In this paper a circuit-based simulation model is defined for a PV cell in order to allow estimating the electrical behaviour of the cell with respect changes on environmental parameter of temperature and irradiance. Maximum power point trackers (MPPT) play an important role in photovoltaic (PV) power systems because they maximize the power output from a PV system for a given set of conditions, and therefore maximize the array efficiency. DC-DC converters together with MPPT systems are used to avoid the energy losses. Different algorithms have been proposed for maximum power point tracking, the Perturb & Observe (P&O) and Incremental Conductance (incCond) methods are illustrated in this work. In this paper the implementation of a photovoltaic model using Matlab/Simulink are presented, which can be representative of PV cell module, for easy use on simulation platform. Taking the effect of sunlight irradiance and cell temperature into consideration, the output current and power characteristics of PV model are simulated and optimized using the proposed model. Next, a voltage control of a photovoltaic system is studied in order to have a constant voltage at the output, always keeping the system to operate at maximum power. Indeed, in most industrial applications, the load must be supplied by a constant voltage. The simulation results are carried out using Matlab/Simulink.