced without the addition of any extra circuitry.