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This article proposes new photovoltaic (PV) models, with which the modeling accuracies are much improved, regardless of wide absolute temperature variations. The desired PV models are designed by an equivalent electrical circuit consisting of a single diode and two proposed nonlinear thermal resistors. The realization of such resistors is therefore the key contribution of this article since they significantly increase the degrees of freedom of similar circuits, including fixed resistors. As a result, the given modeling accuracies are clearly improved not only under standard test conditions but also in more severe climatic environments, characterized by high absolute temperatures. To achieve this goal, the parameters of the two proposed PV models were optimized using the gnetic algorithm, where a fitness function for each PV model is well minimized. Each fitness function was previously formulated from comparing actual output currents, prerecorded from the existing ISOFOTON I-50 PV panel, by predicted output currents, computed using the Lambert-W function. The given performances by the proposed PV models were compared with those provided by the standard PV ones where the given simulation results reveal the superiority of the proposed PV models under different weather conditions. [ABSTRACT FROM AUTHOR]

This paper presents a new linear model design including the KC200GT photovoltaic generator GPV panel, DC-DC boost converter, and resistive load. The small-signal principle is indeed applied to the configuration connecting these three devices that are previously developed graphically using the M a t l a b ® / S i m u l i n k software package. This new model design is established through a set of proposed steps, providing the first contribution of this paper. A new voltage proportional-integral-derivative (PID) controller is synthesized based on the previous linear small-signal model. The controller parameters are computed by proposing a reference open-loop system and using the frequency identification approach, providing the second contribution of this paper. The resulting PID controller is combined with the classical perturb and observe (P &O) algorithm where its fill factor (FF) and its reference tracking dynamic are significantly improved. Improving these two performances for a sudden change of both climatic conditions, i.e., absolute temperature and solar irradiance, constitutes another contribution of this paper. Given improving the previous two performances, the maximum power point tracking (MPPT) scheme with oscillation free tracking of the desired MPP is established for conventional and improved P &O algorithms using S i m p o w e r ® system libraries of the M a t l a b ® / S i m u l i n k environment. The given simulation tests confirm the effectiveness of the proposed P &O-MPPT control strategy in terms of reference tracking accuracy, rise and settling times, and solving the ripple issue that occurred in the DC-DC boost converter output current. [ABSTRACT FROM AUTHOR]

A lot of previous studies have shown a great interest in connecting photovoltaic (PV) arrays to electric power grids. A Maximum Power Point Tracker (MPPT) controlled 100 kW PV array to boost its power that feeds the grid with the help of a three-level inverter. This paper investigated the effects of open-circuit faults of three-level inverter IGBT switches on the performance of the PV array system. This paper proposes a new diagnostic method called the Double Threshold-Trigonometric Coordinates (DT-TC) that relies on the double threshold technique and the trigonometric coordinates, respectively, for early detection and the precise location of open-circuit faults. To the best knowledge of the authors, two simultaneous open-circuit faults were not considered in the previous studies. The obtained simulation results prove the great success of the proposed diagnosis method even under noticeable changes in irradiation, temperature, and the number of PV array connected in series and in parallel. In this study, the reconfigurable fault-tolerant inverter was included to ensure the perfect continuity of the PV array system and its recovery in an extremely very short time up to 7 ms. [ABSTRACT FROM AUTHOR]

