Common-ground transformerless inverter for solar photovoltaic module

This paper presents a new single-phase transformerless inverter providing common ground for grid-connected photovoltaic (PV) systems. It consists of 5 switches, one diode, one capacitor, one small inductor and a small filter at the output stage. A simple Unipolar Sinusoidal Pulse-Width Modulation (SPWM) technique is used to operate the proposed inverter to minimize losses, output current ripple, filter requirements and improve its electromagnetic compatibility (EMC). The proposed topology shares a common ground with the grid and a capacitor is utilized as a virtual DC bus to provide the negative power cycle of the inverter. The capacitor is charged regardless of any switching cycle using a dedicated switch which can in turn reduce the size of capacitor in relation to the switching frequency. The peak ac output voltage is equal to the input DC voltage which reduces the requirement of the high input DC voltages. Simulation and experimental results for a 1 kW prototype are presented to demonstrate the usefulness of the proposed topology.