Maximum power point tracking of photovoltaic water pumping system using fuzzy logic controller

Diode junction photovoltaic (PV) generators exhibit nonlinear V-I characteristics and the maximum power extractable varies with the intensity of solar radiation, temperature and load conditions. A maximum power point tracking (MPPT) controller is therefore usually employed in PV-generator applications to automatically extract maximum power irrespective of the instantaneous conditions of the PV system. This paper presents a fuzzy logic control (FLC) scheme for extracting the maximum power from a stand-alone PV generator for use in a water pumping system. The PV-generator system comprises a solar panel, DC-DC buck chopper, fuzzy MPP tracker and permanent DC-motor driving a centrifugal pump. The fuzzy controller generates a control signal for the pulse-width-modulation generator which in turn adjusts the duty ratio of the buck chopper to match the load impedance to the PV generator, and consequently maximizes the motor speed and the water discharge rate of a coupled centrifugal pump. The control method has been modelled in Matlab/Simulink and simulation results are presented to confirm its significantly improved power extraction performance under different sunlight conditions, when compared with a directly-connected PV-generator energized pumping system operating.