In this work, the microstructural evolution and mechanical properties of 304 austenitic stainless steel welds produced by GTAW process were examined after post weld heat treatment (PWHT). Thermal treatment was carried out at different temperatures ranging from 450 to 1050 °C. The optical microscope and scanning electron microscope were used to study the microstructure and fracture surface of the welded joints. X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) techniques were used to investigate the possible formation of intermetallic phases as σ or chromium carbide. Based on the results, no σ phase or chromium carbide precipitation was found. Also, the mechanical behavior of the joint was evaluated by tensile and microhardness tests. The microstructure of the 304 stainless steel was found to consist of equiaxed austenite grains (γ) of various sizes limited by grain boundaries and twin crystals with small amount of delta ferrite (δ) in grain boundaries. The microstructure of the weld metal was austenite with dendritic structure containing skeletal delta-ferrite. The skeletal type delta-ferrite changed from columnar + equiaxed to cellular type by progression during heat treatment. The base metal (BM) and heat affected zone (HAZ) grain size decreased with increasing heat treatment temperature. Therefore, the mechanical testing results were appropriately correlated with the microstructure analysis. Tensile testing analysis showed that the highest tensile strength value was recorded for the as-welded specimen. On the other hand, the PWHT temperature has less effect on the tensile strengths but improves the elongation of the weldments. The micro-hardness for all the weld zones WZs exhibited lower values than that of the base metal BM and the heat affected zone HAZ. The latter presents similar micro-hardness values for all samples and slightly higher than that of the BM except for the weld heat treated at 850 °C, which attained high micro-hardness values. The weldment solution heat treated at 1050 °C shows the best and stable micro-hardness profile similar to that of the as-weld specimen but with higher values in the weld zone. [ABSTRACT FROM AUTHOR]

The main problem regarding wind power systems is the major discrepancy between the irregular character of the primary source (wind speed is a random, strongly non-stationary process) and the exigent demands regarding the electrical energy quality. This paper presents a feedback linearization controller based particle swarm optimization for maximum power point tracking of wind turbine equipped by PMSG connected to the grid, the proposed method which aims at maximizing the power captured by WECS. In order to drive the system to the optimal operating point using the selection of the controller parameters with particle swarm optimization. The obtained simulation results with a variable wind profile show an adequate dynamic of the conversion system using the proposed approach. [ABSTRACT FROM AUTHOR]

This paper proposes a particle swarm optimization based sliding mode control of squirrel cage induction generator of a variable speed wind energy conversion system. The key feature of sliding mode control is a wisely chosen sliding surface which allows the turbine to operate more or less close to the optimal regimes characteristic. Optimal control parameters which are the convergence speed to the sliding-mode, the slope of the surface and the switching component amplitude of SMC are determined using particle swarm optimization approach. The simulation results prove the viability of the proposed control structure. [ABSTRACT FROM AUTHOR]

In this paper, particle swarm optimization (PSO) is proposed to generate an On-Off Controller. On-Off Control scheme based maximum power point tracking is proposed to control the rotor side converter of wind turbine equipped with doubly fed induction generator connected to the grid with battery storage. The Grid Side Converter (GSC) is controlled in such a way to guarantee a smooth DC voltage and ensure sinusoidal current in the grid side. Simulation results show that the wind turbine can operate at its optimum power point for variable speed and power quality can be improved. [ABSTRACT FROM AUTHOR]

This paper is focused on the estimation of the effect of root pass chemical composition, in multi-pass GTA Weldments, on microstructure and mechanical properties of duplex stainless steel welds. We used two different filler metals, the super duplex ER 2594 and duplex ER 2209. Microstructures of different passes of welded joints are investigated using optical microscope and scanning electron microscope. The relationship between mechanical properties, corrosion resistance, and microstructure of welded joints is evaluated. It is found that the tensile and toughness properties of the first weldment, employing the combination of ER 2594 in the root pass and ER 2209 in the remaining, are better than that of the second weldment employing ER 2209 all passes, due to the root pass grains refinement and its alloy elements content as chromium Cr and nitrogen N. The microstructure indicates the presence of austenite in different forms on the weld zone of ER 2209, same in the case of ER 2594, but with higher content and finer grains size, in particular Widmanstätten austenite WA. Potentiodynamic polarization tests of the first weld metal evaluated in 3.5% NaCl solution at room temperature have been demonstrated a corrosion resistance higher than that of the second weld metal. This work addressed the improvement of the corrosion resistance using appropriate filler metal without getting any structural heterogeneity and detrimental changes in the mechanical properties. [ABSTRACT FROM AUTHOR]

