A new approach for the connection of a three-level inverter to the power grid for applications in solar energy conversion

This paper studies the connection of a photovoltaic energy system to the AC mains by means of a 3-level voltage source inverter (VSI). A proposal for modeling and controlling the inverter is presented, in order to have full controllability of the power transfer and the DC-link voltage balance. The steady-state, the transient analysis and the large-signal operation are studied and the control is implemented combining a linear quadratic regulator (LQR) and gain-scheduling technique. The method is verified using large signal, nonlinear discrete and averaged simulation models.