A single-phase grid-tied transformer-less multilevel solar inverter with voltage boost

Abstract

This work proposes a single-phase multilevel grid-tied transformer-less solar inverter with voltage boost. The system comprises of two cascaded stages: the first is a partially rated dc–dc boost converter to create four dc voltage levels, while the second is a new topology of single-phase multilevel sinusoidal pulse width modulated (SPWM) inverter at rated volt-ampere (VA) coupled to the dc–dc converter output voltage levels. This scheme does not require capacitor voltage balancing due to the floating dc supply created in the dc–dc conversion stage. The inverter is controlled using a multicarrier SPWM logic. This scheme exhibits near sinusoidal line current, hence offering reduced filter requirements and reduced common mode currents during grid integration. The device losses in this scheme are low compared to the existing schemes, thus reducing heat-sink requirements. The voltage boost capability becomes cost-effective due to the partial rated conversion stage that offers seamless integration of the inverter at the grid voltage without any additional coupling transformer. Simulation and experimental study confirm the effectiveness of the proposed scheme in applications of single-phase grid interfaced harnessing of solar photovoltaic energy and injecting the power to the utility network.