•This paper focuses on the grid integration of a large-scale photovoltaic plant through paralleled inverters.•Robust model predictive control is proposed to enhance the power quality.•Optimization ...approach is used to minimize circulating currents in parallel inverters.•Simulation comparisons with conventional control confirm the superiority of the proposed approach.
In this contribution a robust Model Predictive Control (MPC) is proposed to enhance the power quality of a large-scale PV plant connected to the grid through Paralleled Voltage Source Inverters (PVSIs) with common AC and DC buses. Paralleling inverters allow handling high-power export and offer advantages in terms of redundancy which ensure the system reliability. However, due to the physical differences and parameter disparities between the inverters, zero sequence circulating currents will flow through it, which will disturb the performance of the system. Hence, the control goal is to regulate the currents injected into the grid, suppress the zero-sequence circulating current (ZSCC). Consequently, this study proposes an MPC algorithm that is based on optimization approach which allows minimizing circulating currents. In order to show its effectiveness and performance of the proposed control, a comparison with linear PI controller is included. In addition, design control and tuning procedure are detailed. Simulation results show the performance of the proposed controller in ensuring power quality, and suppressing circulating currents. To verify the real-time feasibility of the proposed control scheme, Hardware-In-the-Loop (HIL) setup is carried out with means of Opal-RT and dSPACE rapid prototyping systems.
•The elastic–plastic behavior of the FGM was analysed.•A new technique has been proposed to affect the mechanical properties of the FGM.•Compare this technique which has been named UMM with the usual ...UMAT technique.•Study the effect of different material designs or variation of the graduation index n on the overall behavior of the FGM.•Analyze the displacement force response for the different types of material graduation.•Analyze the propagation path of the crack in the FGM according to the various types of material graduation.
FGM (functionally graded materials) have experienced rapid expansion in recent years in several industrial fields. The analysis of their mechanical behavior by the finite element method requires the use of subroutines established under a FORTRAN compiler given the difficulty in implementing the type of behavior of the materials constituting the FGM. Our work aims to establish a program in MATLAB (UMM) making possible to introduce the behavior of the FGM by element in the mesh model of the structure, hence the advantage and reliability of graded the material in three dimensions for two or even three constituents of FGM and secondly, for different geometric designs. This technique is more sensitive to the mesh, hence the adaptation strategy of a driven mesh in order to improve the precision and the convergence of results under minimal computation time. The constitutive law of our model follows the von Mises equivalent stress flow theory with a hardening variable in incremental form. Moreover, to describe the elastic–plastic behavior of FGM, the model of TTO (Tamura-Tomota-Ozawa) was used for both methods that of UMAT in the form of a numerical algorithm and for our new method in the form of calculated values by the MATLAB code. The parameters used in the two calculation methods are taken from the results of stress–strain tests of the two materials; ceramic (TiB; Titanium mono biorde) and metal (Ti; Titanium). A comparison between the two methods has taken place in the form of load–displacement curves in order to present the capacities of our technique with respect to the usual UMAT technique. However, for damage, the use of the XFEM technique in our UMM method has shown its advantage in the separation of the structure after crack initiation. The crack path as well as its propagation speed under the effect of the volume fraction exponent of the FGM has been highlighted. The two models used in this study (UMM and UMAT) were validated on the one hand with analytics through the TTO model and on the other hand by the experimentation of a tensile test.
To study the effect of antiseptics on bacterial biofilm formation. Biofilm formation and planktonic growth were tested in microtiter plates in the presence of antiseptics. For Escherichia coli G1473 ...in the presence of chlorhexidine or benzalkonium chloride, for Klebsiella pneumoniae CF504 in the presence of chlorhexidine and for Pseudomonas aeruginosa PAO1 in the presence of benzalkonium chloride, biofilm development and planktonic growth were affected at the same concentrations of antiseptics. For PAO1 in the presence of chlorhexidine and CF504 in the presence of benzalkonium chloride, planktonic growth was significantly inhibited by a fourfold lower antiseptic concentration than biofilm development. For Staphylococcus epidermidis CIP53124 in the presence of antiseptics at the minimal inhibitory concentration (MIC), a total inhibition of biofilm formation was observed. For Staph. epidermidis exposed to chlorhexidine at 1/2, 1/4 and 1/8 MIC, or to benzalkonium chloride at 1/8, 1/16 or 1/32 MIC, biofilm formation was increased from 11·4% to 22·5% without any significant effect onto planktonic growth. Chlorhexidine and benzalkonium chloride inhibited biofilm formation of different bacterial species but were able to induce biofilm development for the Staph. epidermidis CIP53124 strain at sub-MICs. Sublethal exposure to cationic antiseptics may contribute to the persistence of staphylococci through biofilm induction.
In this paper, the Adaptive Frequency Droop Virtual Power (AFDPV) method is implemented in a distributed control-based consensus to ensure the State of Charge (SoC) balancing of BESSs (Battery Energy ...Storage Systems), in an AC Microgrid (MG). An average consensus algorithm is used to acquire the average SoC value of the BESSs and the AFDVP strategy is designed in this proposal with a distributed architecture, to balance the SoC of BESSs while maintaining the MG stability, the frequency and the voltage variations between the permissible range the European norm EN 50160. In this distributed control architecture, the SoC balancing, the frequency and voltage restoration are realized, only thanks to local information of the Distributed Generator (DG) and information from their neighbors. A Matlab/Simulink simulation is performed in order to verify the effectiveness of the proposed method in the case of communication failure. In order to compare their performances, a comparison between the proposed distributed control and a centralized control is also provided.
