Adaptive Fractional-Order Fuzzy Logic Control of Grid-Tied Photovoltaic Inverter

Photovoltaic (PV) energy source has gained more interest in recent decades, due to the environmental concerns and depletion in the conventional energy resources reserve such as fossil fuel. Furthermore, this type of energy source has more advantages such as free of pollution, reliability, availability, no mechanical moving part, little maintenances, has long life time, and quietness. In future more, photovoltaic energy source is anticipated to be interfaced with a grid. Beside the low efficiency of a photovoltaic energy source, a controllability of gird-tied based photovoltaic system its main challenge. As the result, interfacing photovoltaic energy source to grid can derived to grid instability, if the system is not appropriately adjusted. Therefore, the control techniques applied to grid-tied photovoltaic energy source becomes of high interest and always important for the sake of accomplish excellent power quality and highest reliability. Those goals can be accomplished by advanced control methods which includes two stages The first stage is MPPT controller based on the fractional-order fuzzy logic controller (FOFLC) to accomplish the objective of maximizing the output power of photovoltaic array during regular and irregular atmospheric conditions. A second stage is the control of H-bridge VSI with unipolar sinusoidal pulse width modulation (SPWM) technique. A control technique of the H-bridge VSI consists of two cascaded loops, where an external loop voltage regulator is employed to stabilize voltage of dc link to a required level, this can be achieved by the means of MPPT algorithm, while an internal loop current regulator is employed to maintain the unity power factor operation. It has been found that from many research studies have been done concerning to the grid-tied photovoltaic energy source which mainly focuses on the internal control loop with less attention to external control loop and lacking of stability analysis. This paper presents the complete control techniques of single-phase grid-tied photovoltaic energy source considering the nonlinear dynamic behavior of photovoltaic energy source. For the validation of an effectiveness, efficiency, and validity of the proposed model the simulation results have accomplished through MATLAB/ Simulink simscope power system.