A multicarrier modular photovoltaic grid-connected inverter with a new phase-shift rule

Photovoltaic grid-connected inverters are distributed power generation devices that convert the dc power from solar panels to high-quality ac power at the utility grid interface. Adopting modular design in these systems improves expandability, serviceability, reliability and efficiency. In this paper, the phase-shifted carrier technique, which is normally used in high-power multiconverter schemes, is applied to a modular residential photovoltaic grid-connected inverter to improve the output power quality. First, it is shown, through analysis and simulation, that in the commonly-used grid-connected inverter topology based on the phase-shift modulated full-bridge converter, the well-known rule for the phase-shift between the carrier signals of the adjacent modules is not effective for both odd and even number of modules. Then, a new general rule for the phase-shift is systematically derived and its effectiveness in improving the output power quality for odd and even numbers of modules is verified through simulation.