Photovoltaic power generation system becomes increasingly important, highly attractive as a clean and renewable energy sources, widely used today in many applications. Recently, researchers have strongly promoted the use of solar energy as a viable source of energy due to its advantages and which it can be integrated into local and regional power supplies. The P–V curve of photovoltaic system exhibits multiple peaks under various conditions of functioning and changes in meteorological conditions which reduces the effectiveness of conventional maximum power point tracking (MPPT) methods and the Particle swarm optimization (PSO) algorithm is considered to be highly efficient for the solution of complicated problems. In this paper, the application of this approach based MPPT algorithm for Photovoltaic power generation system operating under variable conditions is proposed to optimize and to design an intelligent controller comparing to conventional one. PSO Approaches is considered to select and generate an optimal duty cycle which varies with photovoltaic parameters in order to extract the maximum Power. Simulation results show that the proposed approach can track the maximum power point faster and can improve the performance of the system compared to the conventional method. [ABSTRACT FROM AUTHOR]

In this paper, a novel and simplified model representing current-output phase-shift full-bridge DC-DC LCLC resonant converter in arc welding application is thoroughly presented. First, a switched model written in state space representation and featuring a bilinear form is proposed. The latter facilitates the derivation of both the reduced and full order averaged models in continuous conduction mode (ROAM and FOAM). Although the FOAM can be employed in linear or nonlinear control schemes and the derivation of steady state behavior, in this paper the ROAM is considered in designing both voltage mode control and current mode control by using the classical PID and the fractional order PID controllers. Simulation confirms that the switched model, ROAM and FOAM are quite accurate compared to the circuit simulation using SimPowerSystem toolbox of MATLAB/SIMULINK. Results clearly showed that depending on the switching frequency, the proposed topology can be applied either in constant voltage characteristic or dropped characteristic welding machines fulfilling either zero current Switching (ZCS) or zero voltage switching (ZVS). Besides, the fractional order PID controller seems to be more adapted for arc welding application than its traditional version. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the metallurgical and mechanical properties of dissimilar assemblies of 2024 T3 and 7075 T6 structural hardening aluminum alloy by the TIG twine electrode arc welding process. It will include a weld performed according to optimized welding parameters followed by a study of the macroscopic and microscopic evolution of the dissimilar assembly (2024-7075) using optical and scanning electron microscopy (SEM); in addition, the phase compositions were analyzed with an energy dispersive spectrometer (EDS). Tensile and microhardness tests were performed. The tensile fracture was observed by SEM. This paper suggests that when the double tungsten electrode TIG welding is used, a stable arc has been formed with a good bead appearance. The heat dissipated by the arc generates several zones (molten zone (WZ), bonding zones (LZ), heat-affected zones (HAZ)) with different microstructures or precipitates of the type θ (Al2 Cu), S (Al2 Cu, Mg) and η (Mg Zn2), S (Al2 Cu Mg) are formed in the heat-affected zone (HAZ) of base metals 2024 and 7075 respectively. The microhardness is lower in the molten zone and higher in the heat-affected zone of 7075 T6 alloy, which cried out an embrittlement and a 44% and 37% drop in the tensile strength of 7075 T6 and 2024 T3 base metals respectively. [ABSTRACT FROM AUTHOR]

The current paper investigates Backstepping controller using Particle Swarm Optimization for Photovoltaic "PV"/Wind hybrid system. The tested system was connected to the grid by three-phase inverter commissioned to address current depending on the grid parameters and still deliver its reactive power to zero. Backstepping control is a recursive methodology that uses Lyapunov function which can ensure the system stability. The best selection of Lyapunov function gains values should give a good result. In most of the literatures, the choice was based on the expertise of the studied system using hurwitzienne method considered as heuristic choice. The aim of this work is to propose an optimization using a powerful method commonly called Particle Swarm Optimization "PSO" able to calculate the gains values depending on the grid parameters by minimizing a selected criterion. The simulation results show that the PSO Backstepping controller gives good results shown in the current injected to grid with a small harmonic distortion despite climate change in the wind speed and the irradiation, which also shows the robustness of the applied control. [ABSTRACT FROM AUTHOR]

In this paper, a comparison between GAs and PSO Approaches is considered to select and generate an optimal duty cycle which varies with photovoltaic parameter in order to extract the maximum Power from Photovoltaic System using real values of temperature and insolation. The energy storage has very important role in renewable energy. To illustrate the energy storage, we have used a battery type lead-acid simulated in Matlab/Simulink. The obtained simulations results show the effectiveness and the robustness of the proposed approaches. [ABSTRACT FROM AUTHOR]