Design and Control Scheme of Three-phase Photovoltaic Grid-connected Inverter

With the development of power electronics technology, a variety of unbalanced load are connected to the grid, causing the grid voltage imbalance and power quality decline, seriously affect the user's normal use. Traditional three-leg inverter can output three-phase symmetrical voltage in the case of three-phase symmetrical load. But it is difficult to output three-phase symmetrical voltage when the three-phase load is asymmetric. In order to solve the impact of unbalanced load on the power quality, the three-phase four-leg inverter which is obtained with the addition of a bridge arm on the basis of traditional three-leg inverter is adopted in this paper. Therefore, the three-phase symmetrical voltage can be acquired in the case of unbalanced load, at the same time, with the advantages of simple structure, small size, light weight, higher voltage utilization.