Nonlinear controller design for single-phase grid-connected photovoltaic systems

The control problem of photovoltaic (PV) systems connected to the grid, through a single phase inverter and L-filter, is addressed in this paper in order to achieve high efficiency for different power generated by a photovoltaic array and also obtained a lower harmonic distortion. The control objective is threefold i) extracting the maximum power, from the PV array, by acting on the boost chopper; ii) providing a current with sinusoidal waveform and in phase with the grid voltage by means of controlling DC/AC converter (PFC); iii) regulating the DC voltage at the input of the inverter to a desired level. A nonlinear controller based on three loops, is implemented using Backstepping technique for PFC and MPPT objectives. A regulator, of PI type, is used to achieve DC voltage regulation. Simulations, in SIMPOWERS/MATLAB environment, show that the control objectives are achieved.