State-Feedback Nonlinear Control of Three-phase Grid Connected to the Photovoltaic System

In this paper, the control problem of three-phase grid connected to the PV system through a LCL filter is presented. In this work, we seek the achievement of three control objectives: (i) the voltage provided by PV panel must be controlled to achieve the optimum power by means of controlling the input voltage of DC/DC converter; (ii) regulating the DC link voltage to a constant reference value; (iii) Providing a current with sinusoidal waveform and in phase with the grid voltage by means of controlling DC/AC converter (Power Factor Correction). To meet these threefold objectives, a cascade nonlinear controllers is developed making use of the Lyapunov control design technique. The control system includes also a Maximum Power Point Tracking (MPPT) based on Incremental Conductance "with variable step" algorithm.