Common-Ground Transformerless Inverter with Virtual DC Bus Concept for Single-Phase PV Systems

This study investigates a single-phase common-ground transformerless inverter topology for grid-connected photovoltaic (PV) systems. The inverter shares a common ground with the grid and utilizes minimal components for power conversion, making it suitable for use as an integrated microinverter for solar PV modules. The peak of the ac output voltage is the same as the input DC voltage, and a virtual DC bus capacitor is used to provide power during the negative cycle of the inverter. A simple unipolar sinusoidal pulse-width modulation technique is used to modulate the inverter minimizing switching loss, output filter requirements, and output current ripple. Moreover, a double-charging process is employed to minimize the inrush charging current of the virtual DC bus capacitor. Various operating states along with the design guidelines for choosing the constituent components are presented. Finally, some simulation and experimental results are presented for a 1 kW prototype to validate the proposed topology.