High-efficiency switching strategy and neutral-point voltage control in single-phase three-level inverter

To improve the efficiency of the photovoltaic (PV) system using the three-level inverter, PV modules are separately connected to the DC-links. However, in this connection, the output current distortion can be caused by the unbalanced neutral-point voltage. Then, total efficiency is decreased. This paper proposes a high-efficiency switching strategy and a method for the neutral-point voltage control for a single-phase three-level inverter. In the single-phase three-level inverter, this switching method increases efficiency by reducing switch loss. In addition, the proposed method is implemented by changing space vector and modifying the reference voltages to control the neutral-point voltage. As a result, efficiency of the PV system is increased. The proposed method is proven by the simulation results.