A modular photo-voltaic grid-connected inverter based on phase-shifted-carrier technique

Residential photovoltaic grid-connected inverters are modular distributed power generation devices that convert the DC power from the roof-top solar panels to high-quality AC power at the utility grid interface. In this paper, the phase-shifted-carrier technique, which is normally used in high power multi-converter schemes, is applied to a modular grid-connected inverter to improve the output current waveform. First, it is shown, through analysis and simulation, that in the commonly-used photovoltaic grid-connected inverter topology, based on the phase-shift modulated full-bridge converter, the well-known rule of the phase-shift between the carrier signals of the adjacent modules is not valid for both odd and even number of modules. Then, a new general rule for the phase-shift is proposed, and finally, the validity of the proposed rule and its effect on the improvement of the quality of the output current waveform are verified through simulation.