Chafic Salame

Efficiency of magnetic coupled boost DC-DC converters mainly dedicated to renewable energy systems: influence of the coupling factor

Summary This paper presents a specific analysis of an individual basic magnetically coupled direct current-to-direct current (DC–DC) converter specially designed for integration in a distributed architecture of renewable energy generators for smart grid applications. In such distributed architecture dedicated for renewable energy, parallel high-voltage DC presents many advantages over the classical centralized one. We show that in such setup, high voltage can be advantageously produced using a specific magnetically coupled boost converter, and we point out the influence of the coupling factor, generally considered equal to one, on the overall performance of the converter and on the global energy efficiency of the installation. In this study, the generalized concepts of system energy parameters of DC–DC converters are introduced and applied to the transient analysis. Consequently, the operation of a magnetic coupled DC–DC converter with a recovery stage is modeled. The simulation results are compared with those of the behavioral study, deduced from the model pointing out the large influence of the coupling factor value on the global behavior and mainly on the value of the recovery voltage, in all the various parts of the switching cycle. The renewable energy generator operating parameters, such as current and voltage values, can then be predicted in a more useful way to compute new similar DC–DC converter systems. Copyright

Switching times variation of power MOSFET devices after electrical stress.

The switching performance of three power MOSFET devices with different oxide thicknesses is studied after several periods of electrical stress. The thickest oxide reveals a large accumulation of positive charges in the oxide bulk after small periods of stress. These charges affect the switching parameters by increasing the rise time and by decreasing the fall time. Larger periods of stress reduce the effect of positive charges by increasing the number of interface states. The threshold voltage is decreased by the effect of a positive oxide charge and increases with the appearance of interface states. All these phenomena are less observable as we reduce the oxide thickness.

Switching times variation of MOSFET devices with temperature and high-field stress

Switching times of power MOSFET devices are investigated as function of temperature and high-field stress. Measurements show that important variations are obtained on the devices turn-on time. The threshold voltage is decreasing with temperature and varies with stress, especially at low temperatures. The oxide leakage current is found to be having safe values even at high temperatures, stressing the devices does not increase the leakage current to unsafe values except for very high temperatures.

A faster power MOSFET device with electrical stress treatment

Purpose – The aim of this paper is to provide some specific information on the effects of DC voltage stress on the current, rise time (Tr) and fall time (Tf), at switching between on and off state of power n‐MOSFET devices.Design/methodology/approach – A constant positive electrical stress voltage technique is used to study the devices in this work by giving the gate a positively bias with respect to source and a short circuit of the drain with the grounded source. Voltage stress is gradually increased by automatic 1 V step until it reaches the max tolerated value by the gate dielectric (70 V for device studied in this paper). Response of the device for electrical stress was measured for different doses (stress time).Findings – The experimental results show that the rise time increases the beginning of stress dose and then it almost stabilises with time, while fall time decreases at first and then starts to increase for higher stress time. The modification of the device switching time parameters were asso...

Silicon MOSFET devices electrical parameters evolution at high temperatures

Purpose – The purpose of this paper is to discuss the temperature failure effect on electronic components and their electrical parameters variation.Design/methodology/approach – The MOSFET device parameters analysis was done by numerical analysis based on a double exponential model using the integrated pn junction.Findings – The temperature dependence of these parameters is investigated; their evolution allows the evaluation of devices operation reliability in high‐temperature environments.Originality/value – The paper demonstrates how the temperature affect the normal operation of the electronic device and the model accuracy is investigated at high temperature.

Temperature dependence of a silicon power device switching parameters

This study presents measurements of device switching parameters performed on a commercial power metal-oxide-semiconductor field-effect transistor under high-temperature conditions. Measured switching times show that the device response to being turned off becomes faster at high temperatures. The inverse drain-source current rapidly increases above the 300°C limit. I-V curves indicate that the saturation current in the channel increases with temperature.

Evaluation of the electrical properties under extreme stress in photovoltaic solar modules

Purpose – The purpose of this paper is to discuss the effect of electric reverse stress currents on the performance of photovoltaic solar modules.Design/methodology/approach – The effect of a reverse introduced current as a function of time is studied on the I‐V and C‐V characteristics and parameters which were extracted and analyzed using numerical analysis based on a reliable double exponential model.Findings – The effect of an introduced reverse current for different periods simulated the effect of accumulated extreme reverse currents which may arise in solar cells and modules due to different reasons, causing dramatic changes in the shunt resistance as well as other characteristics, mainly when the time of the current application exceeded a certain limit.Originality/value – The paper contributes to the research on the damaging effects of reverse currents on the normal operation of the solar cells and modules.

Evolution of photovoltaic solar modules dark properties after exposition to electrical reverse stress current inducing thermal effect

Purpose – The purpose of this paper is to investigate the dark properties as a function of reverse current induced defects. Dark characteristics of solar modules are very essential in the understanding the functioning of these devices. Design/methodology/approach – Reverse currents were applied on the photovoltaic (PV) modules to create defects. At several time intervals, dark characteristics along with surface temperature were measured. Findings – Current-voltage (I-V) and capacitance-voltage (C-V) characteristics furnished valuable data and threshold values for reverse currents. Maximum module surface temperatures were directly related to each of the induced reverse currents and to the amount of leakage current. Microstructural damages, in the form of hot spots and overheating, are linked to reverse current effects. Experimental evidence showed that different levels of reverse currents are a major degrading factor of the performance of solar cells and modules. Originality/value – These results give a re...

N-channel power MOSFET for fast neutron detection

Developments in neutron detection technology during the past three years are reviewed with special emphasis on application to safety, security, or industrial development.An investigation about the possibility of using N‐channel power MOSFET (metal oxide semiconductor field effect transistor) as a high‐energy neutron sensitive detector is presented here. An empirical expression for neutron fluence detection is derived from the relation between neutron fluence and the evolution of the transistor current measured in the saturation region. This expression is valid for neutron fluence in the range 5×109–1×1014 n cm−2.

Parameters and characteristics of PV solar modules under the influence of thermal stresses

The effect of thermal stress on the performance of PV solar modules under dark and illuminated conditions was evaluated. The (I-V) characteristics and parameters for the PV modules have been measured, in dark and illuminated conditions, after each period of thermal stress. A digital double exponential model was used to analyze the experimental measurements. The changes in characteristics, which are caused from the effect of heat introduced for different stress levels, simulated the effect of accumulated extreme temperature that can occur in the solar cells and modules as the result of shading and other different reasons. The modification for normal operation of PV cells and modules exposed to shadow effects can be deduced from the present study.