Any alternating electric power supply is always characterized by three reference quantities, which are voltage, electric power and frequency. The generators of power stations are synchronous machines. The present work is based on the modelling of the synchronous machine for a study of the stability of the electricity transmission network. The example considered is a thermal power station of the national network. i.e., Algiers port power station. We have developed a computer program based on MATLAB to simulate the calculations of our multi-variable system. The study presented in this article examines the static stability of a thermal power plant. To make this study a reality, it is necessary to model the synchronous machine. We present the three models of the synchronous machine by emphasizing the role of the shock absorbers and the smoothness of the model with three windings. This work is supported by a spectral analysis based on the eigenvalues of the system.

In this research, partial shading influences on the efficiency of photovoltaic modules are explored. First, mathematical modeling of the Mono-crystalline PV module in case of various irradiation levels is presented. A performance assessment of a PV module by considering the electrical influence of the partial shading are then presented. The PVSYST software is used to explain the behavior of a cell or a group of shaded cells in a PV module. The tool allowed a good understanding of the functions of shunt diodes when one or more cells are shaded. Finally, this simulation is applied to the Algerian site of Béchar. In spite of shadowing and an inclination of 30°, the obtained results are good along the year with a maximum power point. The simulation has given the maximum of energy.

The production of electricity based on the conversion of the sunlight by photocells crystalline silicon is the most way using on technological and industrial plan.As a consequence, the development of the applications of energy production requires cells with high efficiency and low cost.We propose two models using either one or two exponentials allowing to simulate the characteristic current-voltage of a solar cell.The goal of our work is to present a comparative study between the model theoretical and experimental aiming at the improvement of the solar cell efficiency.We also determine the parameters of the solar cell from the current-voltage curve.Additionally, we provide a justification for using the two exponential models for improving the cell efficiency.The model with two exponential allowing to investigate the phenomena of recombination in zone of diffusion and space charge in the areas quasi-neutrals of the transmitter and the base.This study underlines the insufficiency of the model to exponential generally used by showing that it leads to the design of the ideal solar cells whereas structures characterized by a factor of quality greater outcome with high efficiency.

Dielectric conductivity of congruent lithium niobate (LiNbO3, LN) crystals was characterized by the classical method using a guard electrode on one face of the sample. The dielectric characterizations of samples are performed by current-tension measurements in the 160-300oC temperature range. The activation energy of LN crystals is deduced by calculation from the obtained characterization experimental results. The method presented in this paper doesn't constitute a novelty itself but the overall process yielding to the determination of the activation energy of LN is originally presented, started from sample preparation to the final calculation and modeling.