Low Current Harmonics PWM for Tow-Level Three-Phase Grid-connected PV Inverter

The advantages of photovoltaic (PV) power generation include no fuel cost and abundance of sunlight. For the grid-connected PV inverter systems, the efficiency is always an important issue. At the PV panel side, a DC/DC converter with maximum power point tracking operation is always used to improve power generation of the system. Further, at the grid-connected inverter side, the generated active power is proportional to the power generation efficiency. Therefore, the grid current is expected to be in phase with the grid voltage and the current harmonics must be low to avoid excessive losses. In this paper, a switching strategy is proposed to generate the grid current with low harmonics. Both baseband harmonics and the side-band harmonics are considered. In the simulation, it is shown that a 79.5% reduction of baseband harmonics and a 34% reduction of the total harmonies distortion are achieved comparing with the conventional switching strategy. The direct advantage is the improvement of the system efficiency.