Simplified Carrier-based PWM for Three-Level Transformer-Less Grid-connected Photovoltaic Inverters

This article proposes a simple and efficient carrier-based Pulse Width Modulation (PWM) technique for three-level transformer-less grid-connected Photovoltaic (PV) inverters. The three-level inverter is prone to an inherent issue of unbalanced DC-link voltages, which, when used in conjunction with transformer-less grid-connected PV systems, gives rise to leakage currents. A simplified carrier-based PWM is proposed to carry out the DC-link voltage balancing and suppress the leakage current -Common Mode CM current CM- in transformer-less grid-connected inverters. The implementation of the proposed strategy is straightforward and does not require complex calculations, in contrast to space vector-based PWM techniques or multi-carrier modulation techniques. The operation of the PWM strategy is demonstrated through simulations and validated through experimental results.