► Photovoltaic panels modeling under partial shading conditions. ► Maximum power point tracking algorithm dealing with shadowing phenomenon. ► Global efficiency increased by considering converter ...losses into the MPPT. ► Losses reduction through the converter with the proposed algorithm. ► Performances verified for different PV panels’ interconnection schemes.
The fact that photovoltaic panels are very sensitive to non-uniform insolation conditions, which can occur several times a day, causes a decrease of efficiency and so increases time for return on investment. This work presents a maximum power point tracking algorithm (MPPT) operating on the load characteristic in order to take the converters losses into account. In addition, the proposed MPPT deals with the problems of shadowing for which the power-load characteristic can present two or more local maximums close to each other. Considering the converters losses it can be shown that the maximum output power of the photovoltaic panels does not necessarily coincide with the maximum output power of the converters. The proposed MPPT algorithm tracks the maximum power with the intention of reducing the total losses including those of converters. Its performance is verified by simulation and confirmed by experimental results.
Nowadays, the adhesive bonding process takes an important place in several industrial fields, especially in aeronautics. Given its advantages over other conventional mechanical processes, this ...process is being extended to be applied in composite materials and, in recent years, more particularly in the bonding of functionally graded materials. In bonded assemblies, the adhesive is the weak link due to its mechanical properties which are very weak compared to those of the two substrates. To this end, current research aims to reduce the concentration of stresses in the adhesive joint by choosing substrates whose mechanical properties are adequate with those of the adhesive in order to minimize load transfer and ensure a robust assembly. The present work analyzes, by the finite element method, the mechanical behavior of a single-lap joint with varying nature of the substrates. The analysis takes into account the variation of stresses in the adhesive of a bonded joint of different types (metal/metal, composite/composite, FGM/metal, FGM/FGM). On the other hand, an attempt has been made to introduce an adhesive with graded mechanical properties made up of two types to ensure efficient joining and reduce stress concentrations at the bond edges. The introduction of the FGM substrate mechanical properties is done using a USDFLD (User subroutine to redefine field variables at a material point) subroutine implemented in the ABAQUS computer code. Different damage approaches were used for the adhesive, namely the virtual crack closure technique (VCCT) and cohesive zone models (CZM) techniques. The effect of the mechanical properties of the substrates and adhesive were considered. The results show clearly that the value of the different stresses can be reduced if the mechanical properties of the substrates are optimized. On the other hand, the different techniques used to model the bonded joint converge towards the same results, emphasizing the agreement of the load–displacement curves with the experimental test, and the variation of the stresses according to the lap length with analysis by analytical models.
Given the field of application and the many advantages, the use of FGM (Functionally Graded Materials) materials has recently been extended in several components and more particularly in cylindrical ...structures, which have been the subject of several recent studies. Our work aims to use the finite element method to analyze a cylindrical structure in FGM with properties gradated in the direction of the radius (Thickness) solicited purely in internal pressure by the implementation of a UMAT subroutine in the calculation code ABAQUS. The elasto-plastic behavior of the FGM is described by the flow theory represented by the equivalent stress of Von Mises and an incremental hardening variable. The TTO model (Tamura-Tomota-Ozawa) was used only to determine the elastic-plastic properties of the FGM material. The radial, tangential and axial stresses according to the thickness were evaluated in the first part of our work. In the second part, these stresses are evaluated under the same conditions but with the presence of a micro-cavity. The results obtained show clearly that these stresses are in direct relation not only with the thickness and properties of the FGM tube but also with the presence of the cavity.
The effect of ultraviolet (UV) irradiation on nanofiltration (NF) membrane biofouling has been studied in pilot scale installations using two identical parallel membrane pilots and a low pressure UV ...reactor. The two pilots were fed either granular activated carbon (GAC)-filtered water or UV-irradiated GAC-filtered water during a filtration run of 20weeks. UV pre-treatment did not affect the organic carbon concentration but decreased the active planktonic bacteria counts and increased the dead planktonic bacteria counts of the feed water. Membrane permeability and longitudinal pressure drop (LPD) were continuously monitored during the experiments. UV irradiation was associated with much lower LPD increase, and moderate permeate flux decline. At the end of the test, spiral-wound modules were autopsied and analysed. Membranes of UV-irradiated pilot harboured decreased amounts of biofoulants (global quantity of deposit, sessile bacteria and ATP concentration and amount of extracellular polymeric substances). In conclusion, both membrane performances monitoring and foulant analysis showed that UV irradiation was an efficient NF pre-treatment to reduce NF membrane biofouling.
► This work is about optimization of nanofiltration process used in drinking water production ► This is an evaluation of a surface water pre-treatment process before nanofiltration ► The results show that UV irradiation limits biofouling
Conventional supply systems of electrical curtains for dielectrophoretic applications generally use as many frequency generators in combination with as many linear high-voltage amplifiers. This paper ...aims to develop an 'all-in-one' compact power supply instead of the conventional supply system. The developed three-phase power supply delivers a voltage up to 1000 V with a variable frequency. The power supply includes a 1 kV DC/HVDC converter, which is then converted into three rectangular shape voltages with a phase shift of 120°. The developed supply was successfully tested and compared with the conventional supply system for the displacement of micronised plastic particles.
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