Multi loop based control of photovoltaic system connected to the single phase grid

This paper investigates the control problems of the single-phase grid connected to the photovoltaic system through an inverter with LCL filter. The control objectives are threefold: (i) forcing the voltage in the output of PV panel to track a reference signal provided by the MPPT block; (ii) regulating the DC link voltage to ensure the power transferring from the source to the grid; (iii) providing a current with sinusoidal waveform and in phase with the grid voltage by means of controlling DC/AC converter (PFC). Firstly, a simulation module based on the mathematical model of a PV panel is utilized to predict the maximum total power from PV array. Secondly, a nonlinear module based on the mathematical equations of the whole controlled system is developed. At last, a nonlinear multi-loop controller is synthesized using the sliding mode technique. The results are confirmed by simulations which show that the proposed regulator is robust with respect to changes of Climate factors.