The aim of this paper is to analyze and evaluate three different forms of Maximum Power Point Tracking (MPPT) techniques under standard and various atmospheric conditions. In the literature, different MPPT methods are proposed and studied by researchers, let us quote the well known Perturb & Observe (P&O), the incremental conductance, fuzzy logic based MPPT, neural networks based MPPT,etc. The major drawback found is the effectiveness of these techniques under sudden variations in weather conditions such as irradiance and temperature. Another drawback of some MPPT techniques is the response time which is important to achieve the optimum power value. In this sense, optimization of P&O method becomes the objective of our work, to track the point of maximum power in a photovoltaic system under different weather conditions. In this paper, we will improve the P&O technique which makes it possible to react quickly to sudden changes in solar radiation and to follow the maximum power point with very low oscillations. The main idea is to use a PID regulator to make the voltage of the PV panel much closer than the MPP voltage, this method is named indirect P&O. The simulation based comparative study showed that the MPPT indirect P&O technique led to better performance.