Single-phase grid tied inverter is one among types of inverters widely used in photovoltaic generation systems due to the advantages they offer, in the absence of the grid, islanding situations occur. This paper describes model and simulation of such inverter in operation as distributed generation in electrical power system under islanding phenomena. In this configuration, it is imperative that the inverter automatically disconnects from the grid without remaining any residual voltage that can be dangerous for the plants and stakeholders. It is important to detect the islanding situation. For this purpose several techniques are used. We present in this article the implementation of the method called Slide-Mode frequency Shift (SMS) in the control of a single phase photovoltaic inverter, for which we provide a description of our SIMULINK implementations and their evaluations performed on the basis of comparison with Active Frequency Drift (AFD) method. Simulation results show that the developed algorithm detects the islanding phenomenon in the time approaching that required by the IEC and IEEE standards that secures the PV system connected to the grid.

This paper presents an evaluation study of two pwm techniques applied to a three-phase voltage source inverter supplied by photovoltaic (PV) energy sources. A Pspice-based model of the pv array is developed and tested. The power and currant of the pv array versus the voltage is plotted. Then the pv array is connected to a basic three phase voltage source inverter VSI. Two control techniques are used. The first one is the classic sinusoidal pulse width modulation spwm, which is based on the comparison of two signals, the sinusoidal reference and a triangular carrier. The second one is based on the principle of harmonic elimination. The system is simulated using orcad-pspice, the results are given, discussed and compared based on different performance indices (output quality, thd, frequency).

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The estimation of the junction temperature (Tj) is very important factor for improving the reliability and efficiency of the power electronic converters. A new electro-thermal (ET) model of low voltage power MOSFET is described in this paper. The electro-thermal model allows fast estimation of the junction temperature, based on the transient thermal impedances (Zth) using the (RC) Foster thermal network model and total power losses. The parameters of the (RC) Foster thermal network model are extracted from the data provided by the manufacturer's datasheet using particle swarm optimization (PSO) method. Moreover, a dc/dc Buck converter is also analyzed by simulation to evaluate the electro-thermal model. The simulation results indicate a good agreement between the proposed model and manufacturer's data. Finally, the electro-thermal (ET) model simulation using this (RC) Foster thermal network model shows a reasonable accuracy for estimating the junction temperature in a Dc/Dc buck converter.