Sliding mode control of a grid-connected photovoltaic source via a three-phase inverter using incremental conductance MPPT

A robust sliding mode controller (SMC) for a grid-connected photovoltaic inverter is proposed in this paper. The objective of the control is to force both the output voltage of the PV source and the grid power factor at the inverter output to follow a certain trajectory reference. The robust sliding mode controller is applied directly to the nonlinear state model of the system composed by the PV source and the inverter with its input and output filters. There is no need to transform the nonlinear state model into two equivalent linear systems. In order to operate the PV system at the maximum power point and to satisfy the environmental factors, such as solar irradiance and ambient temperature, we have to include a Maximum Power Point Tracker. Simulation results illustrate the performance of the proposed control scheme. In addition, we show that the grid current satisfies the harmonic limits imposed by the IEEE standards for interconnecting distributed resources with electric power systems.