Contribution to the Fault Diagnosis of a Doubly Fed Induction Generator for a Closed-loop Controlled Wind Turbine System Associated with a Two-level Energy Storage System

—In this article, a contribution to the fault diagnosis of a doubly fed induction generator for a closed-loop controlled wind turbine system associated with a two-level energy storage system using an on-line fault diagnostic technique is proposed. This technique is proposed to detect the rotor fault in the doubly fed induction generator under non-stationary conditions based on the spectral analysis of stator currents of the doubly fed induction generator by an adaptive fast Fourier transform algorithm. Furthermore, to prevent system deterioration, a fractional-order controller with a simple design method is used for the control of the whole wind turbine system. The fractional-order controller ensures that the system is stable in both healthy and faulty conditions. Additionally, to improve the production capacity under wind speed fluctuations and grid demand changes, a two-level energy storage system consisting of a supercapacitor bank and lead-acid batteries is proposed. The obtained simulation results show that the objectives of the fault diagnosis procedure and control strategy are reached.     

Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition

Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.     

Cryptosporidium Log-inactivation with Ozone Using Effluent CT10, Geometric Mean CT10, Extended Integrated CT10 and Extended CSTR Calculations

The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit.     

Experimental investigation and theoretical modeling of dehydriding process in high-pressure metal hydride hydrogen storage systems

This study explores the endothermic dehydriding (desorption) reaction that takes place in a high-pressure metal hydride (HPMH) hydrogen storage system when hydrogen gas is released to the fuel cell. The reaction is sustained by circulating warm fluid through a heat exchanger embedded in the HPMH powder. A systematic approach to modeling the dehydriding process is presented, which is validated against experimental data using two drastically different heat exchangers, one using a modular tube-fin design and the other a simpler coiled-tube design. Experiments were performed inside a 101.6-mm (4-in) diameter pressure vessel to investigate the influences of hydrogen release rate, heat exchanger fluid flow rate and fluid temperature on the dehydriding process for the HPMH Ti_1.1CrMn. It is shown the dehydriding reaction rate can be accelerated by increasing the fluid temperature and/or the rate of pressure drop. HPMH particles located in warmer locations close to heat exchanger surfaces both began and finished dehydriding earlier than particles farther away. 2-D and 3-D models were created in Fluent to assess the dehydriding performances of the modular tube-fin heat exchanger and coiled-tube heat exchanger, respectively. The models are shown to be quite accurate at predicting the spatial and temporal variations of metal hydride temperature during the dehydriding reaction.     

RF MEMS continuous reversible variable inductor based on a microfluidic network

In this work, RF MEMS continuous reversible variable inductor has been fabricated by using microelectronic technology and lamination process. We review, evaluate and compare this variable inductor with other work. The proposed inductor is a dual circular coil and has an inductance of few nH. The fundamental idea is to place a liquid droplet between the metal turns of a coil in order to modify the capacitive/resistive coupling between metal tracks and hence to change the stored magnetic energy. The SU-8 resin was used to realize the microfluidic channels and Au as metallic tracks. To prove the reversibility of the inductor, two cases were studied: filling and emptying of channels. The tuning range of the inductance is approximately 107 % at 1.6 GHz, making these devices very suitable as building blocks in many RF applications.     

Bench-scale and pilot plant preparation of chemically modified polyester resins

The laboratory preparation procedure of a recently developed unsaturated polyester resin was followed to prepare the resin on a large scale (10- and 200-L pilot plant reactors). The process heating rate, reaction temperature, and agitator tip speed were kept constant on scale-up. The resin was successfully reproduced and its properties were unchanged upon scale-up. The effects of reaction temperature and inert gas flow rate on the polyesterification reaction rate were investigated. It was found that a 10°C increase in temperature or a 50% increase in the gas flow rate results in a 50% increase in the reaction rate.     

Empirical modelling and scale-up of a semi-batch polyestrification process

A semi-empirical kinetic model that fits laboratory data and predicts pilot plant data was developed. The model is a modified version of a recently reported third-order kinetic equation for the reaction of nonstoichiometric amounts of hydroxyl and carboxylic groups. The model can be used to quantify the effects of reaction temperature and inert gas flow rate on the reaction rate. The Arrhenius temperature dependence of the rate constant permitted the calculation of the reaction activation energy (53.6 kJ/mol). The gas flow rate dependence is an empirical function of the molar ratio of reactants to inert gas. The same function is simultaneously used as the process scale-up rule. The mathematical model can be potentially used for commercial-sized reactors.     

Phosphorus and nitrogen in the waters of the El-Kabir River watershed in Syria and Lebanon

In order to assess the quality of the waters of the El‐Kabir River, which forms the border between Lebanon and Syria, water samples were collected for phosphorus (P) and nitrogen analyses at 39 sample stations in the river watershed (18 in Syria, 21 in Lebanon). These samples were collected on the main stem and three major tributaries (Nahr al‐Arous and Nahr Nasrive in Syria, Chadra River in Lebanon). Three major springs also were sampled. The sampling was carried out in September 2001, and January, April and August 2002. Nutrient analyses were carried out on samples taken in September 2001, January and April 2002 in Syria, and in September 2001 and August 2002 in Lebanon. The P concentrations were extremely high throughout the watershed, as were the ammonia‐nitrogen and nitrate‐nitrogen concentrations, indicating extensive pollution. Although the nitrite‐nitrogen concentration was relatively low, it is at the upper end of what might be considered normal, thereby perhaps being indicative of some anthropogenic sources. The spring waters were found to be polluted by nutrients. The nutrient sources contributing to the river pollution were mainly from piped, direct sewage discharges from the many settlements throughout the basin. These were supplemented by diffuse sources directly from agricultural fertilizer use and from the indiscriminate disposal of solid wastes into the river and on the stream banks and lands adjacent to the roads of the watershed.