Sliding mode control of three-level NPC inverter based grid-connected photovoltaic system

This paper presents a sliding mode control method of a three-phase three-level neutral point clamped (NPC) inverter based grid connected photovoltaic system. The three-level NPC inverter is forced to deliver just active power to the grid and regulates its self-sustaining DC bus voltages using three sliding mode controllers. The three-level space vector modulation is used in order to turn-on and turn-off the inverter switches and to ensure also the balance of the DC capacitor voltages. The three-level NPC inverter is connected to the photovoltaic panel through a DC/DC converter. For the optimum use of the PV module, a maximum power point tracking (MPPT) controller is used which enables the maximum power extraction under varying irradiation and temperature conditions. Finally, the effectiveness of the proposed control system is demonstrated with Matlab/Simulink simulations.