JEE_V10_N3_RP1 Amine Daoud Journal on Electrical Engineering 2230 – 7176 10 3 1 10 Single Sensor, MPPT, DC/DC Buck Converter, Variable Step-Size, PV Pumping System In this paper, an improved variable Maximum Power Point Tracking (MPPT) method for photovoltaic (PV) water pumping system is proposed. This method consists on a modified single-voltage-sensor based MPPT algorithm, which is used to fine tune the duty cycle of a DC/DC converter in order to avoid divergences of the MPP under varying irradiance levels. Furthermore, using this technique, only the output voltage of a power converter needs to be sensed in order to find and track the MPP. To investigate the performance of the proposed MPPT method, a PV system that includes solar array, DC/DC buck converter, DC motor-pump, and MPPT control system is considered and simulated on MATLAB platform. The proposed variable step-size method is compared to perturbation and observation classical method with fixed step-size. The simulation results are given and discussed for validation. January - March 2017 Copyright © 2017 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=12410