Multicell Converters Hybrid Sliding Mode Control

International audienceThis paper deals with hybrid sliding mode control of multicell power converter. It takes into account the hybrid aspect of the conversion structure which includes the converter continuous and discrete states. The basic idea used in this paper is to consider the interconnected systems that represent the hybrid model and to generate commutation surfaces based on a Lyapunov function that satisfies asymptotic stability. Simulations are carried-out on a two-cells converter to assess the performances and the robustness of the synthesized controller

A PI/Backstepping Approach for Induction Motor Drives Robust Control

International audienceThis paper presents a robust control design procedure for induction motor drives in case of modeling errors and unknown load torque. The control law is based on the combination of nonlinear PI controllers and a backstepping methodology. More precisely, the controllers are determined by imposing flux-speed tracking in two steps and by using appropriate PI gains that are nonlinear functions of the system state. A comparative study between the proposed PI/Backstepping approach and the feedback linearizing control is made by realistic simulations including load torque changes, parameter variations and measurement noises. Flux-speed tracking results show the proposed method effectiveness in presence of strong disturbances

Uklanjanje klortetraciklin klorhidrata foto-Fentonovim postupkom: eksperimentalna studija i ANN modeliranje

The present work aimed to study the feasibility of photo-Fenton oxidation for the degradation of chlortetracycline chlorhydrate (CTC) in aqueous solutions, as well as the modelling of system behaviour by artificial neural networks. The removal performance of CTC oxidation by the Photo-Fenton process was studied under solar radiation. Different parameters were studied, such as pH (3 to 5), and initial concentrations of CTC (0.1 to 10 mg l–1), hydrogen peroxide (1.701 to 190.478 mg l–1), and ferrous ions (2.8 to 103.6 mg l–1). Results showed that a high removal efficiency of 92 % was achieved at pH 3 under optimised conditions, such as 10 mg l–1 of CTC, 127.552 mg l–1 of H2O2, and 36.4 mg l–1 of Fe2+. The transformation of CTC molecules was proved by UV-visible and HPLC analyses, which showed that almost no CTC molecules were remaining in the treated solution. A multi-layer perceptron artificial neural network has been developed to predict the experimental removal efficiency of CTC based on four dimensionless inputs: molecular weight, and initial concentrations of CTC, hydrogen peroxide and ferrous ions. The best network has been found with a high determination coefficient of 0.9960, and with a very acceptable root mean square error 0.0108. In addition, the global sensitivity analysis confirms that the most influential parameter for the CTC removal by photo-Fenton oxidation is the initial concentration of ferrous cations with a relative importance of 33 %.Cilj ovog rada bio je ispitati razgradnju klortetraciklin klorhidrata (CTC) u vodenoj otopini foto-Fentonovim procesom, kao i modelirati ponašanje sustava primjenom umjetnih neuronskih mreža. Učinkovitost uklanjanja CTC-a foto-Fentonovim procesom ispitana je pod sunčevom svjetlošću. Proučavani su različiti parametri poput pH (3 do 5) te početnih koncentracija CTC-a (0,1 do 10 mg l–1), vodikova peroksida (1,701 do 190,478 mg l–1) i željeznih iona (2,8 do 103,6 mg l–1). Dobivena je učinkovitost uklanjanja od 92 % pri pH 3, uz 10 mg l–1 CTC, 127,552 mg l–1 H2O2 i 36,4 mg l–1 Fe2+. Koncentracija CTC-a praćena je spektrofotometrijski i tekućinskom kormatografijom, te su utvrđene neznatne koncentracije CTC-a u vodenoj otopini nakon obrade. Umjetna neuronska mreža višeslojni perceptron razvijena je za predviđanje eksperimentalne učinkovitosti uklanjanja CTC-a na temelju četiri bezdimenzionalna ulaza: molekulske mase, te početnih koncentracija CTC-a, vodikova peroksida i željeznih iona. Pronađena je najbolja mreža s visokim koeficijentom determinacije od 0,9960 i vrlo prihvatljivom srednjom kvadratnom pogreškom od 0,0108. Globalna analiza osjetljivosti potvrdila je da je najutjecajniji parametar kod uklanjanja CTC-a foto-Fentonovim procesom početna koncentracija kationa željeza s relativnom važnošću od 33 %

Evaluation of Corrosion Inhibition of 316L Stainless Steel by Permanganate Ions in Chloride Solution

The efficiency of permanganates to inhibit the scale deposit captured the attention for more investigation on their role as corrosion inhibitor. In this article, the effect of permanganate as corrosion inhibitor on 316L stainless steel in NaCl solution is investigated. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) have been performed by varying the electrode stirring speed, the concentration of permanganate ions, pH and the temperature. The results show that the permanganate ions increase the cathodic and anodic currents under effect of stirring speed, due to oxygen reduction reaction and the reduction of permanganate ions. Electrochemical results indicate that the deposit of manganese oxide (MnO2) inhibits the pitting corrosion. The inhibition efficiency is up to 98 % for 10−4 mol.dm−3 of permanganate. The temperature reduces the effectiveness of permanganates against pitting corrosion, the pitting potential shifts cathodically from +0.395 V vs. Saturated Calomel Electrode (SCE) at 298 K to +0.275 V vs. SCE at 343 K. Surface morphology of the deposit oxide films and electrode are studied by emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared and Differential Scanning Calorimetry. The analysis of the deposit layer by X-ray diffraction revealed the presence of δ-MnO2 form, with a crystallite size of 3.17 nm.  Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Electrodeposition of CaCO3 on stainless steel 316 L substrate: influence of thermalhydraulics and electrochemical parameters

In this paper we study the effect of the hardness, the rotation speed, the temperature and the cathodic polarization on calcium carbonate scale deposit on rotating stainless steel electrode using electrochemical techniques. The scale deposit was investigated by X-Ray diffraction, scanning electron microscope, Infra-red spectroscopy and electrochemical impedance spectroscopy (EIS). The electrochemical results show that the Oxygen Reduction Reaction (ORR), which is responsible of CaCO3 electrodeposition, takes place with 4 electrons at low rotation speed and 2 electrons at high rotation speed. The morphology of the CaCO3 deposit shows that the crystals formed in the center of the electrode have small sizes compared to those of the periphery. Whatever the hydrodynamic or thermodynamic conditions, the Calcite form remains predominant. Other forms appear in particular conditions: at high temperature the aragonite form and at high cathodic polarization the vaterite form. 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